updated FAQ on Ram MPG improvement (long)
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updated FAQ on Ram MPG improvement (long) - 4/19/2006 11:44:04 AM
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HankL
Posts: 2718
Joined: 8/20/2005
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Ram Pickup MPG improvement discussion :
{last modified May 28 2007}
So where are you now compared to other Ram pickup owners?
Most gasoline 4x4 Ram owners from 1994-2005 report that their
mixed City & Highway MPG is about 12 to 13. For 4x2 add 1.5 MPG.
Although the 5.7 Hemi engine is about 8% more efficient than earlier engines,
Dodge made the 2003+ Ram a little bigger and aerodynamically blunter
and this cancelled out most of the engine efficiency gain - but the higher hp
of the 5.7 is probably tempting too much "heavy foot" as well.
So how much better MPG could you get?
It is likely that the Ram pickup owners with the top 10% of driving skill
can use that alone to get a mixed City & Highway MPG of 15 or more,
just like the bottom 10% of drivers with bad habits get around 9 MPG.
With 90% of the aero, tire and engine mods mentioned in this FAQ,
plus excellent driving habits, 19 MPG in mixed City & Highway is possible,
and Highway MPG of 26 at a steady 60 mph
and 20 MPG at 75 mph is doable.
None of this is going to match a diesel off road motorcycle of 110 MPG
http://www.innovations-report.com/html/reports/logistics/report-35705.html
but a Ram pickup owner can save thousands of dollars per year.
How much money can you save with a 1 MPG improvement?
With the typical gasoline Ram getting 13 MPG, an improvement to 14 MPG
would save about 5.5 gallons for every 1,000 miles you drive.
With the typical owner driving 12,000 to 18,000 miles per year
and gasoline ranging $2.5 to $3.50 this gives the typical owner
a yearly savings of about $250. Most business demand that
investments pay for themselves in 5 years. With vehicles a payback
of 2-3 years might be a better goal.
The most cost effective mods are usually aerodynamic improvements
that help highway MPG, because a factory stock 2003+ Ram has a shape
more like a brick than a bullet, perhaps because many pickup buyers value
the look of big grille over the long term $ benefits of a wind cheating shape.
Second easiest MPG improvement comes when it is time to buy new rubber, where
good choices about the rolling resistance of tires will improve both City and
Highway MPG. Unfortunately finding information about what engineers call Crr
of a tire requires a good deal of looking and most tire makers actually hide
this information.
Many Ram pickup owners start trying to improve MPG by first trying engine
modifications. Unfortunately, the efficiency of most modern engines is
already highly developed after 100 years of improvements, and this is the
toughest place to start. On purpose, I have put engine mods behind
aero and tire mods.
Chrysler spent over $1 billion on its 5.7 Hemi V8. While power went up
on less displacement, and cost to build each engine went dramatically down,
the fuel consumption of the Hemi was only about 8% better than the
Magnum 5.9V8 brought on the market 10 years earlier.
This gain of less than 1% per year in engine fuel efficiency is typical.
Here's what BMW recently said:
"A comparison of engine concepts from former decades with the power units
offered to the customer today clearly confirms the progress achieved: Looking
at a BMW 323i in the 1983 model year versus the {2006} BMW 325i - both of
these models featuring a straight-six power unit - we immediately see the
substantial difference: Fuel consumption is now 20 per cent below the figure
in 1983, and emission management has improved by no less than 95 per cent."
Engine output is up by 57, maximum torque by 24 per cent. Acceleration,
in turn, has improved by 24 per cent. And while vehicle weight is up by
38 per cent, the drag coefficient is 16 per cent lower."
Many Ram owners make bad choices on engine modifications like cold air
intakes and waste money on that could have simply been spent on more gasoline.
However while it is hard to make engines more efficient at the same rpm, all
engines vary quite a bit in efficiency at different rpms and throttle
openings.
There are drivetrain mods that will allow your engine to operate where
it turns fuel into horsepower most efficiently based on the two important
guidelines: (1) having its throttle nearly open but just below where an extra
wasteful percentage of fuel starts getting injected, and
(2) keeping piston speed below the range of 1000-1400 feet per minute
so that friction of the engine's moving parts does not begin to rise at a
dramatically faster rate than most engine owners realize. When these two
needs are met an engine turns fuel into horsepower most efficiently even
before the owner makes expensive engine modifications.
Note in the above paragraph we talk about large throttle openings and "piston
speed" rather than rpm. The dedicated pickup owner will have to be willing to
drop some old myths - myths his father's and grandfather's generation
disproved but that still hang around among those who have not operated
and measured an engine 'hands on'.
Myths like:
some magical "Powerband,"
or trying to run at high vacuum gauge readings,
or that engines "don't work as hard" at higher rpm.
You may have heard the saying:
"It's all about Torque"
For acceleration you want high torque all the time no matter what rpm
your engine is at. Engine builders strive to have a 'broad' torque
curve from low rpm to high.
Consumers brag to one another about their engine's maximum horsepower
but 99% of them don't know what (or why) the Scottish mechanical genius
James Watt invented the term "horsepower" or how it tells you the maximum
torque that can be generated at the rear wheels when a correct ratio set of
gears has been used after the engine's output shaft.
Engine designers brag to one another {when having drinks at the SAE convention
center hotel bar} about the range over which their engine develops 90% or more
of its maximum torque, because they are all aware of how this shows true
design skill.
It is all about Torque in fuel economy too. You want to generate high
torque at as low an rpm as possible without going into fuel enrichment.
This is because low piston ring speed against the bore walls
creates less wasteful internal engine friction. Most vehicle owners don't
know that if you double the RPM the friction inside the engine does not
just double - IT GOES UP ABOUT 8 TIMES.
Last, for the most money and not a small amount of your labor, this FAQ
describes mods for engines that improve fuel efficiency when the throttle
is only partially open. As the value of these mods are described, be prepared
to give up some of the stuff you may have read in old hot rod magazines
that was based on engines operating at full throttle and meant for producing
maximum horsepower in order to win a drag race - no matter the fuel cost.
This is a long article that is divided into five main sections:
Aero mods,
Tire mods,
Gearing & Drivetrain mods,
Engine Mods
Driver Behavior Mods.
At the end are weblinks to much additional information.
Feel free to skip to anything that suits your fancy,
especially the Driver Behavior section near the end
which some might argue are the most cost effective of all,
but many consider 'nagging' or 'boring' despite the fact
that 'Hyper-Milers' drive around corners like maniacs.
Only partly in jest, it is recommended that you print this FAQ out
and keep a copy in the bathroom for reading on the 'throne'.
Don't try to read too much at a time, but to digest it all,
plan to read it at least 3 times. With each reading you might discover
a few more 'Lightbulb Turns On' revelations.
AERODYNAMIC MODS
First the History you might Not Know
At one time Walter P. Chrysler ordered his engineers to be out at the cutting
edge of aerodynamic design and introduced the revolutionary 'AirFlow'
car in 1934.
If the Chrysler Airflow looks somewhat like an old Volvo to you, you
should know that after World War II when Volvo Trucks wanted to start
making cars for the Swedish market they just copied the Airflow design
because they considered it one of the best designs ever produced up to
that year. Ferdinand Porsche also copied it for the original Volkswagon.
"Imitation is the sincerest form of flattery."
Lee Iococoa may have been the designer of the square sided Ford Mustang,
but he also admired aerodynamic designs. When he saw the proposed
redesign of the Dodge Ram pickup for year 1992
Iococoa rejected it and suggested that the designers create a new
pickup customers would either 'Love or Hate' and mentioned they might
copy the sleek 'Big Rig' style of the newly introduced aerodynamic
Kenworth T600 sometimes nicknamed the 'Anteater'
This is how the shape of the '2nd Gen' Ram design of 1994 was born.
It was even officially called the T300 project inside Chrysler considering
it was approximately a half sized T600.
Note the:
more rounded front,
the cut-aways above the headlights, and
the steeper windshield.
These changes made the 1994 Ram the most aerodynamic pickup
ever built up to that time.
But also note the 'In Your Face' grille and massive appearance.
Did it have an effect on customer's psychologies?
As we know, this Dodge Ram greatly increased Ram sales and took
buisness mainly away from pickup sales leader Ford.
Ford thought the secret to the Rams appeal was the aerodynamics,
felt this improved sales effect was similar to their 1983 Thunderbird
and so the 1995 Ford F150 became the
'melted brick' shape that did match the Rams aerodynamics
(both Cd=0.44)
But Ford got it wrong. The new F150 sales were disappointing.
The new more aerodynamic 1995 F150 was called 'soft' and 'girly'
and did not win back the sales lost to Dodge. Ford then regrouped
and came out with the SuperDuty with a big grille and hulking
appearance. The wider, taller, heavier, big grille SuperDuty did
win back sales from Dodge. Dodge managers noticed this too.
So (in a time of low gasoline prices) aerodynamics got the reputation
of being a pickup sales killer.
Auto Company management decided
- rightly or wrongly -
that the pickup customers who could be 'won over' from another
brand had this characteristic - they were insecure psychologically
and deep down wanted to pretend to be Marlboro Man big truck
drivers, as long as the interior of the truck could be ordered like
that of the plushest 'land yacht' Cadillac.
So now Ram, F150 and Titan are bigger, blunter, and heavier
with grille openings 5 times larger than is needed even to pull
a trailer thru the Mojave Desert in summer. Soon the 2007 Toyota
Tundra will be this way too, after the original T100 started with a
Cd of 0.41 and low frontal area. Ex-Chrysler vice chairman
Bob Lutz (now working over at GM) seems to be on the only one
demanding that his 2007 GMT900 Silverado/Sierra be aerodynamic,
but bankruptcy might cancel that. Is this because Bob Lutz was a
Marine Jet Fighter pilot who still flies at age 70+?
The pickups are getting more 'Peterbuilt' than Kenworth T600 (or T2000)
in appearance, but who cared when gasoline prices were in the
$1.00 to $1.25 per gallon range four years ago when this designs were born?
But perhaps we are being too harsh.
DCX employees want to keep their jobs.
DCX management and stockholders want to make profits.
The old saying:
"The secret of profitable automaking is not selling good designs cheaply,
It is about making any cheap design sell good"
may sadly still hold in the USA.
DCX still knows how to make highly aerodynamic vehicles,
like their 'BoxFish Bionic Car' concept:
http://www.theautochannel.com/news/2005/06/07/116396.html
The recent 2007 Toyota Tundra pickup claims a Cd = 0.37
http://www.toyotanation.com/forum/t121001.html
Making your Truck Slip through the Wind
Aerodynamic improvements are usually the cheapest and easiest to get.
A pickup that is not aerodynamic uses more energy than necessary to
heat up the air it pushes through. Quite literally, blunt trucks make the
world "Full of Hot Air".
Edmunds.com has written a very good article called
"Improving Aerodynamics to Boost Fuel Economy"
where they managed to get Chrysler, GM, Ford, Jaguar, and Volvo
engineers to give tips on improving aerodynamics of both cars and pickups.
It is best to read this article "to get up to speed" on the general ideas
before continuing to specific ideas about Ram pickups.
http://makeashorterlink.com/?I17A2100D
or
http://www.edmunds.com/advice/specialreports/articles/106954/article.html?tid=edmunds.a.advicelanding.advice.special.1.*
Starting with the simple first, it is likely that a suspension drop on a Ram
or any pickup truck improves the aerodynamic drag. According to Ford
Motor Company engineer Steve Wegryn:
"an inch of ride height increase degrades the coefficient of drag by about
10 drag counts [.01]".
There is some evidence that on a 1996 Indy Ram a body drop improved
its Cd by a few hundredths. The 3rd gen body on the 2004 SRT10 Ram
uses a 4/6 inch lowered stance, a rear spoiler, tonneau, and partially
blocks off part of the 'big for show, not for go' radiator grille to lower
its aerodynamic Cd from the 0.528 of the 2003 1500 Ram 4x4 to the
SRT10's better value of Cd=0.43 {These numbers come from the official
DCX media website restricted to journalists} Improvements gotten on
the Indy Ram and SRT10 this way are completely in line with the tips
given in the Edmunds.com article.
The early model Dodge Ram SRT10 rear spoiler (the one that mounts to the
bed rails and won't fit a tonneau) has a top surface like you would expect -
a flat surface at a slight 15 degree angle that past research shows reduces
both lift and drag a bit. The original Dodge SRT10 press release bragged
about this spoiler and claimed it decreased both lift and drag at the same
time. Higher degree angles on the upper surface of the spoiler would
decrease lift but increase drag. The bottom surface of the early SRT10
spoiler is slightly different. Where you would expect to see the curved
surface of an upside down airplane wing underneath - instead you see
a mostly flat surface in the front that changes to a 2 inch deep groove
up into the spoiler near the rear. This groove appears to a bed-wide
director that spins a horizontal tornado downwards into the area just
behind the pickup's tailgate. In Engineer Geek Speak this might be a
'longitudinal vortex generator' designed to break up the low pressure
area that forms to the rear of the tailgate and bumper on nearly any
design of pickup truck.
Later model year SRT10 rear spoilers that fit onto the tonneau with 3 mount
points are slightly different. Top surface is similar to the earlier siderail
mount, but the under-surface of the spoiler no longer has the
width-wise groove, but does have a sharp angled notch at the rear.
It is also noteworthy that despite a 500 hp engine's cooling needs
the SRT10 Rams have radiator opening block off plates on left and right
sides of the radiator. Restricting the air going through the grille to
the minimum needed was probably done to improve high speed
aerodynamics on the SRT10. Even SRT10 Rams seen in Florida still have
these block offs installed. These can be seen behind the grille in this
large picture:
http://www.seriouswheels.com/2004/2004-Dodge-Ram-SRT-10-F-1280x960.htm
When Popular Science magazine asked GM 'MPG Guru' Roger Clark for
advice on decreasing pickup fuel consumption at highway cruise he
advised modifying these areas would give easy gains:
more info at:
http://web.archive.org/web/20020803202923/http://www.popsci.com/popsci/auto/article/0,12543,332270,00.html
One reason the Chevy Silverado gets better highway MPG than a Ram is that it
has a lowered body drop for better aerodynamics compared to the Ram
and F150. {The Silverado also is not as high, slightly narrower, is about
400 lbs lighter, and has an 5.3V8 with a shorter stroke and 9.9 compression
ratio.}
In the January 2006 issue of Truckin magazine they quote un-named GM
aerodynamic engineers as saying that a pickup tonneau is good for a gain
of 0.6 MPG.
Back in 1999, Ford Motor Co officially said that a soft tonneau is good for a
a gain in highway mpg on the F150 and tried to get the EPA to allow them
to add this to their official "Highway MPG" rating by re-classifying the
tonneau 'standard equipment'. In a move that didn't make any sense,
EPA denied this to Ford, but a few years later allowed GM to do it on the
Avalanche.
My personal experience confirms that a hard bed tonneau can lower the
aerodynamic drag. I installed a ARE hard tonneau and found it was good for
about 0.5 to 1 mpg improvement at 70 mph, but don't expect to see this unless
you do a good test. The best way to test is with two trucks following one
another 'convoy style' on two identical round trips on a highway at a steady
freeway speed. On the first trip one truck has the tonneau and the other
follows at least 6 truck lengths back. On the second trip the other truck has
the tonneau and the first truck follows with its bed open again.
Be aware that head winds, side winds and tail winds all can easily effect
more than 1 MPG. The second truck and the two trips are used to cancel out
these constantly changing wind effects. Don't underestimate how careful
you have to test to reliably find a 0.6 MPG gain.
This Snugtop F2 hard tonneau has a built-in 'Roofline Extention Spoiler' on
the back that might help MPG a bit more than a conventional design.
Fibernetics has a similar rear spoiler with a bit more angle, shown here on a
F250:
There is an interesting student project on aero improvements tried on a
1998 Dodge Ram model truck several posts down at this link:
http://www.dodgetrucks.org/forums/viewtopic.php?t=52115
If there are asterisks in the above weblink, replace them with the letters
d-o-d-g-e-t-r-u-c-k-s.-o-r-g without any dashes, or go directly to the stored
old pages here:
http://web.archive.org/web/20030414190338/http://mars.acnet.wnec.edu/~ehaffner/did.htm
and
http://web.archive.org/web/20030414234348/mars.acnet.wnec.edu/~ehaffner/Tonneau.htm
Note that the students found that conventional camper tops and removed
tailgates hurt, but tonneaus helped about 11%.
The American Society of Mechanical Engineers (ASME) gave these students
a prize for their experiment.
Unlike the Mythbusters TV show test of up/down tailgates on a 2005 Ford F150
these students found a very slight advantage to having the tailgate down
but the difference is so slight to be not important. The new design F150 does
have significantly deeper pickup bed, higher sides, and taller tailgate than a
1998 Ram so that might explain the slight difference. Any automotive engineer
would tell you that having a pickup run completely out of fuel on high speed
interstate highway might make for a Dramatic & Entertaining TV show
but it is a totally undependable way to measure MPG carefully.
(Note that the Mythbusters built a 'water flume' out of plywood and an
electric
boat trolling motor for their toy F150? They almost certainly got this idea
from
the ASME prize winning website using the toy Dodge Ram listed above)
If you are scientifically minded you will enjoy this short article on using
CFD
to create flow diagrams of airflow over typical pickup truck bodies:
http://www.fluent.com/about/news/newsletters/04v13i2/a14.htm
Bug shields at the front of Rams nearly always hurt MPG. Many times they
also make outside mirrors vibrate or cause extra noise.
The 2nd Gen Dodge Ram Diesel that set the Bonneville speed record had
'Mooneye' wheel cover discs. These are supposed to reduce aero drag
by 1-2% but hurt brake cooling.
Jesel Valvetrain's 3rd Gen QC Ram has similar mods up front and a
custom tonneau with spoiler on the back:
The Jessel pickup has reached 224 mph on the salt flats:
http://www.autoblog.com/2006/08/17/dodge-quad-cab-pickup-sets-224-mph-record/
A MPG test over a roundtrip of a section of I40 at a steady 70 mph showed
0.7 MPG worse without the 1995 Ram's stock front bumper air dam, than with the
stock air dam in place. Other 2500/3500 Diesel Ram owners have reported
better MPG after taking off their air dam on the TDR website - but those tests
did not seem to be carefully done.
I have recently had some aerodynamic success with home-made little aluminum
tabs called 'Wheeler Vortex Generators'. I mounted 5 just behind the side cab
windows, and another 5 just in front of the rear brake lights. These improved
my coasting speed down a 6% grade hill by 2 mph, and also improved MPG at a
steady 70 mph by 1 mpg.
I had previously tried this commercial product on the roof of the truck, but
it did not appear to work in my test runs:
The vortex generators I made were cut from 5 inch by 7 inch aluminum
'flashing' from Home Depot. You cut the flashing into 3 and 9/16th inch
circles, and then bend the sides up to form the 'wings'. A circle of course
has 360 degrees. The front of the wings take up 107 degrees of the circle,
and the back takes up 22 degrees. I used 3M 'Super Strong' outdoor mounting
tape from Target to stick the vortex generators to the truck's sheet metal.
The finished product looks like this:
I am still testing with the Wheeler Vortex generators. I have tried bending
dimes into tiny ones for the mirrors - but no measurable change. I have also
tried little 1.5 inch ones on the bottom of the Ram airdam - felt more stable
but MPG tests showed worse results. The best results have been on the sides of
the cab and on the sides of the pickup bed ahead of the tail lights. This
inexpensive mod can be good for better MPG especially at higher speeds.
It has occurred to me that with a heat gun to soften the plastic you could
make these vortex generators out of the various sized computer CD's or
DVD discs, but I have not tried that yet.
There is also a commercial vortex generator called 'Airtabs' that is perhaps
a bit lower in drag than a home made Wheeler type. These are available in
paintable black, white and clear plastic. They are $3 each.
If you think that vortex generators are something human beings have invented
first, then you ought to look at the notches on the front fin of a humpback
whale:
Yep, those are vortex generators, and as Dr Laurens Howle at Duke's School of
Engineering has tested, they are more highly efficient than man's wing
designs.
Also, have a close up look at sharkskin:
You should also know that a Bumblebee could not fly without the
vortex its wings make - and that engineers only recently began
to understand this.
It should not surprise you that the Ram SRT10 has a
vortex generator on the underside of its rear spoiler.
Want to calculate your own Cd and tire rolling resistance?
This old stored webpage makes it easier:
http://tinyurl.com/3aompw
original also at:
http://web.archive.org/web/20040803073229/http://www.race-technology.com/WebPage2/Other/Utilities/Coastdown/CoastDownCalcs.html
TIRE CHOICES for BETTER MPG
Increasing the air pressure in your tires, and picking a narrow 'rib tread'
commercial delivery truck type tire that has low rolling resistance
definitely will help MPG.
Raising the air pressure by 15 psi to the max 70 psi in Goodyear Wrangler
HT 235/85R16E tires increased my mpg by +1 in a 311 mile
test run - but the ride was bone jarring. A narrow, highway rib tire like the
HT gives the lowest rolling resistance. Wide, aggressive tread tires can be
three times harder to roll. It might pay to have a 4 tire set for the weekday
commute, and a weekend mudder wide tire set.
Several Cummins Diesel Ram owners have reported that buying special
wheels and converting to 19.5 Commercial truck tire designs have
improved both MPG and tire tread life - but these tires are generally
heavier. RicksonTruck is one such special wheel seller:
http://www.ricksontruck.com/
Consumers Reports is the only organization I know of that tests for rolling
resistance of tires but even they do not report the Crr number.
Quote from CR:
" Fuel mileage at a price. Some tires roll with less drag than others. The
lower a tire's rolling resistance, the more fuel you can save. Those savings
can be significant. {Pickup and SUV} Tires with the lowest rolling resistance
delivered nearly 2 mpg more at a steady 65 mph in our highway tests {2003
four-wheel-drive Ford Explorer XLT 4x4} than those with the highest rolling
resistance. The catch: While some high-scoring tires had low rolling
resistance, most tires with the lowest rolling resistance also had lower
overall scores."
In their 11/2004 Pickup & SUV tire test CR the
lowest rolling resistance tires rated 'excellent' were the:
Bridgestone Dueler H/T (D684)
Michelin Cross Terrain
Continental ContiTrac
BF Goodrich Radial Long Trail T/A
The Pickup & SUV tires with the worst rolling resistance were the:
Pirelli Scorpion STA
Kelly Safari Signature
Yokohama Geolander H/T-SG051
A tire with a 'very good' rolling resistance and high scores in other handling
and braking tests was the Hankook DynaPro AS RH03
Hankook recently announced that they had spent $10 million developing a
tire called the fx-Optimo that has even lower rolling resistance and can
give up to a 3% MPG improvement:
http://www.moderntiredealer.com/t_inside.cfm?action=news_det&storyID=5961
In another test of "All Season" tires in November 2005,
CR rated these tires as 'excellent' for low rolling resistance:
Michelin X Radial DT
Michelin Agility Touring
Michelin Harmony
Hankook Mileage Plus GT H707
Kumho Touring 795 A/S
Toyo 800 Ultra
Sumitomo HTR T4
In the same November 2005 issue
'All Terrain' tires were also tested
but only the
Continental ContiTrac TR
got an excellent rating for low rolling resistance in this group.
The California Air Resources board is pressing the tire companies to make
rolling resistance measurements on tires freely available to the public by
2008, one of the few reasonable things CARB has ever done in my opinion
The lower profile 17 and 20 inch tire designs used on the 2003-2005
5.7Hemi Rams have a 'sticker' tire tread and higher rolling resistance than
earlier year Rams. It is probable that if a manufacturer makes available a
235 85 R17 tire in Load Range E it would be lower rolling resistance
than the stock tires and might improve MPG by 1-2 at 70 mph.
The 2006 Ram press release says the new model will have 'low rolling
resistance tires.'
In April 2006 the "independent and non-partisan" US National Academy
of Sciences completed a report on the rolling resistance of tires and how
MPG for the entire country might be easily improved if tire makers
increased their research into how to make tires roll even easier.
The 'meat' of this report starts about page 50 at this weblink:
http://www.trb.org/publications/sr/sr286.pdf
LUBRICANT, EXHAUST & DRIVETRAIN MODS
Switching to synthetic lubricants - - engine oil, diff, synthetic Mopar-spec
transmission fluid, and syn greases in wheel bearings is good for 2-5% MPG
improvement. That is only about 0.5 mpg but every little bit helps.
In the Cummins 'Physics of MPG' white paper they recommend synthetic
lubricants in transmissions & differentials but state that conventional
oils changed often are the best cost compromise in the engine.
Larry Shepard writes in the 'Magnum Engines, 1st Ed' book published by
Mopar Performance that running engine oil and transmission ATF levels
1-0.5 quarts below the 'add' marks on the dipsticks can increase MPG slightly
due to less oil drag. If you do this, you must check levels very frequently
to see that you don't drop oil levels even lower into the 'danger zone' and
some experts on 46/47 overdrive automatic transmissions advise the oiling
passages to the OD unit need to be enlarged for more ATF flow in any case.
Recently there was a post from a Chrysler employee working in their dyno
testing department saying that running a 5.7 Hemi Durango one quart low
(6 quarts instead of 7) on engine oil would give about 3 hp gain at wide
open throttle and high rpm. This supports Larry Shepard's advice but
also confirms any gains are small.
Further support that oil windage can affect hp and torque as low as 3000
rpm on a 350 ci engine filled from 4 quarts to 8 quarts is found in this
carefully done Circle Track magazine article's dyno tests, but the MPG
effect in the 1500-2500 rpm range would be small:
http://circletrack.com/techarticles/ctrp_0603_oil_pans_windage/index.html
Another 'non-sexy' but effective way to increase mpg is to keep an electric
block heater on while the truck is parked. The Dodge PCM computer richens the
mixture until the coolant temperature gets to 147 degrees F. By keeping the
block warm the engine goes into the more fuel efficient 'closed loop' control
sooner. This MPG improvement works best on trucks that do short trips. At 8
cents per kw-hr electric rates, running a 700 watt block heater for 8 hrs
costs 45 cents.
This graph from the FL Dept of Transportation shows how badly MPG is hurt
during the warm up period:
Gearing
Before discussing gearing, one tip to beginners is to drop all
confusing talk of 3.55/3.92/4.10 differential ratios, tire heights,
'effective' ratios, and so forth. It is much less confusing in the long run
to talk about gearing in terms of vehicle speed per 1000 rpm. This is
especially true if the tires have been changed out from the typical 30
inches of factory installed rubber to the 34-38 inch diameter that some
"My self esteem is low but my truck is the tallest"
Ram owners install on ridiculously lifted & unsafe pickups that seldom
if ever leave the blacktop.
If your stock Ram in top gear was showing 1500 rpm on the tachometer
when the speedometer was showing 60 mph, then your gearing was (60/1.5)
or 40 mph per 1000 rpm. This way it is easy to see that if you speeded up
to where your tachometer was showing 2000 rpm, you would be at 80 mph.
In a similar way if you turned your OD off and dropped down to 'direct drive'
third gear you can find the mph/1000 rpm for that gear too. If the tach now
read 2250 rpm at a speed of 60 mph, the gearing for your truck's third gear
is (60/2.250) or about 27 mph per 1000 rpm. You can quickly see that at
4000 rpm you would be going about 108 mph.
It is worthwhile finding this out for all your transmission's gears.
Even better, find out for yourself
where your engine's rpm of
Maximum Torque, then
Maximum Horsepower,
falls in speed (MPH) for each of the transmission's gears.
At this point after figuring out your truck's gearing you should notice that
Dodge engineers felt that to get best MPG at highway cruise the top gearing
needs to be at least around 40 mph/1000rpm or more,
and for acceleration in most "real world" conditions second gear should be
about 17 mph/1000 rpm - which puts second gear at about 30 mph at 1800
rpm where the unlocked torque converter is designed to 'stall' and goes up
to around 90 mph in the 6000 rpm range when you take into account
the percent slip of the unlocked torque converter at high horsepower.
Keep these numbers of 40 and 17 in mind if you intend to modify your
truck's tire sizes or differential gears later. If you have an interest, I
suggest you figure out for yourself what MPH/1000 rpm you should have
in 2nd gear if you want your 0-60 time to be the fastest possible - here
60 mph should occur near your "redline" rpm but you should figure in about
8% slip in the torque converter. In a similar way you can guess where
your quarter mile terminal speed will be and what MPH/1000 rpm
would be best for overall gearing if winning at the dragstrip was at the top
of your wishlist. Should that gear be 3rd or Overdrive 4th?
Now lets discuss gearing and fuel economy.
In city driving gearing doesn't matter nearly as much as not having a
'heavy foot' or hauling a lot of weight in the bed of the truck.
A vehicle that is either overgeared or undergeared will lose MPG at highway
cruise.
An engine is numerically overgeared if it is not cruising at about
60-75% open throttle.
An engine is undergeared and "too weak for the job"
if it has to operate with its pistons going faster than an average of about
1200 feet per minute when at 75% throttle.
Note that you could reduce engine weakness by turbocharging
as well as the much more common thought to just make the engine larger in
cubic inches. This is the reason nearly all diesels have become turbocharged
in the last 20 years.
How do you calculate this average piston speed?
Multiply the stroke of the engine in inches by two (because the piston goes
both up and down on one rpm) and then divide by 12 to convert inches to
feet. Multiply this by the rpm.
So where does 1200 feet per minute end up for various engines?
Here some examples:
For the 3.58 stroke of 3.7, 5.7, 5.9 Dodge engines:
2011 rpm = 1200 ft/min /( 2 x 3.58 inches/12 inches per ft)
For the 3.405 stroke of the Dodge 4.7V8
2114 rpm = 1200/(2x3.405/12)
For the 3.00 stroke of the Ford 5.0L V8
2400 rpm = 1200/(2x3.00/12)
For the 4.72 stroke of the Cummins Inline 6 diesel
1525 rpm = 1200/(2x4.72/12)
Is it possible for an engine to be made to get its best fuel economy at a
piston speed above the typical 1200 feet per minute?
Yes.
Very thin piston rings, using less than the normal 3 rings,
slippery coatings on piston skirts, extremely hard but slick coatings
on bore walls like "NikoSil" and keeping the bore walls very hot
so that the oil there will be thin and less viscous can all allow the
'best economy' piston speed to be raised but even 'state of the art'
giant marine diesel where nearly every trick is used seldom exceed
1500 feet per minute.
Honda has announced that over the next 5 year period that the major
part of their engine research $ will be spent on ways to reduce internal
engine friction, and this is from a company that NASCAR engine builders
already admit has the best rod and crankshaft bearing material for sale.
Which is more important: having the rpms near this 1200 foot per minute
speed for the pistons, or having the throttle in the 65-75% open range?
Answer: it is more important to be in the 70% throttle range and you should
slow down the rpms to get there. There is not much change in efficiency
when piston speed drops from 1200 down to 800 ft/minute but there is a big
change in efficiency when the throttle goes from 70% open to 40% open.
Why?
Imagine that you have a disassembled engine in front of you. Put a loose
piston in a bore and pull it down against the friction of the rings. It won't
be very hard. Now imagine that same piston in the bore has the top of the
bore sealed off and has a vacuum sucked of 12 inches of Mercury.
12 inches of vacuum is about 6 psi of negative pressure. If the piston is
4.00 inches in diameter it has an area of about 12.5 square inches
(remember pi R squared but most cherry pies are round?)
6 pounds per square inch times 12.5 square inches = 75 pounds would be
required to pull the piston down - you probably couldn't do it with the grip
of just a couple fingers! An engine running with a high vacuum in the intake
manifold has to do just this, and for eight cylinders!
Engineers refer to this as one of the two parts of "Pumping Losses". The
other part of Pumping Losses is due to pushing the exhaust out the tailpipe.
Most engine owners easily imagine that exhaust loss, accept it, and spend
a lot of time and money on mufflers, headers, Y pipes etc. These same
engine owners would do well to remember the "Pumping Loss" on the intake side
and try to keep it low during highway cruise conditions.
{Note to engineers: Yea, I know, 'negative pressure' does not really exist and
what actually happened is 14.7 psi of air pressure is pushing the underside
of the piston and there was just less pressure on the top of the piston to
create a delta P - but the general public thinks in 'vacuum' terms.
And it is not just the general public - talk to the biologists who think
-100 psi or more of 'negative' pressure pulls water up capillaries to tree
tops}
Setting Gear Ratios to suit the Customer's Expectations
Most auto manufacturers intentionally overgear their vehicles because they
know from experience that customers will bitterly complain about a vehicle
that downshifts to climb a hill.
Engineers know that to give their customers the best possible highway MPG
the transmission would downshift on EVERY hill, but the sales department
reminds them that that every employee at the automaker (including engineers)
will lose their jobs if customers {even ignorant ones} get mad
and buy someone else's vehicle that meets their expectation.
So vehicles are overgeared to 'feel strong' during the 20% of the time they
are climbing hills in Overdrive, even if it means this hurts MPG a bit during
the 80% of the time the vehicle is on level roads or going downhill.
An engine is numerically undergeared if it is trying to cruise in the
'Power Enrichment' zone above about 80% throtttle opening where the
PCM computer greatly enriches the air to fuel ratio from 14.7 to 11.
On most vehicles with automatic transmissions it is not possible to cruise
in OD on level highways in the power enrichment zone because the
transmission will downshift to a lower gear long before the accelerator
is pressed that far.
For the same reason anyone who presses the accelerator down all the way near
the floor whether they are driving in the city, highway, climbing a hill, or
pulling a trailer is going to get about 25% worse MPG than someone who
presses right up to about 70% throttle but never goes over it.
This is why the old advice to install a vacuum gauge
can certainly help MPG if the driver watches it out of the corner of his eye.
When the vacuum gauge reads about 1 to 6 inches of mercury
you are in the fuel guzzling 'Power Enrichment' zone that you want to avoid
except when you want the highest horsepower and accept the higher fuel usage.
When the vacuum gauge is showing about 7 to 9 inches of mercury vacuum
your engine is converting fuel into horsepower at its most efficient level.
Each engine goes into Power Enrichment at a slightly different MAP sensor
level, but if you listen closely to the engine sound you can hear it happen
as the engine gets a bit smoother with the very rich mixture.
Even better than just a vacuum gauge is to add a Air to Fuel meter than reads
the output of the O2 sensor. Most of the time this AFR gauge will read a
boring 14.7 to 1 air to fuel, but when it starts to drop as the accelerator is
pressed that is the 'fuel enrichment' start point for that rpm. The fuel
enrichment start point usually begins at ever more modest throttle settings
as the rpm rises because at high speed the piston tops, cylinder heads, and
exhaust valves begin to overheat faster and excess fuel is used to cool.
Practical Gearing for Economy when you know the 'Why' of shifting
I changed out my original 3.55 differential gears on my 1995 Ram 5.9V8 46RH
auto to some $75 new-in-box (but 20 years old) Mopar ones of 3.21 ratio in
hopes of better mpg - but only after having first reduced the load on the
engine with aero mods and low rolling resistance tires on the Ram. I got
about a 1 mpg improvement at a steady 70 mph. Quarter mile times got
worse by 0.75 second. My 5.9V8 now accelerates about like a 5.2, but has
about a 5 mph increase in top speed in 3rd gear as the gear ratio is more
matched to peak hp. There is also less engine noise while driving.
The Performance Trends software Fuel Economy Calculator predicts that above 74
mph a totally stock 1995 Ram 5.9V8 gets best MPG with a 3.55 diff gear, but
that if either the truck slows down below 70 mph, or the aerodynamics of the
truck are improved (with such things as a tonneau bed cover or vortex
generators) then a 3.21 diff gear gives better MPG.
It is a general rule that if you reduce the load on an engine with vehicle
mods, you can then get "a second bite of the apple"
by further reducing highway cruise rpm a little bit.
Note that on the 5.7 Hemi with the new 545 auto trans the overdrive gear ratio
was made "taller" to 0.67 from the old 0.69 at the same time that the 17 or 20
inch wheels & tires were made larger in diameter. This has an effect like
changing from 3.55 to 3.21 in the experiment above and is possible because
the longer runners and dual sparkplugs of the 5.7 make much more low rpm
torque available without getting close to gas guzzling power enrichment. You
can confirm this by figuring out for yourself the MPH/1000 rpm discussed
earlier.
Weight reduction is supposed to improve City MPG where acceleration dominates.
The rule of thumb is
" A 10% reduction in weight yields a 6% improvement in City MPG."
So 540 lbs off a 5400 lb Ram might increase 14 MPG to 14.8 mpg.
At a steady 70 mph however, a 10% increase or decrease in weight only affects
MPG by about 3%.
The US Army has been giving some of your tax dollars to Ford as a Research
grant to try out ways to cut the weight of a pickup truck by 25% so that more
vehicles can be airlifted and dropped into combat zones with the 82nd or the
101st.
Aluminum wheels save 40 lbs total. New Aluminum Magnum heads save 46 lbs.
Aluminum diff and rear axles saves 150 lbs. Fiberglass leaf springs save 75
lbs or monoleaf steel springs save 40 lbs. Do Google searches for 'monoleaf
spring' or 'fiberglass spring' to find suppliers who can make such springs for
Ram pickups.
http://flex-a-form.com/
This company makes a 'QuadraLink' rear suspension that does away with leaf
springs on muscle cars and could be adapted to a pickup:
http://detroitspeed.com/QUADRALink10.html
There is at least one supplier of fiberglass fenders for Rams:
http://www.hannemannfiberglass.com/Dodge_Ram.html
Do you really need that rear bumper - are damaged bumpers less expensive to
replace than damaged sheet metal?
Optima batteries are usually 10-20 lbs lighter than conventional.
Reactor brand batteries are even lighter.
Engine modifications
Those with Cummins engines may first want to read the 'White Paper'
from Cummins called:
"Secrets of Better Fuel Economy: The Physics of MPG"
which is oriented toward 18 wheel trucks but 90% applies to Ram pickups too.
http://www.cummins.com/na/pdf/en/products/truck/MPG_Secrets_Whitepape.pdf
Many Ram owners start their gasoline engine modifications with either a
sparkplug
change, fan change or a thermostat change. These will be covered first and
more complicated modifications later.
Sparkplug and ignition advance changes.
I did a careful test run of 311 miles after indexing sparkplugs in a 5.9V8 and
measured what might have been a 3% improvement. That could be random
variation. To index the plugs, buy 16 instead of the usual 8 and choose plugs
that tighten down so that the gap points toward the V of the engine and the
ground electrode is on the fender side. Return the 8 plugs you don't use to
the store or give them to another Ram owner. This puts the metal post of the
ground electrode over against the metal wall of the cylinder head where it
does not block the growth of the flame. See this webpage for a view of the
combustion chamber.
There is an article with several good illustrations of sparkplug indexing at
this Ford site:
http://www.fordmuscle.com/archives/2000/07/indexplugs/index.shtml
On a 5.7Hemi, it is very probable that by re-arranging the stock 16 plugs to
their best position in other cylinders that is 'lucky for them' when they
tighten down, you could achieve indexing without buying more than
4-6 additional plugs at most....perhaps none at all.
My guess: Aim the dual plugs' ground posts each other (toward center of bore)
so the flame kernel can expand un-hindered outward. This leaves a small
spot in the center of the bore with a blocked flame path but it probably
won't matter because that spot is so turbulent anyway.
In the picture below the left hand sparkplug is the way I am talking about
but the right hand sparkplug needs to rotate clockwise another 90 degrees:
The factory stock ignition system that fires the dual plugs on the 5.7 is
apparently VERY good. Recently a few owners with high miles (68K and
108K) on original factory 5.7 sparkplugs have pulled them for inspection
and found these plugs are still firing with worn gaps as great as 0.075
inches.
This brings up the question of whether a 5.7 owner might want to pull his
plugs, sharpen all edges, then re-gap to 0.075 or more and do some MPG
testing to see if the dual larger sparks give enough 'fast burn' to improve
low rpm torque and fuel economy.
A DCx employee whose day job is running dynos reported that the stock
5.7 Hemi Ignition settings in the factory PCM is within 4 degrees of
'Mean Best Torque' at all throttle settings above 2000 rpm so it is not out
of reason that bigger gaps and sparkplug indexing could put you 'spot on'.
Tests of the Bosch+4 sparkplugs at 60 and 70 mph highway speeds with 87 octane
gasoline found no MPG improvement - actually a slight loss - on a 1500 1995 SB
CC Ram with 5.9V8 AT. A further test of the Bosch+4 sparkplugs with one of
the electrodes closest to the exhaust valve cut off (making a Bosch+3) also
showed no MPG gain. Consumers Reports found similar results when trying
Bosch+4 sparkplugs on a Honda.
A careful MPG test of a 1995 1500 SB CC Ram with the 5.9V8 AT (3.21 diff)
with and without the "viscous clutch" radiator fan blades showed a 0.8 MPG
improvement without the fan. No overheating occurred in this steady 70 MPH
test run over 212 miles.
There was also no sign of overheating at stoplights or city driving in
mild winter temperatures. Several Diesel Ram owners have posted that they can
run without a fan in winter and gain 0.5 to 1 MPG.
With the electric fan & clutch fan combo on the 5.7 Hemi Rams it is probable
that the clutch fan could be removed for all but the hottest weather or towing
service.
Underdrive Pulleys
Undersized crank pulleys can increase MPG slightly by driving the power
steering, air conditioning compressor, and water pump at lower rpm where
there will be less friction.
Some who have tried undersized pulley sets report an additional
alternator pulley in a pulley set is generally too slow for the street truck
that may
have to idle a long time without enough rpm to charge the battery.
A pulley that does not slow the alternator down as much as the aftermarket
ones is the factory installed one used on the aluminum block V10 Viper.
This is DC Part Number 5037204AB for a 2003-2007 Ram SRT10 crank
pulley, which usually runs about $60 retail at most Dodge dealerships and
less at discount dealers like Koller.
There have been some warnings posted that the underdrive pulleys for
5.7 Hemi's do not have a torsional damper of correct design. Beware.
Breaking a crankshaft out of warranty is not fun or cheap.
The horsepower that an alternator consumes is
mostly set not by the rpm it turns, but by how much the 'voltage regulator'
inside the Ram pickups PCM computer increases the 'excitation field current'
inside the alternator's rotor. Because of this I see no benefit in slowing an
alternator down - no significant horsepower will be saved or fuel economy
gained. The AC compressor can be simply turned off when you want either
more power or better MPG. NASCAR cooling system guru Howard Stewart
points out that on modern engines like the Chrysler 4.7/5.7 with knock
sensors if you slow down the water pump you might have more horsepower
for the first few seconds at Wide Open Throttle, but then the cylinder head
will begin overheating at its worst spot, some pinging will start, the knock
sensors will trigger, and the PCM computer will start pulling back up to
16 degrees of ignition timing advance - then the horsepower declines
much more than you "saved" with the water pump pulley reduction.
If you must change pulleys it is best to just slow down the power steering
pump alone.
Coolant temperatures and thermostat settings
There is controversy about MPG and thermostat temperatures but there
seems to be a clear trend that higher coolant temperatures controlled by
195-203 setting thermostats improve MPG slightly.
Sadie Carnot's 200 year old thermodynamic theory says
that cooler air intake temperatures would give improved fuel economy
because cooler air takes slightly less work to compress, and if a
140-180 thermostat is used on an old fashioned iron or aluminum
intake manifold with coolant cross-over passages there will
be less temperature rise in the intake air as it passes through.
Modern intake manifolds such as the ones on the 4.7V8 and 5.7 Hemi
are made of insulating Nylon66 plastic so this does not
apply as much - although the incoming air can still pick up
heat from the metal walls of the cylinder head ports.
But hotter oil on cylinder walls has less viscosity and creates less
friction against the piston rings - which can also mean better MPG. The
Cummins 'Secrets of Better Fuel Economy' white paper listed at the top has a
graph showing this on page 12. Theory also predicts that hotter block walls
and cylinder heads will absorb less heat from combustion and permit a greater
pressure 'push' on the piston.
The new four cylinder 'World Engine' in the 2006 Dodge Caliber has two
thermostats: one to feed lots of cooler coolant flow to the cylinder heads
so that pinging will be reduced and an MPG improving higher compression
ratio can be used - but another separate thermostat setting to adjust the flow
to the engine block walls so that they stay hotter and ring friction will be
lower. This may be the best of both needs.
Some Dakota owners who switched to 180 degree thermostats have reported less
ping, peppier acceleration and about +1 mpg, although most reports like this
are just about what their next tank of gasoline yielded - not a careful test
that you can trust. Other Dakota owners reported no mpg change or a loss.
Four Wheeler magazine reported +0.8 mpg gain with a 192 to 180 deg
thermostat swap in a 454 Suburban. Take these reports with a grain of salt
considering who did them and how magazines live on advertising.
My own experiments with a failed thermostat that cracked and stayed open at
around 140 degrees, then later thermostats of 180, 195 (stock) & 205 showed
no significant improvement in MPG at steady 60 mph highway cruise
on a 1995 5.9V8 Ram CCab shortbed, although the 205 did measure a
0.2 MPG gain in one 300 mile test run.
The 180 degree thermostat also did not reducing pinging at least 'by ear',
nor did the 205 thermostat increase pinging by ear, but a better test would
have been to measure with a MSD aftermarket knock sensor, or better yet
read the memory of a J&S aftermarket anti-knock ignition system with its
twin knock sensors and better knock detecting software & chip.
Why would this be if you have read a thousand internet postings that
180 degree thermostats reduce detonation? This may be because the
Dodge PCM computer senses coolant temperature and either
advances or retards ignition timing as necessary according to the
tables in the memory of the computer's software. The cracked
thermostat that stayed open at about 140 did reduce pinging by ear.
When you read that 180 degree thermostats reduced pinging on old
carburetor engines that might be true, but consider that today's
computer controlled engines 'have a mind of their own'
inside the PCM that carb'ed engines did not.
The Fuel Economy Calculator from Performance Trends software predicts that a
change from a 195 degree thermostat to a 175 worsens MPG by about 0.20 at a
steady 70 mph.
The Engine Analyser 3.2 program from Performance Trends predicts
that when a 1995 specification Magnum 5.9 V8 engine is 'throttled back'
to 10 inches of vacuum and a coolant temperature of 195 degrees
at a simulated steady highway cruise at 1600 rpm it
will make 50 horsepower at a fuel economy of 0.604 lbs/hp-hr.
If the coolant temperature is raised to 250 degrees and the throttle
re-adjusted to make 50 horsepower once again at 1600 rpm
the fuel economy improves to 0.571 lbs/hp-hr.
This is about a 5.5% improvement.
Respected tech editor Marlan Davis of Hot Rod magazine has reported that
all things considered, fuel economy is better with coolant at 210 degrees F.
Perhaps that is why the factory thermostat on the 5.7 Hemi is now marked 203
F, which is were it begins opening. Note that on 4.7 and 5.7Hemi engines the
thermostat position and function has been totally redesigned to control the
coolant in, rather than the coolant out temperature. This would lead one to
guess that the coolant coming out of a 5.7 Hemi is hotter still. The 5.7V8
now also has a closing bypass post sticking out from it that closes off the
bypass passage and results in greater coolant flow to the radiator once the
engine is up to designed temperature. This allows the water pump to be run
slightly lower in rpm and saves a bit of fuel.
Someone who is up to doing experiments could remove their thermostat entirely
and cut/weld in an electrically controlled valve in the tall metal nipple
above the thermostat flange. With this electric valve and a temperature
controller
(there are several adjustable ones for on sale for electric fan control)
you could then have an adjustable thermostat.
For much cheaper & simpler you could also just put in a cable operated valve
and keep a 180 thermostat in the housing. Another option would be to
install a set of shutters to restrict air flow through the radiator to bring
up coolant temperature. Either of these would allow you to raise the coolant
temperature while at steady highway cruise to something like 220 with
50/50 conventional coolant mix (or 250-300 with Evans NPG coolant)
which might improve highway MPG by maybe 4 to 6%.
Coolant temperatures also affect bore wall wear, according to experiments
run by aircraft engine manufacturer Continental Engines in the 1960s.
Bore wear is relatively high at 140-160 degrees but begins rapidly leveling
off at 180 and shows no improvement above 205. It is thought that this wear
effect is due to acidic liquids condensing on the metal bore walls and
corroding them. Above a certain coolant temperature the liquids never
condense and remain gases. A similar problem happens in the chimneys
of power plants.
Mufflers & Exhaust Backpressure
A less restrictive muffler can help a wee bit on a Ram. I switched from the
stock stainless steel muffler to Walker's 'QuietFlow' type made of aluminized
steel and gained slightly in MPG and dropped ET a bit in the Q'mile.
The QuietFlow is as quiet as the stock muffler and has a 'Helmholz Resonator'
section to get rid of 'Drone' at highway speed rpms like the stock muffler
had.
Walker also owns DynoMax, and the tech on the telephone told me the
DynoMax is about 10% less restrictive than the QuietFlow but much louder.
After 15,000 miles, my aluminized steel QuietFlow began to rattle and I had
to squeeze a dent in it with a large C-clamp to stop the noise of what I think
was a rusted loose weld. I prefer all stainless steel mufflers.
I later replaced the QuietFlow with a 30 inch long 'straight through' DynoMax
UltraFlo Stainless Steel 2.5 inch in, 2.5 inch out.
http://www.dynomax.com/mufflers.stm
part number 17298. This cut the wide open throttle exhaust backpressure from 7
psi to 5 psi. This reduction in backpressure only yielded a gain of about 0.2
MPG. The Ultraflo 17298 was a little louder than both the stock muffler and
the QuietFlow but just barely. Unfortunately it had a 'drone' at around 1800
rpm because it did not have the Helmholtz Resonator section like the previous
two mufflers. I later had to add an additional 16 inch long UltraFlo at the
very end of the pipe as a tip to eliminate the 1700-2000 rpm resonance when
cruising in overdrive. If you have a muffler without the Helmholtz Resonator
section you need to avoid having your tailpipe length from muffler outlet to
exhaust pipe tip anywhere near 66 inches - otherwise it will make this 'drone
noise' the same way a church organ makes a deep tone with a special length of
pipe. Make your tailpipe either much shorter or much longer.
I also moved my exhaust outlet to face rearward. A rear facing exhaust oulet
has a very very small 'jet engine' push to it - notice most cars exhaust
backwards - but trucks that pull trailers need a side exhaust to safety
exhaust carbon monoxide away from where it could cause
a deadly build up inside a camper or trailer.
On the 5.7 Hemi Rams, the large exhaust pipe sizes, muffler and resonator are
already fairly low restriction. Chrysler deserves credit for designing better
exhaust systems that are still drone free.
Headers are heavily advertised as helping MPG - a psychologically trick that
helps create sales - but in most cases headers don't do much because the
primary pipes on them are too short, the header is exhausting into mufflers,
and their 'reflected pulses' are very weak at part throttle. Many headers are
put on at the same time as new less restrictive exhausts - and the header gets
the credit for what the bigger muffler & lower backpressure actually did.
In the Spring 2007 issue of Enginemasters magazine on page 67
Steve Dulcich tested TTI brand 1.625/1.75 "step" headers
with primary lengths of about 40 inches on a Mopar Performance
Magnum 5.9 V8 300 hp Crate engine (without mufflers)
and found a 3.8% gain at 4600 rpm (12 hp)
but only 0.5% gain (1 hp) down at 2500 rpm,
closer to where daily driving is done.
These gains would be even less with mufflers and catalytic converters.
If you do buy a set of headers, try to get a custom set with primary pipe
lengths around 42-46 inches and don't worry if the primary diameter is
anywhere from 1.375 to 1.750 inches. This is in line with what Larry Shepard
found works best on the street with Mopar smallblock V8s, and it also agrees
with the estimates of the PerformanceTrends software program 'Engine Analyzer
3.0 about getting torque gains from 1500-2000 rpm and then again from
3800-5000 rpm. The short primary pipe lengths that most header companies sell
give gains from 4000-5000 rpm only and don't really improve MPG in day to day
driving. To get the most MPG gains from a set of 42-48 inch primary pipe
headers you would also need to change your differential gears to a lower
numerical number - like 3.55 down to 3.21 - to make use of the extra torque
now available at the lower rpms.
The best general headers & exhaust article that I know of is this one by David
Vizard:
http://superchevy.com/technical/engines_drivetrain/exhaust/0505phr_exh/index.html
Owners of 1994-2002 Magnum 5.2/5.9 V8 owners should consider that the
model year 1992 and 1993 5.2 Magnum V8s had larger diameter outlet
cast iron exhaust manifolds. The driver side Magnum part number is 53006619.
On the passenger side the 1968-1970 E body cast iron exhaust manifold part
number 2863549 is said to flow slightly better than the Magnum passenger side
manifold.
The MPG improvement from these larger manifolds would be small, but they are
said to be good for about 5 hp power gain above 3500 rpm and full throttle if
larger Y pipes to match are fitted at the same time. More info with dyno runs
on other
Mopar SB exhaust options at this weblink by the always excellent tester
Steve Dulcich:
http://www.moparmusclemagazine.com/techarticles/155_0307_mopar_crate_engine_exhaust/
Cylinder Balancing
Each of the cylinders in a Ram pickup engine is a little different than its
neighbor cylinders due to 'production tolerance' at the factory. In the 2003
official Ram Field Service Manual (FSM) specifications for the 5.7 Hemi
the table has a line saying the variation between cylinders can be 25%
and still be acceptable to DaimlerChrysler. Each cylinder's fuel injector
sprays slight different amounts of fuel per second, and each cylinder has
a slightly different airflow through its intake runner, cylinder head port
and valve. If you are lucky, just by chance your engine will have its
highest flowing fuel injectors installed in the cylinders that also have the
highest flowing airflow. If you are unlucky, your 'lemon' engine has the
lowest flowing fuel injectors installed in the cylinders with the highest
airflows, and vice versa.
The amount of air mixed with fuel is called the 'air to fuel ratio' (AFR) and
for decades racers and engineers have known that this AFR ratio affects
fuel economy, torque, and the temperature of the exhaust gas coming out
of the cylinder. Also for decades, people have tried to 'tune' the AFR by
measuring the temperature of the exhaust gas. The best setups for this are
expensive, but you can buy much less expensive instruments today. Sears
has multimeters like this one with a retail price of $40 but is sometimes on
sale for $20:
http://makeashorterlink.com/?G35712BFC
that has a Type K thermocouple that will measure from 0F to 1400F if you are
careful not to burn the insulation, which is only rated to 550F. By drilling a
hole
in your exhaust manifold at the 'traditional' distance of 1 inch out from the
exhaust port and inserting this thermocouple you can measure your
exhaust gas temperature (EGT) and then swap around fuel injectors to the
cylinders where the combinations yield nearly equal EGT for all cylinders.
By equalizing your EGT you can improve both torque and fuel economy - and an
added bonus is that your engine will be less likely to 'ping' on one cylinder.
How much improvement can you get? It depends on how unlucky your engine
was from the factory, but typical improvements if you can get the cylinders
nearly equal are 2-4% better fuel economy at part throttle operation during
highway cruise, and 4% better power at wide open throttle too.
Some notes on EGT testing: If you can find the Sears multimeters on sale for
$20 it might be better to buy 4 and test one side of a V8 at the same time,
then later give away the other 3 multimeters as gifts to friends and family.
With the 36 inch long leads from the thermocouple tip to multimeter you
will have limited distance so mount the meter outside your windshield,
at the rear edge of the hood, perhaps mounting 4 meters on the same board.
Choose a hole size to drill that you can later close off with a blind rivet or
tap and close with a stainless steel screw. Buy a $12 'muffler patch' kit
and use the high temperature felt gasket material to place under and over
the thermocouple wires for protection and insulation, then use a large
stainless steel hose clamp to hold the thermocouple in place during testing.
Make each test run on the same stretch of highway at about the same
air temperature with the same gasoline. Measuring EGT at the rpm of
maximum torque at full throttle is the normal spot to record the
temperatures. Testing on a steep hill where rpm changes more slowly
as the truck climbs and you can stay at legal speed is a wise idea.
Have a partner drive while you watch the meters.
You can gain additional information about the air/fuel ratios of the
various cylinders using a $60 'Colortune' sparkplug:
http://www.niksula.hut.fi/~mdobruck/siililand/mini/diy/10/dyno.htm
http://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=4569
One note on the limitations of EGT testing - your engine's cylinders
also vary in their true 'dynamic' compression ratio due to sloppy
factory tolerances. Cylinders with higher compression ratios will
have LOWER EGT readings even if the AFR is the same. You can get
hints about what cylinders have higher dynamic compression ratio by
doing a compression test on all cylinders before EGT testing. The
best way of balancing AFR on cylinders is to use a 'wide range' O2
sensor in each cylinder's exhaust. This has been very expensive in
the past but the cost of wide range O2 instruments has been coming
down. See these two links:
http://carcraft.com/techarticles/116_0402_tune/
http://performancetrends.com/wide_band_uego.htm
Valve Timing & MPG
It is possible that 'Rhoads' style variable hydraulic lifters installed on a
Magnum engine would increase MPG by opening the exhaust valve later and nearer
bottom dead center and closing the intake valve sooner. One Ram owner with a
heavily modified 406 stroker Magnum V8 measured a 3 MPG gain when Rhoads
lifters were installed, but his camshaft was pretty 'wild' to the point that
he only had 7 inches vacuum at idle originally and that improved to 11 inches
of vacuum after the Rhoads lifters were fitted.
http://www.rhoadslifters.com/new_products.html
A 'RV' grind camshaft with lesser duration does this too.
Lesser duration on the exhaust valve cam lobe usually closes
the valve later toward bottom dead center and gets the last little bit
of energy out of the combustion pressure, increases 1500-2500 torque,
but it also hurts higher rpm WOT horsepower when large amounts of
exhaust gas is trying to escape the cylinder and now has to start
later.
Jim McFarland is an advocate of modifying piston tops. His design for the 4.00
inch Chevy 350 piston could easily be applied on flat top Magnum 5.2 pistons:
The 'soapdish' piston top on Magnum 5.9V8s might need some modification but
the 3 sets of dimples might still go in the same general areas. McFarland
claims 2-5% gains from this piston top modification. More info at:
http://circletrack.com/techarticles/99078/
Special ceramic coatings on the crowns of pistons and on the combustion
chamber of the cylinder head can improve both fuel economy and torque by
holding heat inside where it can produce pressure on the piston. Racing
engine builder Joe Sherman states that these coatings can add 2-3% to
performance, but if professionally applied they can be so expensive that the
mod would not pay for itself in fuel savings. There is an article about
applying coatings yourself at:
http://circletrack.com/techarticles/general/139_0307_coat/
If the top of the piston is the 'floor' of the combustion chamber
then it makes sense to question what the 'roof' of the combustion
chamber ought to look like and be made of. There is a long standing
debate about whether this roof in the cylinder head ought to be made of
cast iron or aluminum for best fuel economy.
These two articles on Chevy products have info on both subjects:
http://www.chevyhiperformance.com/techarticles/97538/index3.html
http://www.superchevy.com/technical/engines_drivetrain/cams_heads_valvetrain/0511sc_vortec/
Honda claims that one of the tricks used in the Insight 3 cylinder engine to
reduce friction is shot peening of the piston's outer diameter. Quote:
"LOW-FRICTION PISTONS In the interest of friction reduction, Honda
engineers specified a new lightweight aluminum-alloy piston design
for the IMA engine. The pistons have a minimal skirt area and the surface
of the skirt has been shot-peened. Shot-peening is a process in which a
metal part, such as a piston or connecting rod, is blasted with shot-like
particles, creating uniform, microscopic dimples on the surface. This
dimpled surface is better able to retain a lubricating oil film. Shot-peening
the IMA engine's pistons accounts for another 1.5- to 2.0-percent
reduction in internal friction."
There are further descriptions of friction reduction techniques used in this
engine, including offset bores for less side load from the con rod, at:
http://www.hondanews.com/categories/837/releases/247
One of the hotrod magazine recently tried their hand at custom tuning a
Honda engine for better fuel economy by modifying air to fuel ratio, ignition
timing and cam advance and retard:
http://hondatuningmagazine.com/tech/0510ht_fuel_economy_tuning/
Rings and Friction
There has been a fairly clear trend over the last few decades to go to
thinner rings in order to create less friction as the piston goes up and
down in the bore.
1971 to 1992 LA 360 V8 top two rings were 0.0781 inches in thickness.
1992 to 2003 Magnum 5.9V8 rings were 0.061 (1.54 mm)
2003+ 5.7 V8 Hemi piston rings are 0.0582 inches (1.481 mm)
There are lower friction coatings to use on bores to reduce friction even
further, but the most common coating called NikaSil can be damaged
by high sulfur in gasoline, as BMW found out in an expensive way:
http://www.bmwworld.com/engines/nikasil.htm
Compression Ratio
This excellent online article by David Vizard is well worth reading before
continuing on to the following section on Compression Ratio mods to your
Ram's engine:
http://popularhotrodding.com/tech/0606phr_understanding_compression_ratio/
It is a shame that the term 'compression ratio' became the standard term used
to describe this important part of engine operation. It is much more valuable
to refer to this as 'expansion ratio.'
Once you begin thinking 'expansion ratio' it becomes common sense as to
how to get better fuel economy in an engine: you want to first generate high
pressures in the combustion chamber from the burning of the fuel and air
when the piston is at the top (so keep the throttle open) and then you want
to expand it as many times as possible to get the last little bit of push on
the piston as it makes its way to near the bottom.
Engines with compression ratios of 9
expand the gases a little less than 9 times
{less because the exhaust valve opens before the piston gets to the bottom}
Engines with compression ratios of 12 expand the gases more and get a last
little "bite of the apple" for a small increase in both fuel economy and
power.
Higher compression ratio pistons are a reliable way to get better MPG.
Usually this means you have to purchase more expensive higher octane gasoline.
Raising the compression ratio from 9 to 9.5 is estimated to give 1% better
MPG. On a Magnum 5.9V8, changing the stock head gasket thickness of 0.047
inches to a Cometic 0.025 gasket will raise the compression ratio from 8.9 to
9.3. Replacing the stock 5.9V8 pistons (with their -13 cc depressions in the
crowns) with flat top pistons of compression height 1.622 inches will raise
the compression ratio from 8.9 to 10.2 Using flat top 1.67 inch compression
height pistons will raise the compression ratio from 8.9 to 11.3
Approximately every 0.0065 inches milled off a Magnum 60 cc cylinder head's
deck will drop the combustion chamber size by 1 cc.
Fitting 6.1 Hemi cylinder heads on a 5.7 Hemi should boost the compression
ratio by about 1 point, and the sodium filled exhaust valve on the 6.1 cyl
head would also help control pinging and detonation with this higher ratio
but there would be a intake manifold port size mis-match to correct.
There are combustion chamber designs that claim to allow compression ratios of
12 to 14 on 87 octane gasoline. You can read about them at:
http://www.theoldone.com/articles/The_Soft_Head_1999/
The USA Environmental Protection Agency has published an interesting paper
on converting a VW TDI diesel engine to sparkplugs so that it can run on
either of the alcohols methanol or ethanol, which have high octane ratings in
the 105 to 109 MON range. This engine runs at a compression ratio of 19.5
and avoids using a throttle (except at idle) by using a turbocharger with
high exhaust gas recirculation.
http://www.epa.gov/otaq/presentations/sae-2002-01-2743.pdf
EPA reports that earlier research showed that increasing the compression ratio
from 8 to 18 improved fuel economy by 16%.
This EPA paper also reports that they tested many port fuel injectors and
found that the 12 hole injectors sold by Holley Inc. gave the best spray
pattern and smallest and most uniform droplets.
The paper is full of 'Geek Speek'
but is worth reading a few times if you are interested in engines.
Note their 'load maps' and how they refer to the area of best fuel economy
as an 'island' that sticks up out of lesser fuel economy areas. The
EPA paper is jammed full of information but it is a shame that they didn't
also make runs with this engine on pure chemical Octane with its
100 rating, which probably would have worked too. The use of the pure
chemical Octane to test engines is traditional as a way to make sure engine
testers are comparing 'apples to apples' when exactly the same gasoline is
not available everywhere.
Exhaust Gas Recirculation and MPG
1992-1995 Dodge Magnum 3.9/5.2/5.9 engines had exhaust gas
recirculation valves. Then from 1996-2003 EGR was dropped, probably
because the 3-way catalytic converters got more efficient at removing
NOx gases from the exhaust. In 2003 the 5.7 Hemi V8 showed up
and it had EGR again along with dual sparkplugs that might be there
to make the EGR work better (they help low RPM torque too).
Legendary MIT professor and former racer John Heywood wrote the
most used college textbook on engines:
http://makeashorterlink.com/?J61155BAC
on page 837 of Heywood's book he has a graph that shows that if you have
an engine with the right cylinder head design (closed chamber & fast burn)
and highly dependable ignition (like dual sparkplugs),
up to 25% EGR flow can improve fuel consumption when the engine is being
run at part throttle like a Dodge Ram pickup would be at highway cruise.
GM's Opel division also thinks EGR can increase MPG about 6%:
http://www.theautochannel.com/news/2002/04/16/038851.html?NEWS
If you are a tinker and have a Ram in the 96-02 gap where EGR is not
used you might consider rigging up a line with a remote control valve
from the exhaust to the air cleaner inlet. Make sure your ignition system
and sparkplugs are in tip top shape because too much EGR flow can also
cause missfires - which kill any MPG gain if they begin occurring.
DRIVING HABITS
The first MPG driver habits technique is the simplest,
but the one few of us want to hear.
I have done several 300-400 mile test runs at steady 60 or 70 mph on I95 with
a 1995 Ram 5.9V8 Ram. Slowing down from 70 to 60 mph saved 3-4 mpg
each time. I also did a 80 mph test run once driving with the crazy flow of
traffic from north of West Palm Beach to Ft Lauderdale. This lowered MPG
by 4 compared to going 70 mph.
Notice that I don't claim this slowing down is 'cheap' because of the
question: 'How much is your time worth ?'
In the Cummins White Paper they cite a study where there was a 30% variation
in MPG between professional drivers in the exact same truck over the same
route.
This is similar to GM research, such as this from from page A3 of The
Wall St Journal on 11-21-2005:
"Roger Clark, GM's senior manager of energy and drive quality in North
America, said the current test does a good job measuring average mileage but
the problem is the variation in how people drive. He cited a GM Study of 209
people driving the same midsize SUV. The fuel economy varied from about 13
miles per gallon to 23 miles per gallon, depending on the driver."
Ford did a test of different drivers in the same vehicles and found an even
greater MPG difference of 38% between the best and worst driver habits and
conditions like low pressure tires, max AC, cargo on roof racks, etc:
Oak Ridge National Laboratory found similar results:
"The problem is that mileage varies so much from one driver to another and one
place to another that the government ratings are a poor predictor of what any
individual driver is likely to get with his or her vehicle," said Bo
Saulsbury, a researcher at Oak Ridge. "If the EPA rates a car at 20 m.p.g.,
the real-world data show that you might do as well as 30 m.p.g. or as poorly
as 10 m.p.g."
There are 'experts' at driving to get the best MPG. You can read about
John and Helen Taylor, a husband & wife couple who are sponsored by
Shell and have won many contests at this link:
http://www.scoop.co.nz/stories/SC0601/S00020.htm
Note the list of good driving techniques for better MPG near the end of the
article about the Taylors.
At the 'extreme' end of driver behavior are the 'Hypermilers'
such as Wayne Gerdes:
http://www.motherjones.com/news/feature/2007/01/king_of_the_hypermilers.html
In April of 2007 UPS announced that they had programmed their computers
to map out delivery van travel to use as many right turns as possible.
This simple switch in the routes driven reportedly saved UPS
about 5% of the fuel they previously consumed before the switch.
FURTHER READING
If you want to read more about MPG improvements that work,
the US government has put a book online at:
http://books.nap.edu/books/0309045304/html/198.html#pagetop
In the Appendix of this book is an interesting table where the Dept of Energy
sent a questionaire to all the auto makers and asked them what various mods
were worth to improving MPG.
The EPA has put out a long report on fuel economy trends from 1975-2005.
There is much good tech info here, especially around page 36.
http://www.theautochannel.com/link.html?http://www.epa.gov/otaq/fetrends.htm
Kevin Gertgen's Fuel Economy Calculator software is very impressive and can be
read about at:
http://www.performancetrends.com/fuel_economy_calculator.htm
There is an online Java based webpage calculator at:
http://www.bgsoflex.com/mpg.html
Jeffery Diamond's Mopar specific gas mileage mod table is worth pondering:
http://victorylibrary.com/mopar/mileage-c.htm
There is a collection of aerodynamic links concentrated on pickup trucks at:
http://www.dodgetrucks.org/forums/viewtopic.php?t=52115&highlight=aero+tricks
Enjoy your truck and enjoy increasing your knowledge of it.
< Message edited by HankL -- 5/28/2007 8:38:03 AM >
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RE: updated FAQ on Ram MPG improvement (long) - 7/24/2006 12:43:46 PM
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HankL
Posts: 2718
Joined: 8/20/2005
Status: offline
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bumping this because it has had a re-write
including sections on indexing sparkplugs
on 5.7 Hemi and 5.2/5.9 Magnum V8s
with new pictures.
There are also new sections on piston rings,
cast iron versus aluminum cylinder heads
and bore coatings
There is presently a proposed new law in the US House of Representatives
that requires tire manufacturers to tell customers how hard each type of tire design is to roll.
If you see your congressman/woman consider urging them to support this bill.
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