Intake manifold swap?
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Intake manifold swap? - 6/18/2006 10:44:58 AM
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TopBanana_102
Posts: 39
Joined: 5/14/2006
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One of the guys in the building I work at has a Charger SRT-8. We were comparing each others' car: driving, interiors, the works.
I do plan to start modding my car, but right now I'm in research / gathering information mode. Information like what are the stock injectors rated (=> is it necessary to get high-flow injectors)? Which of the several sftermarket chips out there is the best compromise of features (=> chips do alot of the same thing...which is easiest to use and flexible)? Is the Daytona R/T exhuast adequate for increase in intake volume (=> is CAI that much better than a panel filter K&N?)? &c. &c.
One thing that I noticed was that the SRT-8 has an aluminum intake manifold whereas ours is made of plastic. My buddy claims that I will notice better performance with the Al-manifold becasue (1) the runners are longer than the plastic; (2) the Al-body keeps cooler than the plastic; and (3) that the plastic is prone to cracking. He also claims that it would be a direct fit swap and no special computer tuning would be required.
I can accept the argument that there may be a torque gain due to the increased runner length.
I'm not convinced that the Al-housing keeps the airstream cooler. Aluminum is one of the best known conductors of heat transfer...plastics generally DO NOT transfer heat---they melt.
I'm on the fence with the choice of materials. When Ford swapped from an aluminium intake on the 4.6 to a plastic one, the plastic did get cracks/leaks which eventually led Ford to replace faulty ones with the original style aluminum (not a recall...just an onwer complaint driven replacement). GM, on the other hand, has had plastic intakes on their engines for a long time without the wailing form their customers. Anyone know whether Chrysler plastic intakes suffer heat stress?
One thing that would be certain: swapping to the aluminum intake would mean losing the engine cover...oh well.
Glenn
_____________________________
Daytona R/T Top Banana #0102
"There's no replacement for displacement." Carroll Shelby
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RE: Intake manifold swap? - 6/18/2006 10:58:22 PM
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74scamp
Posts: 1238
Joined: 1/25/2006
From: Los Lunas, ,NM
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quote:
ORIGINAL: TopBanana_102
I'm not convinced that the Al-housing keeps the airstream cooler. Aluminum is one of the best known conductors of heat transfer...plastics generally DO NOT transfer heat---they melt.
Glenn
Glenn, unless you misspoke, you answered your own questions regarding the heat transfer. The aluminum transfers heat, therefor, it gets rid of the heat. You said that plastics generally "DO NOT" transfer heat---they melt. Not being able to transfer heat means that the plastic is retaining that heat and, thus, the airstream would be hotter than the airstream in the aluminum manifold. If a given material is not transferring heat, then it is retaining the heat, and anything in close proximity will, therefor, get hot and stay hot.
dave
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RE: Intake manifold swap? - 6/19/2006 1:38:36 AM
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TopBanana_102
Posts: 39
Joined: 5/14/2006
Status: offline
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quote:
ORIGINAL: 74scamp
quote:
ORIGINAL: TopBanana_102
I'm not convinced that the Al-housing keeps the airstream cooler. Aluminum is one of the best known conductors of heat transfer...plastics generally DO NOT transfer heat---they melt.
Glenn
Glenn, unless you misspoke, you answered your own questions regarding the heat transfer. The aluminum transfers heat, therefor, it gets rid of the heat. You said that plastics generally "DO NOT" transfer heat---they melt. Not being able to transfer heat means that the plastic is retaining that heat and, thus, the airstream would be hotter than the airstream in the aluminum manifold. If a given material is not transferring heat, then it is retaining the heat, and anything in close proximity will, therefor, get hot and stay hot.
dave
Hmm..interesting; I'm thinking that the air in the plenum is cooler than the air surrounding the engine bay. So, the plastic intake would insulate the cooler air on the inside, whereas an Al-body would transfer heat from warm surrounds of the engine bay to the cooler side of the air stream.
_____________________________
Daytona R/T Top Banana #0102
"There's no replacement for displacement." Carroll Shelby
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RE: Intake manifold swap? - 6/19/2006 10:44:34 AM
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74scamp
Posts: 1238
Joined: 1/25/2006
From: Los Lunas, ,NM
Status: online
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quote:
ORIGINAL: TopBanana_102
quote:
ORIGINAL: 74scamp
quote:
ORIGINAL: TopBanana_102
I'm not convinced that the Al-housing keeps the airstream cooler. Aluminum is one of the best known conductors of heat transfer...plastics generally DO NOT transfer heat---they melt.
Glenn
Glenn, unless you misspoke, you answered your own questions regarding the heat transfer. The aluminum transfers heat, therefor, it gets rid of the heat. You said that plastics generally "DO NOT" transfer heat---they melt. Not being able to transfer heat means that the plastic is retaining that heat and, thus, the airstream would be hotter than the airstream in the aluminum manifold. If a given material is not transferring heat, then it is retaining the heat, and anything in close proximity will, therefor, get hot and stay hot.
dave
Hmm..interesting; I'm thinking that the air in the plenum is cooler than the air surrounding the engine bay. So, the plastic intake would insulate the cooler air on the inside, whereas an Al-body would transfer heat from warm surrounds of the engine bay to the cooler side of the air stream.
Ahhhhh. I see what you're saying. I guess we need someone familiar with thermodynamics to weigh in here on this. I guess a somewhat similar analogy would be comparing cast iron blocks to aluminum blocks and the resulting oil temp in each. And so, the question would be: Does the aluminum block dissipate, or give up, enough extra heat so that the oil temp is lower than it would be in a corresponding cast iron block. Or another way would be to compare water temps in each. Could also, probably, compare aluminum radiators to regular steel radiators.
It will be interesting to see if there are problems with the plastic intakes cracking, too.
dave
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RE: Intake manifold swap? - 6/19/2006 11:45:29 PM
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TopBanana_102
Posts: 39
Joined: 5/14/2006
Status: offline
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[/quote]
Ahhhhh. I see what you're saying. I guess we need someone familiar with thermodynamics to weigh in here on this. I guess a somewhat similar analogy would be comparing cast iron blocks to aluminum blocks and the resulting oil temp in each. And so, the question would be: Does the aluminum block dissipate, or give up, enough extra heat so that the oil temp is lower than it would be in a corresponding cast iron block. Or another way would be to compare water temps in each. Could also, probably, compare aluminum radiators to regular steel radiators.
It will be interesting to see if there are problems with the plastic intakes cracking, too.
dave
[/quote]
Well, I asked an exepert --- my son who is a wiz at math and physics...he said alot, it all made sense and now I'm certain I'll muck it all up!
Yes --- Al and plastic have very different heat cpacities and transfer properties. Without knowing the exact type of plastic, it's all a guess how well it compares to Aluminum. Nonetheless, he did mention that Dow is making high perfromance intakes from thermoplastics. These intakes offer significant improvement over Aluminum: they are much lighter; they keep engine bay heat AWAY from the airstream; and they are much SMOOTHER than cast aluminum.
One drawback is that depending on the plastic used, and the shape of the manifold, they may not be suitable for higher pressure applications ---i.e Nitrous boost or supercharging. Another drawback is that the plastic can deteriorate whereas the metal intakes are much less prone to chemical/heat stress.
His advice was that unless there is a significant difference in the runner lengths, or if we are experiencing engine surging at idle, or an apparent loss of compression (sysmptoms of leaks in the plastic housing), then it's probably best to leave the plastic intake as is.
Glenn
_____________________________
Daytona R/T Top Banana #0102
"There's no replacement for displacement." Carroll Shelby
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