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Unread 05-25-2013, 04:35 PM   #1
jkelley429
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Homemade cold air intake idea

A buddy of mine has built an intake on his 05 liberty with the 3.7L. He has a spectre cone filter directly on the throttle body with a thin walled flexible plastic pipe going from it to the air dam in the grill. My question is, will the cool air coming from the grill offset the warm air from the engine bay? He says he's noticed a definite power and MPG increase. It seems like a cheap alternative to a kit. What are yall's thoughts on it?

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Unread 05-25-2013, 05:19 PM   #2
USFORCES
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There are tons of threads on this, search it
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Unread 05-25-2013, 05:29 PM   #3
jkelley429
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I understand there are threads on cai, but this is a more specific question.
I did attempt to search this issue but the only thing that came up was from a Saturn forum. Although if you happened to find an answer specific to my question I would appreciate if you point me in the right direction.
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Unread 05-25-2013, 05:32 PM   #4
silentbob21
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I highly doubt he noticed a power gain, its more likely he is pushing the skinny pedal further in order to hear the sucking air now.... but I think in order to have a true CAI you need to have the filter isolated as best as possible from the hot air surrounding the engine.

so IMO a "custom" cai as you are describing would hardly improve anything over the stock air box, but if you want to go that route then by all means, you can also use dry vent hose which works pretty well and is insulated.
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Unread 05-25-2013, 05:38 PM   #5
jkelley429
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I was thinking the same thing about just seat of the pants increase, but he said he times his 0-60 and it was about 2 tenths faster and his mileage went up about 1.25 MPG. I'll probably modify it to try to get the filter a little farther away from the hot engine though.
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Unread 05-25-2013, 06:29 PM   #6
LarryDallas
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Quote:
Originally Posted by jkelley429
I was thinking the same thing about just seat of the pants increase, but he said he times his 0-60 and it was about 2 tenths faster and his mileage went up about 1.25 MPG. I'll probably modify it to try to get the filter a little farther away from the hot engine though.
What was his previous air intake set up? If it was a dirty, clogged stock filter just changing to a higher flow clean filter would make a big difference. I think Cai are kind of over rated. Just saying.
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Unread 05-25-2013, 07:19 PM   #7
rm2001wj
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Your question,
Quote:
My question is, will the cool air coming from the grill offset the warm air from the engine bay?
assumes that the engine will run differently with warm air than with cool air.

Your computer controlled engine always monitors the air temperature and injects fuel at a rate that corresponds to the air density (actually the air mass flow rate). Because of that, it won't matter for engine operation whether the air is cool or warm, the operation will be the same.

I know that is hard to believe, but think about what difference you notice between driving in the summer (warm air) and driving in the winter (cool air). Do you really notice any significant mpg and power increases in the winter.
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Unread 05-29-2013, 10:05 AM   #8
jkelley429
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Originally Posted by rm2001wj View Post
Your question, assumes that the engine will run differently with warm air than with cool air.
If intake temp doesn't matter, why do people put inter coolers on forced injection systems? Its not necessarily the temperature, but the density that matters for performance. Cooler air has higher density therefore acts as more air.

I was simply asking if the idea I presented would be a feasible option. I was not trying to start a debate on the effectiveness of cool vs warm air.
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Unread 05-29-2013, 02:54 PM   #9
SirCussFreq
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Quote:
Originally Posted by rm2001wj View Post
Do you really notice any significant mpg and power increases in the winter.
In a turbocharged engine, absolutely. In the WJ? Perhaps not so much...
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Unread 05-29-2013, 03:37 PM   #10
rm2001wj
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Quote:
Originally Posted by jkelley429 View Post
If intake temp doesn't matter, why do people put inter coolers on forced injection systems? Its not necessarily the temperature, but the density that matters for performance. Cooler air has higher density therefore acts as more air.

I was simply asking if the idea I presented would be a feasible option. I was not trying to start a debate on the effectiveness of cool vs warm air.
Although you are not trying to start a debate, your first paragraph in this reply, attempting to dispute what I said, indicates that maybe you are. Let me point out a few of things: (1) The quote that you lifted out of context applies to the computer controlled engines in our WJs. (2) With respect to forced induction (not “forced injection”) the boost pressure increases the air density whether the air is hot or cold, but the process also heats up the intake air causing the temperature to increase. When the hot (and denser) air mixes with the injected fuel in the cylinder, there is the strong possibility that detonation will occur as the air/fuel mixture is compressed in the cylinder. Detonation destroys engines. The simplest way to reduce the possibility of detonation is to pass the heated air coming from the super/turbocharger through an inter cooler in order to reduce the air temperature. The purpose of the inter cooler is to remove heat from the compressed air (thus lowering the temp), not to try to make it more dense.

Finally, I remind you to again consider the fact that our WJs don't perform significantly differently in winter compared to summer.
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Unread 05-29-2013, 03:46 PM   #11
tx_medic
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If the engine could benefit in power and efficiency from something as simple as a cone filter and some tubing (which is probably less expensive than the stock air box), why wouldn't the engineers from Chrysler just build it that way to begin with?
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