Air intake system

riptricket · **Posted:** Mon Dec 11, 2006 12:19 pm

I was wondering if when buying an air intake system, or making my own, do i really need a heat shield?

Jeger · **Posted:** Tue Dec 12, 2006 12:28 pm

I would say yes, you really dont want to be pulling in all of that hot air that is under your hood. Best to route some fresh air towards the filter and block off the rest of the engine bay as best as possible.

Jeepjeepster · **Posted:** Tue Dec 12, 2006 12:44 pm

I just cannot see where a CAI can be any better than the stock air box with a K&N. The air is pulled right from the front of the jeep. A CAI dosent even pull cool air as good as the stock box. They look cool and all, but I just cannot see any use..

Jeger · **Posted:** Tue Dec 12, 2006 1:53 pm

I agree Jeepster, any gains that you might get from most CAI's are probably not worth it for most people. But, people are going to do it anyhow, so they may as well do it right I suppose. If you must have absolutely every last horsepower at any cost so be it.

DarbyWalters · **Posted:** Tue Dec 12, 2006 3:19 pm

Wish we could find a bigger stock airbox that could be modified to fit our space limitations. I think I remembr the airbox on the Dakota 3.7L was about 30% larger than the Liberty 3.7L and the Dakota rated 5hp more than the Liberty. A paper filter 30% larger surface area would be ideal.

OzLtd · **Posted:** Tue Dec 12, 2006 5:23 pm

DarbyWalters wrote:

Wish we could find a bigger stock airbox that could be modified to fit our space limitations. I think I remembr the airbox on the Dakota 3.7L was about 30% larger than the Liberty 3.7L and the Dakota rated 5hp more than the Liberty. A paper filter 30% larger surface area would be ideal.

Bingo. Any pics ?

What about the TJ's long rectangle airbox ? That would sit in there pretty good. I wonder if its larger in surface area (the filter itself)

uvalax236 · **Posted:** Tue Dec 12, 2006 6:19 pm

I was swapping between my home-made CAI and the stock air box (for wheelin). I saw sugnifficant performance increase as well as MPG increase. I drove back from Uwharri to Richmond (about 4.5 hours) with the stock airbox. I think I made it down there on 2 tanks with the CAI and made it back with the airbox at around 3 tanks. Pics are on my photobucket in my sig.

jcphoto20 · **Joined:** Sun Nov 19, 2006 1:36 am **Posts:** 507

i dont know why people keep pushing cold air intake systems. my jeep gets almost 2 mpg MORE when ingesting hot air from under the hood as opposed to getting any cold air from outside. warm air burns more efficiently as i understand it and modern fuel injection systems compensate for it. besides it never gets more than about 100 under your hood anyways. much better in colder climates too as far as start up and drivability, in my experience. i just have my cold air box in to support my cone filter i put on, no lid on it. if you think its too warm under your hood, just take off the gasket at the rear of the engine compartment and you'll let more out.

Neatus · **Posted:** Tue Dec 19, 2006 2:36 pm

jcphoto20 wrote:

i dont know why people keep pushing cold air intake systems. my jeep gets almost 2 mpg MORE when ingesting hot air from under the hood as opposed to getting any cold air from outside. warm air burns more efficiently as i understand it and modern fuel injection systems compensate for it. besides it never gets more than about 100 under your hood anyways. much better in colder climates too as far as start up and drivability, in my experience. i just have my cold air box in to support my cone filter i put on, no lid on it. if you think its too warm under your hood, just take off the gasket at the rear of the engine compartment and you'll let more out.

Warm air is less dense and thus holds less oxygen than colder denser air. Denser air is better for combustion. Your stock air box does actually pull in cooler air from the front of the KJs hood and not from near the hot engine. The problem is that the air box' inlet is very small and is slightly restrictive. A true cold air intake will increase the engines performance marginally and will also benefit other intake/exhaust modifications. They can all piggy back off each other for performance gains i.e. mpg increase, horsepower, torque etc. I have the K&N FIPK and there was a slight increase in gas milage. HP gains are not detectable with my foot and arse though.

Elwenil · **Posted:** Tue Dec 19, 2006 2:40 pm

jcphoto20 wrote:

i dont know why people keep pushing cold air intake systems. my jeep gets almost 2 mpg MORE when ingesting hot air from under the hood as opposed to getting any cold air from outside. warm air burns more efficiently as i understand it and modern fuel injection systems compensate for it. besides it never gets more than about 100 under your hood anyways. much better in colder climates too as far as start up and drivability, in my experience. i just have my cold air box in to support my cone filter i put on, no lid on it. if you think its too warm under your hood, just take off the gasket at the rear of the engine compartment and you'll let more out.

You'll also have more leaves and other debris collecting on top of the engine which can lead to overheating issues, fire hazards and worse.

Also, cold air produces more power from the same amount of fuel burned as compared to warm air. So in fact, cold air is more efficient.

EDIT: Ah, beat me to it, lol...

jcphoto20 · **Joined:** Sun Nov 19, 2006 1:36 am **Posts:** 507

in my experience, my vehicle has performed better and felt better in terms of responsiveness and economy when using under hood air. i removed my scoop and duct so mine doesnt force outside air in. my exhaust has been wrapped from just aft of the O2 sensors to the big cat, and i have a very long 2 1/4" glasspack picked for the very unique to my vehicle sound and the velocity for torque, which ive loved both since the day i got it done. 1400 with the converter locked and step on it a little on an incline, o man, tears to my eyes. i cant wait to get a converter that has a quality 1800-2000 stall and a dyno tune.

even tho everyones liberty would run better if you do a computer reset after making your last change, its my theory that underhood air, while hardly warmer than the average "cold air" system, its a very much more stable temperature. i dont do city driving more than a few times a year, so i cant say this works for stop and go for vehicles prone to running higher than normal temperatures.

mine has the towing package with both fans (and i have a water wetter in the coolant, it stays about a needle-width and a half to the left more than stock) so i expect mine to have a more stable temperature than most. and i tend to drive conservatively.

and its my thought that when dealing with a much smaller variant, the computer can more precisely meter what its been getting used to in those 50 restart cycles it relearns itself....?

im fully aware its all just guessing on my part, but there has to be some truth to it?

DarbyWalters · **Posted:** Tue Dec 19, 2006 5:46 pm

Air Temperature, Humidity and Altitude are 3 of the major factors when it comes to making horsepower...it is just a fact of life for a combustion engine.

High Temp, High Humidity, High Altitude...less dense air so less oxygen...ie...less horsepower.

thebenagade · **Posted:** Tue Dec 19, 2006 6:18 pm

DarbyWalters wrote:

Wish we could find a bigger stock airbox that could be modified to fit our space limitations. I think I remembr the airbox on the Dakota 3.7L was about 30% larger than the Liberty 3.7L and the Dakota rated 5hp more than the Liberty. A paper filter 30% larger surface area would be ideal.

I have an airbox from a 2000 dakota 3.9 if you are interested pay the shipping and it's yours

LiLredLibby · **Posted:** Tue Dec 19, 2006 7:05 pm

DarbyWalters wrote:

Air Temperature, Humidity and Altitude are 3 of the major factors when it comes to making horsepower...it is just a fact of life for a combustion engine.

High Temp, High Humidity, High Altitude...less dense air so less oxygen...ie...less horsepower.

I think Darby hit the nail on the head with his three needs for more horses. Although I think the word everyone is looking for is atomization. Cold air does atomize far quicker than warm air thus ignites much more like a gas rather than a liquid.

sleeve84028 · **Posted:** Tue Dec 19, 2006 8:29 pm

Everyone pretty much hit the major topics as to why it's not ideal to pull in air from the engine bay - I'll add this:

With an open element air filter in the engine bay a mechanical fan (or running electric fan) can introduce fan wash into the air intake path. This choppy air can effect the metering sensors and lead to rough running, poor performing engines.

Another smaller topic of debate: Hotter air intake temperatures can lead to leaner running engines. Under strenuous conditions such as trailer towing, or hilly terrain the engine can start to detonate if it leans out too much. Detonation with hypereutectic pistons can lead to pistons with big holes in them.

Almost all CAI kits (IMHO) are a waste of money.

TheJawsOfDeath · **Joined:** Sun Nov 05, 2006 3:56 am **Posts:** 305

The stock 3.7 airbox is probably second only to a real snorkel in terms of keeping water out of the intake. You'd have to have water up to the front of the hood for the engine to suck any in.

moose_1978 · **Posted:** Tue Dec 19, 2006 10:33 pm

Well I have to say a cai does make a differance.I put a true flow on mine in conjuction with a throttle body spacer and magnaflow muffler and the power is signifiantly better and it is not my imagination.I bought the true flow cone and air tube from rusty's for only $65 total and did some research on all the available filters and found trueflow to be the most flowing and it let's the least amount of dirt into the intake.I have had k-n all my life and they just don't compair.I was taliking to rusty and he said that is all they use on their vehicles and they sell both true flow and k-n.You have to think the cone is sucking much more air than the stock airbox is b/c with the airbox you only have a tiny opening recieving air opposed to the large cone.So in my opinion it is well worth the investment.

tommudd · **Posted:** Tue Dec 19, 2006 11:41 pm

I am running the Rustys air tube with a K&N but I built a box around mine out of a computer case and some pipe wrap, (hey it was laying in the garage and I needed some metal) Opened up the front some where the air flows in . After my last mad dash from Boston home, where I never shut if off, when I raised the hood you could feel the heat on the air tube but the filter was stone cold. Now to wrap the air tube to maintain that cold air all the way to the engine. I have ran it both ways and I still get a little better mileage from the air tube and K&N, plus I like the sound it makes

OzLtd · **Posted:** Wed Dec 20, 2006 5:36 am

sleeve84028 wrote:

Almost all CAI kits (IMHO) are a waste of money.

Not all

I had the current model Integra Type R and putting the Ingen CAI on gave insane HP figures compared to stock. But that particular engine is very sensitive to cold air, as it the Dodge Viper's 8.0Lt V10.

sleeve84028 · **Posted:** Wed Dec 20, 2006 8:33 am

Any engine loves colder air and lots of it, that is a no brainer. The more air - the more power. I never denied that, but I still belive that all open element CAI kits are improperly designed and thus a waste of money. Drawing air from the inner fender well is the smartest choice for almost every car manufacture. I mean think about it, if there was power to be had from using shorter plumbing and less plastic don't you think that every single car built would come equiped like that? The OEM's would be saving around $10.00 a car but they aren't...?

Making a heat shield out of a computer case is pretty cool. As long as the filter is seperated from the engine bay, it's OK in my book.

Air intake system

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