K&N Cold Air Intake

[gamble]

So right now I am definitely more tempted than ever in purchasing a K&N CAI. Are they worth it for a 2003 3.7L Jeep Liberty? Right now they are 20% off where im looking at getting them, and am so tempted to pull the trigger and get one. Any insight is much appreciated. Oh. and is the performance after installation noticeable?

 

[renegade 04]

You will actually lose performance on the liberty and everyone reports a noticeable 2-3 mpg decrease.

 

[gamble]

You will actually lose performance on the liberty and everyone reports a noticeable 2-3 mpg decrease.

I read somewhere that the response time, as well as the power seemed to increase. Is that not true?

 

[renegade 04]

If you want increased throttle you should and increased power you should go with a Fastman throttle body.

 

[tjkj2002]

I read somewhere that the response time, as well as the power seemed to increase. Is that not true?

For a race only vehicle yes,a stock daily driver is a big NO.

Also lets more dirt into the engine for faster wear and you can not take advantage of the increased airflow without internal engine modifications.

Stick with the stock box,that is actually a true cold air intake were the K&N system is actually a hot air intake by sucking hot underhood air in.

 

[tommudd]

I read somewhere that the response time, as well as the power seemed to increase. Is that not true?

Junk do not buy
save your money for things that actually improve your KJ

 

[JavelinAMX]

why not just buy a drop in K&N or Mopar Performance filter? one big plus in my eyes is that they are washable and reuseable.

 

[04Liberty]

If you want increased throttle you should and increased power you should go with a Fastman throttle body.

Not worth the expense without cams and heads modifications to increase the need for it.

 

[tommudd]

why not just buy a drop in K&N or Mopar Performance filter? one big plus in my eyes is that they are washable and reuseable.

and allow more dirt in

Best setup as far as air flow into the engine is the stock box with a good paper filter like one from Napa Gold. Great filter, does a good job of filtering out dirt etc.
You maybe able to wash the K&Ns but that is their ONLY saving grace, otherwise junk

 

[tommudd]

Not worth the expense without cams and heads modifications to increase the need for it.

So right, many of these so called mods people do to the KJs do nothing at all since they need cams, headers, pistons, B&G reflash etc to even take advantage of more air like the larger TBs give you

 

[JasonJ]

Volumetric efficiency people. A 3.7L displacement engine with the CFM flow rate of our cylinder heads, cannot flow more air than what the stock box/intake tube is already capable of.

You can add a 90mm throttle body and have NO air filter, any engine can only suck in as much as it can and that is a fixed amount at max capacity. Won't do any good beyond that.

There are a few formulas to calculate air flow. Take our 3.7L, making max hp at 5200rpm as the example.

Using V = (RPMxCID)/3456 x(VE), and figuring 80% VE (Volumetric efficiency), we get a max CFM of 271.783.

So putting ANY component in the intake or exhaust tract that outflows that number, is completely unnecessary and excessive. Example, suppose the K&N "cold air" intake claims that it flows 500cfm. Yeah? So what. The engine can only move 272CFM of air. No gains to be had.

Throttle bodies and carburetors are the same way. Putting a 650CFM Holley carb on your 350 chevy that only flows a calculated 421CFM is stupidly overkill. A 500CFM is better suited. Obviously cylinder head porting and valve sizing, as well as forced induction changes things (namely, the VE of the engine).

So keep that in mind when shopping for intakes and exhaust headers.

 

[CactusJacked]

Good point, except our 3.7 flows a maximum of 303.4 cfm based on a ve of 80%, not 271.... You use maximum engine rpm (redline @ 5800) in the equation, not down lower where it makes max hp. The engine keeps pumping more air as the rpm's increase, regardless of where the max hp level is.

 

[JasonJ]

Good point, except our 3.7 flows a maximum of 303.4 cfm based on a ve of 80%, not 271.... You use maximum engine rpm (redline @ 5800) in the equation, not down lower where it makes max hp. The engine keeps pumping more air as the rpm's increase, regardless of where the max hp level is.

That is true. I purposely used the max hp rpm as I felt that realistically in a real-world driving scenario, revving the engine past that rpm does very little in terms of increasing acceleration. Perhaps I am mistaken, but that was my thinking.

I mean, crap, I rarely rev my KJ past 3000 in normal driving.

 

[CactusJacked]

Go on youtube and search cold air intakes mythbusted. When dyno tested, the cold air intakes and the drop in K&N filter did no better than the stock air box with a paper filter, some actually performed worse.

 

[krisP]

i know some run an extra tube from stock air box to grill. Same concept ?

 

[jeeptorino68]

i know some run an extra tube from stock air box to grill. Same concept ?

Different concept, this is actually get cold outside air from in front of the vehicle. On my to do list.
See here:
http://www.jeepkj.com/forum/f202/cold-air-ram-air-intake-using-stock-air-box-59600/

 

[tommudd]

i know some run an extra tube from stock air box to grill. Same concept ?

I've ran an extra 3 inch tube on my 04 for over 11 years, making one up for the 03 and 05 here soon as well

 

[CactusJacked]

The guys that did the CAI vs stock box comparison on a 225 hp car, got a little over 1% increase in h.p. (oooooh) by extending the intake tube and putting the cone filter to the front of the car. More cooler incoming air can't hurt, but you're not going to feel any difference.

 

[uss2defiant]

hey!!! that's an increase in HP!!
I can vroom vroom more!

 

[CactusJacked]

hey!!! that's an increase in HP!!
I can vroom vroom more!

Absolutely. Those (maybe) couple extra hp is the difference between the Liberty needing wheelie bars or not. :happy175: