K&N intake VS stock airbox - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 06-25-2007, 02:48 PM Thread Starter
 
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K&N intake VS stock airbox

I have done some reading and it seems that a lot of jeep people prefer the stock air box to a K&N fipk system. I changed to the K&N intake and filter as well as a Airaid throttle body spacer, and frankly, I haven't noticed any performance or mileage gains. This may have been a waste of time and money for me. I have also heard that the K&N filter allows dirt to enter the engine more easily than the stock box.
Can I get some feedback from some of you who know a little about this.
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post #2 of (permalink) Old 06-25-2007, 03:05 PM
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The K&N filter is not a bad product if you can keep the oil out of the sensors. The oil tends to kill off MAF/MAS sensors. Also, think of the Jeep as a system. You disrupt one part, you disrupt another. What happens to all that air the engine gulps? If the exhaust is not up to moving the spent gas out of the engine, it becomes a choke point. If the EFI ECM can't trim the fuel to take into account the new amount of air, the Jeep'll run lean and not enough power will be developed.

IMHO, the K&N is GREAT on carbed engines, but on a EFI controlled engine the power gain/reliability is marginal at best.
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post #3 of (permalink) Old 06-25-2007, 03:29 PM Thread Starter
 
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I also have a Banks stainless header and exhaust on my TJ. It runs great. I just want to get as little dirt in the engine as possible.
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post #4 of (permalink) Old 06-25-2007, 04:12 PM
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May I suggest you read over:

Air Filtration and Flow Test. The conclusion of the test was that airflow for a K&N was best. However that does bring us back to the problem of oil from the filter migrating up to the MAF/MAS/MAP sensor

You may be interested in reading THIS Thread about K&N filteration.
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post #5 of (permalink) Old 06-25-2007, 04:23 PM
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Something that disturbs me about K&N's filters. You take a new filter and run air flow tests against other filters. K&N has more airflow. now pull that filter and hold it up to light. there are tiny pin holes all in the filter where the media just doesn't seal off the dirt (In my opinion).

So I called K&N about this. they asked how often I cleaned it. I said I cleaned -not long back...
-Well, how much dirt is on it?
-None... I just cleaned it.
-well, you need about 1/8" of dirt for it to plug those holes and filter the air.

Is it just me, or is there a contradiction there???? and what's the Air flow rate when plugged with dirt at 1/8" thick????

The belief in a supernatural source of evil is not necessary; men alone are quite capable of every wickedness. - Joseph Conrad
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post #6 of (permalink) Old 06-25-2007, 04:39 PM
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As you have found out the hard way, the spacers do nothing for power.

As for the K&N, when it's clean it may flow a 'little' better than a stock air filter....but the claim of improving gas mileage is false. In a closed loop control system the air restriction has no effect on MPG. The computer is adjusting the fuel flow based on readings from the sensor (MAP or MAF), temp, RPM, O2, etc. A slight restriction in air flow is not going to have any effect. About the only difference the K&N is going to make is under heavy acceleration....which is not real good on MPG anyway.

Since you mentioned headers.....they do nothing for the low end...they only kick in around 75% and up of the RPM....which is something we don't normally use on the trail.

Do be perfectly honest, the stock engine is about as good as you can get for the trail....

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84 CJ7, SOA, 5.7LTBI, 4L60E, 35"x12.5, 4.10 gears, F/Det, R/ARB, Full Roll Cage,
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