The ECU is capable of adjusting the A/F ratio based off the MAF sensor, but the MAF is tuned for the stock intake. Aftermarket intakes can create different air flow patterns (i.e. turbulence or laminar flow patterns) that will cause the carefully calibrated MAF to give improper readings. It's not the MAF or ECU's fault. I guess I'm not arguing with anyone. I'm just saying that if the MAF gave the proper signal to the ECU for the increase in airflow with a CAI, the world would be a happy place. Piggyback computers or reflashing of the ECU accounts for the error in the MAF not being calibrated to the new air flow patterns.

 

this debate is about as answerless as the same debate on the wrx side so i think i will just go the safe and cheap route and pick up a K + N drop-in. thanks for all of your replies guys.

 

Or wait about a week for Green Filter's drop-in competition to K&N. It looks vastly superior for durability, filtering efficiency and pressure drop. I have been contacting their engineering department and was told it should be out in a week. Once you see one in person, you will never buy another K&N filter.

http://www.greenfilterusa.com/

Tim

 

I told you there would be no definitve answer.

 

Aftermarket intakes make power, but not on the stock ecu. Any gains you might see on the stock ecu will be a result of running lean from wacky maf sensor readings. It takes tuning to make additional power with aftermarket intakes. The stock intake is only starts to become a restriction once you start using bigger turbos.

 

Well, the only way to get a definitive answer is to compare apples to apples like any good engineer/scientist would. Measure pressure drop, air temperatures, and overall effect on screwing up the MAF on the most popular intakes. Why doesn't this data exist??? Because it doesn't have to exist. Vendors get by on seat-of-the-pants "engineering" because the consumer lets them. My $.02

Tim

 

why not just replace the plastic piece running from the airbox to the turbo with a 3" induction pipe and use the k&n drop in filter? seems like that would be a good compromise between an open element intake and stock box

 

Actually the reynold's number for flow through the intake pipe is always above the laminar level and thus turbulent. Any skewing of the MAF would be from an uneven velocity distribution of intake air through the sensor, causing more or less cooling of the hot wire element that the MAF uses to calculate mass airflow.

Personally I would like to see a dyno test of a stock intake versus an aftermarket one with the hood closed! I am guessing that the aftermarket intake would then be sourcing hotter air from the engine bay as it would when you drive your car and thus create a more accurate depiction of true gains (if any).

-----------------------------------------------------
2000 WS6 M6, 530 rwhp all motor...

 

For those that think that inlet temps do not matter, why the hell do you think your car is faster when the weather is cooler?

 

I thought he was saying that he did the race before he had the dynoflash. ie, when the only mod he had (at that time) was the catback.

 

Fenris Ulf, Do you think it might have something to do with the compressed air being cooled in the intercooler more because the outside air temp is lower not so much because of the air inlet temp is lower. I'm not trying to start an arguement but you have to consider that. It's the same reason they put an intercooler sprayer on there, to make the intercooler more efficient.

 

My PERSONAL experience with aftermarket air filters with the STi was BAD. Had ARC and Apex'i. Both were crap, IMHO.

Also, read this:
https://www.evolutionm.net/forums/sh...threadid=73189

https://www.evolutionm.net/forums/sh...threadid=74383

I'm NOT convinced that CAI is worth it in WRX/STi/Evo.

If BOV noise is of utmost importance then yes CAI should be good. But other than that, I dunno...

My 2 cents.