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Originally Posted by AtomicLabMonkey
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Originally Posted by sperry
The ECU's uses both MAF and MAP, however, the CAI's just flow too much throught the MAF w/o the MAF voltage changing properly. Up here at Reno altitude, it's not a big issue, since we've got less O2... but in SoCal, where that car's from, it's probably pretty bad.
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Is it a problem with the stock MAF transfer function, like it just doesn't go up high enough for the ECU to interpolate accurately once you've changed the intake tubing? Or does the Subaru MAF hardware just give an inaccurate signal past the factory specified range? Either way, that's just strange to me. You can pretty much change the entire exhaust, intake piping, manifolds, etc. on a Mustang and the computer will compensate for it with the stock meter, as long as the injectors aren't maxed out. Just replacing the intake piping in front of the meter is a very small change to whack out the computer that bad... |
CAIs basically cause the MAF not to correctly read the amount of air flowing into the engine. most of them will flow more than what the MAF sees, so the car gets leaned out. The WRX
will add fuel long term, but when you first get lean, it causes minor detonation which causes the ecu to learn to pull timing, and MBT is more important to making power in an EJ20 than the exact A/F ratio. In closed loop fueling, using the O2 sensor feedback, the ECU does adjust fuel and nothing bad happens. but under WOT/high RPMs when it switched to open loop and goes by the maps in the memory, it's suddenly lean and starts knocking. In open loop, there's not much authority over long term fuel trim, and pulling timing is the first defense against detonation.