cai.....too lean? (possible engine trouble?)

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May-13th-2003, 02:10 PM

#16

pr5owner

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my A/F gauge is hooked directly to the 02 sensor on the first catalytic converter

May-13th-2003, 02:58 PM

#17

Tom Slick

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Location: central coast calif.

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does it read rich all the time? or does it change as you drive?

May-19th-2003, 11:26 PM

#18

pr5owner

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it moves back and forth since the engine burns and exhausts in "Cycles" but it goes to rich every time

May-20th-2003, 08:29 PM

#19

kc5zom

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Location: Houston, TX.

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Re: Hummmmmm

Quote:

Originally posted by pr5zoom
kc5zom

Maybe my wording was vague , with colder air the ecu then corrects with more fuel. Yes the volume and the speed of the air is increased with the CAI however the fuel is also increased with the decrease in temperature (I dont think the the ratio is linear), think of a choke. Thus, we get worse mileage. NOW, with the turbo motor increasing the pressure as well as cooling the air with an intercooler, I was asking if the turbo engine acted the opposite of the N/A motor and ran lean. This was a simple question. With a CAI on a N/A motor COLD AIR Intake, meaning colder air and more fuel. I think that the volume doesnt offset the increase of fuel (Nonlinear curve), Thus the N/A motor runs rich. DOES the turbo motor act the opposite because of the increased pressure and the colder air from the intercooler? Can the WRX ECU compensate for the change with the turbo?
By the way this is the same question as before, just better worded I hope .

Mickey

Sorry I missed this. The ECU will compensate as much as the code inside it is designed for. The sensors have a general idea of how much air is brought in and add enough fuel to compensate. Even though the intercooler compresses the air (as well as the CAI) the air is still accounted for by various sensors and the ECU will add additional fuel for that air. But if the ECU code is intolerant or overly tuned (WRX, although I'm not familiar with their ECU setup) it probably will dislike changes from its normal expectations and you get issues. The WRX ECU is definitely capable (as all modern ECU's are) but it may not be programmed to handle it.

It is pretty much impossible to run too rich but it does cause problems and there are practical limitations:

1. Less oxygen combusts in the cylinder (too much damn gas)
2. Overly cooled combustion chamber
3. Pissing away gas for no damn good reason

Best performance is always at stoichiometry, but it is better to err rich than run lean and lose a motor.

Last edited by kc5zom; May-20th-2003 at 08:33 PM.