07-13-2009, 11:08 AM
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#10 (permalink)
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Base Member
Join Date: Jul 2009
Location: Austin TX
Posts: 52
Drives: Nissan/Infiniti
Rep Power: 267
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Quote:
Originally Posted by K20A2_S
the main reason is b/c they don't know where teh car is going, your a/f ratios will vary greatly running in 100 degree houston weather, than 30 degree Chicago weather........
When the air is that dense in the cold you need more fuel to compensate.........so I'm guessing they "tune" the stock ECU to handle those type of A/F rations b/c it's better to run rich then lean like most have mentioned.....
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Nope, the car has an Air Intake Temp sensor. It will adjust the fuel according to the volume of air, which is calculated via density and flow.
The reason why some car run rich from the factory is because no two cars are alike. We've had cars that are 100% stock and have less than 20k miles on them that have come in at 16:1 at full throttle. Others that have been 11:1 at full throttle. Add aftermarket parts and the situation can be even worse. The ECU adjusts based on what it sees. If there is a bad sensor or a leak then it can't do a great job. Often there is a stuck injector, or a single injector that is flowing too much or too little.
If it's really out of hand, and the ECU targets aren't being hit, it will throw a CEL. It rarely happens on a totally stock car, but we've seen it. Something as simple as an exhaust gasket leak can cause a car to run totally off target.
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