Quote:
Originally Posted by flyingarmadillo
While most engines run rich at wide open throttle introducing more airflow won't do anything to change the mixture since the MAF will sense the increased airflow and the ECU will increase the fuel flow in response to the higher airflow. The only way to change the mixture would be to reprogram the ECU. And you wouldn't like the results - the rich mixture essentually increases the octane of the fuel - the rich mixture retards combustion. Peak power isn't usually achieved in piston engines with a lean or even stochiometric mixture - it's someplace on the rich side. In some small private piston powered aircraft you have manual control over the mixture and the procedure is to lean the mixture for maximum RPM, then richen it up just slightly (100-200 rpm drop). This gives max power. Some of it also depends on what you call polish - a mirror polish will absolutely kill performance on a carburated or throttle body injected engine - some turbulence is needed to keep the fuel suspended in the air, with a mirror polish it tends to deposit on the walls of the intake. On direct injected engines it doesn't make much difference. If you're talking about polishing as in removing machine and casting marks and just cleaning up the intake, then it helps but you still need to leave enough roughness to control the airflow.
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Our car doesn't have a MAF, it has a MAP. Our car will use its O2 sensors (and others) to keep A/F ratios constant.