Quote:
Originally Posted by svtsilversnake  yea it blew smoke...but a richer mixture yealds less power but is better on your parts
.ritht |
Kinda. A slightly rich mixture will keep combustion temps down and keep things safe. An overly rich mixture will carbon up the motor, exhaust and O2 sensors. And, it will overheat the cats, if equipped. Cats work by burning excess HC (hydrocarbons or fuel). If there is too much HC in the exhaust stream, catalyst temps will soar and eventually the catalyst will fail. If you are still utilizing the TWC (three way catalytic) system, you'll end up with catalyst effeciency codes.
Also, the piston rings may become carboned. This build up cannot be completely alleviated without tearing down the motor and re-ringing it. If the mixture is rich for too long, ring seal will be degraded to a point that the oil film will be washed fromt he cylinders and the cylinders will become glazed. Correcting this would require honing or reboring.
11.5-12.0:1 AF is a safe rich limit for a NA motor. Past that is just too rich.
If you are truely at 10.4:1, something is wrong. Too much fuel pressure, too big injectors, dirty/malfunctioning MAF, etc.
A dirty MAF may cause a lean mixture down low and rich up high.