N00b Question

i never got into AFRs but i think your on the right track about it burning hotter when its lean. probably the heat and pressure burns up the rings.

Dang, Tin Man beat me to it.

Most modern direct fuel injected engines have an ECU that will alter the mix from lean to rich and everywhere in between based on the necessities of the engine. As TM pointed out, pre-ignition can occur in ultra-lean mixtures which essentially throws the timing to hell and will keep the engine from running properly if at all. More an more modern vehicles are coming with ECUs that are increasingly hard to crack and mess around with the timing. You can put a turbo on a Mazda 6 V6 for instance, but you'll only get a marginal increase in BHP and WHP due to the fact that the timing and mixture settings can't be "tuned" due to the encrypted ECU. Now, for your more popular tuners, you can get after-market ECUs to replace the OEM ECU, but you're running the risk of messing with the timing and fuel richness to the point where you'll royally eff-up the engine.

As for the lightweight flywheel, you decrease the curb weight of the vehicle AND increase wheel torque though not necessarily WHP. The flywheel is what keeps the engine turning when you aren't actually feeding it gas. Using a lightweight flywheel is great for engines with a broad power-band and close gear ratio as you'll get the benefits of the reduced weight, however, the smaller the power-band on your car, the faster you have to shift otherwise your revs will drop below the shift point and the flywheel's lack of mass becomes counter productive. Flywheels rely on their mass to keep them spinning. To make them lighter you remove mass which means that it won't spin as long which can cause a drop in revs which will cause you to stall if you don't shift quickly enough. No problem on straightaways, but in cornering, it can be a biiiiiig issue.

In worse case scenario a lean condition could warrant a visit from Mr. Squeeky.  You will damage a motor.  If this is happening something like "man this thing is running better than it ever has"  will probably be going thru your head right before it smokes.  Guys with turbos have to richen the fuel/air mixture(less air to more fuel) to compensate for a performance enhancement as drastic as a turbo.  The more power the more fuel required to cool things down.  It's under heavy debate how well and to what extent stock electronic fuel systems handle modification.

Edited by Lightningbolt - 01 March 2009 at 12:12am