How do I cure a lean condition?

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Originally Posted by camelll

Where did largeorangefont go? I would like him to explain some of this shiiiiit to me cause I really don't know. I understand about timing, advancing or retarding and when I am under boost the load is basically on 99 percent. I just don't understand how all of these tie together with rpm and manifold pressure.

Sorry, Had to do some actual work. I gotta head out to a customer, so here is a brief overview.

In reality \keeping an engine alive comes down to EGT (exhaust gas temperature) and knock.

You use a balance of AFR and timing to keep both factors in check. You can't crank up both and expect an engine to live.

Think of fuel as coolant for the combustion chamber. Think of ignition advance as how hot the fire burns. Obviously if the fire burns too hot, bad things happen. If it burns too cool, the car runs like crap and is slow. The temperature of that fire is EGT. You can control EGT by adding more coolant (fuel) or turning down the intensity of the flame (ignition retard).

OEM supercharged cars will (generally!!) run low timing and a high AFR to increase fuel economy and reduce emissions. My Cobra for example ran in the high 13 AFR range under load, but only had 10 degrees of ignition advance from the factory.

I now run the AFR and 11.3:1 AFR under load, and 21 degrees of ignition advance, and picked up 30 some odd HP and torque. It runs like a different car. The increased timing makes the car more responsive on tip in (passing etc.), and much more driveable. Power "under the curve" is increased as well as peak power.

EGTs in both scenarios were VERY similar, at around 1300F. From this example, you can see there are many ways to the same end. Some produce more power than others.

Knock is another factor to be wary of. Again, to get rid of knock you can add more fuel, or retard timing. Strategies can vary on how to get rid of knock, especially in turbo applications.