[Diy_efi] A/F mixture, EGT and engine damage

[Michael Richards]

> I have heard that going too rich can damage the engine
> by "washing" the oil film off the cylinder walls. Is
> there a safe lower limit on A/F or EGT ?

If there were a magical number that gave you the best economy or the 
best power for all engines then the numbers would be well published and 
recited by everyone. Your 13.2 number sounds like a happy medium 
between cruise and power. 

Personally I would try going a little richer under load and a little 
leaner under cruise. Some engines don't mind being run high into the 
15's for cruise but others will not tolerate it at all. Some engines 
make more power NA into the 12:1 AFR but some are better run lean 
around 12.8:1 or 13:1. Everything is a balancing act. If your EGTs are 
too high try advancing the ignition and/or richening it up a little.

I wouldn't worry about washing the cylinder walls at these ratios. Run 
it 10:1 and richer and you could have a problem.

-Michael
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