Effect of timing on AFR

[Philip Lochner]

Hi guys
 
What is the effect of ignition timing on AFR?  In other words, to what extent is the AFR that I get at any given point affected by ignition timing? I'm not referring to situations where timing is excessively advanced or retarded but to situations where the timing is, say, within +-3 deg of "perfect".
 
 
Kind regards
Philip Lochner

 

Posted by email.

[Kevin Wood]

> What is the effect of ignition timing on AFR? In other words, to what
> extent is the AFR that I get at any given point affected by ignition
> timing?

Very little in the instances you refer to. The same amount of air and fuel
enter the cylinder and produce roughly the same exhaust gases. The
combustion just occurs at a slightly different point in the engine's cycle
and thus would produce more or less power depending on the optimum timing.

That's why it's easiest when tuning to get the AFR correct and then worry
about the timing.

Kevin

Posted by email.

[keithmac]

Yep I`d agree, I tuned Fuel first then fine tuned the timing table and it made very little if any difference to the AFR`s.