Aries hi-performance muffler application.

[MikeK]

Originally Posted by Benson

Mike K,

Did you ever check the A.F.R at idle?

I am curious what fuel ratio you find works well for a good idle?

I find 12.3 to 12.1 works better than a 13.5.


Thanks

My idle A.F.R. is best at 14.0. I run a thermostat, so I'm always 165-175. Air swirl and turbulence in your head and plug placement also affect how well you can light off a small low pressure idle charge and how completely it burns, so the ideal AFR varies. Also, I always make a series of nicks on the leading edge of the throttle plate in the 1/4" that covers the idle ports. That helps generate turbulence, vaporizing the cold gas. A slight raised burr or ridge on the throttle bore, just past the idle opening will do the same thing, helping to lift the fuel away from the bore wall. I didn't learn that "nick" trick from any carb guys, I learned it years ago voicing organ flue pipes. Pipe organ builders understood air flow and resonance dynamics 100 years before the first carburetor. An organ pipe will "speak" it's true waveform much faster after air starts to flow past the languid if the mouth is nicked. Nicking Link Before I was into A's, I spent many years crawling organ chambers.