MSefi.com read only forum (Jan.15,2018)

My engine starts and warms up well, I really have no complaints.
RIght now, AFR is quite rich when cold, maybe 10-11.
It slowly improves as the engine warms up and idles smoothly around 13:1 AFR.
I'm wondering if it needs to be so rich when cold?
Is it possible (or even recommended) to have an AFR closer to the mid 12s or even 13 even when cold?
What kind of AFR are you guys seeing during warmup?

try going into the warmup wizard and lowering the enrichment numbers. Seems rich to me. You can watch the afr numbers as you adjust and pay attention to the way the motor runs. Mine likes to idle smoothest at about 13.5, warmed up. Each engine is going to be different. Billk

flatbill wrote:try going into the warmup wizard and lowering the enrichment numbers. Seems rich to me. You can watch the afr numbers as you adjust and pay attention to the way the motor runs. Mine likes to idle smoothest at about 13.5, warmed up. Each engine is going to be different. Billk

Will your engine idle smoothly during warmup with an AFR of 13.5?
When it had a carburetor, the AFR was around 10.5 or so with choke on. At the time, that's what I thought the engine needed during warmup.
Now I'm wondering if that was just they way the carb worked since it was all or nothing and it had to work with very cold temperatures.

My experiments show you'll get a reliable idle with a mixture far richer than it need be.

Mine idles at 14.1 to 14.5 and its a nice idle. On start up it is about 13.6 and slowly goes up to 14.5. It runs and idels perfect.

2vwjones wrote:Mine idles at 14.1 to 14.5 and its a nice idle. On start up it is about 13.6 and slowly goes up to 14.5. It runs and idels perfect.

Yup - assuming reasonable valve timing etc somewhere round about 1.5% CO should be achievable, and satisfy the environmentalists. ;-)

2vwjones wrote:Mine idles at 14.1 to 14.5 and its a nice idle. On start up it is about 13.6 and slowly goes up to 14.5. It runs and idels perfect.

That's exactly what I was looking for. I can easily adjust warmup enrichment for a target AFR at a given temperature.
I'll probably shoot for high 12's, maybe low 13's during warmup for now. My bike is very happy with those numbers.
It makes sense that AFR is AFR regardless of engine temperature. I guess the carb numbers threw me off.

Thanks guys!

Yes, my motor idles smoothly at 13.5 when warm. It will still idle smooth at 13 warm, but I thing that it is unnecessary to run idle so rich. I think it starts out quite rich like yours then gets to 12 or so then leaner up to 13.5 I have tried to lean out the warm idle afr and my motor doesn't like it. Billk

Really the best way to find the ideal warmup AFR for your setup is to experiment. Try leaning it out and see how it runs. My truck likes to be around 13:1 when cold (temps around 40degF) and gradually leaner til hot at 14.5:1.

It's not linear either. curve starts out with a much more aggressive slope then flattens out.

Hope this helps.

Victor