Does anyone have experience with Warm up AF ratios that work with a slant on either EFI or carbs. Mine is set at about 13:1 during warm up, but I suspect it could be raised progressively in search of a leaner mixture that still drives OK. Any experience out there?

Sam

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Mine does not like to idle leaner than 13.3:1 after being warmed up...not sure what is causing it. I also spoke to the maker of the extreme velocity carb hats. He has a 490" big block chrysler with a vortech/paxton and a blow thru and it needs to be at 12.5:1 for any type of idle quality. Just a couple of examples I know of. Not sure if it helps.

Thanks for the reply. This engine will idle at 16:1 when warm with the EFI. But it is tuned to be at 14.8:1. When it first starts up after a short rest it runs leaner for some reason. Tha's how I know it will idle at 16:1. Within a minute or so, it will be back to 14.8:1. Feed back is not hooked up yet. Still too busy tuning to let the feedback into the picture.

So maybe this question is for those with EFI.

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Mine will idle at 14.x:1 too but as soon as I put it in gear it dies.

With port fuel injection, you can start with around 13:1 and ramp up A/F quickly after start-up. Central EFI needs to run richer for a longer period of time due to the much larger manifold surface exposed to fuel and the 'wetting' of this surface. I would just keep leaning until your idle becomes unstable and then add some fuel back in.

Mitch

Thanks Mitch. I guess that is what I will do. Since I drive just 4 miles to work, the engine never really gets warm. The result is that the economy of driving this car will depend to a large extent on how lean I can get it to run when cold. How much I drive ti at all will depend on how the drivability goes in the cold weather. We will see.

Sam

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