What AFR do you guys aim for when mapping the post-start/warm-up area of the map?

During the really cold snowy weather recently my car reached areas of the map it hasn’t before, with coolant temps first thing in the morning of -16°C common for weeks. The car was running sub-10:1 AFR so I reduced the enrichment and have found that it actually idled at 13:1 perfectly well, and I’ve got it running 13.3:1 at 0°C.

What AFR do people run during warm-up? Is there a reason to keep it so rich? The stock ECU seems to run 11-12:1.

have just looked at the stock ecu

Ambient circa 4 degrees according the phone. Startup afr circa 11.8 up to circa 12.w after a minute then 14.7 after about another minute . Water temp just off the bottom of stock gauge so circa 40

5\( if it runs I'd stick with what you have. I ran about 12.5 on the PFC with very little correction as it got colder

Mine runs about 11-12:1. Leaner when it gets warmer.

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ST185 CS #1845

Have you tried leaning it out any further?



Thanks for that, I wonder if it needs to be that low though? My car seems to flood and is difficult to start with such a rich AFR. Particularly when it's -16°C and the oil is like treacle! 13:1 seems to work better, though it was -6° up here this morning and it didn't want to start as the battery was dead!

If your's starts and runs fine as is then I wouldn't change it

I can't see any benefit from pouring in nice colld fuel when you're trying to get it warmed up. Apart from the grin factor of the dawn chorus turning to a coughing hacking fit and sparrows falling out of treed

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Yes, then the idle starts getting worse. I have to make it leaner every year for the smogtest. Runs about 13, to 14:1 then.

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ST185 CS #1845

Mine used to be lumpy, but now sits within about ±10rpm of the target rpm during warm-up. I've found that getting the SM4 to slow the dynamic response speed of the IAC valve and instead using a steep delta-rpm ignition timing curve really helps to hold it solid.

I always target mine at 13:1 until it's at about 60C, seems to be fairly happy but I do get really sooted plugs after a bit of idling, so I was tempted to lean it out further and earlier.