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isn't that same sort of thing with running too rich and retarded timing? I know exhausts glow with either or worst together.

Yes, majorly retarded timing or running too lean are both ways to cook things.

I agree with timing retarded and lean causing overheat particular in the exhaust valve area. It's fairly basic with more cylinder wall exposed to the heat due to the slower burn rate. Rich cools. I have an EVO and their maps show 9:1 at high RPM high boost. I haven't got into that area because of my cars state of tune but where it is it reaches (not logged yet) the 10:1 with no sign of misfire. All my research says they tuned it that way to reduce engine temp and reduce warranty claims.

but that rich would wash the lubricant off the cylinder walls I'd of thought?

so what about running leaner than the peak EGT? 17-18:1 from my understanding it quite cool.

Well this car had 100,00km on it when I got it and I have flogged it around the track for the last 3 years and I finally cracked all 4 pistons this year obviously caused by detonation and there was no bore wear at all. You could still see the original hone marks. I have seen comments on forums about how rich they run. It uses about 50L per 100kms on the track and shows no sign of sooting on the plugs in fact they look a little too white for my liking.

where's it all going I wonder?

Into HP. These little gas guzzlers rum nearly 280hp std and with a few mods and a tune up to 400.

I know this is an old thread, but many may find the following of interest.
I have been playing around with lean cruise since 2008, mainly on my LS1.
My conclusions are:
Standard Holden settings are too lean on the whole - torque drop-off is the killer.
Every engine is different.
I have tried 50 - 110+ kph and 13 - 17 AFR. At most speeds there is a peak economy/torque mixture.
For my engine, at most speeds it turned out to be 15.4AFR!, not at all what I expected, but this was the result of a Lot of logging and I am confident with it. The difference between 14.68 and 15.4 sounds small but is worth around about 20%, works for me.
BTW if you are stuck in the suburbs work on DFCO, it is worth the effort at low speeds.
Cheers, Steve.

good info and I agree, all engines are different and its a matter of how much time you want to spent playing with it.

dfco also helps slow the car down without needing the brake too!

DFCO is great, lots of hills around where I live, knock the auto down a couple of gears and you don't need to use the brake to control your speed and you save fuel

However, my missus has a heavy right foot and I haven't managed to tune that out and to try would not be wise. Hopefully when my boys start to drive I can educate them a little better.