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Old 10-02-2004, 12:07 AM
john banks john banks is offline
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Join Date: Feb 2004
Location: UK
Posts: 5
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I've been playing in the range 25-32 degrees BTDC at 6000 RPM at 19 PSI approx.

Retarding the timing did fix the det with the 50/50 but the power was killed by doing so. EGTs easily got over 900C. Since the power was nothing like optimum despite trying a range of AFRs (limited by EGTs usually if I tried to lean it out) I don't think I got to MBT.

The problem with saying lean it out until there is no excess hydrocarbon is that the engine would have melted I believe. I really don't like EGTs over 900C that are achieved so quickly, on a very prolonged thrash I would tolerate up to 920C which is hotter than most would allow, and that is just before the turbo.

I don't think I can control conditions tightly enough to state the effect of ignition timing on EGTs although I know the theory. The things that affect my EGTs are boost, AFR and how much alcohol was used.

There are other variables that may make my findings different from the theory that water would be better. Probably lots of them.

I just plumped for what was easy to get power from without fear that I wasn't going to melt my engine or det.

Trying yo get my head around what my wideband is doing, I've ended up mapping to EGTs in the high 800s Celcius so far, "12.2" on the wideband seems to get there. Going leaner kills the timing and doesn't seem to add power.
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