ECU talk

[Dan Thompson]

On 6/25/07, Ben Fenner <fenfam at sc.rr.com> wrote:
> I didn't know that I'd start this sort of disscusion. I'm sorry about that.

This has turned into something a bit more "religious" than terry cloth
versus chamois. :)


> How hard can it be to keep a/f ratios within spec, EGTs in check, and
> knock at bay? =]

Harder than you may believe.  A/F isn't too hard -- to a point.  A
good wideband can help you to get that nailed down pretty well...
unless you tune your setup to the ragged edge on "normal" gas, then
inadvertently fill up with E10 or (worse yet) E85.

EGTs?  That's another subject to be debated as religiously as engine
management and terry/chamois.

Knock?  Let me tell you a bit about knock...

I have the good (bad?) fortune of having VERY high quality gas in my
home town.  My car was in an excellent state of tune, with timing
being at the very edge of what was possible with 93 octane fuel.
Power and economy were remarkable for a stock turbo'd WRX.  Then I
started working in Buffalo.  And filling up with fuel from Buffalo

I can say with reasonable certainty that I didn't exceed the capacity
of the fuel system.  I've poured over my logs extensively and didn't
see where I went over 95% injector duty cycle, and I wasn't beyond 75%
when the "event" occurred.  I can also say with reasonable certainty
that the octane of the fuel from my home town is higher than that of
the 93 octane I bought in Buffalo.  It appears that I've got to run
upwards of 6 degrees less timing at higher loads with Buffalo fuel
than with hometown stuff.

I suppose I could have saved my engine if I'd pulled over immediately
when I noticed something amiss with the logs I was taking, poured over
them, then reflashed the ECU with maps to account for the behavior I
was seeing.  But I kinda doubt it -- I imagine the damage was already
done.

I hope to find out today what the exact damage is to my engine.  I'm
fairly certain it's a rod bearing, though the fact that the car was
smoking as I pulled it off the trailer at the shop doesn't rule out
the possibility of a cracked ring land as well.  Either way, I've got
a new short block waiting to go in so I can get back on the road --
with a MUCH more conservative tune.


-Dan