Questions from a newbie

[Marteney, Steven J.]

Ah yes, the sweet smell of rich exhaust, the calculated 12.5:1 AFR at
cruise, the 17mpg, the happy ECM doing nothing about it, the cash pouring
out the wallet.  I know it all too well.  I've installed a new O2 sensor,
made no difference.  I've installed a dedicated ground line from O2 to head
ground, absolutely no difference.  Headers vs. manifolds, no change,
although headers may have made it worse, but virtually undetectable.  My
take on this is the cam overlap allows more air to escape while the exhaust
valve is still open.  This "fools" the O2 into seeing a false lean condition
and adds fuel, hence the advertised "computer-friendly" cams.  Doesn't
matter what you do to adjust the BLMs, its all a game.  The O2 fights back
to where you were.  Sounds like the thing to do is force open loop condition
(don't know how) and tune fuel until it's right, just to see what's going
on.  Problem is, hook up the O2 and you're back to square one.  Hence, I've
been attempting to build the wideband circuitry.  Now if only I had the
sensor...

Be interested in seeing how you make out.  I might be able to learn a bit.

Steve (my opinions count very little, since I too am a newbie, albeit with 1
year of experience.  Long road ahead.)

-----Original Message-----
From: Drew Skinner [mailto:drew.skinner at lcra.org]
Sent: Wednesday, January 17, 2001 2:26 PM
To: gmecm at diy-efi.org
Subject: Re: Questions from a newbie


Yep, been there done that, it made things worse. Like I said for some reason
the ECM is dumping in fuel thinking that things are lean when they aren't.
Dunno why but the INT and BLM values don't seem to jive with what's actually
going on. I've read tuning tips multiple times now and lately I've been
trying to understand the anht_hac.

Anybody know of a way to test an 02?

Thanks!
Drew

>>> xybertron at cox-internet.com 01/17 12:33 PM >>>
You take the BLM and divide it by 128.  If it is say 150 then you multiply
the VE by 1.17 so the VE goes up because you are lean and need more fuel.
If the BLM is 100 then you multiply the VE by 0.78125 since you are running
rich and want less fuel.  Following now?


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