Questions from a newbie

[Dan Townsend]

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?

Dan

----- Original Message -----
From: "Drew Skinner" <drew.skinner at lcra.org>
To: <gmecm at diy-efi.org>
Sent: Wednesday, January 17, 2001 8:20 AM
Subject: Re: Questions from a newbie


> Yeah, that's what got me thinking that I had a vacuum leak. My stock VE
along with the cam netted some 4-5ms pulsewidths at idle, which had me
changing fuel soaked plugs every week and not odriving the car for fear of
washing out rings and ther nasty things. After reading Bruce's tuning tips
and prog101, I tried the old take %error in BLM and multiply VE and that
made everything much worse (~6-7ms PW) so I went the other way with VE.
>
> My stock programming at 40-50KPA and 750 or so rpm had the ECM looking at
VEs in the mid-high 60%, so I cut that back little by little and the idle
PWs have come down to 2.0-2.4ms. I'm kinda at a loss, because this is
obviously the opposite of what the ECM seems to want, but the engine is much
happier. People (tuners) I have talked to with bigger cams and such have
mentioned that at low rpm (idle) larger cams with lots of overlap are less
efficient and therefore require less fuel or VE in the table. Looking at
Bruce's VE table for the crossfire stuff I'm thinking I'm on the right
track, I tried building a table closer to his and the car wouldn't idle. So
I think I've found the two extremes and just need more iterations to get it
right. As it is I haven't touched the upper VE table so the car hesitates as
it crosses the magical 1600rpm limit into the other VE table and PWs jump up
about 1.5ms or so.
>
> Does this logic sound completely screwy or does it seem like I'm doing
alright here?
>
> Drew (waiting for the king sized CSH)
> '89 IROC
>
> >>> RRauscher at nni.com 01/16 6:51 PM >>>
>
> Drew,
>
> You mentioned trying to lean the VE table down, maybe a typo, but high
BLMs
> would be adding fuel. A 40-45 Kpa idle sounds good, about 16" vac. With a
> 224 @ .050 & .465" lift, 108 LDA, runs about 50-55 Kpa in a 327.
>
> BobR.

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