Tuning 7747

[Carl Summers]

Hi,
   Since it seems you have enough fuel at WOT, I am wondering if you have an
egr??? If you don't and don't have it disabled in the .bin this will lean
out the engine tremendously at part throttle...hth's
-Carl Summers




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-----Original Message-----
From: owner-gmecm at diy-efi.org [mailto:owner-gmecm at diy-efi.org]On Behalf
Of WEG1192 at aol.com
Sent: Monday, September 18, 2000 2:09 PM
To: gmecm at diy-efi.org
Subject: Re: Tuning 7747


Tuning my first 7747 based system. I put a GM 5.7L TBI and GM 7747 on a Jeep
360. Would hardly run at first until BLMs had done some major corrections by
adding a lot of fuel. I have probably added over 40% to all values of the
MAP
vs. RPM VE table. At this point, all VE values above 50 KPa and 1200 RPM are
over 61 when they were initially down around 40. I read in Bruce's Prog 101
that the VE adder and the VE table values can't add up to more than 100%,
otherwise the VE will be clipped at 100. Does this mean that any VE values I
program over 61 are clipped at 61? I guess I don't understand the VE adder
table. I zeroed this table out to see if it was PE mode only and the engine
stalled so I guess its full time. Do I need to lower the VE adder table and
compensate in the main fuel table? All my BLMs are still in the 150-160
range
at all cruise loads and I reset the BLMs to 128 before each tuning run. It
makes sense that I would have to add a lot of fuel since this truck only
gets
12 MPG compared to a Chevy 5.7L which gets 20+ MPG, but should I have to add
this much? One comforting thing is that I do have 750 to 850 mV O2 at WOT so
I am getting enough fuel. Just don't know where its coming from.

Thanks, and I hope to write up my tuning experiences for all future newbies
for the GMECM site. Maybe it will help and maybe it won't.

JW
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