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Re: Tuning 7747
Poor mileage can result from too lean of a fuel curve as well as too
rich... You are getting alot less fuel than you need, so the throttles are
open a lot more for said condition, but power is way down from what it
could be...
O2's of 750mV to 850mV aren't necessarily safe... I had a 3800 V6 that
below 900mV would buck, surge and detonate even on 93 octane.
At 05:08 PM 09/18/2000, you wrote:
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.
===========================================================
David Cooley N5XMT Internet: N5XMT@triad.rr.com
Packet: N5XMT@KQ4LO.#INT.NC.USA.NA T.A.P.R. Member #7068
I am Pentium of Borg... Division is Futile!
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