auxiliary fuel control that modifies factory ECM pulse widths

[Raymond Brantley]

Jason, I'm going to assume your tuning a GM :>) But I am tuning a Vortech'd
speed density Ford Lightning (EEC-IV and EEC-Tuner) and wrestling with the
same problem. My load/VE is 99% around 10lbs of boost. The VE lookup tables
can only go to .999 (based off a stock displacement of 351cid) so it goes
extremely lean under boost. What I am hoping to do is change the engine
displacement multiplier (the Ford code is funky for S/D displacement, long
story) to a larger number in hopes that will equate to a larger displacement
engine. So when the PCM references the VE table and calculates airflow at
99% VE for a 451 (or whatever, I haven't calculated what CID a 351 at 10lbs is)
pulsewidths will be longer. I may be waaaay off and I hope the more
experienced on the list will comment :>)

The easy way is to edit the fuel tables (heavily), but I really want to see
if I can do it via engine displacement.


Thanks,
Raymond




-----Original Message-----
From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
Behalf Of Jason R. Haines
Sent: Thursday, March 22, 2001 7:48 AM
To: diy_efi at diy-efi.org
Subject: Re: auxiliary fuel control that modifies factory ECM pulse
widths



Thanks for the links. The Chipstar system looks like it works like the
Dastek Unichip system someone else posted. Both systems take in the factory
sensors and modify the signals to allow tuning the engine management system
(without having to change the factory tuning). The problem is we already
have calibration capability in the factory ECM so we can make many of those
changes already. The bigger problem is that we are already at basically
100+% VE at 5 volts input for the MAP sensor (the engine we are working on
is a speed density system) so you can't fool the computer into adding any
more fuel than it already is. We need something that goes between the ECM
and the injectors and increases the duty cycle based on auxiliary inputs (in
our case a boost or 3 bar MAP input).

I spoke with a Dastek distributor and the Unichip can do what we need but
because we are running a V8 sequential system we would need 8 of their
devices (they claim to use them between the ECM and the injector on single
injector TBI applications).

Jason


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