A '747 for ignition only (tested)

[Bruce Plecan]

-----Original Message-----
From: rr <RRauscher at nni.com>
To: diy_efi at esl.eng.ohio-state.edu <diy_efi at esl.eng.ohio-state.edu>
Date: Friday, March 26, 1999 4:42 PM
Subject: Re: A '747 for ignition only (tested)

If ya wouldn't mind, I'd like a copy of the bin, just incase someone tries
this.
I was concerned that it would have been in limp home mode.
Interesting, that it works that well.
Bruce   nacelp at bright.net


>OK, back from the test drive. Quick re-cap: I'm trying a complete
>'747 ECM/sensor/distributor system, minus the TBI in a small block
>chevy. This is a hot-rodded setup: headers, duals, cam, al. heads,
>cold air, gears, all the stuff to go fast. Oh, I'm using a Carter
>625CFM AFB carb, aftermarket, on an Edelbrock Perf. RPM manifold.
>
>The other thing is, that this is a first for the entire system. It
>has been installed over the last 4 months, and first fired up today.
>It started with the first click of the key, the grin on my mug gives
>that away. (I'm still smiling).
>
>I used an 8-in-1 EPROM that I can switch between programs. This I
>was able to do without shutting off the engine. (a '256Kb prom, with
>eight dip switch selected banks).
>
>I burned in 3 different programs, with just the timing tables changed
>between them. One table is what B.P. used in one of his vehicles, the
>other two being what a centrifugal advance distributor would be like.
>One of which has 6deg more timing, across the board, than the other. I
>set the intial advance to 6deg, and the warm bias in the prom to the
>same. Cold bias to 12deg. It hot cranks just fine, this is good.
>
>The timing table is along the lines of: 14 initial, 36 total, in by
>3200 RPM. The other table has 6 deg more across the board. This table
>did give some knock counts, but without a feeling of lost power. The
>knock filter I used is from a 4.3L Astro van, as the bore size matches
>(4"). I have one from a 305 to try, but that is a smaller bore engine.
>
>The engine runs as good as, or better than it did with the electronic
>distributor and CDI ignition. Under WOT, the power was good. I don't
>have a performance measuring device (well, my butt), but I'll do
>something here soon.
>
>B.P.'s table was interesting, it was lazy at low engine speeds, and
>came on with a bang. Our cams are two differents beasts anyway. I'm
>running an Isky 280 Mega cam: 224deg @ .050, .465 lift, 108deg LDA.
>That and I'm running a 5-spd, while B.P. has an auto.
>
>Oddly, I am getting a trouble code 33, MAP sensor high. This might be
>due to the battery being shot, and a reset occuring during crank. I
>do know that the ALDL scanner resets at crank. I'm not too worried
>about it. (might also be an interaction of the TPS, which isn't moving).
>
>The system does go into closed loop and learn mode. Along with the
>INT and BLM moving. It even sees cross-counts, as the carb is fairly
>well tuned. But, this doesn't seem to have any effect on the system as
>it's now being used. The VSS is reporting correct mph, along with
>the map at 57.5-60KPa at idle. The ECM even reports that I've hit
>the A/C switch. Man this is great.
>
>It has a better cold idle than the orig system. I have no choke on
>the carb, but additional advance occurs during warm up, due to the
>ECM control.
>
>I made other minor changes to the prom maps, as far as knock retard
>degrees and PE mode.  For the above testing, I disabled the error
>codes for the O2 sensor and TPS.
>
>Sometime down the road, I'll get the TBI on it, along with the
>high pressure fuel system.
>
>Well, in closing, I'm going to leave the system like this for a
>while, and do some futher testing. If anyone has any ideas or
>requests, let me know...
>
>BobR.
>
>--
>