A '747 for ignition only (tested)

[rr]

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.

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