7747 tuning again

[rr]

As for the VE tables, what I did was to put 20% at all locations of the
extended table (the 400 to 6300 rpm tbl). Then do the drivability stuff
in the low speed table ( the 400 to 3200 rpm tbl). Once that is done,
the extended table can be used to lower the VE at the > 3200 rpms
area (the VE typically starts dropping after 2400-3000 rpm or so).

Remember, with 20% in the extended table, 80% is the max for
the low speed table.

Unlike a carb, the fuel pressure on efi is critical. A changing fuel
pressure will affect delivery volume.

Would probably be a good idea to get the ecm into the pass compartment,
away from heat and ign noise.

BobR.


WEG1192 at aol.com wrote:

> I re-checked my fuel pressure and I apparently misread the gauge. I only have
> 15 PSIG and it dips about 1/2 a PSI when I blip the throttle. I tried to
> check it on the road with a long fuel line but the hood pinches off the line
> when I close it.
>
> I did another run this afternoon and on a whim, I changed the BPW constant
> from 140 to 160. Well, now I have BLMs down around 108 to 120 with the exact
> same fuel tables as before. Integrator numbers hovered around 128 the whole
> time. I drove 47 miles with about 30 of those miles at 70 MPH, and the other
> 17 at around 55 to 60. I got a whopping 15.1 MPG. I topped off the tank
> before and after the trip to get the gallons used. I also checked the MPG on
> a previous tuning run where I did some fairly heavy accelerating to check my
> WOT O2 volts and I got 10.5 MPG. I also had drained some of the fuel into a
> reserve tank when I checked the return line for back pressure to see if it
> was keeping my F/P high. I think this is pretty good for a 4x4 5000 lb. truck
> with full time FWD.
>
> But now I have to ask, Should I back out my fuel tables to where I just hit
> the 255 maximums, i.e. reduce the VE in both tables so that I have the same 0
> to 255 numbers that I do now, but with greater resolution in the lower part
> of the tables. Since I pushed all the numbers way above 255 and was getting
> some major clipping, I think I could regain some fuel preciseness on the
> lower end by reducing all the numbers back down to where the clipping just
> starts to occur. Overall, I'm pleased with the results, just trying to make
> sense of where I am so I can duplicate results on other AMC 360 engines.
>
> One last thing, I noticed a random skip at about 70 MPH coming back. When it
> started to skip, I noticed my scantool randomly reporting engine speeds
> around 5000 RPM. Is this possibly due to having the ECM mounted in the heat
> of the engine bay? Or rather am I getting some EMI from the GM ignition
> module mounted only inches from the ECM? I have noticed the skip before after
> the engine has been running for a while. The BLMs were right on the money and
> nothing else seemed out of the ordinary.
> ----------------------------------------------------------------------------
>

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