Multiport vs TBI, and DIS conversion.

[Canyonero]

I would say there was no change. I dropped the ALDL spark to zero and burned it, no other changes to the bin. I didn't drive it as far, hence the lower counts.

[robertisaar]

hmm.....

what a pain these old TBI setups are...

i know that to test the knock sensor, the ECM purposely bumps up the advance by 4-8 degrees, and you should see a knock then, but that's it, it shouldn't do it again...

drop the whole table by 5* and see what happens?

[Canyonero]

Think we made some progress. I retarded the whole table by FIFTEEN degrees before I saw any real change in the spark counts. That's where it's at now.

Props to the ECU for making it drivable the way it was. So there must be some issue with my timing scale and/or the harmonic balancer I used, because we checked and re-checked my timing. The light says it's at 10 degrees BTDC. DIS using the crank sensor will take all guesswork out of it, then I should be getting exactly what's in the table. Right?

[robertisaar]

notice any change in power? 15* is a LOT.

and if you're using the XDF i made, it should have the bias built in to the calculation... i think.

[Canyonero]

I didn't really notice any loss of power. I expected some after the first 5 degrees, but I broke the tires loose leaving my driveway, so when I saw it was still knocking a short ways up the highway I pulled over and knocked another 5 degrees off. It still accelerated well up the highway, but was still knocking, so then I dropped the last 5 degrees off. Just by the feel and the reduction in knocking, I think I'm in the ballpark.

What is the bias? There is a Main Spark Table Bias in this XDF, which is at zero.

[robertisaar]

if the bias is zero, then it won't make a difference. if it's anything other than zero, that number gets either added or subtracted from main spark, i forget which.

sounds like it was just WAY too far advanced.

[Canyonero]

So I just need to bring my dizzy timing back by about 12-15 and I should be doing alright. Though I do still intend to switch over to DIS.

[robertisaar]

Though I do still intend to switch over to DIS.

and some MPFI goodness while you're at it?

[Canyonero]

I had MPFI for a time actually, and I hope to go back someday. Maybe on a different Trooper.

My grand plan was to switch the manifold and rewire for a 1227727 ECU. I actually have the wiring and ECU, but getting everything to fit with the new intake was more work than I thought, so I gave up and threw the TBI on there so I could have a truck to drive for winter.

[jwvess00]

Hi there!

To go DIS, you'll need to account for the ~60 degrees offset in timing for the DIS vs. distributor. I think all you need to do is set the base timing value in the chip to -60, but that's both a very old memory, and second-hand (from a source I trust). Other than that, it should be a direct swap. Let me know how this goes, as I have a 3.4V6 coil pack and want to do this once I get a 3.4 for my truck. The 3.4 I had went into the Blazer...

TunerCat supports the '8062. What does the '7747 have that the '8062 doesn't? I would have guessed weird code issues with the '7747 since it was 4.3V6 and V8 only (no 60 degree 6). I guess this means the internal ROM's not getting in the way?

I'd love SFI or MPI, but if I keep TBI I may swap to the 16197427 (1994-1995 4.3V6 trucks/vans) as it's a much better TBI computer.

[Canyonero]

I don't think there is any advantage of the 7747 over the 8062, now that I have an equal xdf to use with it. I'm running on the 8062 now.

I have some question about the BPC/BPW values though, the ECU from my 2.8's 8062 had a BPW that matched up with the 3.1L when I did the math. However the 4.3L's BPW correctly figured out to the correct value for the 4.3L.

I changed the BPW to match the 3.4L displacement w/ 4.3L injectors and my fuel table values seem higher than they should be (near 100 in places), but my BLMs are sitting near 128 so it seems ok. I might switch back to the 7747 just for some further experimentation.

On my multiport setup, I did run a dizzy BIN with DIS by setting the initial advance to 60º, ran fine. I never drove it with that BIN or ECU, was just testing my new wiring harness, ECU, and that BIN. I need to use that harness on something, I put in many hours working on that.

I've never used TunerCat, just TunerPro, WinALDL, and MS Excel.

[robertisaar]

TBI BPC is always weird to me...

[Canyonero]

Ok, I just took my dizzy back to what reads on the scale as about -2 degrees. Let's reset the BIN go for a drive!

[Canyonero]

Well I don't know what to think anymore...

I have DIS installed, and it runs, but knocks worse than it ever did! Nothing I do with the initial advance seems to do anything!

The EST seems to be working, when I open the EST bypass it does what it should. Timing light shows the timing at 4 degrees BTDC, though I don't trust that scale a bit, with the dizzy I had it set at about -2 to run correctly (where it should have been 10). So if 2 ATDC about equals 10 BTDC, then the DIS with EST bypassed is running 16 degrees BTDC.

I can't even find the mark without EST bypassed, it must be hiding just out of my sight. I was only about to find it when I was using the 3/6 coil.

[Fierobsessed]

Look into the 94-95 16197427 computer. I've been working with it, and it is an excellent computer. Its meant for trucks running anything from 4.3L up to 7.4L
It features:
Speed Density (MAP sensor)
Distributor Ignition
Two Injector Control Circuits (Meant for TBI, but might be good for batch fire MPFI)
Full support for electronic 4 Speed transmissions (4L60-E, 4l80-E)
Option switch for Torque converter clutch only transmissions (4L60, TH350)
Single full main VE Table (There is a closed throttle table in addition)
Single full main Spark table (There is a closed throttle table for this too, but its identical)
8192 High speed ALDL Interface
Full Tunerpro and TunerCat support
Hacks and source files are easy to come by.
Super Abundant, Practically every Truck and Van GM made between 94-95 has it, including many 93's and some 96's.

Im probably going to test this ECM out on my 3.4 DOHC Fiero. Since that has DIS and is a Manual, with MPFI, so it is well outside the ECM's intended use, but its so easy to work with, I feel it's worth a shot. I've been using it on my highly modified Van's engine for years and love it. There is nothing complicated about the computer.

jwvess00 beat me to it a couple days ago... missed that.