8 pin HEI Dwell settings

[drholl]

I replaced an old kettering style (points) distributor with a brand new 8 pin HEI distributor. The old car (59) was running great with the Megasquirt controlling fuel and spark except for the points bounce, which would freak out the CPU for a second or two. That's why I decided to switch. Right now I have the reluctor phased at about 10 degrees BTDC. It appears that I have no spark, no squirts and the fuel pump does not cycle on as I crank. So my guess is that during the swap I missed something such as the tach signal or power to the 8 pin module, or the old "just because it's new, doesn't mean it's good". But as I was searching that out, a question arose. When I switched from the points I had a dwell setting in there for dwell 3.5 and a spark of 0.5. What should I put in the "Maximum Dwell Duration (msec)" and the "Maximum Spark Duration (msec)" settings in Megatune with the 8 pin HEI? Zero and Zero?

And Matt, I want to apologize for missing the ignition settings for the 7-8 pin HEI's. That BIG 18 point Bold font just slipped right past these old eyes.

Thanks for the help.
Holl

[Matt Cramer]

If the coil is the same, I'd leave the dwell and max spark duration right where they are. Do you get spark if you remove the B pin?

[drholl]

Do you get spark if you remove the B pin?

See sentence #2. posting.php?mode=reply&f=89&t=39939#
Thanks for the quick response Matt. But, besides not being able to see the 18 point Bold printing at the top of the HEI page for the HEI settings, I also failed to notice the 1K resistor that pulled the points signal high as the points opened. posting.php?mode=reply&f=89&t=39939# I clipped that resistor out and the car fired up so fast, it made my head spin. Wow, that was great news. OK, but... You just knew there was going to be a "but". Anyway, my "points" miss is still there at the same RPM, about 2000 RPM in my case. Just as it was with the points distributor. It just won't rev beyond about 2000 without "popping" (popping back through the TBI) and sputtering (a really unhappy motor). OK, it's only fair for me to tell you what I have. so that you have some idea about the car. MS-2, V-3, 2.886 code in a 1959 Cadillac with really big fins, and a 454 using a '88 - '92 vintage 2 barrel TBI with the two 88 pound injectors. It now has the 8 pin HEI distributor now. The engine has a torque camshaft that will, maybe, reach 4600 – 4800 RPM tops. This car is a heavy cruiser, certainly not a hot rod. It’s my daughters’ car. She loves this car and she cruises. But now with the about 2000 RPM limit it’s unsafe to drive on the highway any faster than 50 MPH or so, tops. With the points controlling the MS-II it popped some if I “woofed” on it. But it would cruise on the highway just fine, at say 70MPH.
Anyway, the dwell was at about 3.5ms with the points. I decided to try shortening the dwell time to 1ms on the ignition settings / dwell for the HEI. Well, the car just barely idled then. It sounded like it did before at 2000, only now at 650 RPM, slower and easier popping. No power and it sounded like it was sometimes missing inconsistently. So I said if shortening the dwell time made it worse, let’s try longer, so I put it up to 8ms. Well, it’s back up to 2000 RPM again before it pops and sputters badly. i.e. 50 MPH, not even 55. With that dwell change it’s leading me to believe it’s something I have set incorrectly in the Megasquirt-II settings that I don’t see.
The popping is like the sound of an engine starving for fuel. Like a lean, cold engine pops back through a carburetor when stepped on. So I tried to “fatten” it up, so the VE table is now rich. I had it, and saved the settings, dialed in for about 16:1 when cruising to get decent mileage. No change, still pops around 2000 RPM. Oh yeah, either D1 or D2 has been removed from the optoisolator circuit, I don’t remember which. I have a short Datalog and the MSQ enclosed. The manual marks show the two pops and there is another at 246, at 346 to 350, I decided to woof on it, and although the TPS was woofed hard the RPMs were about the same 1800-2000RPM. Another pop at 379. A real small one at 390. At around 746 is when I tried 1ms dwell for about 30 seconds in neutral before giving up and going back to 3.5ms to get out of the parking lot. A pop at 846 and suddenly “Zero” RPM, ignition masking probably.
She’s coming back from collage in June, so I’d really like to get this piece of automotive art running properly. I originally set this MS-II up identically to the one in my wife’s 1971 Monte Carlo which runs awesome.

Thanks for the help. it is truely appreciated.
Holl

[drholl]

Well, thought I'd try again. I put both D1 and D2 back into the circuit. Cleaned the board to ensure no solder blobs and I set the megasquirt.ini to max_coil_dwell of 25.5, and then set the "Ignition set-up/dwell" to 25.5 as the module on the 8 pin HEI controls dwell. Richened up the VE by 7 percent to ensure it's not going lean and I got to 2000 - 2200 RPM before the serious popping started. Since I was there already, I woofed on it until I thought the air cleaner would go through the hood. It didn't get any more RPM though, just major popping, even though it was WOT it only get up to @ 2200 RPM in second gear. It just wouldn't go any higher. It did this with points control for the MS-II using the VB921 transistor coil control and now with 8 Pin HEI. Can I use the 8 pin HEI to signal the MS-II and use the VB921 to control the coil? I'm starting to run out of ideas.
Any Ideas, anybody?

Thanks
Holl

Oh yeah, I'll swap out the TBI with another one tomorrow, Friday the 22nd. After I check this forum for any good ideas....

[Matt Cramer]

Well, thought I'd try again. I put both D1 and D2 back into the circuit. Cleaned the board to ensure no solder blobs and I set the megasquirt.ini to max_coil_dwell of 25.5, and then set the "Ignition set-up/dwell" to 25.5 as the module on the 8 pin HEI controls dwell.

Er, most HEI modules I've seen do not control dwell unless the B pin is disconnected. Trying to send it a 50% duty cycle could result in enough dwell to damage the module at low RPM.

[drholl]

Still 2200.

I’m still stuck. The car runs fine, up to 40 MPH, and driving like a little old lady, but after that…
When I first setup this engine it had points as a trigger. At that time, I had a miss with a spike down to zero RPMs around 2200 RPM once in a while. I thought it was the points. So I put in a new 8 pin HEI (8 pin), which also wouldn’t pass 2200 RPM without stumbling, popping and backfiring through the TBI. That was worse than the points! After thinking about that for a while I looked at schematics for the 8 pin and decided I’d use the MS-2 to do my dwell and coil firing. So I used just the cranking (limp home) base 8 pin output to trigger the MS-2. I didn’t use the “V Ref” signal to the 8 pin and didn’t connect the 8 pin coil output to the coil terminal. I used pin 36 from the MS. In other words, I think I turned the 8 pin computer controlled distributor to a 4 pin HEI with locked mechanical and vacuum with the MS doing the spark AND fuel duties. The timing stays spot on when I check it at various RPMs while parked, it reads 25-30 degrees advanced when the trigger wizard says it should. So I believe I have the settings correct to at least run OK. The car is a cruiser, but I cannot have my daughter take it on the open highway as it just doesn’t go faster than about 45 MPH without feeling real funny, it’s just not happy. In my earlier posts I didn’t mention that the 502 Chevy has a medium rise dual plane Edelbrock manifold on it, that’s all that will fit under the hood of this old Caddie.

On the datalog looking at the time from 190 to 196 with a lot of throttle applied (61%) in second gear it gets up to 2200 RPM and just seems to stay at about 22-2300 RPM for five seconds on this datalog. The datalog says it’s running lean but it sure feels like it’s fat (possible misfiring?).
The only odd thing that happens sometimes during these episodes the TRIGGFER+- decrements.
What does TRIGGER+- mean? TRIGGER +- drops like a rock at 192.

Total build recap:
Originally 454 TBI with MS-2 fuel and points to trigger MS-2 from the coil. I wanted to get rid of points as they would be a reliability problem. Ran OK.
Then: 454 TBI with MS-2 fuel and points to trigger MS-2, spark through the VB921. Still had points but they only ran the trigger (no load), pretty good reliability. A miss now and then around 22-2300 RPM, but still not fully reliable.
Then: 454 TBI with MS-2 fuel and 8 pin HEI. Popping, backfiring through the TBI (BIG backfires) and missing around 22-2300 RPM.
Then: 454 TBI with MS-2 fuel and the above referred to 4 pin HEI to trigger MS-2, spark through the VB921. 22-2300 it just runs like it’s sick with a flu. It’s not happy.

Right now, I don’t know if it’s spark or fuel. Although it ran pretty good with just fuel control, except for an occasional miss. Does anyone have any ideas that I haven’t thought of???

This is my third ‘squirted vehicle, but I’m pulling my hair out on this one! The other two were cakewalks. One 454 TBI on a Chevy 350. My first squirted car. I had a couple of issues, but no biggie. Then a port injected 327 Chevy. No problems at all. Gee, I thought I knew what I was doing! Well, this one told me how much I really knew!!!

In advance I want to say “Thanks for the help.”
Holl

[trakkies]

If you've locked the original mechanical and vacuum advance, have you checked the phasing of the rotor arm to cap contacts? With mechanical advance this is always in the correct place as it 'follows' the spark. When you lock things up, it no longer does - and can be difficult to get spot on especially with an 8 cylinder.

The best way to check it to make a hole in the cap big enough to see the rotor/ contact position, and view using a timing light. This will freeze where it is at the actual spark time.

Sorry if you've already done this. I found it critical when I modified a Lucas dizzy for my RV8. But went to EDIS anyway. ;-)

[drholl]

Trakkies,

The best way to check it to make a hole in the cap big enough to see the rotor/ contact position, and view using a timing light. This will freeze where it is at the actual spark time.

I know what you mean by the rotor phasing with the cap as timing advances, set your rotor to full retard when locking the Dizzy so that as timing advances the rotor becomes more in line with the cap terminal.But no, I havn't tried that "YET", the reason is that I "see" the RPM signal drop to "zero" during the "bad time" around 2200 RPMs. But maybe that's just "masking" issues, so I'll limit masking to 1ms and 10%. Thanks that's a good idea of the hole with a timing light.

But here's some interesting news. I fixed it, but only momentarily. I kept looking at the datalog WB-O2-AFR as the problem would occur. Each time the problem occurs the AFR gets unusually noisy. On a guess, I reloaded the WBO2 sensor (LC-1), using the “Tools/Calibrate AFR Tables” and the engine ran beautifully for that datalog. It was great for that datalog marked “Excellent”. And I thought the problem was fixed, I was thrilled! But since I had been messing with the VE for quite some time with the 2200RPM problem, I took the datalog and ran it through MegaLogViewer to quickly move it back into the ballpark. When I did that, and tested the car again the problem reoccurred. So, I ran the “Tools/Calibrate AFR Tables” for the LC-1 again, took it for a drive and the problem was still there (again at 2200 RPM). The "Fail" datalog. I went through my grounds again and made sure all my sensor grounds were on the one “Sensor Ground” wire of my MS-2, so as to avoid noise. Is there something I’m missing for keeping the LC-1 calibration in the MS-2? Can I verify it by looking at the .INI file or some other file? IS this really the solution or just a fluke? Configurator has a “Set” for the LC-1 in the mtcfg file, or is there something else that I’m forgetting?

Thanks for the good ideas and trying to help!
Holl (I know engines, but I don’t do code!)

I also threw in the .msq that these datalogs were based on.

[trakkies]

You could try disabling the WB sensor totally - it isn't essential to decent running. More the icing on the cake.

[drholl]

Cool. What do you do to quit the WB?
Thanks Trakkies.
Holl

[drholl]

well I fell back to the standard 8 pin HEI distributor as I was loading the msq and then the LC-1 afr table and the VB921 got too hot and quit functioning. Too much current through the coil with the key on and the engine off probably. But I have a spare V3 board for another project that I can "borrow" if needed. But with my butchery of the 8 pin HEI into a 4 pin HEI not making any difference at all to my 2200 RPM problem, *I'll just leave the VB921 out and use the 8 pin HEI as it was intended by GM. All my problems started with a cheap 8 pin HEI that I bought. maybe I needed a better one. But EDIS is starting to look good! I really want my kids car to be running well when she comes home from the university for a month.
I also want to thank All who have read and tried to help. Thanks Matt and Thanks Trakkies. I'm an old guy who has been pulling my hair out for three weeks. But I still have more hair!!! The wierd part was when I downloaded the LC-1 tables and the car ran great all day. Then with the adjustment of the VE all it went south again.

Thanks Guys
Holl
I'll keep trying and if I find it, I'll let you know what it was. But I was so sure that the LC-1 tables would have fixed it forever.
If anyone comes up with any more good ideas, just let me know. Thanks

[drholl]

I found the solution.
I'm embarrassed to say this, but a defective relay caused a lowering of the fuel pressure.
If it had been a carb, it would have suddenly starved for fuel. But with EFI it only produced enough fuel for a certain RPM and throttle position. What gave it away was when I put my foot down further and faster it just died. Just like a carb. I finally put a pressure regulator on the line so that I could monitor the pressure while I drove it. Oh, a dead giveaway.

A pressure gauge is now a standard part of my tool kit.

Thanks for the help from all the guys.
Holl