My notes for 83zxt to MSnS-e on v3 PCB (Hall and VB921)

[Guest 1seymour]

i'm running 2.3ms dwell for running, 4.0 for cranking and 0.1 min discharge. i found this to work by turning down the dwell until the idle started sounding different and then turned it up another 0.2. probably a rough setting but it seems to have solved my issue with the spark cutting yet still runs the engine. i took the car for a drive and my spark cut issue seems to be gone. i kept the rpms under 2500, though, because i still have some more tuning to do.

 

for future reference and since i didn't see it mentioned in the MS docs, i thought i'd mention how i *think* you can use the hei4 with the v3 board. i'm pretty sure you could hook up "top of r26" to ign directly and make sure igbtout is not jumpered to ign. this should let you run pin 36 of the ms harness as the input signal for the hei (rather than the negative side of the coil for use with the vb921). i came to this conclusion because i saw mention that the vb921 uses a 5v signal and i see that moby uses a 5v pullup for the hei input. someone please confirm this and i'll edit as necessary. i'll also try it out (or whatever the solution is), since i wired up the hei 4 i had sitting here last night and seemingly solved my issue without even needing it.

[mobythevan]

i'm running 2.3ms dwell for running, 4.0 for cranking and 0.1 min discharge. i found this to work by turning down the dwell until the idle started sounding different and then turned it up another 0.2. probably a rough setting but it seems to have solved my issue with the spark cutting yet still runs the engine. i took the car for a drive and my spark cut issue seems to be gone. i kept the rpms under 2500, though, because i still have some more tuning to do.

 

what kind of dwell control were you running before when the ignition would not work? for reference

[Guest 1seymour]

3 running, 6 cranking and 0.1 min discharge was the default setting i originally used. the vb921 wasn't getting hot and the coil was warm but not hot.

[z-ya]

Anyone resolve the VB921 overheating problem? I'm testing a customers unit using a stimulator, and a ZX coil. The VB921 will overheat in a matter of 30s or so. I tried adding a ballast resistor, but that will just make it spark a little bit longer. I'm also having reaet problems when the VB921 is connected to the coil. I post any fixes I figure out or find.

[Tony D]

I'm going to mention for no other reason than I saw it above, that I am using CHT on my 260ZT conversion, and scaled it using Easytherm, and it's dead spot-on. Temperature I read there during idle is lower than thermostat housing, but during loaded operation and acceleration is about 10 degrees higher than thermostat housing. So it's seemingly a more sensitive location based on load, which is probably a good thing.

 

If you are having spark issues, and you are using an HEI in any service whatsoever, don't use a cheap one! i had an Autozone Wells part for a while and was disgusted by the spark quality from it. Upgraded to a Pertronix unit and spark quality was dramatically increased. Of course, that upgrade came after the Wells part fried itself after only about a coule weeks of intermittent troubleshooting. After that, the Pertronix unit has functioned flawlessly.

 

On running and then not running. Occasionally the thing gets corrupted. Perhaps the Ms got a static discharge through the box, and the chip got a bit freaked. Have you tried reloading the software and trying it again? I had that issue when I was originally doing the setup. Running fine, then blah baaah blahhh buu buu buu..... Bang my head against the wall for a few weeks then finally reload the program and everything is fine again. ???????

 

just a thought...

[z-ya]

OK, found the problem when I put a scope on the signal (LED14) that is driving the VB921. The signal is inverted from what it should be, so the VB921 is sourcing current at a very high duty cycle through the coil. Yep, that would cause it to get hot. You MUST invert the spark output in Megatune! Go to "Spark => Spark Settings", then change the "Spark Output Inverted" to "yes"

 

Now the VB921 only gets hot if I run the stim at 7000RPM for an extended period. For race applications where the RPMs will be higher for longer periods, an additional heat sink should be fitted to the VB921. For street and drag racers, the standard V3 heat sink is fine.

 

For the dwell settings, I changed the crank dwell to 4mS, and the running dwell to 3mS. Any more than 3mS does not appear to make the spark any hotter (makes the VB921 hot though!). I used a 280ZX coil for this test.

[Tony D]

Scope the Spark Output as well!

Put the thing on a SUN Scope or something and run a lead on one of the plugs to a variable gap ignition tester (like a spark plug with a threaded ground electrode, you can increase the gap without getting zapped.)

 

Watch the flashover peak on the scope till the thing misfires, then try increasing dwell to see if you can reinitiate spark. if it does, repeat.

 

You will eventually find a "diminishing returns" point. I mean, after 60KV, the spark has a tendency to jump dirty plug porcelan, through wires' insulation, from the coil to the "-" terminal on the coil.... You end up having to dielectric every high tension lead you have and continaully look for spark leakage...

 

But you rarely have a misfire problem that is associated with the plug gap!

 

Of course, if it does misfire... then you start seeing all the stuff I mentioned above...

 

BTW, try using a 300ZX Coil (Z31) and be amazed at how sparky they are! On mine, with the pertronix flame thrower HEI, I'm jumping almost 3" of visible blue-white spark that I can see in broad daylight! That coil is HOT! It was after I put that coil in that I found out the PCV hose on the top of the valve cover was made of conductive rubber! Coil wire was "placed in a safe area" and POP POP POP! Was wondering WTF, cranked it again and the POP POP POP was from the coil lead across air to the brand new upper PCV hose I had just installed! Every time it went "POP" when the spark landed it made a little "poof" of smoke rise from the PCV Hose. It was neat as hell, I still show people when they come over, everybody thinks it's cool to see "rubber conducts electricity"! LOL

 

The little poofs of smoke are mighitily impressive as well. 'Dat Sum Spark!'

 

Get it? he he he he he

[trippintl0]

you know, i'm using the autozone HEI module, with stock 280zx coil (can't remember if it is turbo or non-turbo). I haven't really had any problems, and I've driven for hours without it dying or anything, for the last 3 months, but I wonder if I could improve it by using a better quality HEI and a 300zx coil? BTW, is that 300zx non-turbo or turbo coil? or does it matter?

 

 

also, I originally had the same issue with the VB921 running great for a few minutes, then getting weaker and weaker and eventually dying. I decided to just go with HEI at the time.

[z-ya]

trippintl0, I'm not using an HEI module, I am using the VB921 in the Megasquirt to drive the coil directly. You should also have the spark output set to inverted even if you are using the HEI module.

 

Tony, I did have a spark plug connected when I was testing the VB921. I adjusted the dwell until the spark stopped getting brighter with no misfires, and then backed it off just a hair. The plug actually get's hot if you let it run long enough. I let it run at 4000RPM for about 2 hours, and the plug was too hot too touch!

[trippintl0]

Well, i know it says to have the output inverted for the external modules. but strangely enough, mine only works when it is NOT inverted. The way I have it (not-inverted), my car idles fine, runs pretty well, even up to high rpms. It does have occasional 'misses' during idle.

 

When I set spark output to inverted, (and adjust timing compensation) the car will idle erraticly - up to 1200 then down to 600 and so forth. it still revs up OK, but when driving, i can smell LOTS of gas in the exhaust fumes, whereas with the ouput not-inverted, exhaust seems to smell OK...?

 

With spark output not-inverted, i keep the dwell settings on "Fixed Duty-75%" although it seems to run just the same on 50%. With output Inverted, I set the dwell settings to 50% (like it says to), but the car still wasn't running well at all.

[trippintl0]

ok on second thought, i looked again, and it says that for HEI module to control dwell, invert output should NOT be checked. see this pic (ignore the fact that it is also a VR pickup using a second HEI module, and look at the bottom module that drives the coil):

 

[speeder]

I'm beginning a MS 3.0 install using an 83 ZXT distributor. In the several threads dealing with this configuration here no one has mentioned modifying the trigger wheel-to-rotor indexing.

 

Does this mean that in unmodified form (with stock distributor/ oil pump drive indexing) the trigger wheel is already providing the ~ 60 degrees advance necessary?

 

Pretty sure I know the answer but will ask anyway and save the trouble of testing it myself:biggrin: .

 

Thanks.

[Matt Cramer]

Megasquirt does not absolutely need 60 degrees or so of trigger advance; you can also set the trigger angle to 15 degrees or less and it will predict the next interval instead. That's how I'm running it on my Mopar slant six.

 

But you can adjust the '83 turbo distributor far enough to give you 60 degrees of advance.

[z-ya]

I'm not sure you can just turn the distibutor to get more advance. Eventually you will jump to the next post in the distibutor cap, right? From what I have read, using the disty as an input trigger, and a means to distrubte the spark to the appropriate cylinder, limits your timing adjustment range. Your maximum adjustment is determined by the angle of each plug wire post, right?

 

Go with a crank trigger, and direct fire, it is not all that much more work, and you can eliminate the distibutor. Another option is EDIS, which so far is working like a charm on my supercharged L6.

[speeder]

I tried to talk the car owner into a 60-2 crank trigger and COP LS-1 coils but he didn't want to pop for the extra $. I will do that one on a later project.

 

Looking at the ZX distributor installed in the stock configuration at #1 TDC, the offset angle of the trigger window to rotor appears to be very close to 30 (distributor) degrees = ~ 60 crankshaft degrees, with proper rotor - to cap indexing - so all looks good.

 

I'll get the exact number by test and report, but it looks as if others have used a trigger angle of 63-78 with success.

[FoundSoul]

You are definitely correct that Spark Output MUST be inverted when using the VB921 or you will cook it. When DAT240Z sent his cooked unit in the the first time around I found this setting set to NO and the VB921 was therefore cooked, we fixed it and returned it and the second time he sent it in it tested out just fine and the setting was still correct from when we had sent it back, I suspect something else in the install or settings just wasn't right so he hadn't gotten it to pop off for some reason yet (I've seen loaded up plugs make you think the ECU is installed wrong, change the plugs and it fires right off). Carl if you stll need help with the install (not sure where it stands now) maybe I can point you in the direction of someone who can help with it. What area are you in again? I've got connections on both coasts that can help, and possibly in MO as well, if I recall you weren't coastal, don't remember off hand exactly where you were though and I'm not in the office to check at the moment (home with a 4 day old baby girl!).

 

As for everyone else, SPARK OUTPUT MUST BE INVERTED when using a VB921, and Dwell Control must be enabled. Check out the MegaManual (www.megamanual.com) or the MSnS-E manual (http://www.msextra.com/manuals/MS_Extra_Manual_Index.htm) for full info on tuning the dwell, both repeat the need for these settings with the VB921's MANY times for exactly these reasons. People just try to plug them in without reading the manual, burn them up, and then blame the vb921. Granted I know there is alot of reading but the things are rock solid when treated properly and the documentation does show you how to do that.

 

I've also summed up the ignition pieces of 'squirting 82-83 280zxt at http://www.diyautotune.com/tech_articles/how_to_megasquirt_your_280zx_turbo.htm which also mentions this again in the config section since I know alot of people won't read the entire manual.

 

BUT-- that said... please read the whole manual. I know it's long, but this is your baby you're talking about here... this stuff should be fun to read!

[mobythevan]

I'm not sure you can just turn the distibutor to get more advance. Eventually you will jump to the next post in the distibutor cap, right? From what I have read, using the disty as an input trigger, and a means to distrubte the spark to the appropriate cylinder, limits your timing adjustment range. Your maximum adjustment is determined by the angle of each plug wire post, right?

 

This is all true, that is why when you look into an 83 280zx distributor you will notice that the rotor arm has a "wide" wiper to allow more adjustment to be made by a computer, and this also allows the trigger angle to be changed more than a non-efi distributor without spark jumping posts.

[DAT240Z]

Hey Jerry,

I'm still around and still having problems with my unit. I have only had the car running for a week since the installation in may. I have lost spark again I do have injector pulse but that’s it. I could only get the car to run by installing a GM HEI. module when it ran for a week. I'm in Indiana do you know of anyone in the area that can helps I'm willing to composite them.

It's ironic how it was me that asked you build me a box and document the build for us Z guys, and had my friend draw up the relay board diagram to go with the documentation, and seems like everyone can get the cars to run but me . LOL