The Val

[Lawso]

Hmmm, i would have thought that charge time would be longer than discharge, just thinking of the old points trigger wheels, short discharge, long charge.

It's interesting to hear how the delco controls dwell.

I guess one way to find out would be to apply 5V to the module and see if it opens or closes the circuit to ground?

Just confirmed, 5V - Coil charge, 0v - coil discharge, so it's firing the coil on the trailing edge.

[VL400]

If you measured 5v then your not on the coil output of the module.

The switched coil output is ground switched, goes low to start dwell and goes high to fire the coil. Ignition voltage is on the positive terminal. Were using the old negative wire to trigger the MSD, means we still have module mode for cranking and then the ECU takes over.


EDIT: are you looking at the EST signal from ECU to module? This page shows the EST as you describe and on the bench I see the same thing .. http://www.megamanual.com/ms2/GM_7pinHEI.htm
And the dwell times (when its high) are around 5mS at 1k RPM just like some of the scope caps from testing yesterday.

[vn5000]

[quote="VL400"]
EDIT: With no MSD it runs fine but falls over under full load from just over 4k RPM - made right on 400RWHP at that point.


Did you find out why it was breaking down at such a low rpm , my vn 5.0lt revs to 6000 rpm no worries without breaking down and i using std ing system with a bosch transformer coil ,maybe the coil was fucked.

[VL400]

Revved to 6500rpm fine on the old engine, identical setup in terms of ecu and ignition. But once we went to the stroker it really struggled to get decent spark even after replacing everything. Tried a few coils, standard, msd and ice. Thinking it was spark energy added the msd and giant coil, it improved it but still not right. Have not seen a camira module pushed as hard so was not certain it was spark energy just figured you can never have too much and would hopefully eliminate one thing.

But here we are still with a bloody misfire!

[vn5000]

If your scope images look good at high rpm then maybe itcould be something simple like your rotor button or your posts not lining up .Have you checked at about 25 deg btdc that the rotor lines up to the post.

[Lawso]

Hmmm, as you say, the edge should be ok, I just know I had issues with the same setup. Changed to a Haltech sprint, triggered the MSD direct from the ECU and the ignition problems went away. Still trying to understand why?

As suggested, rotor phasing might be worth looking at, If you have an old dissy cap, you can drill a hole in the cap adjacent to #1cyl and scribe a line down the centre of the rotor button. Should be able to see the rotor with the timing light through the hole with the engine running and adjust the dissy to line up the button with the post.

How do the plugs look? Are they fouling? All cylinders the same? Are the gaps consistant?

Might also be worth running through the rockers and making sure the clearances are ok?

Logging the actual advance may also be useful. The innovate stuff can do it by comparing the ref with the module output?

[VL400]

I dont think rotor phasing is ideal and was another reason to go to a crank trigger. The leading corner of the rotor is just inline with the post at the WOT advance of 34 deg BTDC (and can see the rotor being worn more on this corner than anywhere else). The chrysler cap is fairly small, cant see any evidence of arcing on the trailing edge but could be an issue.

Plugs are ok, will be replacing them for next season as the engine will be out shortly for a freshen up. Gaps are all the same, cant remember what we sent them too at the moment but will check it out. There is a very slight cyl imbalance when looking at plug colour. Its getting a new intake manifold for next season and will actually be port matched this time Injector angles on the new manifold are better too, the current one is a carb job which we added injector bosses to. Injectors were new a few years back and have not been flow checked since then so will suggest doing that to confirm.

Have got an Innovate LMA3 so will log advance next time its running - based on the shitty RPM signal in the TP logs its prob rubbish too.

[vn5000]

I was looking at your log with the spike to 9600 rpm where the rev limitor cut in and switched the inj off.When you think about it the only things that could cause that is a poor reluctor signal or a faulty ign module provided the wiring and ecm are ok.I was reading in that megasquirt link that some people were having problems getting a clean signal out of the after market modules.What is yours ,genuine gm ,and have you tried replacing it.
Also you could make an electronic pulse generator to analyse it properly at high speed without the engine screaming at you or risking out of balance trigger wheels flying off and hiting you .

[VL400]

Have a new module on the way to replace it with (current is a genuine but from a wrecker), hopefully will arrive this week and will test it. Having now tested using a clean reluctor signal its less likely to be the module, as I would have thought that would have shown up in the testing the other day? Will get a scope cap of what the reluctor and ref out looks like with the engine running, its really bad.

I have a simulator that provides a 5v square wave up to 9000RPM and simulates a variety of wheels - 4/6/8 cyl dizzy, 18x/3x, all the GM DIS wheels, missing tooth, toyota etc The dangerous (and very out of balance ) wheel was only for simulating the reluctor and varying the widths of slots and teeth. Not a fan of using it, if the toothed wheel comes flying off its gonna get ugly.

[vn5000]

Maybe both are giving you problems .The pick up sig causing poor rpm signal in your log and the module breaking down causing that big spike in rpm.Maybe when you had the coil connected to module before the msd,because it was under a lot more load than triggering the msd,it caused it to break down easier.Hence the improvement when you connected the msd up.