gm dis timing problems

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gm dis timing problems

Postby Chevyalltheway95 » Tue Dec 19, 2017 2:15 am

I have a gm 3400 run by a ms v3.57 and while attempting to set offset via trigger wizard my timing appears to be way off and dosent seem to respond to any changes. I do not currently have the bypass wire run to a relay yet but I would think that I should still see timing response. also I noticed that the spark cut rev limiter and launch control do not work but I can get it to fuel cut only. any help or advice would be appreciated
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Chevyalltheway95
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Re: gm dis timing problems

Postby Chevyalltheway95 » Tue Dec 19, 2017 11:14 am

i have seen conflicting information between what others running dis and the write-ups in the ms manual have as far as settings and the use of the bypass relay so i probed my bypass wire that i have run straight to the icm and got a reading of 2v so would using this wire to trigger a relay to pull 5v from the tps fix my problem?
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Re: gm dis timing problems

Postby Matt Cramer » Wed Dec 20, 2017 10:26 am

If the bypass pin isn't getting 5 volts, it's going to stay locked at default timing and no MS2 settings changes will move the timing.
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Re: gm dis timing problems

Postby Chevyalltheway95 » Wed Dec 20, 2017 11:42 am

Ok so after I put the bypass on a relay can you tell me if my settings are correct as far as the ignition capture and trigger? I have seen a few sources with different settings
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Re: gm dis timing problems

Postby Matt Cramer » Thu Dec 21, 2017 6:59 am

It depends - how exactly is the board hardware configured for CKP input and spark output?
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Re: gm dis timing problems

Postby Chevyalltheway95 » Thu Dec 21, 2017 9:05 am

The only modification I made to the board was the launch control circuit
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Re: gm dis timing problems

Postby Six_Shooter » Sat Dec 23, 2017 10:57 pm

I haven't looked at your MSQ, because I haven't figured out any easy way to look at other's MSQs without modifying an existing project or starting a new one...

Anyway, You need to use "same cylinder timing" meaning 50* or greater in the "Trigger Angle/Offset" box. IIRC mine is set to around 60 degrees, which is pretty close to what the OEM sets this same setting to.

I also noticed in my case that using "standard dwell" caused misfires at high RPM and when in boost. Using fixed duty cycle at 50% fixed the issue.

As stated, without 5V being applied to the bypass wire, the module will stay in base timing mode and no changes in the ECM will make a change to actual timing. I prefer the method described in the manual for HEI ignition (signals are virtually identical between HEI dizzy and GM OBD1 DIS, save for the timing of the ESC signal). where the 5V is triggered from the ECM above the start RPM., default is 600 RPM, I change it to 400 RPM, mostly because again, this is the factory setting for this in the Delco ECMs, but this also keeps the ECU from going into start up mode, even when the engine drops fairly low in RPM. The rest is just like the HEI setup.
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