~5K Sync loss with no reason

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planet6racing
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~5K Sync loss with no reason

Post by planet6racing »

Hello:

I am sure this has been covered before, but my search-fu is not finding it.

I am running into a "rev limit" at about 5K on my MS3X installation. Composite logger shows sync loss, but Megalogviewer only shows code 51 - GM7X. No other reason for loss. I am using the Dual VR2.1 signal conditioner from JBPerf and have turned the pots 8 turns CCW, then 3 turns CW (note: 3.57 board).

Composite log is attached along with MSQ file.
racingmini_mtl
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Re: ~5K Sync loss with no reason

Post by racingmini_mtl »

Where have you connected the dual VR board inputs and outputs? With it, you should have simply bypassed the on-board circuit so the pots position should be totally irrelevant.

Jean
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billr
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Re: ~5K Sync loss with no reason

Post by billr »

I gotta ask... this is an S-series Satrun, correct? Aren't those crank sensors VR, not Hall? The talk about going full CCW, then back 3-turns CW relates to Hall, as I recall. With Jean's board in there it is probably a moot point, but Jean may be able to help you better if it is clear what type crank sensor you are using.
planet6racing
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Re: ~5K Sync loss with no reason

Post by planet6racing »

Yes, VR sensor and the old Saturn again.

The input for the VR Conditioner is from middle pin of JP1 (pulling from standard input to board) and negative is connected to pin 3 of the DB37 connector. Output goes to pin 4 of J1. Power and ground are pulled from the spare 5V and ground on the board (S5 and SG).

I believed the pot position to be irrelevant, but put them in about the middle. I noted it in my comments in case I was in error. (BTW, Jean, I hope you are feeling better.)

I am also attaching my megalog - taken at the same time as the composite logger. Any insight as to how to resolve this is welcome. I am confused about the sync loss - why is it occurring without an error code?

Thank you.
racingmini_mtl
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Re: ~5K Sync loss with no reason

Post by racingmini_mtl »

Those connections are as they should be for a V3.57 board. And the pot positions are inconsequential.

What you should try is to use a shunt resistor; put a 10k resistor between VR+ and VR-. That is a common issue and that's the easiest solution. You may need to go to a lower value if you still can't rev up to your RPM limit but try to keep the resistor within the 1k to 10k range. A value that is too low may affect low RPM operation.

Jean
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planet6racing
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Re: ~5K Sync loss with no reason

Post by planet6racing »

Understood - 10K shunt resistor between VR+ and VR-. May be able to decrease from 10K, but best place to start.

Thank you!
hardline
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Re: ~5K Sync loss with no reason

Post by hardline »

This is such a common thing, that when I build MS kits for users that use VR sensors, I install a shunt resistor(s, if using cam as well) on the board during assembly.
2000 ZX2 : Sequential COP, MS3 + MS3X + TinyIOx, PWM Returnless Fuel, Flex Fuel, Variable Geometry Intake Manifold, Garrett GTX2863R .82AR housing @ 15 psi
planet6racing
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Re: ~5K Sync loss with no reason

Post by planet6racing »

Just as a report back - this seems to have solved the problem. I was able to rev to 6K freely once. Then, bad things happened inside the engine...

Once the engine issue is resolved, I'll add more to this thread if there are further questions/problems.
billr
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Re: ~5K Sync loss with no reason

Post by billr »

Would you be willing to explain those "bad things" in the "Extra Pits" forum? I have three early DOHC S-series (none with MS) and am always curious of what may go wrong
planet6racing
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Re: ~5K Sync loss with no reason

Post by planet6racing »

Bad things were not so bad. Adjustable cam sprockets decided to auto-adjust. Bolts that held position backed off and were hitting side cover, giving sounds of bad things. Problems resolved (replaced adjustable with stock sprockets) and engine almost ready to be re-installed. Should be back up and running this weekend.
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