New Tuner Sync Loss Issue

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carmaniac37
MS/Extra Newbie
Posts: 34
Joined: Tue Oct 14, 2014 8:23 pm

New Tuner Sync Loss Issue

Post by carmaniac37 »

Hello MSExtra members,

My Megasquirt project is on a 3.2L twin cam M104 straight six Mercedes engine swapped into a 1991 Mercedes 190e. I have MS3X running version 1.3.2 with a 60-2 VR trigger wheel setup, a single tooth VR Cam, six injectors, and three high current coil packs with shared cylinders driven by three of the four outputs on the DIY Autotune Quadspark. The shared cylinders coil pack is the factory Mercedes setup and the theory behind it has been confirmed in my head. The coils are paired so that when one fires on a power stroke, the paired cylinder is exhausting.

My sync loss (reason 2) occurs at almost exactly 5600 rpm every time. I have a rev limiter set at 6200 and disabling that has no effect. The sync loss occurs irrespective of throttle position. With the cam input enabled, the engine would stutter above 4000 rpm then die out at 5600. With the cam disabled, it climbs normally then dies abruptly at 5600. From what I've read so far, there's potential in adjusting the pots on the mainboard, reversed polarity, and interference. Adding a resistor is for Hall sensors only right? I don't think it would be interference, the VR sensor is wired with a grounded shield twisted pair of wires from sensor to ECU. The wheel is clean and the mounting bracket is sturdy. I'd love to know what you all think is going on.

I've attached my tune file, a data log of the sync loss, and the sync error logger file from tunerstudio. I'm all ears, thanks in advance.
93supercoupe
Master MS/Extra'er
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Location: New Haven, Ct, USA

Re: New Tuner Sync Loss Issue

Post by 93supercoupe »

get a tooth log of the situation.

But wiring in a resistor also works for VR's. I recently had an issue where i was losing sync (reason 2) on my VR 60-2 wheel and using a 15k inline resistor on the VR positive leg completely cleared it up.
BootlegTuned
carmaniac37
MS/Extra Newbie
Posts: 34
Joined: Tue Oct 14, 2014 8:23 pm

Re: New Tuner Sync Loss Issue

Post by carmaniac37 »

Here's a tooth log for it. Sync loss occurs at row 1721.

I tried wiring in a resistor on the VR Positive. I used a 15.8K ohm resistor as the store was out of 15K. All that did was make it difficult to start, not idle properly, and sputter at higher rpm, still didn't make it past 5600. Should I try again with a smaller resistor? Does adjusting the pots on the MS3 mainboard have any affect?

In the interest of learning, what sort of things do you guys look for in these logs? I know there's a huge number of variables but what are some of the common indicators?
billr
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Location: Walnut Creek, Calif. USA

Re: New Tuner Sync Loss Issue

Post by billr »

How are the mainboard pots adjusted now? Those should be fully CCW for a VR sensor, at least to begin with. Did you build the mainboard, are you sure those pots aren't installed backwards? Post a "tooth time" log.
carmaniac37
MS/Extra Newbie
Posts: 34
Joined: Tue Oct 14, 2014 8:23 pm

Re: New Tuner Sync Loss Issue

Post by carmaniac37 »

I assembled the mainboard, the pots are definitely in the correct orientation and are adjusted fully CCW as described in the manual.
Those should be fully CCW for a VR sensor, at least to begin with.
So I'm past beginning, what sort of adjustment can I do now?

Also did I not already post a tooth time log? If not, what's the difference between that and what I did already posted.

Thanks for the input.
carmaniac37
MS/Extra Newbie
Posts: 34
Joined: Tue Oct 14, 2014 8:23 pm

Re: New Tuner Sync Loss Issue

Post by carmaniac37 »

I just realized that I'm also getting sync loss at startup. Every time I crank it, it revs to about 700 stutters quickly then fires up normally and will give zero issues unless I hit 5600 rpm. It starts like a super cammy V8. Sounds like this:
*clears throat*
"Crank Crank Crank Crank vraaahVROOOOOOMMMMMmmmmmmmmmmmm... then it's good.
Stutter happens at the lower case h.

Any more thoughts on this?
Matt Cramer
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Re: New Tuner Sync Loss Issue

Post by Matt Cramer »

Can the starting issues be data logged?
Matt Cramer -1966 Dodge Dart slant six running on MS3X
carmaniac37
MS/Extra Newbie
Posts: 34
Joined: Tue Oct 14, 2014 8:23 pm

Re: New Tuner Sync Loss Issue

Post by carmaniac37 »

Here's a few more documents. There's a datalog and a composite tooth log of the startup. There's also a tooth count log of a rev up to 5600.
Matt Cramer
Super MS/Extra'er
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Joined: Thu Apr 16, 2009 8:08 pm

Re: New Tuner Sync Loss Issue

Post by Matt Cramer »

A tooth log is a bit easier to read than a composite log for 60-2 wheels. But you may be able to adjust the VR trim pots to help.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
carmaniac37
MS/Extra Newbie
Posts: 34
Joined: Tue Oct 14, 2014 8:23 pm

Re: New Tuner Sync Loss Issue

Post by carmaniac37 »

Solved! VR Sensor Polarity was reversed. Works properly now. Thanks for the help.
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