Megasquirt Support Forum (MSEXTRA)

Hi all,

While trying to get traction control working I've come across a sync loss problem. The car has been running the MS3 for a couple of years, I have not had a drama with sync since the early days.

To simplify the problem, I've disabled Traction control for now. What happens is that when I give it a boot and it bounces off the rev limiter (8000 with 200 RPM hysteresis) , the engine pops a few times (which is expected) but I get a bunch of sync loss, reason 17 and reason 11, the CEL starts flashing 8 flashes at me. The engine runs fine otherwise. With TC enabled, i think the cutting of spark had the same effect, sync loss.

A composite log is attached. The CAS is a standard Mazda Nippondenso 12/1 or 24/2 dual wheel item. Around 7300mSecs an additional spike of the secondary wheel is present for a period of time, 4 teeth into the 12 teeth cycle there is an additional secondary wheel detection.

I am currently running FW1.4.1. The problem was first noticed on FW1.5a4 so I rolled back and the problem persisted.

My next thoughts would be to adjust the VR sensor trim pot for that wheel, or to look at the software noise filtering though I'd rather solve the issue rather than filter it out.

Any advice on how to remove the trigger problem would be very much appreciated.

Misfires can cause noise from the ignition system. How are you powering and grounding the system?

get a jbperf vr board and forget about sync losses.

JBPerf board is interesting. Can I retro fit the internal version inside the case, replacing both the MS3 mainboard and MS3X VR circuits without adding extra wires to the loom or extra pins to the plug?

For the wiring, when the MS was installed the engine bay received a full rewire incorporating the MS3 and 3X looms, with a new power block, new battery cables, new grounding setup.

I have a relay dedicated to the MS3, and a relay dedicated to the fuel pump. I've implemented the signal ground and power ground concepts. The coils are LS2 non-truck d514, and have a signal and power ground.

It's going to be a difficult problem to resolve! What about dropping in a 3.57 main board? It has different VR circuits I think

This solved all my sync-loss issues on my 13BT: http://fullfunctioneng.com/product/fc-mag/
I made an extension harness from the existing CAS wiring to the trigger pickup and it also reuses the VR1 circuit and inputs on the V3 board. It required virtually no mechanical work and made a noticeable difference in how the car ran. There are some interesting videos on youtube showing back-to-back comparison of the timing “walking” with OEM trigger and staying dead on the timing marks with the FFE kit.

arran wrote:JBPerf board is interesting. Can I retro fit the internal version inside the case, replacing both the MS3 mainboard and MS3X VR circuits without adding extra wires to the loom or extra pins to the plug?

For the wiring, when the MS was installed the engine bay received a full rewire incorporating the MS3 and 3X looms, with a new power block, new battery cables, new grounding setup.

I have a relay dedicated to the MS3, and a relay dedicated to the fuel pump. I've implemented the signal ground and power ground concepts. The coils are LS2 non-truck d514, and have a signal and power ground.

It's going to be a difficult problem to resolve! What about dropping in a 3.57 main board? It has different VR circuits I think

Where exactly is everything grounded? Engine? Battery? Chassis? Can you outline where everything goes?

Ken

Thanks for taking the time.

The main ground point is the Chassis rail on the left hand side of the car. The ground wire from battery negative goes to this point, and there is a 30cm length over to the engine block.

The numerous Megasquirt ground wires run from the Megasquirt to the chassis ground.

The signal ground runs from the engine bay (picks up the ground of a number of sensors), into the cabin (picks up another ground or two) into the Megasquirt. Fairly wild picture to illustrate

OK, most likley this is causing you issues. You want the MS and most everything else to go straight to the battery if possible. If not then at least ground the MS to the engine.

Thanks again, changing the grounding scheme to converge at the battery is not an easy thing to change.

I based my grounding design on MS recommendations. The attached pictures are an excerpt from the current v4 manual. It shows the main grounding point to be at engine block. This is how my setup has been configured, with the small deviation that there is 30cm of gauge 0 wire between the chassis and the engine block which from my understanding didn't seem like an issue. It does not say to go back to the battery. I guess I'm a little confused here, because if the manual did say to go back to battery I certainly would have done that.

If I was getting a sync loss problem at engine start, I would be thinking that there is possibly noise being injected due to volt drop on the ground wires. With the car already running, assuming that the alternator is of sufficient capacity to run the car without drawing from the battery (which it is) the power earth circuit for the coils will be from alternator body, through the engine block, across that short gauge 0 wire to chassis. The coils are earthed to the same chassis point. I think as a test without upsetting the wiring too much, I could reroute the chassis earth point to the block, and then the gauge 0 link will be back to chassis. This would take the 30cm of gauge 0 wire out of the equation. However, because of the thought process around the ground path and circumstances it just seems to be a low likelihood of success.

Grounding to the body/chassis has never been recommended.

James

Thanks, not sure I said it was

arran wrote:Thanks, not sure I said it was

But you still grounded to the chassis.

Yes, I did, because it was neater and I have not built a junker. I did so based on the logic I described above.

I've been out of town for work this week and am back home tonight. Taking a look under the bonnet I can swap over the way it's grounded without too much trouble. I'll eat humble pie if it fixes the problem, which is the name of the game here and I do appreciate the advice.

Another possibility is the spark plugs.
Also how about the V3.57 board? Understand that may be a tricky question to answer for commercial reasons

I don't normally drive around bouncing off the limiter, I have however done so in the past months/years and it has not cause a sync loss problem until recently. I have the perception that the behavior wasn't so harsh in the past. The rev limiter seems to be much harsher than it used to be. I have not changed the rev limiter settings for over a year, is there anything that has changed in the software that has uncovered this problem with my car?

Shaniac, missed your post,I'll take a look

What method are you using for traction control? Just spark cut or cut and retard?
Spark cut traction control alone will be much more violent than rev limiter with soft cut. Are you saying that your limiter without traction interfering is also more harsh?

You mention spark plugs, are you using OEM NGKs?
If you're using an aftermarket plug without a resistor that probably isn't helping. I've had good luck with NGK BR10EG plugs. They're a colder heat range but have a resistor and are gapable. Closing the cap to around 0.025" also cleaned up my spark some because it prevented misfires under boost.

I'm running AC, so there is another pulley to contend with and the compressor sits where the sensor mounting bracket is designed to be positioned unfortunately.
Where/when was the sync loss happening on your engine?

shainiac wrote:This solved all my sync-loss issues on my 13BT: http://fullfunctioneng.com/product/fc-mag/
I made an extension harness from the existing CAS wiring to the trigger pickup and it also reuses the VR1 circuit and inputs on the V3 board. It required virtually no mechanical work and made a noticeable difference in how the car ran. There are some interesting videos on youtube showing back-to-back comparison of the timing “walking” with OEM trigger and staying dead on the timing marks with the FFE kit.

I was getting sync loss on cranking (probably a tired starter motor) and between 3-4000rpm, usually on heavy tip-in.

For the moment I've disabled traction control, I first noticed the problem with TC, but can make the problem happen under rev limiter so that is what I'm testing with. The aggressive limiter I have referred to is rev limiter spark cut.

Plugs are NGK B9EGV x 4, they are non-resistor, been running them for 10 years. However since I fixed the sync loss I had shortly after getting the car on the road under MS power a couple of years ago, the ignition system has been faultless. I haven't changed anything (except try to get TC to work which I've since disabled), and have developed a sync loss problem.

shainiac wrote:What method are you using for traction control? Just spark cut or cut and retard?
Spark cut traction control alone will be much more violent than rev limiter with soft cut. Are you saying that your limiter without traction interfering is also more harsh?

You mention spark plugs, are you using OEM NGKs?
If you're using an aftermarket plug without a resistor that probably isn't helping. I've had good luck with NGK BR10EG plugs. They're a colder heat range but have a resistor and are gapable. Closing the cap to around 0.025" also cleaned up my spark some because it prevented misfires under boost.

That will be a situation more prone to ground noise for two reasons:
1) your wiring is drawing heavy current so volt drop will become a factor
2) with a VR circuit slow engine speeds result in a generated lower voltage, a given noise level will result in a lower Signal to Noise ratio at low RPM compared to higher RPM.

shainiac wrote:I was getting sync loss on cranking (probably a tired starter motor) and between 3-4000rpm, usually on heavy tip-in.

It might be worth putting new plugs in and increasing the soft limiter dead band from 200 to 3-400 rpm. I had my soft limiter set at 7500 and very retarded and hard cut at 8000 and cannot recall ever hearing spark cut. Preventing misfires may help.

Today I had a chance for just a short drive. I turned the rev limit down to 6000 to see if the problem would surface without needing to wind the rpm all the way out to 8000.

Sync loss would not occur with a 6000 rpm limit.