Cutout at 5600 rpm MS2

[JIMBOkye]

Bit of background... Car '89 325is, stock motor.
MS2 kit from Dederic Motorsport installed because the car was cutting out at 5600 rpm previously and I have eventual plans to go to wasted spark and to eventually supercharge.

At this point I'd say I'm still very new to "tuning".

My previous thread on the 5600 rpm cut out is below:

https://www.r3vlimited.com/board/showthread.php?t=417320

Link to current tune and log (tunerstudio) showing the cutout (car in neutral in driveway):

https://drive.google.com/drive/folders/17KSCj9dYb_ykuQTbvEReqSIdLraiVsg_?usp=sharing

So after installing the MS2, the car was driving fantastically. But then all of a sudden, the cut at 5600 rpm came back! Cuts out every time at about 5600 rpm.

So, looking at the log it looks to me like the car is losing the crank position sensor because the RPM's are all over the place. But the MAP and AFR's are also all over the place (but maybe due to fuel cut...?) Could I be losing multiple sensors at once?

I've changed the Crank Position Sensor 3 times in a year. I feel like that shouldn't be the issue. Looking for some opinions before changing it again.

[m3boost]

Bit of background... Car '89 325is, stock motor.
MS2 kit from Dederic Motorsport installed because the car was cutting out at 5600 rpm previously and I have eventual plans to go to wasted spark and to eventually supercharge.

At this point I'd say I'm still very new to "tuning".

My previous thread on the 5600 rpm cut out is below:

https://www.r3vlimited.com/board/showthread.php?t=417320

Link to current tune and log (tunerstudio) showing the cutout (car in neutral in driveway):

https://drive.google.com/drive/folders/17KSCj9dYb_ykuQTbvEReqSIdLraiVsg_?usp=sharing

So after installing the MS2, the car was driving fantastically. But then all of a sudden, the cut at 5600 rpm came back! Cuts out every time at about 5600 rpm.

So, looking at the log it looks to me like the car is losing the crank position sensor because the RPM's are all over the place. But the MAP and AFR's are also all over the place (but maybe due to fuel cut...?) Could I be losing multiple sensors at once?

I've changed the Crank Position Sensor 3 times in a year. I feel like that shouldn't be the issue. Looking for some opinions before changing it again.

what gap on spark plugs?

[digger]

MS has issues with the crank sensor what is the gap to the toothed wheel?

[JIMBOkye]

To spec in Haynes manual, 0.028"

[JIMBOkye]

0.028" is the plug gap. I'll check the CPS gap again tomorrow. I've read it is supposed to be about 0.040" (anyone confirm?), and it was last I checked (before MS went in).

[Jaxx_]

looking at your log, your issue isn't spark related. It is, as you suspect, crank sensor related. Your log shows error 2, which is "missing tooth wrong time." You should have the crank sensor as close as damn possible. As I recall, it is a 2 wire VR sensor, so closer is generally better(as long as it doesn't rub). I have my M10's install at .030".

It is impossible to tell from this datalog what exactly is causing your sync loss issue. It could be noise related, or a hardware issue. You need to provide a high speed log of sync loss and regular cranking tooth trigger log.

[pazi88]

VR sensors have quite often issues with megasquirt. Grab cherry hall sensor, configure ms2 to use hall sensor and your problems are gone.

[citizen_insane]

Many people are using VR sensors without issue (myself included). Use the high speed crank logger to check, but based on what you're saying, it sounds like a CPS issue.

Have you already opened up your MS2 and turned both the VR regulation pots all the way counter clockwise? If not, do that first and then see if it improves it. If not, take your question to the msextra forums, they're the best people to ask about these kind of detail questions regarding Megasquirt.

[nando]

VR sensors have quite often issues with megasquirt. Grab cherry hall sensor, configure ms2 to use hall sensor and your problems are gone.

yeah, that's just not true. I've run with a VR sensor for 11 years now (MS2 and MS3). It's actually often a misconfiguration (wrong jumpers or settings) or a hardware issue (sensor gap, etc).

[ForcedFirebird]

I put my money on CPS gap, had it happen to me on multiple cars. I just put it as close as you can without rubbing, as mentioned. Rotate the crank so a tooth is at the sensor, push it in until it touches, then back it off ever so slight. The stock ECU doesn't seem to care much.

[pazi88]

yeah, that's just not true. I've run with a VR sensor for 11 years now (MS2 and MS3). It's actually often a misconfiguration (wrong jumpers or settings) or a hardware issue (sensor gap, etc).

I didn't say it's impossible to run vr sensor with megasquirt. It just can be really fiddly to get it working reliably by getting rid of the noise and get the pots adjusted properly especially without scope. I don't say it can't be done. But easier way is to swap to hall sensor.

[nando]

I've set up many and I've never found it fiddly. I've never even messed with the sensor gap.

[Digitalwave]

Are your new CPS's the OEM style metal body ones or the plastic ones? I had issues with my CPS that were fine with Motronic, but gave me hell with Megasquirt. The Dederic board has a 10k resistor on the VR signal. DIYAutotune recommends an 18k resistor. I had tried that and it did not make a difference. Replacing the CPS with a new metal body one fixed my issue. I have mine set at the stock distance spec which I believe is 0.040"/1mm.

If it is not the sensor, I would check that 1) your crank wheel is okay 2) start checking and testing the wiring between the CPS and the ECU.

Your unit is Microsquirt based, so it does not have a potentiometer for adjusting the VR signal resistor like MS2 boards have. Like others have chimed in, once I fixed my issue, I have not had any trouble constantly running this M20 w/ CPS to 7,200 RPM all day long without any sync loss on the track.

Here is a copypasta of a reply from Derek when I was diagnosing my CPS lost sync issue:

You are correct in that microsquirt inverts the VR signal. There are a few things in this email I can have you check/change but I cannot guarantee a solution—these are only what I can think of off the top of my head, from my experience. You may try all or none of them, but usually the ECU’s are as sound as could be. I have tested them on a variety of m20’s for long lengths time, with many different engine harnesses, all with varying degrees of wear. The product is as stable as I can make it, but may take a bit of ironing-out to suit your specific vehicle.

On to the stuff you could check:

• Try the 18k 1/4w resistor in place of the 10k, it may help buffer the signal. I would try this first, as it’s the cheapest and easiest.
• Replace the CPS. Sometimes these fail for MS, and not Motronic. Motronic may have a better designed buffer for the VR circuit, since the circuit in the factory ECU was designed for this system specifically.
• Check your engine harness terminals for wear
  • check resistance while moving around the connectors and terminals. The m20 harness in my experience tends to die at about 25 years from failing terminals, corrosion, etc…. Some last only 20, some haven’t died yet. This could be a culprit, I’ve had a customer chase a ghost just to find out it was the harness that failed. I have yet to take on the task of cutting and replacing all of the terminals on a harness, but it is something to consider if it is too expensive to replace in whole.
• When was the last time you changed your crankshaft harmonic balancer?
  • I’ve only had one vehicle lose sync, right in the same RPMs too. I changed everything I could think of from the CPS to the mount, the settings in MS, to the ECU from MS back to Motronic, and in the end it was from a faulty crankshaft dampener/toothed-wheel/harmonic balancer.
    • The crank dampener is constructed of two main pieces, the inner ring (6 hole mount to crank), and the outer ring (timing wheel, 60-2); This outer wheel is mounted the inner wheel with a ring of molded rubber. When the rubber fails, which is hard to diagnose from just looking at it, you may lose sync. I theorize because the tooth wheel is either shifting or harmonically untrue; 60-2 teeth vibrating out of balance causing sync-loss.
    • M20b25 Standard “i” Dampener – 11231726961
    • M20b27 “Super eta” Dampener (also requires water pump pulley) - 11231714855

I hope this helps. LMK what happens.

-Derek

[nando]

Mine has a metal body, same as the original stock one.

Also make sure the plastic cover is on the sensor wires as they pass behind the water pump pulley, or they can rub on the pulley and short out.

[Digitalwave]

I was talking to the OP, Chris. ;) I've heard bad things about the plastic body CPS's, which are way less expensive. I went right for a metal body one when I replaced mine.