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Rpm signal loss


seattlejester

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When I did my coil test I just laid the spark plug outside the hole and watched the fireworks!

I thought wasted COP was only for a set up like mine- wired like sequential but firing like wasted.

Now have some fun tuning

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Yea, that was going to be the next step to actually confirm physical spark. I know it's been done a whole bunch, but just something about leaving an open spark plug bothered me so I spent 15$ on spark detectors. 

 

Yes, I believe you are correct, the wasted COP setting is more likely for MS3x where you can wire in individual cylinders, but you just run them in wasted format. Not having the latter half is probably problematic for the whole setup.

 

Really really really really really looking forward to that aspect. 

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  • 1 month later...

A bit of an update, I have been playing around with the car a bit. 

 

Things noticed so far...

 

Car does not see boost according to megasquirt, will have to fit a manual gauge for testing, no whoosh sound from blow off valve either so either the blow off is making a leak, the waste gate is not closing, or another boost leak of some sort. I was hoping to drive it off the waste gate spring pressure for a while, but I will plumb in the boost control solenoid to help close it if it is a weak spring causing the issue.

 

Motor will not rev past 4k. At about 4k it looses rpm signal and thinks it is cranking until the rev drops below 4k. That sounds like a rev limit, and I believe I have set a couple of limiters so those will be looked at. Will take my laptop and run a log to see if I can see anything else obvious when it occurs.

 

Not sure if I mentioned, but oil gauge fault traces back to back oil pressure sending unit out of the box. Company says the supplier is at fault, and will sort it out and send a new one when they can switch to a new supplier.

 

Car runs pig rich on acceleration (below 10), will have to run a few more auto tune sessions, maybe take a look at accel enrichment, definitely uncomfortable when getting on throttle with the bucking.

 

Shadow dash app is finicky at best, when it works it works great, but sometimes just cuts out and crashes. Thinking of moving over to MSdroid and trying the hardwire option, currently MSdroid cannot detect my ECU version, despite having generated the file it is searching for.

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Can you post a current MSQ?

I just wonder about the 4k limit, that seems strange. Makes me think that you have an AFR safety or a knock sensor that is limiting you. Could be something like you are so rich the the sensor reads lean for a moment and trips the AFR Safety.

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I will definitely get some time in later this week.

 

I remembered while driving home that I did enable a throttle dependent rev limit in addition to the coolant based rev limit, I am pretty sure that is the culprit or at least a factor, as I wasn't flooring it in the little straight I was playing with. I think I got a little too involved with setting limiters after watching a Ferris Bueller rerun. 

 

I definitely know how annoying it is to try and help without both those pieces of data, so I will adjust and report back this weekend.

 

Regarding boost, I have it currently set to PSI, and I have not seen it go positive maybe up to 1 or 2 psi, but usually in the negative range. I can switch it back to kpa and see if it reads any different.

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Just a pre work update,

 

The MSQ is the same MSQ as previously used.

 

The throttle rev limiter is set at 5000 rpm with 80% throttle, and the coolant temp based rev limiter also kicks in until the car reaches 120.

 

Car was not revving past 4k rpm fully warmed up (temp 180). This was load independent as well.

 

 

 

Thoughts thus far:

 

Hall effect sensor needs adjustment

Need to zero out and then play with the adjustment pots

Need to add capacitor, although voltage does not drop enough to indicate this

 

Throws in the dark:

Board setting is set incorrectly, need to re-examine jumpers

Someone with a similar problem solved with removing c12 and c30

 

More info to follow.

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I've messed with a lot of different rpm inputs over the years and if your sensor or pots are out of adjustment, it definitely can feel like a rev limiter.  Although it will usually show up in the logs as a jagged rpm signal when it happens. Or in the case of my 6-1 flywheel setup, when the VR sensor couldn't read above 5500rpm, it would just drop a few hundred rpms in the log. The engine would still be accelerating making the car buck and all sorts of unpleasant things.

 

I've always had to mess with the pots a little bit when using a new sensor. Just reset, rev it up, adjust, and repeat. Hopefully that's all it is.

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Related files attached.

 

Current MSQ

Compiled Datalog

Toothlog

 

Reset pots R52 and R56, and moved R56 two turns clockwise as mentioned earlier in this thread (will double check, but I had this thread opened when I did it so whichever one it said)

 

Moved the hall effect sensor closer as well, but still cutting out near 4000rpm. 

 

Removed rev-limiter as well still behaving the same.

 

Symptoms:

Looses RPM signal, goes from 4k to 1k or 0 and then back up to 3k as the revs drop

Registers signal loss

Gauge cluster indicated cranking when RPM signal lost

Catches after letting off the throttle

Runs rich enough to not register, lower then 10AFR

 

 

From what I can tell from the tooth log as the RPM increases the time between the teeth shrinks to around the 0.4ms mark which coincides with an RPM of about 4150rpm

 

1ms / 0.4ms/time between teeth = 2.5 time between teeth/ms 

2.5 TBT/ms * 1000ms/ second = 2500 TBT/s

2500 TBT/s * 60 s/min = 150000 TBT/min

150000TBT/min * 1 Rotation/36TBT = 4166rotations/minute = 4166rpm

 

So it comes down to the teeth are not being read.

 

Either it is mechanical or electrical or ECU.

 

Mechanically the hall effect sensor may have trouble at higher rpm? Although it is the one DIY suggests

Electrically, the wire is not carrying the signal at that speed?

Or the pots need some additional adjusting, although I do not see how you can get any more adjustment then opening zeroing out the pot completely.

 

Any insight would be helpful.

MSQ and datalog 07-06-14.zip

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Your tooth log looks pretty similar to mine. I didn't count all the marks in the log, but the sections I did count look correct with 34 short and a tall 35th. Obviously it's reading some teeth better than others, but the tall one is important. If it were reading wrong, you'll end up with multiple tall teeth in a row.

 

Short of using an oscilloscope you need to try what I said for tweaking the pots. I can never remember which does what, but one acts like a noise filter and one affects the shape of the signal. Reset both and  you want to mess with the one in the middle of the board. Rev the piss out of the engine and adjust half a turn at a time until it stops cutting out. If you run out of adjustment, then you'll want to investigate other things or get someone with a scope to help you.

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Newzed, starter is not engaged when this happens. Unless you are indicating maybe a failure to retract all the way, but I think then the starter  would have worn out by now.

 

Metro: Gotcha, glad to see a light at the end of the tunnel, I'll give that a shot. The only thing I can think of that is left is to redo the trigger wheel and hall effect sensor if the pots fail. After that I am back in the stumped bin.

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Newzed: gotcha, I don't think it is noise though, as that would show as extraneous teeth and cause the RPM's to jump not drop suddenly, I am leaning towards maybe too much noise filtering drowning out the actual RPM signal, and the wire is shielded, not sure what else I could try and do to lower more noise, additional shielding? More grounds?

 

AkRev: Eyeballing about 1mm. I basically made the sensor touch the teeth and then backed it out half a turn or so. 

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Oh, I thought closer would be more helpful, you have found further out lost less signal? I am using the threaded type that says 1.5mm maximum air gap. 

 

Well current plan:

 

Mess with pots slowly turning center pot clockwise until maxed out or revs don't disappear.

 

Adjust sensor away from teeth to look for signal improvement.

 

Make measurements to make a thicker steel mount, consider ordering new wheel and bolt adapters as well as the tabbed hall effect sensor.

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Blah, read it too fast, you are correct, good eye, didn't make much sense to me either. Did make me look at the other sensor though, it has a larger range in both RPM and it seems resolution, may be worth while to make that the basis of my next visit on the mechanical side.

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Ok.  When I had it at a .75MM gap between the sensor and the trigger wheel I got no signal.  At a 1mm gap from the trigger wheel I had some trigger loss.  At 1.5mm gap from the trigger wheel I had perfect signal.  At 1.75mm gap from the trigger wheel I had no signal...

 

So you may need to dial in the sweet spot on your sensor...  At least I had to do that...

Edited by Kirkster
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