Got first start, but sync loss at 2500rpm

[grom_e30]

how does the tool log look on a running engine?

[sjf911]

It looks like your engine speed variability during cranking is obscuring the missing tooth. How healthy is your starter and what compression ratio are you running?

[billjam]

Grom, I haven't been able to start the engine yet, so running log not available.
Steve, I see what you mean. Engine internals are standard 3.6 so CR is 11:1. Starter is a new HiTorque unit.

[sjf911]

I would remove the resistor and see what it's like without. IIRC, the resistor is more helpful when engine speed increases.

[billjam]

Steve, the first few logs I ran didn't have the resistor fitted and they look the same.

Tooth log 3.jpg

[sjf911]

Wow, I wonder how motronic solved this. Is there a chance your starter is failing or your having voltage/wiring/connection issues at the starter? Would a hall sensor make better sense in this situation?

[sjf911]

Something doesn't look right with this. You should have 3 compression events per crank revolution so 3 slow and 3 fast cycles between missing teeth yet that is not what I'm seeing if you are running a 60-2 wheel.

[jsmcortina]

I doubt that a hall sensor would make any difference.

I can't tell where the missing tooth is by eye. Usually it is very easy to spot by eye - even in cases where the code is having trouble.

So... if I can't spot it, it is very unlikely that the code will.

James

[sjf911]

Looking at it a little closer, there does appear to be a repeating pattern of 3X decelerations but the tooth count far exceeds 60-2 within this. I count 116 teeth so it appears to be double counting teeth.

[sjf911]

Pull your spark plugs and turn off your ignition and fuel injectors and crank without a load doing a composite log.

[grom_e30]

the first log posted was pretty close this last screen shot is way off its not showing the missing teeth at all

[billjam]

I followed up on some of your suggestions today with some confusing results.
I switched the ignition settings to "wasted COP" and "single wheel with missing tooth".
R56 was also cranked up another 2 turns so that is now at 4 turns CW.

I removed one set of plugs and ran a log with no compression. This immediately smoothed out the log with clearly defined spikes every 58 bars. I think this is what we should see with a 60-2 trigger wheel.

Tooth log 7a.jpg

It gets a bit confusing when no changes are made other than installing spark plugs. The log changes so that the spikes are at intervals of 36!
The flywheel is definitely 60-2 (I counted the teeth today) and this is what I have set in Ignition Options.
I suspect that the extra two turns of R56 helped flatten the bars in this log and makes the spikes more prominent compared to earlier logs, but why the change of spike intervals from 58 to 36 just by adding compression load?

Tooth log 8c.jpg

[billjam]

I just noticed that the last log above has secondary spikes at approximately 55 intervals. Why 55 and not 58?
Maybe these are the missing teeth and they are getting overwhelmed by the spikes due to engine slowing down on compression? But then why are those peaks at intervals of 36?

Tooth log 8dd.jpg

[sjf911]

It looks like a lot of teeth are fused together on the graph. It may just be an artifact of the display. Looks like you've made a lot of progress. Have you tried to start the car?

[billjam]

Yes, I tried a start after I took the last log. I didn't really expect it to run and I wasn't disappointed.
As it turned over, there was a mixture of actual firing, back firing and explosions and flames from the exhausts, so it seems that ignition is being driven by these spikes but they aren't all occurring at the correct part of the cycle.

[grom_e30]

i still don't this looks rite the longer the bars means the longer time between teeth i believe so the long bars are always at the top of a compression if im reading it correct, and it is failing to show the missing teeth at all. this is my 60-2 bmw cranking with plugs in but coils disabled its an inline 6 cylinder and my tooth1 angle is 84 which if i remember is very close to yours 87? possible. this is sorta what your aiming for

[billjam]

So far I have turned up R56 by 4 turns and R52 by one turn CW.
How many turns are available on these pots?
Are more turns of R56 likely to reduce the effect of the high cranking pulses?
I guess it won't do any harm to try, but it would be handy to know how many turns are available.

[billjam]

It has been suggested on another forum that the source of false peaks in the trigger logs could be starter-related noise so I ran a few tests today to try and confirm that with no real progress.
1. Moved the main ground from engine to chassis ... no improvement
2. Wired starter 12v direct to a separate battery ... no improvement
3. Wired starter and solenoid to separate battery ... no improvement

By "no improvement" I mean that the log still looks the same with large spikes (B) every 35 teeth and smaller ones (A) still visible at about 51 like this ...

Tooth log 11b.jpg

Actually, there is a change, the large spikes are much larger than they were on previous logs!
Is it possible for the starter to create noise in the crank sensor circuit even though it is electrically separate? If so, I will try the original Bosch starter for the next test session.
Also forgot to try cranking up R56. Maybe tomorrow.

[grom_e30]

How did the tooth log look with the starting point from the manual with both pots fully counter clock wise? also is the vr cable screened? and whats the air gap on the sensor?

[Lapkritis]

Spark plugs need resistors... that much clean up removing them is remarkable.