Crank errors at certain rpm

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x30xe
Posts: 64
Joined: Tue Jul 26, 2011 2:56 am
ECU Model: S60 Pro

Crank errors at certain rpm

Post by x30xe »

Hi,

I have BMW M20 engine with original sensors, ignition and 60-2. Crank errors occur at 7000rpm and engine hits like rev limiter (which is located some distance above). Crank sensor is original, shielded wire, earthed as per instructions. Even the box (S60) is earthed.

Any ideas how to start tackle the problem? It is likely that there are some amount of harmonic vibrations at crank.
SMR
Posts: 137
Joined: Tue Jan 16, 2018 9:38 am
ECU Model: S100 Pro
Distributor: DTA
Location: Aberdeen

Re: Crank errors at certain rpm

Post by SMR »

Is it a two-wire VR type sensor? Any chance you could have the two wires swapped around?
x30xe
Posts: 64
Joined: Tue Jul 26, 2011 2:56 am
ECU Model: S60 Pro

Re: Crank errors at certain rpm

Post by x30xe »

VR type, original Bosch sensor. Wired as per manual, Tyco Raychem stuff.

Engine runs perfectly otherwise, but somewhere near 7000 crank errors occur. Stroked BMW M20's are known to have harmonic vibration issues, so I'm primarily expecting that somehow being the rootcause. But how to tackle that?

I think I'll try to put some more airgap first (now it is sdt 1.0mm). But I'd be interested what the filter setting at General - menu does? Product manual is not really informative explaining the phenomena that the setting is made for.

Has anybody tested using resistor in the signal wires to reduce the voltage?
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Crank errors at certain rpm

Post by stevieturbo »

I cannot imagine a resistor doing the signal any favours at all.

If you want less voltage, larger air gap.

Ideally a scope trace when the problem is occurring would let you see if the signal is good and clean or not.
JON-TEC-RALLYE
Posts: 38
Joined: Sat Jul 30, 2011 4:35 pm
ECU Model: S100 Pro
Distributor: JON-TEC-RALLYE
Firmware Version: 89
Location: Canary-Island

Re: Crank errors at certain rpm

Post by JON-TEC-RALLYE »

good morning, my experience with this type of error, is to bring the sensor closer to the pulley, in that bmw 20 model it is fixed and the adjustment is not possible, check if the pulley is centered since it is mounted on rubber and it is common for it to faded with years of use.

the configuration to be 60-2 and filter 2000.

rpm sensor connector. wire order.
pin 1 signal.
pin 2 ecu ground
pin3 chassis ground shielded cable.

If it doesn't work, simply replace the sensor.
DTA--MoTec--Link--Ecumaster--HONDATA
x30xe
Posts: 64
Joined: Tue Jul 26, 2011 2:56 am
ECU Model: S60 Pro

Re: Crank errors at certain rpm

Post by x30xe »

I increased airgap from 1.2 to 1.4mm. During first acceleration test engine turned to rev limiter (7500) withour errors. Then during subsequent trials it hitted crank errors approximately at 7000-7200.

Increasing airgap made very small difference, but did not solve the problem.

Next time I think I try to alter the filter values.
x30xe
Posts: 64
Joined: Tue Jul 26, 2011 2:56 am
ECU Model: S60 Pro

Re: Crank errors at certain rpm

Post by x30xe »

New sensor made no difference.

1.85mm air gap makes engine run flawlessly to current redline 7500rpm. I have no idea why it loves so big cap. Factory gap is about 1mm.
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Crank errors at certain rpm

Post by stevieturbo »

Maybe a lot of movement with the crank or something ?

But if it works it works.
x30xe
Posts: 64
Joined: Tue Jul 26, 2011 2:56 am
ECU Model: S60 Pro

Re: Crank errors at certain rpm

Post by x30xe »

stevieturbo wrote: Tue Aug 02, 2022 12:47 pm But if it works it works.
This is good saying!

I'd still be curious to understand what the "filter" setting does and what is the theory behind it. I understand that some of the settings are hard to explain for the ECU manufacturer and they perhaps do not want uneducated "tuners" to mess with settings... but anyway.
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Crank errors at certain rpm

Post by stevieturbo »

I just wish all ecu makers would incorporate a scope that records a trace when it has come across errors, or just an ability to view a proper scope trace of the crank/cam patterns.

At least then it gives you a proper visual to try and diagnose what about it is making the ecu unhappy.

Without a scope trace, you're largely working blind.

or of course you can hook up an external scope to see.
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