BMW S50B30
I have an issue where after 5500 rpm the third trigger position goes higher, a bit erratic, about 90 degrees higher than where it actually is. Load on the engine doesn't matter, happens free revving as well.
It's not clear to me, but but it could be false triggering (noise) on third trigger input? I may hook up my Rigol scope and check it out. SDA input has 10k resistor in-line, 10nF towards ground and 1N4007 diode for protection.
FIXED Internal 54 kOhm pull-up inside CPU on SDA pin is not enough (naturally), now mounted 2.4 kOhm pull-up to +5 Volt inside ECU before 10k protection resistor.
This is almost certainly due to the next or previous trigger tooth being picked up by VEMS as with 8 teeth there is a 90deg angle between them. I would think this to be a software issue rather then a hardware issue. - Gunni
Details below.
Hardware setup
- Third trigger : 8 points on intake cam equally spaced.
- Second trigger : 1 point on intake cam.
This is the most retarded position (at rest, cranking) :
Software
Download [triggerlog] and [vemslog]
The measure tooth can be set to 0 or 15 to reach as low angle on the third trigger as possible, 5-35 degrees is recommended. At rest (most retarded) the third trigger occurs at the missing tooth, and every 15 teeth. I've tried other measure tooth settings (0-15 is all that is possible) and I still get this same problem.
Log view of free revving the engine
Fixed the missing/weak pull-up on (SDA) trigger input.
Hello Mattias,
Comprehensive and detailed report, very nice! I reviewed trigger and vemslog, my observations:
- chosen measure tooth is very close to third trigger pulse (3-5 deg) difference, can cause a problem when belt slap/chain resonance at high rpm if it moves before, suggested measure tooth adjustment to 10-11 range..
- strong pull-up (like 2k7) to 5v before the 10k/10nf RC filter to SDA pin is not listed, is it present ?
- Not it was not present, thanks Dave - that fixed the issue!
- Voltage on trigger input pin at sensor connector measured 4.96 Volts to signal ground, but was weak. Shorted with 2.4k and got only 220 mV voltage drop over it...
- Ignition HV pulse (during normal running) might be causing trigger noise on the HALL signal of the third trigger review and provide scope shots if possible.
Best regards, Dave