Stage 3 - Control misc. devices
- Control Idle solenoid - working now, firmware development was necessary, MembersPage/GergelyLezsak/IdleControl
- Drive tachometer (need scope to get original specs.)
- Wire-in fuel-pump relay - done
- Show oil temp. (No info on sensor either)
- Control fuel consumption gauge (?)
- drive a boost control solenoid
- Install egt (hardware installation is tricky, need to remove the whole exhaust system)
- Install knock sensor - No factory placement on M20 engine to mount, experiences are appreciated.
Tachometer
As for driving BMW E30 series (inline 6 engine) tachometer, one needs to find out how original ECU (ie. Motronic) drives tachometer.
Unfortunately I dont know driving signal waveform/type and hence currently can't help, reason because we did not measure orignal waveforms before dismantled original ecu and wireloom from car.
But, if someone could measure...
Engine speed output is routed from Motronic 'ECU (55 pin) connector' pin 6 and signal goes to instrument cluster pin A7.
NEWS 2005.11.04:
Just tried the simple way and gave the tacho the signal of ignition and it's working more or less.
(Actually it gets fix +12V through a 10KOhm resistor (pullup) and that's going towards to the ignition pin of GenBoard through a diode)
+12V - - - - -10KOhm- - - - -tacho_signal- - - -|>|- - -ign.driver
So it's working but I see a bit lower RPM values on the tacho than the LCD shows. (maybe 10-20% lower, haven't tested much)
What can be wrong? Lazy gauge, or my signal needs more care? :)
Fuel Consumption Gauge
- The actual gauge uses a linear voltage between 0 and 1.5 Volts. See my page here: MembersPage/MattiasSandgren/BmwEthirtyIx
- You would need to bypass the electronics to get to it.
- Could be used as a MAP gauge (10 litres/100km = 100 kPa).
- Interesting idea, I like reusing factory gauges :)
As what comes to controlling fuel consumption gauge, it seems that inside instrument cluster has some kind of adaptation module, which is engine type specific (size, number of cylinders etc.) - somehow it derives consumption from above mentioned tachometer signal and/or following two signals;
- vehicle speed signal: from Motronic ecu pin 29 which also goes to the instrument cluster.
- fuel rate output signal: from Motronic ecu pin 32 -> goes to instrument cluster pin A11.
Don't know for sure, but 'Fuel rate output' signal might be some kind of pulses per second or pwm signal ? Someone could measure ?
Hope these help ?
I'm affraid we are talking about different motronic versions. Autodata catalog says that motronic pin 29 is ignition signal TO motronic. I can confirm that, since car was not running on motronic until I connected back that pin. Pin 32 is "throttle position control module" which might be some "cruise control" system. I'm not sure. I think my motronic didn't know the car's speed since my speedometer is fine without it :) (So signal from differential goes to the speedometer directly?)
Instead, maybe the instrument panel calculates fuel consumption based on fuel rate signal and speed?
Actually I only miss my tachometer, fuel cons. was inaccurate for ages (different size injectors and fuel pressure :)
Thanks however, and I still seeking tachometer signal specifications. No one using factory tachometer? I guess I have to wire back motronic to measure somehow :(
(or by phone# 1-2209238 in the evening)