MoTeC
12-11-2003, 06:49 PM
Hi Guys,
As you may have heard already the team from Germany had ECU/electrical problems all weekend. Unfortunately these could not be fixed with the fitment of an M4. http://fsae.com/groupee_common/emoticons/icon_frown.gif I thought I would give you guys some background so the problem does not surface again, it ruined their weekend it could ruin yours.
The car was fitted with a reworked factory ECU, Bosch I believe (or something similar). The ECU required a 36-2 trigger disc which is fairly normal for European stuff and a magnetic sensor. The ECU seemed to be firing fuel and ignition but not reliably enough to run the engine, this is where the N.S.W. guys stepped in with the offer of a spare M4. I was asked to wire the thing in and get it going, no problem the boss seems to pay me to do this sort of stuff.
The ECU was wired in, all the inputs and outputs checked, no worries. Now try to start the thing.....Hmmmm it comes up with a few errors....get the scope. Oh dear, one of the wrost crank trigger traces I have ever seen. Not because there was heaps of background noise but it was a trace you would ecpect from an engine that was not turning over at a constant rpm. Take the spark plugs out and check again....no change. Basically it looked like the teeth were not concentric with the crank and this was causing pluses that ranged from 2volts peak to peak to about 8.5volts peak to peak, that's pretty bad. Our ECU was picking this up as an extremely rapid change in RPM and causing errors that would not allow the ECU to start the engine either.
The old ECU went back on and luckily for me it suffered the same error. The interesting thing is that because it is based on a factory ECU there is a ton of contingencies for just getting the thing started to limp to the work shop, aftermarket ECU generally do not do this, they rely on a good signal. The car did a couple of laps but unfortunately that was it.
A quick bit of testing on the lathe back at the office gave me this:
With a trigger disc with a 145mm diameter and about 0.3mm out of concentricity (is that the right word) I scoped a pattern that had an average pulse of 3.6 volts at 300rpm the range of pulses was + or - 900mvolts around this, that is nearly one volt! Also on another test going from 0.5mm air gap to 1mm air gap halves the pulse (logical when you think about it).
Moral of the story: If you are going to retrofit different components to your engines make sure you check everything!!!! Another issue with the German car was that ther was not enough clearance between the chassis and the engine to get the trigger disc or the sensor out for modification. The other BIG downfall for me is that I have to explain to the boss why I could not get the car to run....not an easy thing to do. http://fsae.com/groupee_common/emoticons/icon_frown.gif
Hopefully the boys can get this sorted for the next event.
Mark McCoy/Donna Arbuckle
As you may have heard already the team from Germany had ECU/electrical problems all weekend. Unfortunately these could not be fixed with the fitment of an M4. http://fsae.com/groupee_common/emoticons/icon_frown.gif I thought I would give you guys some background so the problem does not surface again, it ruined their weekend it could ruin yours.
The car was fitted with a reworked factory ECU, Bosch I believe (or something similar). The ECU required a 36-2 trigger disc which is fairly normal for European stuff and a magnetic sensor. The ECU seemed to be firing fuel and ignition but not reliably enough to run the engine, this is where the N.S.W. guys stepped in with the offer of a spare M4. I was asked to wire the thing in and get it going, no problem the boss seems to pay me to do this sort of stuff.
The ECU was wired in, all the inputs and outputs checked, no worries. Now try to start the thing.....Hmmmm it comes up with a few errors....get the scope. Oh dear, one of the wrost crank trigger traces I have ever seen. Not because there was heaps of background noise but it was a trace you would ecpect from an engine that was not turning over at a constant rpm. Take the spark plugs out and check again....no change. Basically it looked like the teeth were not concentric with the crank and this was causing pluses that ranged from 2volts peak to peak to about 8.5volts peak to peak, that's pretty bad. Our ECU was picking this up as an extremely rapid change in RPM and causing errors that would not allow the ECU to start the engine either.
The old ECU went back on and luckily for me it suffered the same error. The interesting thing is that because it is based on a factory ECU there is a ton of contingencies for just getting the thing started to limp to the work shop, aftermarket ECU generally do not do this, they rely on a good signal. The car did a couple of laps but unfortunately that was it.
A quick bit of testing on the lathe back at the office gave me this:
With a trigger disc with a 145mm diameter and about 0.3mm out of concentricity (is that the right word) I scoped a pattern that had an average pulse of 3.6 volts at 300rpm the range of pulses was + or - 900mvolts around this, that is nearly one volt! Also on another test going from 0.5mm air gap to 1mm air gap halves the pulse (logical when you think about it).
Moral of the story: If you are going to retrofit different components to your engines make sure you check everything!!!! Another issue with the German car was that ther was not enough clearance between the chassis and the engine to get the trigger disc or the sensor out for modification. The other BIG downfall for me is that I have to explain to the boss why I could not get the car to run....not an easy thing to do. http://fsae.com/groupee_common/emoticons/icon_frown.gif
Hopefully the boys can get this sorted for the next event.
Mark McCoy/Donna Arbuckle