Ms hardware changes

[Martin Wagner]

My bother and I have raced 2 cars using microsquirt for over a year. Two weeks ago, his car shut off during a race. A few minutes later the car started and ran fine. Every session after that the car would start fine, idle for extended periods, and quit within 2 laps on the track. We tried changing most external electrical components but the problem continued. Last weekend we installed my computer in his car and it ran for over an hour on the track with no other changes.

We are using a 36-1 crank wheel with a ford VR sensor driving injectors and coils directly. When the unit fails, the tach drops and jumps a few times in the 3 to 4000 range, and the car either backfires or ignites unburnt fuel in the exhaust like the unit has lost sync or reset, then it quits completely. Any ideas what component(s) might cause this? VB921s? 5 volt regulator? Poly fuse?

[Bruce Bowling]

I am not sure which board version you have, but the earlier ones (red) under high temps the diode leakage can increase causing a dropout. The issue and fix is outlined here:

http://www.microsquirt.com/viewtopic.php?f=87&t=23063

- Brce

[Martin Wagner]

Bruce,
Both cars are V1 boards. I had already read the topic but it started with D5 and went on to several different diode, capacitor, and resistor changes and finally ended up with a code fix. We did install code version 2.890. I assume you are suggesting the D5 change and not the other changes mentioned in the topic.

Since I will have to order parts anyway, what part did you use to replace the SS12's on the V2 board. The SMD part looks large enough to solder without too much trouble.

Thanks,
Marty

[Bruce Bowling]

Put in a 1N4148 there - you can actually use a leaded (thru-hole) one, bend the leads to fit the pads and solder. Its pretty easy to do...

- Bruce

[Martin Wagner]

I installed the 1N4148 and finally got a chance to test the unit in my car. It worked fine for 5 laps and then shut off. When it failed the tach was working correctly so the unit was still powered up and crank wheel detection was working. After turning off power and waiting 30-60 seconds, the car started fine.

I installed a V2 microsquirt I have just purchased from DIYAutotune and the car ran fine for a 6 lap heat race. The V2 then failed with the same symptoms on the second lap of the feature race.

So, I now have 2 cars that both run with 1 V1 unit and fail with either a second V1 unit or a V2 unit.

Anyone got any ideas?????????

[Bruce Bowling]

Do you have a datalog during the shutdown? This would help pinpoint the issue - it could be a number of things.

- Bruce

[Martin Wagner]

The only way I can datalog is with a laptop and I haven't yet figured out a way to securely mount one and still be able to access the keyboard to start a datalog. Our next track date is late June and we would like to try something for that weekend.

Since the tach out signal was still working, power and vr in must have been working. I wouldn't think map, clt, or iat being out of spec would cause a shutdown. If map went to 0kpa it might be so lean it wouldn't ignite in the engine. I did hear a couple of pops in the exhaust while coasting to a stop in gear. But the problem happened in 2 different cars with 2 different sets of sensors. We are using both ign and inj outputs so I wouldn't expect both ign or both inj outputs to quit at the same time. I wasn't too surprised that the v1 unit still failed after the diode change but I was VERY surprised when the new v2 unit failed so quickly with the same symptoms.

I will figure out some way to mount the laptop but would still like to try something.

Marty

[Bruce Bowling]

What injectors are you using (i.e. how many per bank and the impedance)?

- Bruce

[Martin Wagner]

It's a 4 cyl engine with 2 14.0 ohm injectors per inj output. There is 1 coil per ign output. I don't have a LC meter but the coils measure 1.1 ohm (after waiting ~5 seconds).

Marty

[Bruce Bowling]

At this point its hard to exactly diagnose because we are flying blind. Unfortunately you are going to have to see if its fuel or spark that you are using. You indicate that there is a tach when it dies, so this checks out 90% of the system. Only thing left is ignition and fuel.

The injector loads are fine. One thing I would look into is to use remote coil drivers. Although I do not think this is the problem, especially since you have the same thing with VB921 and BIB373 drivers, doing this may help. Again, grasping at straws here without evidence of where it is failing. So get it in the bad mode and quickly check the spark and the fuel.

Be sure to check other systems like fuel, etc.

- Bruce