YFZ450 CDI box problems

[gwilki2]

My school has been running a YFZ450 engine using megasquirt for fuel injection and CDI just like the ATV uses from the factory. For some reason if we don't follow a certain procedure for restarting the engine (whether after a stall or kill using the kill switch) we fry the CDI box.

Our EE who has done the fuel injection system the past 3 years graduated last year and doesn't have the time to dedicate to helping us solve the problem definitely, and nobody on the team this year had much involvement at all in last year's engine team, so there isn't much support out there for us to turn to.

I know there aren't many teams that run these engines, but I was wondering if any have had similar problems, and if they're willing to share some tips with us. Our only idea is that the problem must be in the megasquirt computer, as that's the only part we have that isn't on the ATV, and obviously the ATV's don't have the same problems we're having. We tried eliminating the CDI completely by using a cam position sensor to allow megasquirt to run the ignition, but that idea has fallen through (complication with mounting the sensor perfectly to reliably pick up a signal). The car runs strong on the MS + CDI set up, so we're not really opposed to keeping it that way, although we like the idea of more precise timing that comes with a crank or cam position sensor. Either way we can't have the CDI box going out in the middle of the enduro event as it did last year. Any help anyone can offer is greatly appreciated.

[B Lewis @ PE Engine Management]

Maybe we can help. Can you post a diagram that shows how everything is wired on the engine? Also, what are the "good" and "bad" procedures for restarting?

[gwilki2]

I'll see if I can get a diagram of it.

As far as we can tell, if you stall the car, leave all the switches on, and hit the start button to start it back up, the CDI box is toast. Failing to start up the first time might cause this too (ie, turn all switches on, press start button, engine fails to start, and you press the start button again without flipping any switches off and on). So pretty much our "good" procedure right now is to flip the master switch off and on before attempting to start the car.

The problem is we don't necessarily know exactly when the surge (or whatever it is) occurs. We just find the aftermath. As we start to finish up the bulk of the fabrication of the car, more of our attention is being turned to solve this problem.

[Grant Mahler]

What version of MS hardware?
What version of MS software?
What is MS running - fuel only?
What switches do you have?
What relays do you have?

[stu.pattison]

One thing to watch out for with fuel injected bike engines is make sure you use the kill switch to turn the engine off, not the key/ignition. Have seen it a few people destroy their ecu's on normal road bikes by always using the ignition to turn the bike off. The kill switch allows the ecu to reset itself, where the ignition just cuts power to it no matter what it is doing - do that often enough it'll kill the ecu. Not sure if that's your problem, but it's a good habit to get into regardless

[gwilki2]

What version of MS hardware?
What version of MS software?
What is MS running - fuel only?
What switches do you have?
What relays do you have?

1) We are using MicroSquirt V1 (which is MS2 I believe)
2) MegaTune 2.25
3) Yes, no ignition. My understanding is that MS could not run the ignition given the signal from the stock engine. Hence our trigger wheel idea, which has pretty much failed (packaging issues).
4) We have a kill switch on the side of the car and a kill switch inside for the driver. We have a switch for the radiator fan and a push button for starting.
5) Our EE made a daughter board for the MS to eliminate all relays.

[Grant Mahler]

So you have the stock ECU triggering the CDI box, and stock wires from the CDI to the plugs?

You cut the fuel injector wires from the ECU, and run your own from MicroSquirt?

What are you using to determine load and crank/cam position to fire your injectors?

I would start with making sure your grounds are solid. I've had strange things occur with wires staying charged that shouldn't when the grounds on coils weren't thick enough gage, or clean enough contact with your vehicle ground. It fried 2-post coils; I would imagine it would also fry CDI/ECU boxes if it stayed hot.

[Storbeck]

So it sounds like the stock cdi is running the ignition, and the ms is running the injection, pretty much completely independant of each other. Are you running the stock wiring harness from the quad, or did you make your own.

Since it sounds like there isn't much knowledge on the engine/electrical side of things on your team you need to do one of two options.

1. Do what's simple and easy and move on to other things: get a completely unmolested stock wiring harness and use it, with stock components, for your ignition system. Sounds like the MS is pretty much completely independant and is working fine.

2. Find somebody that is willing and able to step up and really figure it out, which probably means redoing the whole thing. Sometimes it's easier in these situations to redo the whole thing from scratch, figure it out on your own from the beggining, than trying to figure out what somebody else did.

Just the $.02 of some random idiot on the internet http://fsae.com/groupee_common/emoticons/icon_smile.gif.