Flyback Failure & Q1 change???

[swooshcmk]

Hey Guys,
So I'm using a Megasquirt 1 v2.2PCB on my Ford plow truck with a GM throttlebody injection unit and the stock GM 1.2ohm injectors. I was using PWM and managed to blow out my flyback circuit. I ordered all the parts to replace it and noticed that Q1 that I had installed in the board when I built it (around 2001, it sat on a shelf most of these years) was a TIP32C, however the current BOM and flyback repair documentation all points to a TIP42C. I thought at first maybe I had gotten a mis-boxed item when I first built the MS, however looking at the original BOM I printed off when I build it the old BOM points to a TIP32C. Was this transistor upgraded at some point? It looks to be rated for roughly twice of the TIP32C.

Also, after I repaired the flyback I plugged the ECU in and fired it up. ran great. So I shut it back down and installed some 7.5 Ohm resistors with the injectors to run them as high impedance. However I don't think it's allowing enough current to the injectors as setting the PWM to 100% and 25.4 as suggested results in absolutily no signs of life, right after having just started in PWM mode so I don't think the injectors are opening at all.

So, with this "upgrade" on Q1, will I be much less likely to blow the flyback circuit a second time (w/o any resistors running one 1.2ohm injector per channel)?
Should I get smaller injector resistors? Seems to me I would maybe have to run resistors AND PWM?
Or should I just order the flyback daughterboard? (leaning this option vs buying more 25W resistors)

On disassembly Q1 didn't look burned or charred, but it looked like it got hot as it was more of a glossy dark look, and a big sniff right on top of it smelled *slightly* burnt. I'm just hoping that the TIP42 over the TIP32 will give me a good dependable flyback that I can run it as is in PWM, but if others think burning it up again is inevitable I'll just order the flyback kit. Remember it's a plow truck so I do see a good amount of high-load work while at lower RPMs. More snow on the way tomorrow so I'm hoping as-is PWM will be solid enough to last. Overall an awesome little ECU.

Oh, and before it died I was running 73% PWM (anythign less and the truck would sputter and die when lifting/turning the plow, otherwise w/o the plow I was running about 65% and at 59% the engine stumbled and died at idle) and 0.9mS pwm threshold. 1mS injector opening time and 0.2mS/v drop She was running great!

Thanks for any input guys!

[swooshcmk]

Failure is inevitable.

[Joe]

Having played the GMtbi game you are playing right now the best solution I found was just to run the P&H board.
After 2 failures of the original flyback I switched to the new board. been working good for years now.

Take a look and consider it. You will not regret it. And it's reasonably priced.

http://www.jbperf.com (P&H board)

Joe-

[swooshcmk]

Thanks! I never heard of the P&H board. I already ordered the flyback mod kit for my v2.2, so if I blow it out a third time I'll definitely go this route! I built my MS years ago and I've been away for a while as it was sitting on the shelf for a few years until another project came around that I could use it on. Perhaps I should order it just to have it on hand! Towing the whole truck home is getting to be a bad ritual!

Thanks!