Megasquirt update

Okay, for those of you looking at the Megasquirt Fuel Injection system here is a bit of advice. If you don't get the v3.0 board then you need to invest in the flyback daughter board. Sunday morning my V2.2 board killed itself. I have been running 2 low-impedence injectors in my GM TBI. It has been running great for over 800 miles. Sunday morning I started it up. it ran for about 10 seconds then died. It would not restart. Pulled the computer and found this:



This is the driver for the injector control circuit. As you can see its a crispy critter. This is what the directions mean by fly-back failure. I had PWM turned on and set up correctly. So that is not the issue. I knew this could happen but thought I had taken appropriate percautions. So either get the fly-back board or go with the V3.0 board which has the flyback circuit built into it.

 

You let the blue smoke out!

Every good engineer knows that electronics are all run on blue smoke, not electricity. If you break something and let the blue smoke out, it stops working.

Let the blue smoke out of a computer power supply once. LOTS of it....

 

Man I have got to read up on this stuff more.
On the up note you were at home right?

 

Interesting. What is the component? I presume you were sinking too much current with the low impedance injectors(?)

 

Brian, I know well the effects of letting the magical genie out. It was the favorite catch phrase of one of my electronics profs in college. "If you let the genie out. It won't work anymore."

Jerry, yes I was at home.

Tim, that is the FET (Field Effect Transistor) driver. It controls the FETs that turn the injectors on and off. And yes, too much current with low impedence injectors is the culprit. The solution is to either use ballast resistors (7 Ohm 25 Watt/injector) or the Fly Back Circuit which eliminates the risk of this happening. Sad part is it probalby blew the FETs as well although there is not any physical evidence I can see. So I will have to replace 3 seperate components and maybe more depending on if I blew the power supply circuit as well.

 

Yeah, I'd think you'd have to blow the big FETs to blow the driver.

This whole Megasquirt project is intriguing. I was planning to get the Howell CA-legal kit for my truck, but a move to CA is on hold for now. MA only requires a safety check.

 

Nice thing about Texas, if its 25 years old or more it only needs a safety check. They do a visual for the stock emmisions setup. But the law states as long as you have the origional controls or it has been replaced with something better then it is legal. FI with 02 feedback is way better then the stock emmisions junk on my 5. I am thinking of having a cat installed just because I like the idea of it being as clean as possible.

 

Good thing I spent a little extra and got the V3.0 board. Just waiting for the surge tank a friend of mine fabbed and mailed to me yesterday. Boy that transistor sure got fried. Is the PCB still good? Looks like a little grendae went off in it.

 

Oh. Oh! That's an 8-pin DIP. Wow, melted the socket too. So blackened I didn't recognize it.

 

I'm going to have to research this a bit. Guess I missed the start of this Mega conversion.

 

Yeah the dip and the chip are now fused into one lump. I will have to desolder the pins to get them off. The board looks okay, I have not taken it out of the case yet to check the backside. But I should only have to replace the fried components to have a spare for my tool box. But this time I will integrate the fly-back board onto it so this won't happen again.

 

...crossed over to a high-speed dual inverting MOSFET driver...shouldn't be too expensive...good luck !