newbie question

[CHEVEN]

can the megasquirt be used with an older GM TBI ? I don't want the port injectors and the wiring, i want to hide the system under the air cleaner for an older carburated car.

[Bernard Fife]

Cheven,

Yes. I have done this before. These injectors have less than 1 Ohm DC resistance. You need to use pulse width modulation (PWM) or resistors to limit the current in the injectors. I used PWM with ~0.7 millisecond opening time, and ~20% PWM for the injector(s).

If you use a V2.2 main board, you will need the flyback board. If you use a V3 main bard, the flyback components are installed directly on the main board.

You can read more about this here: http://www.megamanual.com/v22manual/minj.htm#pwm

The GM throttle bodies have a idle air controller (IAC) built in, it is a stepper type IAC. This works well with MS-II. You can read about it here: http://www.megamanual.com/ms2/IAC.htm.

They also have a throttle position sensor built in.

The throttle bodies have a suitable fuel pressure regulator built in. You will need a return line to the tank, though (I ran mine back to a nipple epoxied into the metal filler neck). See: http://www.megamanual.com/v22manual/minj.htm#supply. I did not need a surge tank for the fuel supply.

Then you just need to add coolant and air temperature sensors, and a fuel pump capable of supplying a steady 11 psi (normally an electric pump), and you are set to go.

Lance.

[CHEVEN]

WOW, great !! Thanks for the reply, my question was rejected before ?

I'm new to the site after tripping over an article in hotrod . I didn't want to get in too deep if it couldn't be done, I have no interest in doing injection any other way. (don't want to see injectors and wires) I have a 69 cutlass, and 72 lemans both 350's with their respective motors. I'm not looking to win races or make HP, I just want to improve driveabilty and mileage but not because I'm green, but because I can't afford to ENJOY my cars anymore

Now that I know it can be done, now I'll invest the time into learning more about these systems as I'm near clueless to the differences in systems and such.


Thanks again for the response !!

[Bernard Fife]

Cheven,

Your post probably wasn't rejected (if it is the first one above), it's just that the first few post from all new users is 'moderated' (has to be approved) because of the huge volume of spam we get.

My initial megasquirt project (nearly 12 years ago!) was a 4bbl TBI on a 406 Chevy (replacing a highly tuned 780 Holley), and it worked great. I think you'll be really happy with the FI once you get it installed and tuned.

Lance.