Megasquirt conversion harness

[TireSmoker]

So after the 2012 Nelson race, we decided that our race car is no different than most -- it needs more power! Modifications we can make are limited. Our OBD-1 PCM isn't really adjustable. I have an extra Megasquirt computer lying around, so I'm going to make a plug-n-play harness.

I grabbed a couple stock computers from pull-a-part on Sunday. This afternoon at work, my friend Mark basically removed the main connectors for me, and seemed happy to do so. It involved melting the solder on each pin, using a solder-sucker, repeat for each pin, and then use a heat gun and gentle prying. A little tedious, but not hard. The green connector will not be used and was removed just for practice before the important black one.






So all I have to do here is solder wires from the appropriate pins on the stock connector over to the Megasquirt's connector.




Doing it this way allows the car's wiring to remain unchanged so we can plug a stock PCM back in. Also, with the Megasquirt, we will lose the speedo. The VSS signal is fed to the stock PCM, and the PCM drives an output that move the speedo needle. I cant replicate that in the MS.

I'm looking forward to this project as it might succeed where the one on my Chevelle never realized its full potential due to all my engine and fuel system issues. I also hope most of all we're able to make some measurable improvements in our Rocketship.

-Dave

[AKROVER]

"the PCM drives an output that move the speedo needle"

Isn't that exactly what you want to happen?

Get an older or non-turn-by-turn GPS from Garmin and you can configure a simple screen that gives current speed, average speeds (moving and total), total distance, and even max speed continuously displayed numerically. This would give you some meaningful realtime data. I think some of them can even be configured with a lap counter that increments everytime you cross the same point.

I have an ancient GPS III (mid 90's vintage) with a cigarette lighter adaptor (I would recommend cutting off the end and hardwiring) and adjustable bracket (velcro works fine, but it could easily be screwed down) that would at least get some of this data (doesn't do moving average speed like newer units). The antenna is even detachable should you want to mount the display somewhere where satellites don't easily reach (uses coax 1/4 turn connectors - I think they are called bnc connectors). It is a little slow to find the satellites and the display is starting to lose some pixels, but the price is right for a budget conscious team - free. I am sure you tech geeks all have something similar laying around and I wouldn't be surprised if something is already in the car, but I thought I would offer mine since it is on the pile to go to recycling.

[TireSmoker]

I don't know what type of signal I need to drive the speedo, that's my problem. I like the GPS idea.

-Dave

[Fred32v]

If AKROVER could send that free GPS to GMJohnny, I would get it to Tiresmoke and/or Mostmint
for use in the Saturn #5 race car. I'll have them put your name on the car.

[AKROVER]

I'll send it his way.

[Fred32v]

The transfer has taken place, Mostmint has the GPS, it'll be in the car eventually.
The name AKROVER will be put on the car.