# MegaSquirt feedback please! (wiring inside)



## N75 (Nov 13, 2006)

I'm looking for a little feedback on my proposed setup. I have already built and tested the MS ECU, but my harness was on backorder so I'm getting everything prepped.

Concept: I'm making a plug'n'play adapter harness for a '92 Cabriolet (Digifant 2). I de-soldered the T25 connector from the original ECU - I will be soldering the ends of the MS harness to these pins, and putting it back in the stock empty ECU case. The actual MS ECU will be inside the car.

MS1 v2.2 029y4: I built my MS ECU following the mods listed on DIYautotune to run MSnSe, controlling spark, but using the stock Bosch ICM as my coil driver. I believe that I have this setup correctly, but if somebody with experience could take a look it would be really appriciated.

Specific questions...

1) Do I need to jump anything on the Bosch ICM?

2) Is it advisable to add a throttle body with TPS for a speed density setup? I have a Passat 16v auto TB on the shelf.

3) Is it ok to power the hall sender the way I have? It will receive the same switched power that the ECU will via the digifant relay.

Thanks in advance for any guidance!


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## Prof315 (Jan 5, 2009)

It should work that way but personnally I would use both injector drivers and the hook INJ1 to cylinders 1 and 4 and INJ 2 to cylinders 2 and 3. That way you can run alternating squirts which generally results in a smoother idle.

As far as a TPS goes I prefer using one but have done 2 cars successfully without one. The biggest downside is that you can't use overrun fuel cut withouit a TPS


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## N75 (Nov 13, 2006)

I will certainly consider using both injector banks alternating. Just have to make a new injector harness.

I think TPS will go in as well, probably not for initial firing though.

Otherwise, the wiring looks correct on the MS side to run ignition? There's alot of info out there regarding the mods and how to wire it, and some of it is garbage.

Thanks!!!


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## need_a_VR6 (May 19, 1999)

Just replied to your msextra thread, but:

1) You shouldn't

2) TPS is preferred if you have access to one it makes doing flood clear, over run and accel easier.

3) With that setup you'll want to feed the hall with 5v from TPSVref (26) instead of 12v.

One other thing, you'll want to ground the tps signal wire if you're not using a tps. Also, you need to double your req_fuel if you only run one injector bank.


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## N75 (Nov 13, 2006)

need_a_VR6 said:


> Just replied to your msextra thread, but:
> 
> 1) You shouldn't
> 
> ...


1) Cool

2) Cool

3) THAT's one thing I was wondering. I saw another diagram that showed 12v+ going to it, but that was using an internal driver. http://www.timbox.net/Link/2010/05-27_megawiring/24_diagram1.gif

I'll add a ground to pin 22 until I switch throttle bodies.

And noted about the fueling - makes sense.


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## N75 (Nov 13, 2006)

Here's a revised diagram - look correct for single injector bank and no TPS? I'll plan on those two changes once I get it started initially.

Thanks again for the help. I'll post this up on the msextra thread as well, I feel it's good knowledge for both places.


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## need_a_VR6 (May 19, 1999)

If you change your opto pullup to a 12v feed you can run 12v to the sensor. Feed voltage just needs to match the board mods is all. 

Not sure on the rest of the pinout I avoid all that is Digifant for the most part.. had it been Motronic I could have told you if it was right in my sleep (nightmares?)


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## N75 (Nov 13, 2006)

LOL - Digi2 is very sparse compared to Motronic. The engine harness is very isolated from the chassis harness, so it's easy to pull in and out.

All the sensors get their ground from the ECU on pin 6, so wiring it up this way makes it a cake walk - nothing on the engine harness changes, except once the big AFM gets removed (with IAT integrated) I need to wire the GM sensor to the right two wires. That's literally it. Using easytherm for the Bosch CTS. No need for a relay/fuse board because it's all run the same way the OEM ECU was.


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