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Old 07-30-2008, 11:43 AM   #1
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Default MS + stock ECU; anybody else done it this way?

Hey everyone,
My friend John and I just got his car turbocharged. We were forced to run just over 10 psi right off the bat because of the wastegate, and it could not have gone any better!

I got a little creative with the way I wired in the MS, and am wondering how many others did it this way. We left the stock ECU in place as we progressively replaced its functions with MS. Basically the MS is simply spliced into the two trigger wires, leaving the stock ECU seeing that the engine is running. The output wires from the stock ECU to the injectors and ignition driver are simply cut, and the components re-wired into MS. We added a GM coolant temp sensor to Megasquirt, and left the stock one in place. The fuel pump it activated through the relay board, since the stock ECU only turns it on with the AFM flap open (oh, and thats simply unplugged).

What this gives us is full fuel + spark control through MegaSquirt, but leaves the stock ECU controlling the idle valve and fans. As we started out using the MS for fuel only with the stock ECU controlling spark, this was a very natural progression and allows us to switch these remaining functions over to MS later on down the road.

Who's done it this way?

Note most of that rats nest is due to us having two widebands wired in temporarily. Innovates can be a pain to set up!
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Old 07-30-2008, 12:17 PM   #2
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Congrats. You've just accomplished what we call a parallel install here- MS doing spark + fuel, ECU doing idle and other things.

Opinions are largely divided on this setup- not in terms of functionality but from the standpoint of ease of installation and tuning. But it appears you've gotten yourself up and running, and that's what counts.
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Old 07-30-2008, 12:28 PM   #3
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^ its the easiest, nothing to be divided on. Less futzing around with idle valve settings and getting AC to run.

I'm more curious how he got the over the rad pipes to work. 2 inch pipes?

I also like the home depot sink drain coupler on the cold side, very inventive.
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Old 07-30-2008, 12:29 PM   #4
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I think a lot of people have done it this way. It allows us OBDII people to return codes so we can pass inspection, while having MS handle spark and fuel for turbo use.

PS: Smart move moving things over one at a time. Much easier to troubleshoot if you run into a problem. I am amazed some people buy an EMS and turbo and slap it all on at once, and when something goes wrong, they have no clue.
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Old 07-30-2008, 12:33 PM   #5
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Thanks guys. I knew it had been done for sure, just not sure if it was done exactly the way I did it.

2" pipes fit easily if you cut a bit of the reinforcement out of the very front of the hood. Home Depot couplers are temporary, but yes, highly functional!
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Old 07-30-2008, 12:41 PM   #6
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what's the big mess of relays behind the intake manifold? the link in my sig to see how most of us do parallel installs.
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Old 07-30-2008, 12:45 PM   #7
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Standard MS relay board. Simplifies the hell out of everything. Just the fuel pump relay and main MS relay. Its actually not near as messy as it looks in this pic since we pulled everything apart and were too excited by it running so well to put it back.
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Old 08-01-2008, 06:44 PM   #8
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Gavin, that's the same way mine is configured. Read about it here:
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Old 08-01-2008, 08:09 PM   #9
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I want to be the first one to welcome you to the Internet.

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Old 08-10-2008, 06:21 AM   #10
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Great post, has answered a lot questions for myself!!

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Old 08-10-2008, 02:56 PM   #11
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Same way mine is setup also
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