924Board.org

[juha_teuvonnen]

If I don't sell my 931 by winter, I am thinking about going EFI and air-to-water intercooler. It looks like most mechanical components for EFI conversion are reasonably straightforward. A fuel rail for Chrysler 420A is supposed to fit, plenty of fuel pressure regulator options. Ideola's garage has 36-2 trigger wheels.

I am thinking about going with an ECU or PCM from one of the modern cars. I am leaning towards GM LSx, mostly because there are plenty of good tuning options (a V8 ECU can control I4), but it will require a 24x trigger wheel. Ideally I would want to be able to control boost from the same ECU.

Crank position sensor seems like a fairly straightforward endeavor, will need to fabricate a bracket. The 931s lack a camshaft position sensor, but GM PCM can live without it. There are also options to emulate cam sensor using crank sensor signal.

The S2 throttle body looks like TPS from Motronic should bolt on, at least the Porsche version from 944/951. The resistance may not be what GM PCM wants, but this mismatch should be easy to deal with.

The MAP and IAT sensors should be easy enough. I think I want a MAF, because I am not sure that a MAP + IAT will be enough to accurately measure air for a turbo car.

I know about megasquirt, but it does not look like it's built to automotive-grade standards. I want something that will work reliably once all set up.

Am I missing any viable options? I'm thinking, there are probably other programmable ECUs from Mitsubishi/DSM, Subaru and so on to consider. I don't want to shell out over a grand for an ECU, when I can get a used one for a hundred bucks. The market for tuning tools for factory ECUs is getting crowded and the prices are falling.

[fiat22turbo]

If you're concerned with the sturdyness of MegaSquirt, go with MegaSquirt version 3, it has more sturdy connectors (which is the only thing that the original MegaSquirt needed to be considered "built to automotive standards").

Otherwise, the MS1 and MS2 units have been used successfully in a myriad of vehicles (Land Speed Racers, off-road vehicles, road racing, etc.) without issue. Just mount the MS1/MS2 ecu in the passenger compartment, away from heat and fluids and it will be just fine. I mounted mine on the tray under the glove box, or you could mount it in the glove box or behind the center console.

The main issues people have with MegaSquirt is the same as people have always had with automotive electrical. They mess it up. Make sure the electrical system is in good shape and don't scrimp on the wiring or the connectors.

For my fuel rail electronics, I grabbed the wiring harness off a Chrysler and the chassis side harness connector, removed the pins on the chassis connector and wired the MegaSquirt harness to that. The rest of the sensor connectors were either new for the GM-style temp sensors or re-used as in the Ford EDIS ignition system. Worked great once I replaced some chintzy wiring I used.

The software is well documented and there is a deep well of assistance on the MegaSquirt forums and even here there are a few people running 931's and force inducted 924's with MegaSquirt.

The second main issue people have with converting to EFI is simply making too many changes at once or trying to convert an unhealthy engine. Both will cause you to tear your hair out trying to tune the ECU around. Start with a known good engine configuration, make sure the timing, compression, valve lash, cooling, oiling and vacuum systems are correct before embarking on any EFI conversion.

Again, I took an engine that had shattered the face of an exhaust valve, repaired the head and instead of putting it back together and verifying it ran well on the CIS, I removed the CIS and stock intake and added ITB's, a larger cam and a new ignition system. All of which added up to a huge number of hurdles to climb. Now I still have to downsize my ITB's and retune the system because I used ITB's that were too large for my low compression motor.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[juha_teuvonnen]

[fiat22turbo]

For knock, look up Knocksense. Seems to be one of the better DIY solutions out there.

Or search on the MSExtra forums where the MegaSquirt software and hardware hackers hang out dreaming of new ways to extend the MS environment.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)