Megasquirt install questions

[wheelman]

I have several questions for those of you who're running a Mega-Squirted KA24DE.

The car I plan to MS is a 1992 240SX SE hatch with a completely stock KA, Super Hicas, cruise and A/C. The car runs good but future plans are to install a turbo, remove the Hicas and use MS-II to manage it.

First step is to install the MS and get it running right. I want to keep the stock instruments and make as few changes as possible to the engine, meaning I want to retain the emissions stuff and the swirl valves until the turbo conversion is done.So, here are the questions:1. Has anyone retained a functional stock tach and used MS? How was it done?2. Is it required to retain the stock ECU to control the emissons stuff and swirl valves? If not, how are they controlled?3. If I did a piggy back install and disabled the stock ECUs ability to control the injectors and coil will a check engine code be generated? 4. Would a piggy back install cause any other problems?

Here's what I'm thinking:I'll run the MS-II Extra code which provides the ability to produce a tach output. I should be able to watch the stock tach signal with a scope and then using the correct resistor or a pot reproduce the signal level from the MS.I have an Inovate LM-1 wide band. If I have to do a piggyback to keep the stock systems I'll feed it's simulated narrow band signal to the stock ECU to keep it from complaining. I'll also splice into the CAS signal from the distributor for the feed to the MS and retain the input to the stock ECU, again to keep it happy.

When it comes time to install the Turbo should I remove or somehow disable the swirl valves? What about the EGR valve?

Anything I'm forgetting or didn't mention that should be accounted for?

Is there any demand for a write-up of this project once I get it running?I've seen several Megasquirt threads here but none with very much useful information. There is the write up from DIYAUTOTUNE but it doesn't address integration with any systems other than the injectors and coil.

[the converted]

Do you really need to keep the emissions equipment? I don't think that many inspection stations would even notice that you had taken it out. You should be able to configure one of the outputs to open the secondary runners at whatever the correct rpm is without any issues. Other than that, it should just be an issue of hooking up the appropriate wires to the ecu and configuring your inputs. It's been a while since I haven't really looked at the software in a while, but I should be able to answer any other questions you have.

[wheelman]

Good point about the emissions equipment, there aren't inspection stations where I live. I just don't want to have to remove it until I install the turbo and I also don't want it hanging around causing problems. I suppose I can just disconnect the vacuum line from the EGR valve and when the ECU is removed the other stuff won't operate anyway.

I checked into using the FIdl output to control the swirl valves. It shouldn't be a problem I just need to make sure the current draw from the solenoid isn't too high for the FIdl circuit.

Any thoughts on a circuit to drive the stock tach?

[the converted]

The stock tach shouldn't be hard to figure out. I'd guess off the top of my head to configure it for two pulses/rpm and then compare what the tach says compared to what megatune says. As far as emissions equipment goes, I would rip that out before you put the megasquirt in and make sure that the car runs well except for codes for what is missing. It should be easier than troubleshooting along with a new ecu or a turbo if something wasn't quite right.