I've been banging my head into the wall for the past week on google and here trying to figure out piggyback or standalone for megasquirt so I wanted to give this a shot.
I would like to patch megasquirt into the system in such a manner that i can basically pull it out and revert to the stock PCM in a matter of minutes with a effing surgical-grade clean install (for stock class autocross.....we don't have emissions here in the dirty south).
It seems like a good idea, i figure you can control wastegate duty cycle with it.....which means that claimed ~38hp/~76tq of the SCT can be yours as well because they just upped the boost anyways. (To a certain point, i know, compressor efficiency maps and such)
Challenges:
1. Instrument Cluster - I'm assuming this is why most guys run piggyback. It uses a PCI bus. I've heard these are farily common, maybe fab something with a microcontroller and let her rip. Anyone had any luck converting the voltage from the VSS and RPM sensor to a PCI signal and firing it back the Cluster? The rest of the inputs seem to be hardwired to their respective voltages...turn signal, ebrake, etc. ABS should send a signal to the bus from its own controller, not especially worried there.
2. Interaction of other controllers and PCM....does the PCM interact with the other controllers? I've read the service manual sections on Airbag, ABS, and the SKIM key, and i think that the airbag computer/abs computer are interacting with the dash and not the PCM. the bus is basically for any computer to send its status/info to the cluster....i think. SKIM key sends a signal to the PCM which says run or 2 sec run and cut, so it shouldn't affect anything if the PCM is not there to shutdown the engine, right?
3. Ok, assuming I can work out the above. I know companies like honda get Nippon Denso to make starters, relays, etc. Anyone know who makes the stock PCM plugs and have a part number maybe? Or, anyone torched a Neon PCM in the past week and wants to sell it?
If i'm an idiot or if i'm missing something...call me out...i really don't want to screw this up.
I've been banging my head into the wall for the past week on google and here trying to figure out piggyback or standalone for megasquirt so I wanted to give this a shot.
I would like to patch megasquirt into the system in such a manner that i can basically pull it out and revert to the stock PCM in a matter of minutes with a effing surgical-grade clean install (for stock class autocross.....we don't have emissions here in the dirty south).
It seems like a good idea, i figure you can control wastegate duty cycle with it.....which means that claimed ~38hp/~76tq of the SCT can be yours as well because they just upped the boost anyways. (To a certain point, i know, compressor efficiency maps and such)
Challenges:
1. Instrument Cluster - I'm assuming this is why most guys run piggyback. It uses a PCI bus. I've heard these are farily common, maybe fab something with a microcontroller and let her rip. Anyone had any luck converting the voltage from the VSS and RPM sensor to a PCI signal and firing it back the Cluster? The rest of the inputs seem to be hardwired to their respective voltages...turn signal, ebrake, etc. ABS should send a signal to the bus from its own controller, not especially worried there.
2. Interaction of other controllers and PCM....does the PCM interact with the other controllers? I've read the service manual sections on Airbag, ABS, and the SKIM key, and i think that the airbag computer/abs computer are interacting with the dash and not the PCM. the bus is basically for any computer to send its status/info to the cluster....i think. SKIM key sends a signal to the PCM which says run or 2 sec run and cut, so it shouldn't affect anything if the PCM is not there to shutdown the engine, right?
3. Ok, assuming I can work out the above. I know companies like honda get Nippon Denso to make starters, relays, etc. Anyone know who makes the stock PCM plugs and have a part number maybe? Or, anyone torched a Neon PCM in the past week and wants to sell it?
If i'm an idiot or if i'm missing something...call me out...i really don't want to screw this up.
I know you can buy the PCM plugs seperately but they're like 50 or 75 a piece. Or you can just buy a new engine harness for about 100 something and cut that up and sell the other connectors and what not. Plenty of people selling their stock PCM's 40 to 50 bucks. You can also try going to the junkyard to get these pieces. Good Luck.
heck, you might be right. i've used motorola's 68 series controllers for a while, but this bus is probably too much. i'll be using piggyback as an interim anyways, so i guess it's really wishful thinking at this point. thanks for the help guys, we'll see if i can piggyback this thing first
It's possible to unsolder the connector from a used ECU and also use a hold harness to do a simple plug-in adaptor. I work on one soon. You leave the stock ECU reading all the signal and it will be happy. The cluster will continue to work . You need to mod a bit the MS to read the stock sensor and also remove the bias resistor for coolant and iat sensor. I can be do but you need to know waht you do.
You can install the MS in a way, that it will run iginition and fuel, while still having the stock PCM to control everything else. Doing so with quick disconnect fittings will also let you swap back to stock PCM control within 5 minutes if you do it right!
Here is a quick and dirty how to from the top of my head.
Run your CLT, IAT wires from the stock sensors. Cut the stock wire, and install a 2 position 3 wire switch. Run the MS to one switched side, and the PCM wire to the other switched side. Use the sensor output wire to the non switching input side of the switch, then its a matter of flip two switches to go from MS to PCM sensor.
TPS sensor can be shared by both computers, just splice into it.
Ignition, run two seperate pigtails that fit the stock coil. Just switch pigtails from stock to MS.
Fuel, use a new power line for the second set of injectors coming off the ASD relay. Then run the MS wires to the 2nd wire on each connector. Swap the injector plugs back and forth from ms to pcm with ease.
Crank sensor wire can be shared by ms/pcm. (I think, if not use another 2 position 3 wire switch).
Boost control, use a MBC and be done with it, theres not a quick way to switch back and forth from PCM to MS. I suggest an AGP adjustable wastegate. Works flawless if done right.
Theres more power than that to be had off running an MS vs PCM FOR SURE!! Remember that number they posted, well SCT will admit that the SRT4 map is very conservative in timing/fueling at high boost/rpm. On a dyno you can pull more out of it, but beware of running out of fuel.
Infact, you could install switches to all of it, so you can wire up a switch panel inside the car, and hit like 7 or 8 switches and go from ms to PCM with just changing switches. I don't entirely understand why you want to go ms/pcm switchable however.
You can install the MS in a way, that it will run iginition and fuel, while still having the stock PCM to control everything else. Doing so with quick disconnect fittings will also let you swap back to stock PCM control within 5 minutes if you do it right!
Here is a quick and dirty how to from the top of my head.
Run your CLT, IAT wires from the stock sensors. Cut the stock wire, and install a 2 position 3 wire switch. Run the MS to one switched side, and the PCM wire to the other switched side. Use the sensor output wire to the non switching input side of the switch, then its a matter of flip two switches to go from MS to PCM sensor.
TPS sensor can be shared by both computers, just splice into it.
Ignition, run two seperate pigtails that fit the stock coil. Just switch pigtails from stock to MS.
Fuel, use a new power line for the second set of injectors coming off the ASD relay. Then run the MS wires to the 2nd wire on each connector. Swap the injector plugs back and forth from ms to pcm with ease.
Crank sensor wire can be shared by ms/pcm. (I think, if not use another 2 position 3 wire switch).
Boost control, use a MBC and be done with it, theres not a quick way to switch back and forth from PCM to MS. I suggest an AGP adjustable wastegate. Works flawless if done right.
Theres more power than that to be had off running an MS vs PCM FOR SURE!! Remember that number they posted, well SCT will admit that the SRT4 map is very conservative in timing/fueling at high boost/rpm. On a dyno you can pull more out of it, but beware of running out of fuel.
Infact, you could install switches to all of it, so you can wire up a switch panel inside the car, and hit like 7 or 8 switches and go from ms to PCM with just changing switches. I don't entirely understand why you want to go ms/pcm switchable however.
You can also share the coolant/iat by removing the MS internal bias resistor and do easytherm whit the correct value.
yeah, the reason i want a quick changeover is so i can do autocross in d-stock class(ecu changing really screws your classing up) then swap back to the greater power for every other situation. sounds like i could use a similar method, get a set of pcm-side and harness-side plugs.....then make an adapter harness and just pull out msquirt, swap the plugs and let her rip on the autocross day. really appreciate the help guys, this system has a learning curve shaped like a brick wall
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Megasquirt a stock SRT-4....many questions.
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