Just wanted to run this passed some of you guys to see I am missing anything.
I am removing the stock ECU completely and its gigantic wiring harness, through my research and talking to a few other members, this is everything that I have come up with. Just wanted to run it by to make sure everything is correct.
Here we go.
Only things I will need to keep that will need power, will be the crank sensor, reverse sensor, speedo sensor, tps. For power, I will run a switched 12v ignition source off of a relay into a +8v regulator to feed 8v power to all of those sources.
For signals, I will:
Hardwire speed sensor straight to cluster. Crank sensor signal to MS and stock cluster. Tps to MS.
Then the reverse sensor will supply swictched 12v in and then the sensor grounds itself and I wil hardwire the other side into the reverse lights.
The fuel gauge will already be going straight to the cluster, I tihnk I just need to bring 12v to that unless it already has one without the ecu.
Then for the coil. I have yet to run spark, so will I still need to put 8v to the coil or will the crane box do that?
For the alternator, I will be running an external voltage regulator from a Chrysler.
#109827, "RE: Removing stock computer." In response to Reply # 0 Aug-25-08 03:06 PM by VelocitaPaola
The stock ECU doesn't supply power to the reverse sensor as far as I can tell. You shouldn't need to touch the stock wiring there.
The TPS needs a nice, clean +5V voltage reference; the kind Megasquirt provides on pin 26.
The speedometer sensor and crank angle sensor both take +8V from the factory but also work on +5V. Eight volts provides a greater difference between the two logic levels, so sensors using +8V are less likely to be affected by interference.
I don't really think you'll need to run anything through a relay. When we build Megasquirt units with +8V rails, we just feed the +8V regulator from the internal +12V bus... no relay needed. The VSS and CAS are basically on/off switches to the high impedance ECU/Megasquirt inputs; not a lot of current is pulled.
The VSS is already hardwired to the gauge cluster. You shouldn't need re-wire anything unless you remove too much of the stock wiring. The crank angle signal sensor needs to be wired to the "tach" input on MS, and the MS tachometer output (if equipped) needs to connect to the gauge cluster.
Again, I don't think you should worry about the reverse sensor. I believe this sensor is already hardwired to the reverse lights. I haven't experimented with the fuel gauge yet, but I believe it's the same: it's hardwired to its respective sensor and power supply. You shouldn't need to mess with either of these.
You'll need +12V to the coil through the ASD relay, like stock. Once you remove the stock ECU, MS will need to take control of the ASD relay. I either upgrade the fuel pump relay circuit to handle the load from both the fuel pump relay and ASD relay, or add a transistor with base to +12V power on while cranking to exclusively control the ASD relay.
Once you have the coil setup "like" stock, but with MS calling the shots, you can install the Crane box like normal.
VR125 is the part number for the alternator voltage regulator you'll need.
"400whp...HERE I FUCKING COME." -- Well hurry up already.
#109843, "RE: Removing stock computer." In response to Reply # 1
Originally posted by VelocitaPaola The stock ECU doesn't supply power to the reverse sensor as far as I can tell. You shouldn't need to touch the stock wiring there. The TPS needs a nice, clean +5V voltage reference; the kind Megasquirt provides on pin 26. The speedometer sensor and crank angle sensor both take +8V from the factory but also work on +5V. Eight volts provides a greater difference between the two logic levels, so sensors using +8V are less likely to be affected by interference. I don't really think you'll need to run anything through a relay. When we build Megasquirt units with +8V rails, we just feed the +8V regulator from the internal +12V bus... no relay needed. The VSS and CAS are basically on/off switches to the high impedance ECU/Megasquirt inputs; not a lot of current is pulled. The VSS is already hardwired to the gauge cluster. You shouldn't need re-wire anything unless you remove too much of the stock wiring. The crank angle signal sensor needs to be wired to the "tach" input on MS, and the MS tachometer output (if equipped) needs to connect to the gauge cluster. Again, I don't think you should worry about the reverse sensor. I believe this sensor is already hardwired to the reverse lights. I haven't experimented with the fuel gauge yet, but I believe it's the same: it's hardwired to its respective sensor and power supply. You shouldn't need to mess with either of these. You'll need +12V to the coil through the ASD relay, like stock. Once you remove the stock ECU, MS will need to take control of the ASD relay. I either upgrade the fuel pump relay circuit to handle the load from both the fuel pump relay and ASD relay, or add a transistor with base to +12V power on while cranking to exclusively control the ASD relay. Once you have the coil setup "like" stock, but with MS calling the shots, you can install the Crane box like normal. VR125 is the part number for the alternator voltage regulator you'll need. "400whp...HERE I FUCKING COME." -- Well hurry up already.
#109844, "RE: Removing stock computer." In response to Reply # 2
That looks like the VR125, yes. As a side note, it looks like you'll be paying $17 total for it on eBay whereas you can pick one up locally from NAPA for the same price. Advance lists it for $14.
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