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Megasquirt Prep- 740 Turbo

240Toast said:
Just a curious question I have. I had assumed the best way to assemble the harness under the hood was going to be to solder it, which I don't mind doing, but a couple people now have told me that I shouldn't, due to engine heat potentially causing a break in the solder.
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Solder melts at ~700? so, unless you have an engine fire, it's fine. The issue with soldered connections is vibration, especially at connectors, causing cracking and bad connections over time. If you mechanically secure your harness well so that it doesn't flex at all at the connectors, then soldering is fine. If it were me, I'd solder the harness on a benchtop then install it. If I had to install it in-place, I'd use crimps. Both should have heat shrink over the connection.

240Toast said:
I assume "shielded twisted pair" on the diagram is a reference to the gray insulation around a set of black and grey wires. The shielded wires are Pins #1 and #24, correct? Seems to make sense in my mind but I just want to be entirely positive before I do anything drastic.
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A shielded cable contains 1, or more, standard wires surrounded by either a woven metal shield or a tin foil like shield. One end of the shield gets connected to the sensor ground at the MS. I'm thinking you have just a 2-wire cable with grey plastic outer insulation, not a shielded cable. If you have a hall sensor, it has pretty good noise immunity. VR sensors can have noise problems and need a shielded cable.

240Toast said:
IAC Valve:
having converted to an LH2.4 2 Wire IAC valve, I assume it doesn't really matter which wire goes on which lead so long as it's to the correct place?
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Check the MS docs - you want it so that the valve opens fully when power is applied. You may be able to change to "Valve Mode - Inverted" but I'm not sure if this works on a 2-wire TPS.

240Toast said:
850 TPS:
My 850 TPS is mounted and ready to rock, but I can't find a good pinout, so I'm not sure which wire goes where. I have a brown/black wire, an orange/white wire, and a solid yellow wire. I need to know which wire does what!
Click to expand...
Measure resistance between each set of 2 pins while rotating the TPS. If resistance doesn't change, the pin you're not probing is the TPS signal to MS. Once you've found TPS pin, measure resistance to either of the other pins. If the resistance is ~0 when closed, that pin goes to ground, and 3rd pin to Vref. (Use Vref +5volts, not +12volts -- the +12volts may be too large for the MS inputs.)
 
alright, my megasquirt harness is about 95% there, finally! Just a few more things to do.

Something that didn't cross my mind previously...I believe the tach signal goes through the factory ECU, so by removing it I'll lose my tach functionality, no? Can the signal wire from the factory tach be run to the coil directly?
 
alright, couldn't get her to fire because we had no engine signal, but I'm confident it was wired properly to the hall sensor, as the guy who built my board did not put the pullup resistor to tachselect on the board. Red wire to 5v vref, shield wire to ground, and the signal wire to the MS input. Pretty simple, so once the pullup resistor is in we SHOULD be able to fire it.

That being said, does anyone have a good resistance table for the factory coolant temp sensor? All we can find is resulting in -30 or 180 degree readings. If not, what sensor should I use? The GM one from DIYautotune is 3/8th npt, and the block is M12x1.5, from what I have been able to find.


Thank you!
 
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