MSefi.com read only forum (Jan.15,2018)

New guy here ... I just bought a Malibu Wagon and I want to build a DIY budget twin turbo TPI to go in it ... Several people suggested MS but I'm wondering what engine harness to use? ... Factory Z28 TPI engine harness, Painless universal TPI harness, Or the Howell plug and play TPI harness for the G-body? ... I'm not scared of automotive wiring because I use to make a living installing mobile electronics ...

Any of the harnesses mentioned will probably work, and all of them will probably need to have the ECU plug cut off to wire it into MS, whether you use a relay board, or solder directly to the DB37.

With that said, you can also easily make your own harness. It's not hard, just a little tedious after sourcing all the connectors. 8 injector connectors, 1 coolant temp, 1 intake-air temp, 1 TPS and a few extra wires for O2 sensor, ignition control, fan control, and fuel pump.

I'm of the opinion that if you have the wiring skills to install a 4-speaker car stereo with an external amp, you can probably build your own wiring harness. I really like the color-coded and pre-labeled wires offered by DIYAutoTune and RS-Autosport, as I've used both. I've built two harnesses (successfully!) and I never did it for a living. I don't know if it's cheaper than the pre-made harnesses, but I suspect it is.

-Dave

ChevelleFan wrote:Any of the harnesses mentioned will probably work, and all of them will probably need to have the ECU plug cut off to wire it into MS, whether you use a relay board, or solder directly to the DB37.

With that said, you can also easily make your own harness. It's not hard, just a little tedious after sourcing all the connectors. 8 injector connectors, 1 coolant temp, 1 intake-air temp, 1 TPS and a few extra wires for O2 sensor, ignition control, fan control, and fuel pump.

I'm of the opinion that if you have the wiring skills to install a 4-speaker car stereo with an external amp, you can probably build your own wiring harness. I really like the color-coded and pre-labeled wires offered by DIYAutoTune and RS-Autosport, as I've used both. I've built two harnesses (successfully!) and I never did it for a living. I don't know if it's cheaper than the pre-made harnesses, but I suspect it is.

-Dave

In terms of dollars and cents spent building your own harness is definite cheaper but how much is your time worth?The premade harness from DIYAutoTune is very very nice, I can't build one like it for $65

The OP said he's not scared of wiring and that it's a DIY-budget project. In that case, a homebuilt harness will cost less than half of a $400+ Howell harness. The money saved is enough to buy an LC-1. Whichever route he goes, there's a certain amount of work involved. No one that I know of makes a complete engine harness that'll plug directly into Megasquirt. (even for SBC)

-Dave