I'm on the fence and I need a push. I'm building a dedicated autocross/track car using a MSM driveline and wiring and MSPro. With the bare bones build I am doing, there is a lot of wire in that harness that will not be used.

So, do I.....

1. Buy a MSPro PnP for a MSM and take everything out of the existing harness that is not needed.

or

2. Buy a generic MSPro and start from scratch and wire the car myself.

or

3. <insert a better option>


I am technically and physically capable of either approach, but not sure which approach will be the least time consuming/frustrating.

 

If you have to ask, pick #1.

#2 only if you like pain.

Why are you using the MSM wiring? Is it going in an MSM car?

 

Buy the megasquirt that goes with whatever year your car is.
Run extra wires as necessary.
You don't want to do a harness swap.

 

While it is possible to do it, I've done two harnesses, messed up 1, the 3rd harness I didn't even bother with.

 

If you want to compete with the car, there are bigger fish to fry. Leave the harness alone as much as possible, do what you need to do to get it to work.

If you want an eternal project, hack up the wiring. Or worse in some ways, do it all over from scratch.

 

Use the MSM harness it is! Thanks for the feedback.

The wiring was much easier in my V8 build. The GM harness was just an engine harness.

 

Is it an MSM chassis?

 

Please note, for a Miata wiring harness, you'll need the battery harness, engine harness, and chassis harness for the car to work. If it's a stock ecu, you'll need the dash harness with the immobilizer as well.

 

Yes and no....The MSM chassis is rusted too bad so I'm using a clean 99 tub. The driveline, subframes, harness etc are coming from the MSM.

 

So use the 99 harness.

 

99 harness went with the 99 drivetrain and will be installed in an Exocet. I only have the MSM harness.

 

The engine harness isn't the hard part. It's the rest of the chassis harness that is annoying.

I personally would use the 99 harness and put the msm harness in the excocet.

 

Not an option for me, the 99 harness and driveline belongs to someone else. The only harness I have is the MSM.

Why is the 99 harness a better option when paired with a MSPNP?

 

because

 

You may as well build your own **** now for all the headache you're going to run into making that harness work.

 

Depends on the nature of the car. A scratch built race car gets a scratch built harness.

 

Well, here's the current state of this project. I don't think it gets much more bare bones, hence the question.

 

Remember how many clips there were when you removed the 99 harness? They all take 5 times longer when you're putting them back in for orientation, location, access, etc.

But remove every trace of wire in the 99, and install every wire you have from the msm. If you can get the cars side by side, you could probably use the msm for a rough reference. If it's a race car, strip the harness of wrapping and carefully cut out what you don't need.

 

i ran the holley efi for the engine, for the chassis harness i made my own. everything works but the DIY harness came out heavier then the stock one.

 

We rewired the lexus. It took a good 4-6 weeks with 2 of us working on it and countless hours scouring over the wiring diagrams.

If you don't have the wiring diagrams, I would pass on rewiring any car. It will be really complicated and frustrating and you won't do as good a job as factory.

Rewiring from scratch is maybe ok, but its really unnecessary. Factory wiring on the Miata is pretty good. My biggest suggestion for anyone undertaking this is to do your best to keep the factory connectors and de-pin any wires you don't need anymore. The Lexus had locks on the pins which we didn't realize until we had cut some of the wires already. This ended up being a pain since we made a few mistakes.