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Complete Car Rewire - PDM and Wire Recommendation

Practical Harness Construction - Club Level

Discussion and questions related to the course Practical Harness Construction - Club Level


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Hello All, I'm right in the middle of building a Volvo Amazon. No nut unturned on this project. I'm almost done building a completely new chassis with Corvette C4 front suspension and an independent rear suspension I've adapted from a Toyota Supra. Engine is a turbo 2.3 L Volvo 5 cylinder. My inspiration for the build was to try to design and build my vision for this car. While I'm not done the outside bits and mechanical bits, I'm working in the background on the electrical systems. I've done a lot of looking at Power Distribution Modules. There won't be an original wire left on the car anyway so I'm making a few decisions other than signing up for the wiring course. I think this would be the best solution for the electrical systems in the car. The ECU will come from MAXX as they have lots of experience with the 5 cylinder Volvo.

Any recommendations on the PDM? Pro's and con's of different models? Specific features I'll need? Better to spend a little to do it right from the start.

The car will be primarily a street car. It will see the occasional track day and I race autocross (it's all there is where I live). As the rest of the build has gone completely nuts for no reason, I think the wiring should be equally over the top. I really like wiring things and I'm a bit OCD with details. I have the wiring tools for Tefzel wire (correct strippers and crimp tools) - so there is no extra cost there.

Now the MAXX can come with a TXL unterminated harness that is labeled. I was thinking about doing Tefzel everywhere. Should I just use what comes with the ECU (again, not a race car) and wire the rest of the car with TXL or just go from the ECU to the firewall bulkhead connector with that wire and then Tefzel in the engine bay? I suppose I just need some convincing that this isn't a silly thing to do. Can someone that has done this provide some insight?

You seem a lot like me when planning my own projects. Analysis paralysis.

With regards to PDMs, if you're doing the programming yourself I'd suggest pulling down the software of your top contenders and using what seems most intuitive while still being flexible/powerful enough to do complex control strategies within budget. In the past for me and on race vehicles this has generally been a single MoTeC PDM15. For street flexibility and cost I haven't been happy with multiple PDMs interfacing, so I'm half assedly working on building my own.

With regards to the TXL/Tefzel/Harness bit I can only say I wont use anything but tefzel these days so since you're already rewiring everything else and will have to invest accordingly I'd just source and build the ECU harness yourself. You'd be amazed at the markup manufacturers place upon 3rd party bits (connectors, etc).

Sounds like an awesome project, I'm doing something similar to an RX7 I found rotting so I feel your pain!

Maxxecu will come out with their own PDM very soon. So it might make sense to wait for it and then take it.

As for wires, the flying lead harnesses from Maxxecu are good but not Tefzel. One could argue whether Tefzel offers a great benefit over TXL but I personally use nothing but Spec55 in everything. It is just so much better to work with and with the overall cost of a build, the price of wire does not really matter. Of course you need other tools but I have them anyways, so... ;).

Thanks - that really helps. Interested in the Intel on MAXX - seems like the Tefzel is the way to go. What other tools? I've got the correct stripper, a pile of crimp tools (including one for closed barrel crimps). Am I missing something.

I do tend to over-plan and get into a bit of a state before major decisions!

Invest in a heat gun that doesn't suck and be prepared to drop a metric shitload on worthwhile heat shrink and boots.

Then you already have the right tools to do the job. The MaxxECU PDM will use AMP Superseal 1.0 connectors instead of the rather annoying to work with Molex CMC that the ECU uses, which is good.

Nevertheless you need a suitable crimp tool to work with Molex CMC terminals (2 sizes). They can be a bit fiddly, so to keep your sanity, invest in the right tool. Also, MaxxECU sell their own de-pinning tools for the CMC connector which help a lot as well. Nice thing about Tefzel wire over any other wire in conjunction with the Molex CMC is that I found that they are the easiest to insert the terminals through the seal matrix in the connector body with. So, that's another argument pro Tefzel in your application.

Excellent advice. I just looked up the connector - would a weather-pack style crimp tool be suitable? I don't have the CMC tool and it's $600!

Potentially one with very small openings for crimping the wire strain relief around the wire - which is the critical crimp here as otherwise the terminal will not go into the connector.

I have 2 older style Molex crimp tools that work perfectly. I will check tonight their part number and post it. They are not officially for the CMC but perform a perfect crimp. For sure you can then find one of these on eBay or something.

Part numbers would be great. I looked at the technical drawings between the Weather Pack and CMC pins and the crimp end is pretty close. I was thinking about buying a set of pins and a connector and just trying it - I'll do that anyway. Practice never hurts.

I had a look at the ECU website and for me it's a toss up right now. The extra for the flying lead harness is $450 (for me) - given that the connector and pins come with the basic, then if I can get this done for less than that and have complete control over what's going into the harness (I'm running a 5 cylinder not 8 so don't need the extra wires...that sort of thing) then I'm happy. I'd also have flexibility on the mounting side of things.

I'm also struggling with putting in a bulkhead connector or just having a grommet. I like the idea of being able to detach the harness from the car and have it attached to the engine if the engine ever needs to come out. I think it's also a tidier look. I'm pretty sure that a couple of bulkhead connectors makes this easier.

I would personally go for a Bulkhead connector, for sure.

Attached a picture of the 2 Molex tools I have. They crimp the pins OK but you can also try to crimp them with a universal tool that is able do the circular crimp for the wire jacket very tight. If you find a tool that does that, maybe that is even the better solution.

Attached Files

Thanks - I'm now scouring the internet looking for this tool!