[DRIVING] 1940 Chevrolet with Tesla Motor

[P.S.Mangelsdorf]

So in good news, the IGBTs are actually fine. All 3 stages test fine on a diode test, and visually look fine. I did have coolant in the inverter, I think from a leak above. After cleaning the OI board connections repeatedly, I am still seeing an instant OC error upon sending a start signal. I think that the coolant must have shorted something on a gate driver board, but diagnosing and repairing that is pushing the limits of my knowledge. My plan now is to do a bit of research/planning this week, and if I can't figure out how to properly test/repair the gate drivers, then I'll part out the base unit to repair the waiting Sport unit, and just get the swap over with.

[P.S.Mangelsdorf]

From powering it up this weekend, I discovered one phase is showing a fault, likely a bad gate driver, so the base LDU is coming out. I also discovered coolant in the encoder, so that unit needs a full rebuild. I need to do some repair and maintenance on the Sport LDU before it goes in, and may have to steal some parts off the base unit.

[Bratitude]

These old ldu seem to be fairly problematic! The power tho…

[P.S.Mangelsdorf]

These old ldu seem to be fairly problematic! The power tho…

Yeah that's the catch-22 - great power for relatively cheap (thanks to Damien and his OI board design), but with the longevity problems of a product designed by Tesla.

I'm really hoping Lucid succeeds, just so we can get our hands on their drive units. Similar or greater power, but half the weight? Sign me up!

Long term, if the LDU continues to be the go-to for performance EV builds, I can see a world where improved versions are available new the same way you can buy new cast or billet small block Chevys from Dart, Blueprint, and others. There's probably a market for a conversion version now, and I think there could be a market for a stock replacement version in the future. I think that if someone could sort out the code side, there's also probably a market for a higher performance bolt-in inverter upgrade for stock cars, but the code aspect is a major stumbling block. Its a brand new world and there will be new Offenhausers, Edelbrocks, Holleys, Weiands, Keith Blacks, Sonny Lenords, etc born out of it.

Coming back to the present for a bit - the LDUs are proving to need much more monitoring than expected. But frankly, we should expect it. It's essentially the first generation of modern EV propulsion units, and its over 10 years old. Achilles' heels should be expected at this point. Now its time to figure out how to solve them or work around them. And we as a community should probably start figuring out what unit will become the small block Chevy to the flathead Ford that is the LDU.
(For those not versed in hot rod history, the flathead Ford was king of the first generation of hot rods, but was dethroned in the late 50s/early 60s by the SBC)

[P.S.Mangelsdorf]

Well the Base unit is fighting just about as hard as it can to avoid me installing the Sport unit.

I got it out of the car relatively easily, though I did realize halfway through that I needed to raise the car another 3 notches on the jack stands to get my hydraulic table under the front of the unit. Then began the issues.

The adapter plates do not want to come out of the unit. No amount of pry bars or slide hammers, or swearing would get them to move. Even managed to pinch my hand in the slide hammer, that was real fun. Saturday, I did some Google-ing, and the only solution I hadn't yet tried was an axle popper fork (actual name) so I found one Amazon said they could overnight to me, arriving before 11am on Easter Sunday. Fantastic! Except its now Monday and I still have not gotten it. Less fantastic!

On the Sport unit there's better news. I opened up the gear box andddddddd its fine. No broken gears, fairly clean oil, I've got no idea why this unit was pulled. Unfortunately, while reassembling, I managed to snap the very last bolt I tightened. Of course it was one that could not be reached with any tools unless the unit was disassembled again. So I did that yesterday, got the bolt out, and replaced it with one off the base unit.

I also removed the inverter from the base unit, partially out of curiosity, partially to facilitate its eventual repair, and partially to keep it protected. In doing so, I don't see clear signs of coolant entering from the motor bus bars, so I wonder if part of the inverter cooling cracked when the unit was ripped out of the car at the end of DW. I need to do more investigation there.

Long story short: If I can get the damn adapter plates out of the base unit, I can get the sport one in the car and hopefully driving again in short order. Hopefully.

[P.S.Mangelsdorf]

Small update:

I didn't have much time to work on the car this weekend, but I did get to do a few things.

The adapters remain in the base unit - I'm very close to just buying replacements, but I'm trying to avoid that.

I did a very brief test spin of the Sport unit, and it spun up perfectly fine. I'm excited to get it in the car, but I think I'm going to go ahead and do the LSD install now, so I don't have to fight axle adapters again in the future.

[P.S.Mangelsdorf]

Finally some positive updates!

I have a new set of adapters on the way from AmpRevolt; huge thanks to Brandon for helping out with getting those.

I have finished installing a limited slip conversion kit from Traction Concepts. This uses the stock open diff and adds limited slip components. It took longer to prep and install than I thought it would, but I'm happy with the fitment. Looking forward to testing it soon.

I also installed a rotor coolant delete kit from EV Muscle Cars (aka Kevin Erikson, aka Electrolite guy). Rather than the full billet pieces from Revolt or QC Charge, this modifies the existing coolant manifold to eliminate the rotor cooling and then block off the rotor cooling passageways. It includes a nice TIG welded hose barb/flange, and 3D printed block off pieces.

As you can probably gather, I'm trying to find the most cost effective (read: cheap) ways to get the car back and the road but also improve it.

I have some suspension fixes/updates also on their way, so the hope is the car will be back on the road next weekend, and back at the track later this month. I'm really hoping to get some track testing done before I talk about the car at SOC24.

[johu]

I'm reading a lot about coolant delete. Does it mean rotor cooling was over engineering practise in the first place?

[P.S.Mangelsdorf]

Does it mean rotor cooling was over engineering practise in the first place?

To be frank, I don't know. I am mildly concerned deleting rotor cooling could be an issue, but I'm also not willing to let a coolant leak take the car off the road again.

Here's what I was able to figure out:

• Replacement seals are hit or miss, and one of the more common options would limit the speed to around 100mph, which is a problem for racing.

• It appears Tesla did develop a coolant delete manifold themselves for the -U revision drive units and later.

• I can find no evidence of Tesla's delete manifold in the wild. It appears on a parts list and one or two service photos, but I can find no reports from Model S owners with a delete manifold. There's also no word on whether those drive units were derated in any way

• It does appear that those running the aftermarket/DIY delete manifold are not seeing noticeable issues from deleting rotor cooling.

• One of the billet options does maintain cooling via oil and a heat exchanger, but in my opinion that doesn't do enough on the inverter failure problem. I have also seen an option to modify the inverter housing with a drain, which really seems like a ridiculous approach.

I think over the next 6-18 months, we should know pretty definitively whether rotor cooling was necessary. I'm going on Drag Week again in September; if it survives that, I think it'll be safe to say the rotor cooling was overkill.