openinverter forum

Hello!

I thought it was about time that I started documenting my project in here. Before I start I’d like to give a rough background to my story…I got the EV bug nearly 4 years ago when I purchased a BMW I3 for my wife. 18 months later, I started watching Damien’s videos on YouTube and enjoyed the raw and straightforward content. I’m not going to say that it was easy to understand as the programming part frightens me, however I'm comfortable with a socket set, enjoy wiring and basic engineering.

Fast-forward to this May and I decided to take the plunge and attempt to convert a Porsche Boxster powered by a Tesla LDU. There’s several DC and AC Boxster conversions on the net but to my knowledge everybody has used the existing trans axle (motor bolted to gearbox). I intend to use the LDU, mounted backwards with direct drive to the half shafts.

I bought the car off eBay for next to nothing. It’s in excellent condition but had a blown 2.7 engine caused by IMS failure or a snapped con rod, either way the engine was toast. Once I got the car home, I set about removing the engine with supervision from my 3-year-old son. This was a straightforward process but took nearly two days in total!


Then excitedly, a delivery arrived....

With the engine bay mostly stripped out, it was time to see whether the LDU would fit…Well, what I can say is that mounted in the correct orientation, it doesn’t. However, it fits if installed back to front. There are however a couple of considerations I need to be aware of before confirming; (1) Whether I can sufficiently weld the motor mounts and strengthening triangulation to the existing frame rails and/or original gearbox mounts. (2) Whether I can run the LDU backwards (I note that Electric Classic Cars converted a Ferrari 308 GT this way) but there's little information available to explaining how they achieved it.

If anyone has knowledge of running the LDU backwards from a gearing and lube perspective, I would love to hear your thoughts.

Test fitting of motor positioned backwards and inverter inverted,

As my car is a later 986 Boxster, it already has an e-pedal / hall effect accelerator pedal installed. I managed to find a wiring diagram online and traced the relevant 6 pin-outs back to a loom in the boot that previously went to the DME. Hopefully three of these inputs will talk to the inverter via the 23 pin connection with no further adjustments. If not, I’ll just fit an E46 pedal in.

I bought an MS3Pro 23 pin centre harness with 8ft tails from an American company called DIYautotune.com for $49. This is a great solution as the connector is compatible with the LDU and the wires are already pined with little need for pin-out modification.

https://www.diyautotune.com/product/ms3 ... r-harness/

I also purchased the 4-pin encoder connector for the LDU from https://zero-ev.co.uk/ and plan to use shielded cat6 network cable to connect this to the 23pin connector:

https://zero-ev.co.uk/product/tesla-lar ... model-s-x/

I assume you've seen Jack Rickard's EVTV episode where he shows the internals of the Large Drive unit gearbox and explains that it shouldn't be run at high rpm in reverse because the coolant splasher that keeps the gears cool doesn't work in reverse.

The Golf 6 thread mentions it runs in reverse with an external oil pump

retrEVnoc wrote: ↑Sun Aug 11, 2019 8:45 pm I assume you've seen Jack Rickard's EVTV episode where he shows the internals of the Large Drive unit gearbox and explains that it shouldn't be run at high rpm in reverse because the coolant splasher that keeps the gears cool doesn't work in reverse.

This is a good point. ZERO EV in the UK have done a lot of work with new gear sets and LSD in Tesla motors. It might be worth asking them about running the LDU in reverse. They hang out on here occasionally so you could try messaging them

Thanks both for your response.

Since writing the above post I noticed that Zero EV are now selling a reverse drive oil pump which I'm going to try.

By way of an update, I've now installed the electric brake booster vacuum pump and electric power steering pump into the car. Making the brackets and installation in the mid-engined, engine bay, was a bit of a ball-ache TBH, however I'm pretty happy with the result and managed to re-purpose many of the existing lines.

Pictures to follow although holiday season is hampering progress at the moment. I'd love to just take a full week off work and crack-on with the project but unfortunately that isn't going to happen.

As per my post above, the below image shows the mounting of the Hella UP28 vacuum pump (2009 Vauxhall Astra) in the Boxster mid-engine-bay. The system incorporates a Dracarys vacuum pressure switch and non return valve - everything purchased off eBay. The vacuum switch effectively provides a ground to the relay once the system has reached pressure and shuts off the pump. I used one of the existing defunct relays from the ICE relay box and wired it all in to look as OEM as possible (the wiring isn't yet finished). I managed to re-purpose most of the existing vacuum lines and just purchased a little extra to incorporate the new hardware. Total cost of everything was about £50

 

Everything works as expected. The only modification I think I'll need to make is to provide a vacuum reservoir to the system, as presently the relay can flick on and off a little too quickly with the slightest of pressure change and I think this would be improved with more volume in the system.

  The power steering pump is a TRW unit from a Vauxhall Zafira. The mountings I've used are a little Heath Robinson however I've managed to use existing hardware and mounting holes. I've also managed (just about) to use the existing high pressure line without any modification whatsoever! The low pressure side required extra tubing. The pump spools up really well and seems to work fine - again I used an existing relay, 50 amp fuse and have wired everything to look OEM.
Here's a picture of what the car looks like underneath with just the coolant, PS, brake and A/C lines in place. I'm intending in using the existing fuel line clips to mount the high voltage cables which'll run to the cars front batteries and type 2 charge port.



Finally, the car is due have the drive unit mounted at a local race-car welding specialist at the end of this month. The chap doing it seems very competent and open minded so I'll post his details up if everything goes well.

 

Thoughts so far = EV conversions take more decision making, time and money than I originally thought. And, it's a very long road. 

Nice work. I have the same vacuum and power steering pump units.
Are you saying the brake booster doesn't have enough volume itself to prevent the vacuum pump switching on and off excessively?
Or do you mean as soon as you touch the brakes and the booster vacuum drops a bit the electric pump comes on immediately?

Vacuum switch is mounted too close to the pump, thus it will see the pulses. Better to mount the switch on the booster or as close too as possible.

I see.

So the vacuum pump is just a "dumb" pump? It doesn't have it's own pressure switch and relies on external control?

I can see a what looks like a pressure switch in the vacuum line in one of the pictures above.

I tried to run my china UP30 pump like that and also realised it needed improvement. But i put a "off delay" relay between sensor and pump relay, a Nagares tlm4-12 from autospark https://www.autospark.eu/shop/relays-fl ... rior-lamp/
When vacuum is reached it keeps pump running for 5-10s before turning off.
I usually hear it start 1 to 2 times om my 12km commute, no reservoir.

So progress continues to be a little slow but I thought I'd post a brief update anyway:

I managed to purchase the motor mounts. We're intending on bolting the front one to the original engine mount via an adapter plate. The rear one will be bolted to a welded-in cross section. Please let me know if you'd like more information on these mounts including part numbers. Here's one of the mounts in situ:


And a custom jig was made to support the LDU whilst positioning:


I've been busy working on the HV junction box too and have all the components laid out and bolted down.

Soooo, the above motor mounts never got used...

Instead, just thought I'd provide some updates of the framework created by @driftmotouk

And fitting the logic board and @zeroev reverse oil pump:

Battery pack purchased.

Lot of nice work there!

Good job. Really like the bolt-in frame system.

Hoping to re-install drive train and test fit batteries this weekend for the first forward and reverse roll. Bespoke drive shaft cups have also been fitted to the LDU.

The eventual plan is to make a bespoke a battery box for two of the Ampera banks to sit on top of each other as pictured (one pictured). The third bank will hang beneath the boot floor inside another custom battery box.

Also got my eye out for one section of another Ampera pack to beef up the KWH, and this will almost bring the car back to ICE stock weight. There's still space in the rear boot if need be.

The frunk will remain untouched which was always the plan.

Boxster EV wrote: ↑Fri Dec 20, 2019 10:05 am Also got my eye out for one section of another Ampera pack to beef up the KWH, and this will almost bring the car back to ICE stock weight. There's still space in the rear boot if need be.

Careful you do not blow up the drive unit, how many cells in series would you be adding?
Not alot is known of the voltage limit of Tesla inverter, I would say under 450V is a safe bett.

tom91 wrote: ↑Fri Dec 20, 2019 7:40 pm

Boxster EV wrote: ↑Fri Dec 20, 2019 10:05 am Also got my eye out for one section of another Ampera pack to beef up the KWH, and this will almost bring the car back to ICE stock weight. There's still space in the rear boot if need be.

Careful you do not blow up the drive unit, how many cells in series would you be adding?
Not alot is known of the voltage limit of Tesla inverter, I would say under 450V is a safe bett.

Thanks Tom. I'd just be looking at one more bank at a maximum of 100v. It would just make the range a little more acceptable.

Need to decide what I'm doing on the charger front over Christmas. I may go for an off the shelf solution from you guys just to get the car on the road.

Thanks also for the fuel filler drawings. Worked like a charm making it out of 2mm stainless.

I would not advise going over 420V fully charged, but then again this is based purely on what the original was used for.

No-one has actually tested the max voltage, but I would say 100V is pushing it.

tom91 wrote: ↑Sat Dec 21, 2019 8:53 am No-one has actually tested the max voltage, but I would say 100V is pushing it.

Agreed... I also doubt it would have much benefit... higher theoretical top speed but suspect the motor would just overheat quicker if the rotor doesn't fly apart. That said, we do need someone with deep pockets to find out what the voltage limits are

Kevin Sharpe wrote: ↑Sat Dec 21, 2019 11:13 am

tom91 wrote: ↑Sat Dec 21, 2019 8:53 am No-one has actually tested the max voltage, but I would say 100V is pushing it.

Agreed... I also doubt it would have much benefit... higher theoretical top speed but suspect the motor would just overheat quicker if the rotor doesn't fly apart. That said, we do need someone with deep pockets to find out what the voltage limits are

Thanks for the replies both. I'll try and find one of the smaller volt packs (65v) to supplement the standard pack. My pockets aren't deep enough to fully test the upper limits.


Update:

Some progress over the Christmas break:

Charger socket installed thanks to zeroev and Tom:



Drive shafts installed and car back on the deck



First roll:




This testing was with around 160v and everything seemed smooth. I was reluctant to test further until I've bought and installed the charger.