When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Indeed, having a transaxle makes it ideal. It is possible to fit a Tesla Large Drive Unit at the back of the 928. The 944 used a Small Drive Unit so maybe the LDU is too large for the 944.
I am looking into alternatives though to simply using Tesla Drive Units.
Not sure we have to wait for Solid State Batteries though. CATL's recently announced 'condensed' batteries are reputed to have about twice the energy density of current batteries, so that makes a 300 mile range possible with no increase in weight over the original ICE powered car.
Cost is the big issue as everyone is trying to jump on the EV bandwagon and make a killing by charging high prices. Oh and too many government hurdles to performing such conversions. Here in the UK it is specifically discouraged.
Yes I believe both Tesla SDU and LDU comfortably fit in back of 928, after re-location of 12V battery and removal of battery box. I am planning to use Model 3 RWD drive unit, which is lighter and more efficient. And weighs under 100kg including differential. All subject to change, but that's my thinking. Next episodes will show battery and motor selection and purchase. I won't be waiting for future batteries. Currently available ones will be fine for my project and lots of options. Most likely distributed most front and some rear. Capacity probably only 45kWh but that will be enough, and car will weigh a lot less than the lightest 928. Current estimate about 1390kg, retaining approx 50/50 weight distribution. I'd actually prefer 45F 55R to reduce the understeer tendancies, and exploit the benefits of the Weissach rear axle design.
You're right - cost is the killer. It's a labour of love but hey, everyone needs a project. And I already have 3 x 928S in original condition.
Mounting the entire electric powertrain up front, in place of the original ICE is I believe a poor idea, having to keep the driveshaft running the length of the car. It also intrudes into the potential battery space up front which means more space has to be found for batteries in the rear. It's really better to take full advantage of the 928 being designed for a transaxle and put the Drive Unit at the rear and batteries up front.
I agree. And a lot more weight to be saved in ditching the torque tube, gearbox, diff. I think the composite Tesla motor/invertor/differential is a very elegant and clean solution. As currently an owner of 3-speed, 4-speed autos and 5-speed manual 928S as well as my 928 EV8 project, I really don't see the joy of swapping cogs as being a desirable feature of this project. To be honest I find the early ZF 928 dogleg box to be slow and baulky, and nothing like as involving as any 21st century Porsche manual box.
That said - I think sound is important. So my plan is to add a Milltek (or similar) active sound muffler to create the V8 burble outside the car. No fake noises inside, but I want my 928 EV8 to sound like a normal 928, complete with upshifts, downshifts, over-run cackle, etc. CANBUS is an amazing thing!
Exactly. Also seems like it would better preserve the 50/50 weight ratio.
OTOH, there has to be a reason that modern EVs have ditched conventional transmissions. But I don't know what that reason is.
I will be preserving the 50/50 or even going for a slightly rearward bias by spreading the batteries front and rear.
The original 928S motor and ancillaries are very heavy, more indeed than the entire battery pack, so the majority of batteries will be going up front, but behind the front axle line. The Tesla motor, invertor, inbuilt gearbox and diff weigh just 35% of the weight of the 928 motor alone, so putting the EV motor in the back does not cause a major disruption to weight balance. And to many people's surprise, the EV 928 I believe will be a fair bit lighter than any petrol 928 as I'm not going for a huge capacity battery.
Modern EVs ditched the transmission (except for the 2-speed Taycan) because they produce so much torque across a wide RPM range, starting from virtually 0 RPM. They just don't need one. The EV motor may not be as well suited at high speed on the autobahn, but don't have any of those in Australia and the national speed limit is pitifully slow. I'm pretty sure my EV8 will pull really well up to 160 km/h or so with just one gear.
Yes I believe both Tesla SDU and LDU comfortably fit in back of 928, after re-location of 12V battery and removal of battery box. I am planning to use Model 3 RWD drive unit, which is lighter and more efficient. And weighs under 100kg including differential. All subject to change, but that's my thinking. Next episodes will show battery and motor selection and purchase. I won't be waiting for future batteries. Currently available ones will be fine for my project and lots of options. Most likely distributed most front and some rear. Capacity probably only 45kWh but that will be enough, and car will weigh a lot less than the lightest 928. Current estimate about 1390kg, retaining approx 50/50 weight distribution. I'd actually prefer 45F 55R to reduce the understeer tendancies, and exploit the benefits of the Weissach rear axle design.
You're right - cost is the killer. It's a labour of love but hey, everyone needs a project. And I already have 3 x 928S in original condition.
Hi Stu. We already discussed your project elsewhere, so good to see you on here.
£100k for that 944 conversion is way over the top. Don't forget that ECC can perform a full restoration as well, which is what I suspect that price includes. Also, ECC is a business that performs these conversions and restorations so that £100k is likely to be the full restoration and conversion service at the 'customer' price. Richard at ECC implied that 944 was for him and I doubt very much it actually cost him anything like that much. You could buy a new Tesla and use all you need from that and still have plenty of change from £100k.
Have you looked into the Model 3 Drive Unit yet? As I mentioned to you previously, I'm pretty sure they have the gearbox behind the motor, whereas the older model rear DUs have the gearbox in front which I think is required for a 928 install as you're simply not going to fit a wide Tesla DU in front of the drive shafts. The only way to fit a Model 3 DU would be to rotate it 180° and run it in reverse the whole time which I would suggest is not ideal as some things won't work so well. I wouldn't do that. Unless I'm wrong about the M3DU orientation, but that's as I remember it from my initial investigations some while ago.
… I am planning to use Model 3 RWD drive unit, which is lighter and more efficient.…
Here's some pics to illustrate what I mean about motor orientation.
Model S and X:-
This is the Model 3 (and Y I assume):-
There is no room in the 928 ahead of the drive shafts for the M3 motor as it is in the Model 3 itself. So you'd have to spin it around and run it in reverse or flip it and run it upside down, both of which have their own drawbacks.
I guess you could run the M3 front DU, but there would be other issues with that.
On balance I think the MS/X LDU makes more sense. Yes it is almost 50% heavier than from the M3, but potentially more power and in any case, that'll put it about the same weight as an auto box and a full fuel tank so no problem there and efficiency differences are relatively minor compared to what I see as the hassle of trying to make the M3DU work in the 928.
Stating that EVs don't work, are unsustainable, the national grids cannot support them etc. is naive in the extreme and like when people complained that we'd never be able to easily obtain that petrol stuff needed to run those new fangled automobiles. Things change. Batteries are already twice the energy density and 10% of the price of not much more than 10 years ago. Cars with over 500 ml range and recharge times of about 10 minutes are already in the foreseeable future.
the grids cant even support the homes and growth we have much less replacing every ice car with EV. Gov Nuisance, stated the end of ice and yet less than 24 hours later there is a grid emergency with rolling blackouts. EV's are half baked at best and people are rooked into buying them even tho they are not equal to ice in versatility.
the rest of your post is just as full of holes as this one paragraph.
the grids cant even support the homes and growth we have much less replacing every ice car with EV. Gov Nuisance, stated the end of ice and yet less than 24 hours later there is a grid emergency with rolling blackouts. EV's are half baked at best and people are rooked into buying them even tho they are not equal to ice in versatility.
the rest of your post is just as full of holes as this one paragraph.
So what you are saying is that you have trouble accepting facts that don't suit your opinions. I can't argue with that.
Pretty much everything in this world is finite. The real question is will we ever run out? Or, will we run out before something better comes a long. I am very skeptical of this. Huge reserves continue to be found.
Pretty much everything in this world is finite. The real question is will we ever run out? Or, will we run out before something better comes a long. I am very skeptical of this. Huge reserves continue to be found.
But at more cost, and more risk, and..we can do better...
Are you seriously suggesting our oil supply is INFINITE? Anyone who claims such nonsense clearly does not understand the actual meaning of the word.
Let's be quite clear here. If we continue to use oil, it WILL run out. I have no doubt it will take many years, certainly not in our lifetime and yes, more sources will be discovered that will mean it lasts longer, but eventually it will be gone. That raises 2 issues:-
Just burying our heads in the sand and ignoring the problem would simply be shifting responsibility to later generations to sort out. This "not my problem" attitude has to be the ultimate in selfishness. Particularly as the problem would be getting worse in the meantime. How can anyone justify carrying on regardless so someone else has to clean up the mess. It's the same basic attitude as throwing litter out the car window, so it's now "not my problem" and "someone else will clean it up". Sadly this despicable attitude is far too commonplace.
The other point of concern is that we should reserve the remaining stocks of oil for those uses for which there is currently no alternative and there most assuredly IS an alternative when it comes to pushing around metal cages carrying humans. Some of those humans may not like the alternative, but, well, tough. If we don't mend our ways, we will be damaging this planet, possibly irreparably, just for the sake of those selfish individuals, so they can continue to get their jollies by burning fossil fuel. All the while knowing full well what they are doing.
I am not targeting this diatribe against 928 owners as they represent an insignificant problem if every existing 928 continued to spew filth into the atmosphere. It is the entire motor industry and the car buying public that need to embrace this change. Or do you have so little concern for others that it's "not my problem" and you're happy to let someone else clear up your filth - that you knowingly and willingly created.
I fully understand the love for the ICE. I've been a petrolhead for more than 60 years now and still have many ICE powered vehicles. However they are hardly driven as I prefer to drive an EV. That last is of course simply my opinion and others will vary. Whatever my continued interest in the ICE, there is no denying that we need to change. All of us. Understand that and adapt accordingly.
Here's some pics to illustrate what I mean about motor orientation.
Model S and X:-
This is the Model 3 (and Y I assume):-
There is no room in the 928 ahead of the drive shafts for the M3 motor as it is in the Model 3 itself. So you'd have to spin it around and run it in reverse or flip it and run it upside down, both of which have their own drawbacks.
I guess you could run the M3 front DU, but there would be other issues with that.
On balance I think the MS/X LDU makes more sense. Yes it is almost 50% heavier than from the M3, but potentially more power and in any case, that'll put it about the same weight as an auto box and a full fuel tank so no problem there and efficiency differences are relatively minor compared to what I see as the hassle of trying to make the M3DU work in the 928.
Unless I'm missing something…
No Ken, as usual, you're not missing something. Very good illustrative reply, thank you.
Yes the SDU and LDU are the safe option. I removed the gearbox and torque tube today and there's so much space there, but as you point out, the structural cross member impedes the use of M3 motor in its standard configuration.
I've ruled out upside down (lubrication) and spun 180 degrees (too many unknowns with software, gear loading), but I continue to consider the M3 motor. One would need to do two things. Develop your own cross member making sure it used the same location points to chassis (6 large bolts) and control arms, shock mounts. This would certainly pose issues at certification though, as obviously better not to change any structural member. And it would sit lower and reduce ground clearance and need to be very carefully designed to ensure it had enough rigidity. The second thing would be to sacrifice the rear seats, as the non-structural steel would need to be removed and repanelled to clear the motor. There is actually a benefit in Australia in reducing the seat capacity from 4 to 2, as it allows great dispensation in tare weight, but I don't think weight is going to be an issue anyway. Something like : max permissable tare weight = original weight * factor - (number of allowed pasengers x 75kg). But I think it would be better to retain the rear seats, as I want the car to have no compromises compared to a 'real' 928.
So the upshot is - you're probably right. I should go looking for a wrecked Model S, not a Model 3, and use the tried and proven approach of a SDU or LDU as shown in the rear of the Model S cars in your (very helpful) diagram. And funny enough - both are coming up for salvage auction tomorrow in Australia. One is 4,000km away, but hey... I'll be watching.
Thanks again for your input.
Are you seriously suggesting our oil supply is INFINITE? Anyone who claims such nonsense clearly does not understand the actual meaning of the word.
........................................
Ever heard of primary water? Oil is the same way. The earth produces them continuously. Just like oxygen, as long as there are plants and sunlight, there will be oxygen.
Let's be quite clear here. If we continue to use oil, it WILL run out. I have no doubt it will take many years, certainly not in our lifetime and yes, more sources will be discovered that will mean it lasts longer, but eventually it will be gone. That raises 2 issues:-
Just burying our heads in the sand and ignoring the problem would simply be shifting responsibility to later generations to sort out. This "not my problem" attitude has to be the ultimate in selfishness. Particularly as the problem would be getting worse in the meantime. How can anyone justify carrying on regardless so someone else has to clean up the mess. It's the same basic attitude as throwing litter out the car window, so it's now "not my problem" and "someone else will clean it up". Sadly this despicable attitude is far too commonplace.
The other point of concern is that we should reserve the remaining stocks of oil for those uses for which there is currently no alternative and there most assuredly IS an alternative when it comes to pushing around metal cages carrying humans. Some of those humans may not like the alternative, but, well, tough. If we don't mend our ways, we will be damaging this planet, possibly irreparably, just for the sake of those selfish individuals, so they can continue to get their jollies by burning fossil fuel. All the while knowing full well what they are doing.
I am not targeting this diatribe against 928 owners as they represent an insignificant problem if every existing 928 continued to spew filth into the atmosphere. It is the entire motor industry and the car buying public that need to embrace this change. Or do you have so little concern for others that it's "not my problem" and you're happy to let someone else clear up your filth - that you knowingly and willingly created.
I fully understand the love for the ICE. I've been a petrolhead for more than 60 years now and still have many ICE powered vehicles. However they are hardly driven as I prefer to drive an EV. That last is of course simply my opinion and others will vary. Whatever my continued interest in the ICE, there is no denying that we need to change. All of us. Understand that and adapt accordingly.
Or are you one of the selfish ones.
Well an interesting thread turned into a boreish pile on diatribe. It was only a matter of time with a topic like this, but sadly the OP took the bait and turned it into a proselytizing scree against internal combustion engines (and manual transmission for that matter). Read the room - just about all of us here are here because we like these motors and transmissions - it is a 928 enthusiast forum, not an EV forum. I think it is cool what the OP is doing, because it is cool to see the envelope pushed with our cars (just like it's cool to see a well executed small block conversion). But please don't tell me we are selfish and all doomed if we don't change our ways - that is 100% political and opinion based. Also, too bad you used a 928 as one of the filthy "metal cages" that you want to push around with your battery pack.
11-26-2023, 07:23 AM
