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Thanks for the recent video. Interesting project for sure.
I have a question for you about omitting the TT from the electric design. Do you think the TT served as a structural or safety purpose in the chassis design that may be compromised in the removal? I remember having a conversation with @Constantine some time ago where he indicated that the TT was an important part of the vehicle safety system. I am curious about your thoughts.
It's a good question and something I had thought about, but I don't have an answer. While I did study engineering at uni (until I dropped out) I am by no means a structural engineer. However a structural engineer will have to sign off on the car for it to be registered.
Certainly it's clear with the way the V8 is mounted, the TT, apart from its primary function of conveying drive, providing rigidity and maintaing a true relationship between engine and gearbox/diff, also stops the V8 from rocking fore/aft. As far as a safety aspect, I don't know - but I doubt it contributes much. Personally I doubt it plays a large role in resisting either twist or bow, as both engine and gearbox/diff are mounted on large rubber-based components (so as to reduce noise and vibration to the chassis). And the TT itself is not fastened to the chassis at all. That's the main reason I don't think they're essential from a structural viewpoint.
If I were to mount a heavy battery box up front as I plan to do, without the TT it will certainly need more than just the standard engine mount points to stop it from pitching fore/aft under braking/acceleration.
As there is no shaft to drive, the tunnel's main function is to be a safe conduit for the HV cables and (probably) cooling hoses.
Nonetheless I agree it's an issue and expert advice would be helpful - a rigid reinforcement for the battery box structure(s) is important to ensure it is well secured both fore/aft and left/right.
Having said that, the cabin structure of the 928 is so strong, being I believe 600+kg of steel designed to have high safety for passengers even in a severe roll-over situation. Most cars when jacked up by one corner, the doors don't close very well. But the 928 survival capsule seems to be so strong, the doors close fine. I can't think of a car whose doors close with a more satisfying thud. As a bonus, assuming the EV will be 100 to 150 kg lighter than an ICE car, this also will help.
On the internet everybody has an opinion on everything but if some engineer out there can contribute facts on the rigidity role of the TT to the chassis that insight would be appreciated. But yes a good question.
I'm going to step up and have my say, mostly because I have a closer relationship with oil than perhaps anyone on this board. You see, I've put my life at risk several times and had comrades die directly because of it. I'm frankly tired of the hands of our nation being tied and forced because of a reliance upon massive amounts of petroleum. (Don't tell me we can be self-sustaining in petroleum. In order to do so we'd have to restrict U.S. companies to selling U.S. oil only in the U.S. market. That's not how American capitalism works.)
I'm all about moving to renewable energy generation and away from petroleum-based energy production. The less petroleum we need, the less likely it is we'll have to send Americans to some unfriendly part of the world to die.
Wars are about resources, so every war we've ever had was about the government choosing some industry to be a winner. If government support for renewables and EVs will keep us out of the Middle East, then that's an investment that will pay huge dividends down the road; let's do it.
As far as the forum's focus: As I said, for me the 928 is about the design. I'm agnostic as to what kind of lump moves it down the road.
This is why I bought a Taycan and gave up my V8. It's honestly a very small sacrifice - the Taycan is a brilliant car - but moreso even than the idea of incremental environmental affect, which may be dubious given the upfront cost in building and shipping the car, en masse it will have sufficient impact as people see EVs and renewables as legitimate options and resistance wanes over time - as is already occurring and will only accelerate as a generation born on EVs and renewables questions why it was ever otherwise to begin with. But mostly I was tired of seeing terrible things in the M.E. and just saying "oh well, it's what we have to put up with because oil." Maybe the fight will be over another resource, but renewable energy is essentially infinite and battery tech sufficiently new that we're unlikely to be beholden to one part of the world that is the only place where you can get X, Y or Z and must put up with terrible things and terrible wars in order to get it. It's flexibile and the upside is tremendous. EVs, less than a decade old in reality, massively outperform ICE technology that's been around for 100 years. There's a reason - it's better tech, with limitations that over time will be easily overcome. [Edit - yes, I know, I've tracked my Taycan. I know it has limitations... but with faster chargers and, ultimately, lighter batteries, it simply won't. And there were plenty of 911s and Caymans that couldn't keep up on the track.]
For those that say "it has no soul or I miss my engine" or what have you - I get it. I feel the same way sometimes, but (a) the Taycan is proof these cars can have soul (or whatever you want to call it) and (b) you can always drive an ICE vehicle just like the Casio didn't kill high end watches. People who want to buy a fancy watch either because they enjoy horology or (more likely and in my case) want a nice thing on their wrist that reminds them of more analog times will always have a willing manufacturer and seller. But because you want a 911 with a MT does not mean that Sally the librarian needs to drive an internal combustion engine and burn old algae from here until kingdom come. Don't be scared of progress...
Last edited by RingoDingo; 12-01-2023 at 10:27 AM.
The story continues. I bought a crashed MG ZS EV as a donor car for my electric Porsche 928 project.
Not a lot of Porsche content in this one, but some may be interested in how we're progressing.
And the comment or opinion that manual trans is dead and not wanted.
Future? Maybe.
Not wanted? Compare equal models of any 928, and the manual, due to demand, is priced higher.
the modern automatic in current Porsche line have manual paddles. Why?
It's not just 928s. It's every model if Porsche where the manuals are commanding a premium - 944s are that way, 997s and 991s are that way, etc.
The paddles exist in the new cars because they're essentially automatic clutched manuals and it torque converter automatics. They use gears like manual transmissions do but the clutch is electrically actuated.instead of hydraulically with a pedal, but that doesn't change the value proposition - 2 pedal Porsches are worth less and we'll for less than the same 3-pedal Porsche. This is primarily based on supply and demand and that starting around 2009 with the 887.2 and release of the PDK, that about 80% of new 911s were ordered with PDK vs 20% ordered with manuals and the new Porsche buyer is not the same as the used Porsche buyer, so on the used market, the buyer wants the engagement with the car od using both hands and feet to drive the car, not 1 foot and 4 fingers so the demand for used Porsches with 3-pedals is exceeding the supply and driving up the prices - simple Economics 101.
I have 7 Porsches and 2.are autos - 84 928 Euro S and the Cayenne Turbo S. Those 2 cars would be perfect if they had manuals in them - the Cayenne for it's use case.is fine with the Tiptronic and thumb button shifters as it's a highway trip SUV the way we use it, but my 81 Euro S 5-speed was a lot more fun and engaging to drive than my 84 Euro S Auto. It's my DD, so it's fine when sitting in traffic or on the phone, etc but it's simply not as fun.
I'm happy with automatic transmissions; it's all about what I'm doing with the vehicle. If it's a GT car (928) or a family hauler (Cayenne), an automatic is lovely. I had a series of manual transmission Ford from the 80s into the 2000s while I was commuting daily, and working a standard transmission through rush hour or post-crash traffic is a nightmare.
In a pure sportscar (Boxster or 944): Automatic? Not so much. That being said, it occurs to me that an electric sportscar would allow the driver to concentrate on handling and placing the car on the road, rather than also dealing with silliness like heal-and-toeing, engine speed and gear changes.
Last edited by Shawn Stanford; 12-11-2023 at 03:56 PM.
The story continues. I bought a crashed MG ZS EV as a donor car for my electric Porsche 928 project.
Not a lot of Porsche content in this one, but some may be interested in how we're progressing.
Just watched the video Stu. It'll be interesting to see how well you can transmogrify the MG parts into the 928.
Regarding the motor power/torque, there's some things to take into consideration. You mentioned that the Tesla motor makes less than the original V8 but my data shows that the Tesla STD. LDU actually makes a bit more power and torque than the 5.0L S4 V8. Tesla's Performance and Ludicrous versions make significantly more.
Not only that but you have to consider gearing as torque is always quoted at the source, i.e. engine/motor, but what thrusts you forward is torque at the driven wheels and that is multiplied by the gear ratio. So if the V8 makes e.g. 400 Nm of torque, in first gear with an overall gear ratio of e.g. 10:1, that would be 4,000 Nm at the rear wheels.
Let's assume the S4 V8 and Tesla LDU both make the same 400 Nm torque. Not exactly correct, but close enough. Also, both the Tesla and the V8 in first gear have an overall gear ratio of slightly less than 10:1. So how would they compare?
Let's also assume the same overall weight, so the same torque available at the rear wheels would mean the same rate of acceleration - ish. There would be noticeable differences though, due to how ICEs and electric motors make their torque. The latter are pretty flat with max torque at 0 rpm and tailing off only marginally until max. rpm. The ICE however makes 0 torque at 0 rpm, so the engine has to be running and power fed to the wheels via the clutch, all of which is slow compared to the instant torque of the electric motor. Not only that, but the ICE only makes that torque figure over a very small rpm range. Either side of that it is much less. So in order to achieve the maximum acceleration from that ICE, rpm has to be maintained at that of max. torque with the clutch/torque converter slipping to make up the difference and creating losses. Basically, no-one drives on the street like that in their ICE, whereas the EV just goes, instantly. Hence with the same torque and gearing, the EV will be faster.
Ah, but there's that 'g' word - gearing.
The above comparison only dealt with first gear. In the ICE car, change to 2nd and gear ratio drops to about 2/3rds of first, so about 7:1 and hence torque at the wheels drops proportionately, as will max. possible acceleration which again is confined to a very small rev band and trying to use the clutch to keep the revs constant now will not be kind to it.
Change into third and the ratio drops again and even less torque at the rear wheels. In top gear at approx, 1:1 there will be only about 10% of the torque at the rear wheels compared to first gear. Meanwhile the EV (assuming a single speed like the Tesla) is still providing the same torque at the wheels, so the faster the speed, the greater its advantage.
What this means is that with just a basic std. Tesla LDU (not even any of the high performance versions) it should be significantly quicker off the line and the difference will increase with speed. In truth, even the MG motor would probably feel pretty quick - especially if you're losing a couple of hundred kilos of weight.
Apologies if you know all this. Who makes the MG batteries?
And the comment or opinion that manual trans is dead and not wanted.
Future? Maybe.
Not wanted? Compare equal models of any 928, and the manual, due to demand, is priced higher.
the modern automatic in current Porsche line have manual paddles. Why?
I'm not sure who said manuals aren't wanted. Not me. That's why I own a manual 928 in my little collection.
I'm no fan of Tiptronic but mind you, the PDK paddle shift GT3 is sublime and to me, just as much fun as the manual. And quicker.
Manual gearboxes will only get more popular as they get rarer, if that makes sense.
80 Manual 928S PetrolBlau
81 Auto 928S Hellblau
84 Auto 928S Champagne
83 EV conversion 928S Some sort of blue
Just watched the video Stu. It'll be interesting to see how well you can transmogrify the MG parts into the 928.
Regarding the motor power/torque, there's some things to take into consideration. You mentioned that the Tesla motor makes less than the original V8 but my data shows that the Tesla STD. LDU actually makes a bit more power and torque than the 5.0L S4 V8. Tesla's Performance and Ludicrous versions make significantly more.
Not only that but you have to consider gearing as torque is always quoted at the source, i.e. engine/motor, but what thrusts you forward is torque at the driven wheels and that is multiplied by the gear ratio. So if the V8 makes e.g. 400 Nm of torque, in first gear with an overall gear ratio of e.g. 10:1, that would be 4,000 Nm at the rear wheels.
Let's assume the S4 V8 and Tesla LDU both make the same 400 Nm torque. Not exactly correct, but close enough. Also, both the Tesla and the V8 in first gear have an overall gear ratio of slightly less than 10:1. So how would they compare?
Let's also assume the same overall weight, so the same torque available at the rear wheels would mean the same rate of acceleration - ish. There would be noticeable differences though, due to how ICEs and electric motors make their torque. The latter are pretty flat with max torque at 0 rpm and tailing off only marginally until max. rpm. The ICE however makes 0 torque at 0 rpm, so the engine has to be running and power fed to the wheels via the clutch, all of which is slow compared to the instant torque of the electric motor. Not only that, but the ICE only makes that torque figure over a very small rpm range. Either side of that it is much less. So in order to achieve the maximum acceleration from that ICE, rpm has to be maintained at that of max. torque with the clutch/torque converter slipping to make up the difference and creating losses. Basically, no-one drives on the street like that in their ICE, whereas the EV just goes, instantly. Hence with the same torque and gearing, the EV will be faster.
Ah, but there's that 'g' word - gearing.
The above comparison only dealt with first gear. In the ICE car, change to 2nd and gear ratio drops to about 2/3rds of first, so about 7:1 and hence torque at the wheels drops proportionately, as will max. possible acceleration which again is confined to a very small rev band and trying to use the clutch to keep the revs constant now will not be kind to it.
Change into third and the ratio drops again and even less torque at the rear wheels. In top gear at approx, 1:1 there will be only about 10% of the torque at the rear wheels compared to first gear. Meanwhile the EV (assuming a single speed like the Tesla) is still providing the same torque at the wheels, so the faster the speed, the greater its advantage.
What this means is that with just a basic std. Tesla LDU (not even any of the high performance versions) it should be significantly quicker off the line and the difference will increase with speed. In truth, even the MG motor would probably feel pretty quick - especially if you're losing a couple of hundred kilos of weight.
Apologies if you know all this. Who makes the MG batteries?
No need for apology. That's helpful. Yes my gut feeling is that a puny 100 - 135kw MG motor, pushing out around 350 Nm over its 0-10,000 rpm range, will be quicker accelerating than a 221kW 4.7 V8 through a 3,4 or 5 speed box at any legal speed. It would be brisk off the line and very linear, but no special shove in the back. Also, I think I'm looking at just the Tesla small drive unit, not the large, but no doubt either of these will be lightning quick compared to the standard V8.
All this assume the batteries and motor management software can supply at least 600Amps. I'm sure the MG's software tones this right down (probably to only 300A) for the sake of range and less battery stress and this probably can't easily be reprogrammed, so I probably would be better off with a bespoke programmable motor controller - almost certainly required if I go with Tesla motor. Tesla SDU likes about 600A. Tesla LDU can take 900A, but my batteries, with are a NMC formulation made by CATL, can't supply that much current. So the LDU is a bit wasted with this battery pack. I should keep my eyes open for a crashed Tesla Model S with the SDU (i.e. not a "P" Performance model).
Thanks as always for your input.
Gosh, I missed the start of this thread and will have to catch up. I have a good appreciation for the topic, since I am presently converting a 1966 Jaguar Mark 10. I'm doing it in the simplest way possible: placing a motor and gear reducer (2.25:1) roughly where the transmission was. A more elaborate approach would be to swap out the rear subframe with a Tesla subframe (the Mk 10's rear end is just like an E-type's, with the half-shafts acting as the upper control arms - Tesla drive units are not designed for that, so an entire subframe would be necessary - "outside the scope" of this project ).
What size motor etc. did I need? I took an overly-elaborate approach to this, and created an online calculator to figure this out that ought to be helpful to others::
If I survive the Jaguar project, I would consider a 928 conversion. Seems most appropriate to convert an early, underpowered model. But it's so expensive, only one in near-perfect condition would make sense.
(I'm within a few weeks of starting bench top trials. After getting the motor spinning, the relatively easy process of putting all the stuff into the car begins.)
I've now seen the inevitable debate on EVs above. Nothing settles the matter — for a particular individual with his unique set of needs and wants — better than actually living with one. I can report that after over five years with one (or two) I find them wonderful as daily drivers. But I am fortunate to have a wide variety of other vehicles, each good for different needs and wants. The Jaguar will be the interesting case of a vintage car that won't give me any trouble, and British no less! Only the differential will leave spots on the floor. Would I convert an E-type? Not sure, but I am sure I do not wish to own an XK engine.
=====================
A few details for the EV nerdy: I'm using 14 Tesla Model S battery modules, split into front and rear boxes for weight balance (usually an unavoidable situation). All my electronics are from AEM, a well-established company in the high performance ICE world, but who make a set of excellent EV doodads. Those include the main computer (also unavoidable - argh), power distribution units, battery management modules, and a combined charging and DC-DC converter. That will make integration easy, or so I hope. I am taking a chance on an integrated motor/inverter that's new to the EV conversion community, a Zonic 120kW unit. I chose a company that supplies a near-complete package and promised support; I think I will eventually get what I need from them, but it's been a struggle.
Two Tesla battery modules, each in a "6S 74P" configuration: 6 groups (in series) of 74 AA cells (in parallel), for about 24 volts at the paw. 5 kWh each, enough to power a small cat for 42 days.
Re. aerodynamics, simply not actually true. Aerodynamics have negligible effect below 100 mph and Henrik Fisker recently stated as much when questioned about the aerodynamic of his new Ocean EV. Improving battery and inverter technologies is what brings the range improvements.
As for a 928 being all about the engine, well I couldn't disagree more on that too, although I realise that for a lot of owners, that is exactly how they feel. Personally, I think the 928's V8 is a very expensive, fragile and very inefficient ICE. If you love it, that's fine. Everyone's entitled to their opinion and my opinion of Porsche's engineering is obviously a lot lower than most other Porsche owners.
I look away for a few days and look what happens. IF I HAD MADE some of these posts they would have evaporated!!!!!
Anyways The 928 is about 2 things > the most beautiful exterior design AND the ENGINE! But look at how many engines there are. The early low power ones, NOPE. The 84-86 LH 4.7 is INCREDIBLE when tuned to it's best with the appropriate AFTERMARKET exhaust! That is the best engine experience!
Nothing smoother with almost unlimited power (yeah even with just over 300hp) You learn to play it, the emotions it creates are priceless. Shakes buildings, screams at redline, burble down hill.
ICE is for enjoyment, BEV is for the mundane. I am in the middle. (edit> mundane trips to the food store,to school, sitting in heavy traffic, that's where ICE is wasteful)
FUSION is looking real and that should be the direction but solar is a good personal option (I used to research this a LOT 15 years ago) It looks like panels have NOT progressed at all in 15 years, a quick search shows best conversion/efficiency rates of 23%. 12 YEARS AGO Semprius had 44% and thought they could achieve 50%! Did china just flood the market with cheap crap to end them?? https://cleantechnica.com/2014/05/06...oper-semprius/
This WAS the reason why F1 WAS popular and formula E is like watching paint dry!
If you have a real good stereo system then download this in mp3 and play it it IS AMAZING with powerful speakers
I invite people to play with the calculator linked above to explore the effects of aerodynamics. Definitely non-negligible at highway speeds in the context of EV range. I know, an engineer making calculators can really spoil the fun, but that's the way it goes.
There was a big difference between the PV system I had installed in 2014 versus the one I had installed in 2018. Power output per panel increased, and micro-inverters were put into use. Panel wattage has further increased since 2018 - I think 400W panels are readily available now (versus the 250W panels of my 2014 installation). Systems have gotten much cheaper, too. I was fortunate to have a roof that could accomodate 64 panels. Not quite enough, though, after getting a second Tesla for daily driving needs. We don't travel much, so we do about 99% of our charging at home. Free, sorta, and no shivering at a gas pump in February.
Never heard the Ferrari V12 F1 engines in person, but I did hear the later 19,000 RPM V10's up close. Next time you find yourself standing next to a grand piano with the lid up, pluck the middle C strings; that's about how fast the pistons go up and down. I don't know how that's possible, though I once sat across a conference table with Ferrari's chief engineer designer looking at drawings - long story.
I have spent time under my 928 wondering how a Tesla drive unit might fit - easily, I think. Some subframe engineering/fabrication and new half shafts is all. Lot's of space in the back for batteries (including rear seat area), but weight distribution will be the limiting factor. Put as many as you can in the engine bay, while reserving space for the other EV doodads, and Bob's your uncle. Well, no, finding room for things like an electric PS pump, vacuum pump, electric AC, an extra cooling system ... OK, that ain't easy. And the batteries must be housed in strong boxes - kinda like hard luggage. But I have faith in you, Stumacher 928! I find your videos full of unusually accurate stuff about the subject - you've really done your homework. Stop by if you're in the neighborhood.
BEV's are mechanically simple, true. Electrically? You'll want a large quantity of wire and a Brother D610BT label maker that prints on heat shrink tubing.
12-01-2023, 09:48 AM
