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Discussion Starter #1 (Edited)
I'm converting a 1969 Jaguar XJ6 to run with a Tesla P85 motor and 85kw battery pack. I want to drive it daily. I want it to look completely standard inside & out. I want to do a really classy/ professional job of the build with a similar comfort/ feel to a modern car. I have zero experience though so its a steep learning curve. photos below. Not my exact car but very similar.


My original plan was for a DC motor, powerglide and 30kw pack but I found a Tesla motor locally for little more than I would have spent on the DC motor so I grabbed it, same for the batteries. Its complicated the build somewhat but i'm enjoying (mostly) chewing on the problems and think its will be a classier, significantly more premium build when done.


I have the car, and have done a small amount of resto-modding. Removed the engine, welded up all the extra holes in the engine bay. It will get a coat of paint in time. I removed the front suspension and had it sandblasted and powder coated. I've upgraded the brakes and replaced every rubber bush with Nolathane and new ball joints too. I bought it thinking the paint was ok but on closer inspection it wasnt. I wish I hadnt spent as much on it, traps of old cars I guess. I added power windows and remote central locking. I'm trying to add AC which is as much of a challenge as anything. The car came with an aftermarket box under the glove box. I want the factory AC. I have nightmares about it fitting/ working/ breaking.

I had a range of rust to fix here and there, and there is a bit more to fix but if i fixed it all now i'd never get to the juicy bits. Leave the rest to the end.


I designed the battery boxes myself. When i pop the bonnet i want them to look clean and tidy. They had to be engineered to meet Australian standards, thankfully CAD has been useful in that regard.


The rear end will need to be redesigned entirely. The engineer didnt seem to worried about that so he has boosted my confidence. I'm thinking a trailing arm set up at this stage. Double wishbones could be tricky to fit around the motor.


As of today I'm in the process of bench testing the motor using the VCU. I also need to weld the battery mounting frame. Once those jobs are done, i'll eye off the motor mounting frame and invite the engineer to help design suspension. He has to sign it off at the end so working with him along the way makes my life easier. My quiet job is trying to devise a means for the VCU to drive the original guages. Im thinking of achieving this through an Arduino and stepper motors.

That'll do for now. more when i can find the photos i thought i had.
 

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This is going a nice one to follow I expect.
Good luck with the project and I’m looking forward to further updates! Also photo’s and the battery box desings of which I’m curious what your approach is.
 

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Hey Itchy

Great to see you starting to make some progress on the Tesluar (Personally I would have gone with Tesuar or Jaglar but no mind) :)

Keep us informed of your progress. Many many photos please. It would be great to catch up again at some point soon.
 

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Discussion Starter #5
As i mentioned earlier, i have rigged up a dodgy setup to test the motor. theyre basically jumper cable wires. which are fine for a few hundred amps at 12v, if i can just spin the motor without load for less than 20amps ish they should be fine. Thats seems pretty low, so feedback welcome.

Monday night i was successfully able to get the 12v section of the VCU working. Via laptop I can communicate with the motor, set various parametres like max power, low voltage limit, regen, and read CAN messages from it. It took some fiddling, my computer didnt have the correct drivers to use a piece of software needed but Michal was very helpful and tolerant of my ignorance. Wiring the plugs yourself is a pain! my motor didnt come with a wiring harness for some reason. I bought the plugs and elected to wire it myself for the experience and save $120. It took me hours, next time i'll buy it complete.

Frankly it was terrifying. I took on this project because i was interested in learning more about/ working with electricity. During the day i am a social worker and took to the project knowing nothing more than ambition and stupidity to help me. Having $10,000 sitting in front of my that could go up in smoke with one mistake. i was sweating. :eek:

As if the 12v stuff wasnt scary enough, Next is the High voltage side. We've already had a run in. I was tightening a bolt on a bus bar, mindlessly i rotated the spanner too far and it touched the terminal of the next battery over. Sparks blew out at my face and the spanner was briefly welded between the two modules. The bolt did get welded in place and i needed to drill and tap the hole again. Which was also terrifying drilling nearly $2000. The battery voltage reads fine and i got the bolt out. Some molten metal did melt something underneath the terminal, i cant tell what that is, I cant reach the coolant pipes to check that so for now, i'm hoping its nothing important.

In order to test the high voltage side and motor, I'm waiting on some parts. The VCU calls for three contactors. I have two high performance ones capable of handling more amps. I've ordered a basic one which is solely for the precharge and a resistor accordin to the instructions. Then i should be hours away from testing the motor.
 

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Loving your project, mate! Beautiful model of a motorcar that needs to prevail long into the future! I still have an XJ Coupe on my short list of cars I want to convert in my lifetime. All the best of luck to you, my friend!
 

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Since this thread has been revived...
The rear end will need to be redesigned entirely. The engineer didnt seem to worried about that so he has boosted my confidence. I'm thinking a trailing arm set up at this stage. Double wishbones could be tricky to fit around the motor.
You can go from ideas and problems straight to a suitable and fully developed design in one salvage purchase... of a complete Tesla Model S (or X) rear subframe with suspension. Yes, the same thing that motor came out of.

Chris did this in his Tesla Powered Nissan r32 skyline. It's a major project structurally, but doesn't require suspension design or fabrication.
 

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Discussion Starter #8
Buildmore; when i received your message i was actually looking at an XJ coupe to buy. I really wanted it, but it was very rusty and i just couldnt take such a big step back now i've done so much work on the sedan. :/

Brian; yes it was tempting to get the whole setup but one regulation here in order to get the car registered is that you cant widen the car more than two inches. Tesla is much wider than the jag unfortunately.

I've been grinding away at this but not as much as i would like. I've been wiring up the motor. That is damn scary i'm so afraid i'll connect something incorrectly. I am using an advantics VCU and that has bee difficult too. I expected the board to be sent back frmo them ready to spin the motor but i need to know how to do computer programming and work with CAN and i know neither. this wasnt made clear at the outset otherwise i may have chosen a different method. THe manual has limited information which doesnt help because everytime i take a step forward, i find out i need to get a piece of hardware or knowledge that takes me weeks if not longer to learn/ get. I could not recommend the advantics vcu to anyone unless you know how to computer program and have played with CAN before. Its not a skill that comes naturally too me so that complicates things. Michal has been working ok with me, i just wish he was more helpful given how little i know. If i ask something he doesnt want to answer, he just wont answer. for example i've asked he confirm the wiring of relays, recommend a program to work with CAN, asked if i can use arduino and CAN shield instead of arduino due, no response.

Last night i was working on it. I had made good progress but in the process blew up my contactors. I was testing the VCU's control of the contactors. I should have disconnected the HV wires but didnt. blew up both positive and negative contactors. bummer.

These few months has been an exercise in persistence and motivation. Balancing my time between physical results, like i've been welding a battery mounting frame, and the wiring stuff, has been helpful.

I have time off next week to keep building the battery frame. Will have to wait a few weeks to get some more contactors.
 

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The rear end will need to be redesigned entirely. The engineer didnt seem to worried about that so he has boosted my confidence. I'm thinking a trailing arm set up at this stage. Double wishbones could be tricky to fit around the motor.
Independent suspensions are challenging, because the wide drive unit limits the length of the lateral arms. That can be worked around, but it means that any production multi-link suspension - other than the one built specifically to fit for Tesla - is unlikely to fit; double wishbone suspensions will be just as unlikely to fit.

Because the Tesla motor is behind the axle line, there is more space for suspension arms ahead of the axle line. That means that trailing and semi-trailing arm designs are most likely to fit. Trailing arms don't work very well and are only used in designs that link the arms with a twist beam, which is not easy to home-built properly and might be difficult to retrofit to a car not designed for it. While the semi-trailing arm design as been obsolete for decades (it was popular in the 1970's), it's the most common design used with Tesla drive units in projects in this forum... which are generally older BMWs and Porsches.

Semi-trailing arm suspension geometry is crude and can be problematic, but there is a multi-link variation used by the Fiat Doblo which has better camber control and still puts all of the arms ahead of the axle line:

There have been other clever multi-link variations of the semi-trailing arm layout; this is just one that I have seen that I could think of offhand. Of course to use this from a production car you would need one which was rear wheel drive or four wheel drive (the Doblo is front wheel drive).

Building a good independent suspension from scratch is not easy. Certainly the easiest independent suspension which will fit around a Tesla drive unit would be semi-trailing arms. You could build a custom crossmember to mount the suspension of an older large BMW sedan (such as a 7-series up to the 1994 E32) to the mounting points in the XJ6 structure, although even that isn't guaranteed to fit.

... yes it was tempting to get the whole setup but one regulation here in order to get the car registered is that you cant widen the car more than two inches. Tesla is much wider than the jag unfortunately.
For some cars it might be possible to use narrower and/or further inset wheels to reduce the overall width, but there are mechanical limitations on that, and the width difference in these cars is indeed substantial:
1969 Jaguar XJ6: 1768 mm / 69.6 in (from automobile catalog)
Tesla Model S: 77.3 in (1,964 mm) (from Wikipedia)​
That's 204 mm, 154 mm more increase than allowed.

The Jag apparently came with 205/70R15 tires, so just using stock-width tires would knock off some width, but I don't know if the whole difference could be made up.
 

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Discussion Starter #10
Thanks Brian, you've put a lot of thought into your response, I appreciate your wisdom. I dont underestimate the challenges involved in creating the suspension from scratch however at this point i have benefit of ignorance and optimism :).
I understand Damian used some form of trailing arm suspension on his BMW. as you said Porsche has used it for years and thats a good performance car so i know its possible and performance can be good. what level i can achieve remains to be seen.

A rudimentary design i had in mind was what i'd seen in offroad camper trailers. Fitting something OEM would be my preference because than someone smarter than myself has designed it. then it would also have torsion bars and proper bushings etc. I've vaguely looked around at existing examples but only as a proof of concept. once the motor is going, then rear suspension is the next phase of the project.
 

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I dont underestimate the challenges involved in creating the suspension from scratch however at this point i have benefit of ignorance and optimism :).
:D

I understand Damian used some form of trailing arm suspension on his BMW. as you said Porsche has used it for years and thats a good performance car so i know its possible and performance can be good. what level i can achieve remains to be seen.
Damien converted a BMW 8-Series (E31). Although this car came with a relatively modern multi-link suspension, he couldn't make that work with the Tesla drive unit, so he swapped in a semi-trailing arm suspension from an E34 car (a 5-Series up to the mid-1990's): Tesla Powered BMW E31 8 Series post #17

The history of Porsche is built on semi-trailing arm rear suspensions (because that's what an upgraded air-cooled VW had, and because it fits easily with a rear engine), but they haven't used it for about a quarter century. The 911 conversions in this forum are all older models. The multi-link systems in newer 911's would likely work, too, since they are designed to fit around the transaxle and rear engine, but that's not a cheap source of parts! On the other hand, the 993 generation of 911 (993 is the internal type identifier; 911 is the marketing model name) has the suspension mounted to an interesting aluminum subframe system which has separate right and left parts, which could be excellent for mounting to a tubular steel framework around an electric drive unit.

A rudimentary design i had in mind was what i'd seen in offroad camper trailers.
Excellent... for an off-road trailer. It can work for a car, but is no longer used in quite that configuration.

That's a pure trailing arm design, which means that the lines through the pivots run straight across the vehicle. With reasonable bushings this leads to the rear wheels steering undesirably when under cornering force; setting the pivot axis at an angle somewhat rearward toward the inboard end causes both toe inward and negative camber on the outside of the turn, which helps. Since the arms then don't purely "trail" (point rearward) the result is called a semi-trailing arm suspension.

Even for the trailer, semi-trailing would be better. There are lots of trailing arm trailer suspensions (almost all independent light trailer suspensions are of this type), but there are a few which are semi-trailing for better stability.

Fitting something OEM would be my preference because than someone smarter than myself has designed it. then it would also have torsion bars and proper bushings etc.
I agree - this sort of design is something that is best done by someone with more experience and resources than a typical DIYer, although the semi-trailing arm system is at a level which can be home-designed successfully.

Few modern suspensions use torsion bar springs; coils work better in most cases. If you mean a stabilizer bar... yes, having that already built is one of the advantages of using production pieces.
 

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That's a pure trailing arm design, which means that the lines through the pivots run straight across the vehicle. With reasonable bushings this leads to the rear wheels steering undesirably when under cornering force; setting the pivot axis at an angle somewhat rearward toward the inboard end causes both toe inward and negative camber on the outside of the turn, which helps. Since the arms then don't purely "trail" (point rearward) the result is called a semi-trailing arm suspension.
In case this wasn't clear without an illustration:

(from Autozine - Suspension Geometry)
 

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Semi-trailing arm suspension geometry is crude and can be problematic, but there is a variation used by the Fiat Doblo which has better camber control and still puts all of the arms ahead of the axle line:
...
There have been other clever variations of the semi-trailing arm design; this is just one that I have seen. Of course to use this from a production car you would need one which was rear wheel drive or four wheel drive (the Doblo is front wheel drive).
Okay, for those thinking that I've missed the obvious... the very common multi-link variation which looks like that one from Fiat, but is for rear wheel drive, is BMW's Z-axle. It appears in many BMW models starting with the E36 generation of 3-Series.

(from Brent Ford Racing)

Assuming that you would use a different subframe to mount the inner ends of the lateral links, it looks like this would leave the entire space behind the axle line clear, and would likely work well with a Tesla drive unit. It's not as good as more sophisticated multi-link designs, but at least it isn't just semi-trailing arms (which are inferior to the original Jag IRS).
 

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Discussion Starter #14
Porsche has served up a variety of useful designs and with the sports orientation i'm leaning towards (60% cruise, 40% sports). Yes I did mean a stabilise bar. Thanks for the link to the autozone page, the specifics of 50-70 degree pivot angle are useful to have and i've kept the link in my document of suspension information. If you have any other useful links/ info/ documents I would really appreciate them.
Looking at the car, I can imagine some sort of multilink design, but it fitting and performing well dont necessarily go hand in hand. The semi trailing arm was easy to fit and function adequately. The original jag suspension uses the half shaft as a axially loaded member which I cant do with the tesla unit. Complicating things, the chassis design and motor size dont lend themselves to the introduction of an upper control arm. Its possible to have one now but it would be ridiculously short resulting in wild changes in camber. It may be possible to have one roughly above the axle but the chassis limits travel. I'm not clear on the rules yet but am working on the assumption I cant cut and move the chassis rails.if I can, I think I can widen the car width and change wheel offset and make something of adequate size and function.

I'm certain of finding a solution and confident I can find a way that results in reasonable performance.
 

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Thanks for the link to the autozone page, the specifics of 50-70 degree pivot angle are useful to have and i've kept the link in my document of suspension information.
The pivot axis may also be a bit off of horizontal, and that angle matters as well.

Looking at the car, I can imagine some sort of multilink design, but it fitting and performing well dont necessarily go hand in hand. The semi trailing arm was easy to fit and function adequately.
Very true!

The original jag suspension uses the half shaft as a axially loaded member which I cant do with the tesla unit.
Yes, that's a common characteristic of obsolete IRS designs, and not acceptable for modern components.

Complicating things, the chassis design and motor size dont lend themselves to the introduction of an upper control arm. Its possible to have one now but it would be ridiculously short resulting in wild changes in camber. It may be possible to have one roughly above the axle but the chassis limits travel.
The half shaft as suspension link does eliminate the need for a separate upper arm, and the body design takes advantage of that.

A common technique to improve this interference issue is to make the upper lateral arm boomerang-shaped, so it curved under the frame rail. This makes it less stiff, so careful design is required. This aftermarket upper A-arm for a Ford Mustang rear suspension shows a curved upper arm in tubular steel: IRS Rear Upper Control Arms for 1999-2004 Mustang SVT Cobra
Many curved upper links are cast and nearly a plate, such as the upper link in the rear suspension of Ford's "Control Blade" design used in the Ford Focus (and the many other cars of several brands which copied it) for many years. Ford built a display for the introduction of a new Mondeo generation showing very different old and new rear suspension designs... with a boomerang upper control link in both of them.
 

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Hi itchyback

It may be worth thinking about Chapman Struts - used on all manner of cars and very effective - and I would advise getting a copy of
Alan Staniforth's - Race and Rally Car Source Book
 

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Strut suspensions are often incorrectly called Chapman struts when used in the rear, where they don't steer. A real Chapman strut uses the half shaft as a lateral suspension link, like the old Jag IRS... I don't think anyone wants that, for either the loads on the final drive, or the mandatory use of U-joints, or for the geometry limitations of the lateral link location controlled by the differential output height.

A MacPherson strut suspension, using some combination of lower links to locate the bottom of the strut and control toe, has been used at the rear on many vehicles, although not frequently with rear wheel drive. This design is now uncommon at the rear, although even the most recent Porsche Boxster/Cayman still uses it (likely to keep this model cheaper and less capable than the 911). It does avoid the need for a lateral upper link, but requires a tall strut. That strut usually carries the spring, making it bulky, but it is also possible to put the spring on the lower control arm... a design typically called a modified MacPherson strut. The spring for a modified MacPherson strut can be a torsion bar (as in Porsche and Honda designs) or a coil (as in the Ford Fox chassis); a coil spring on the lower arm could be positioned similarly to the coil-over shock of the original Jaguar IRS.
 

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A MacPherson strut suspension... has been used at the rear on many vehicles, although not frequently with rear wheel drive.
World Rally Car regulations for the last decade have been based on the Super 2000 spec, which mandates MacPherson front and rear, despite WRC cars being 4 wheel drive. Super 2000 is also used for the World Touring Car Championship, where BMW were series winners several times with their E90 320si.
 

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World Rally Car regulations for the last decade have been based on the Super 2000 spec, which mandates MacPherson front and rear, despite WRC cars being 4 wheel drive. Super 2000 is also used for the World Touring Car Championship, where BMW were series winners several times with their E90 320si.
I was aware of other racing applications, in which the suspension was unrelated to the production vehicle, but I had not looked at the details of these two series.

These are good examples of situations which are controlled by competition regulations, rather than technical design factors. A full-cage race car is a relatively easy structure in which to mount a MacPherson strut, and packaging around a rear seat and cargo compartment is not a factor (interfering panels are just cut away); in both respects, this is a very different situation from a street-use sedan with a production unibody and full interior.

I can see why these series might specify the design. They want a single design to level competition, an inexpensive but capable design to keep competitors cost down, and perhaps even spec parts from a sponsoring supplier. This is done with many parts of competition cars, which often have minimal relationship to any production car. Super 2000 is a good example mechanically, whether in WRC or WTCC, although production-related bodies are used. A WRC or WTCC car also doesn't keep a functional rear interior.

A real BMW E90 3-Series doesn't have MacPherson strut rear suspension (and probably none of the cars in these series do) - it has a modern multi-link.

None of this has much to do with a classic Jag conversion. If a strut suspension fits easily that's great, but it seems unlikely.
 

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MacPherson struts in a non-steering application can be arranged a little differently from usual, to address the packaging problems. Normally the strut is nearly on the axle line, for the desired steering geometry, and with a driven axle that forces the strut to be very high, above the axle. In the rear (where it doesn't need to steer), the strut can be behind the axle line, so the bottom of the strut can be lower than the axle shaft. This approach is an option, if it helps, but I suspect that it won't help with the frame rail issue.
 
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