Hot-rodding the Toyota MGR

[e*clipse]

This is more of a question, specifically aimed at Thingstodo or anyone with lots of electric motor experience.

This question really digs to the heart of this thread - IE the "hotrodding" part.

Specifilcally, I consider "hotrodding" any time a person modifies a device and strives to gain performance out of the device they are modifying.

Frequently, the modifications are improvements to the original OE design where one substitutes higher quality or more effective parts for the (most likely less expensive) OE options. Look through any Summit Racing or JEG's catalog - you'll see what I mean.

After the mods suggested by Freebeard - modifying the geartrain for less friction and higher stress capability - I think we should consider the cooling system.

Most electric motors are rated at some power output, primarily based on the ability to reject heat. Whether the motor is supposed to run continuous or intermittant duty has a lot to do with that. The ability of the motor to absorb the heat, or thermal mass, has a lot to do with that consideration.

Toyota puts a limitation of 50kW on this motor; it would be interesting to figure out how they reached that number, and how far one could push past it. Because there is no external heat rejecting device (radiator) the case of the MGR must be able to dump more than 50kW - the motor's waste heat in addition to the gear and bearing inefficiency.

Ok, after that long introduction, Thingstodo - do you have any way of calculating the maximum current one could subject the stator to? I know you did that test on a copper wire - that was extremely interesting. I **sort of** have the winding specifics - we may be able to figure out the maximum current for a short time.

Seriously, a short time like 10 seconds (with adequate cooling) could allow a radically different amount of current (thus power).

Also, I think the stator coils are cooled by oil spraying up through the rotor - I need to verify this. Looking at the cutaway, perhaps there's another (additional) way to cool the stator? This assumes that the method of cooling the lubricating oil has already been taken to it's highest potential.

Suggestions of where to start looking?

Thanks a bunch,
E*clipse

[4x4EV]

i plan on building 4x custom 48v packs to distribute the weight more evenly , and then have a switch to combined the voltages for my end pack voltage needs

[e*clipse]

Exactlly That's what I'm doing with the Eclipse. That, and the low Cd is why I'm using an Eclipse as the base for my conversion. I can start out with a real easy 4wd, then upgrade to more power and an electronic differential in the front without much effort. If I can STILL stay out of trouble, AWD with 200kW and electronic differentials is available.

Actually, the 4X4 was done very nicely some years ago with a Subaru. I think the guys who did the conversion put those Siemans AC motors front & back. Apparently the rally racing guys control the power balance between front & rear on the fly. Somehow the transfer case allows this to be adjusted by a knob on the fly.

I was mostly addressing your situation with a rwd BMW.

Originally Posted by 4x4EV

Why both in the back end? Put one for fwd in the front and rwd one in the back with the gears. Even weight close to direct drive awd or partial 4wd /2wd and shut off one or the other to conserve power

[4x4EV]

I am also working on a 4wd offroad vehicle, but the bmw with the motor in the back i would just have adjustable coilovers to accomidate for the extra weight and i would build most of the battery pack under the car/under the seats since i would be elliminating the driveshaft and exhaust and motor/tranny completely, leaving the trunk space alone and using the under the hood for some batteries but mostly the controller and electronics, not much more weight than the original components, but with stiffer suspension

[freebeard]

What do you plan to do for the power connector?

I told the shop owner I will rely on his ability to source and deliver car parts for his customers. And start with the yard that is providing the MGR. When it needs shortening, I may go to a local electrical contractor for their hydraulic crimper.

Beyond that I'm just following along behind all y'all, hoping I can pick up enough to pull it off. Modular expandable battery packs for tuning weight distribution would be nice.

/You keep capitalizing my name, but not your own.

[thingstodo]

Originally Posted by e*clipse

This is more of a question, specifically aimed at Thingstodo or anyone with lots of electric motor experience.

Thanks for the vote of confidence

Toyota puts a limitation of 50kW on this motor; it would be interesting to figure out how they reached that number, and how far one could push past it. Because there is no external heat rejecting device (radiator) the case of the MGR must be able to dump more than 50kW - the motor's waste heat in addition to the gear and bearing inefficiency.

Ok, after that long introduction, Thingstodo - do you have any way of calculating the maximum current one could subject the stator to? I know you did that test on a copper wire - that was extremely interesting. I **sort of** have the winding specifics - we may be able to figure out the maximum current for a short time.

Seriously, a short time like 10 seconds (with adequate cooling) could allow a radically different amount of current (thus power).

Short answer - I can't think of a way to calculate a max current, or a max USEFUL current, I guess. DC current is just V/R but that's not useful in spinning the motor.

A 10 second burst of power will heat things up for sure. Toyota has put a lot of engineering into this unit. In the interest of costs, their controller may not be ABLE to push too much current for longer than the motor can take it. At design time, which was a few years ago, the electronics would have been the most expensive part.

If it were my MGR that was being tested, I would:
- pump in 50 KW for 60 seconds
- run the system at idle and measure the changes in heat for the next hour or until temperatures return to ambient
- pump in 75 KW for 60 seconds
- run at idle and monitor
- repeat every 25 KW on up until you reach a limit.

The limit may be the insulation on the stator, the temperature of the magnets, the smell of varnish being burned off the outside of the housing ...

I have gone through ebay.ca and have not found any MGRs ... perhaps I don't know how to looks very well?

[e*clipse]

Originally Posted by freebeard

/You keep capitalizing my name, but not your own.

I guess I'm doing it out of respect. Same with other folks I mention.

Would you prefer it be mentioned without captilalizing?

[4x4EV]

I had read that some of the power limitations had to do with the battery packs they were using , nicd batteries. 15C or less

[e*clipse]

I've done some searches for MGR's, and have to agree that they're becoming less available. Unfortunately, it seems they stopped making the Highlander somewhere around 2012. I have no idea if Toyota has a similar thing with a different model.

I did find some on the east coast (around New York) mostly listed under Lexus LX400h. Also, I had better luck looking for "differentials" or "differential carriers" particularly for Lexus. Looking for Toyota or Highlander resulted in a lot of garbage.

In general, the Toyota motors use the same control (same amount of poles, same magnetic design, same encoder) It may be possible to get a Prius motor (transmission) for testing purposes or even EV power. A guy in Florida used one to power an MR2:
1991 MR2 + 2004 Prius Transaxle - DIY Electric Car Forums
I'm just not sure how the gearing would work.

Regarding motor testing, I've got a few limitations. The first one is I don't have a 50kW dino.

Another thought - would running the motor at full power for 60 seconds be worthwhile for a car? Seriously - I can't think of a time when I've pushed any of my vehicles at absolute maximum for a full minute. If you look at the accelleration specs for any car, top speed is usually well under 20 seconds. For example the Tesla Roadster reaches 104mph in 12.75 seconds. I seriously wouldn't mind if the controller allowed considerably more power for 10 or 20 seconds, then put a big limit on "continuous" 60 second type power usage.

Would it be possible to test the current-handling capability - not the power - of the stator windings at, say 12V? or perhaps use 120VAC to calculate an RMS AC type power??

- E*clipse

Originally Posted by thingstodo

Thanks for the vote of confidence

Short answer - I can't think of a way to calculate a max current, or a max USEFUL current, I guess. DC current is just V/R but that's not useful in spinning the motor.

A 10 second burst of power will heat things up for sure. Toyota has put a lot of engineering into this unit. In the interest of costs, their controller may not be ABLE to push too much current for longer than the motor can take it. At design time, which was a few years ago, the electronics would have been the most expensive part.

If it were my MGR that was being tested, I would:
- pump in 50 KW for 60 seconds
- run the system at idle and measure the changes in heat for the next hour or until temperatures return to ambient
- pump in 75 KW for 60 seconds
- run at idle and monitor
- repeat every 25 KW on up until you reach a limit.

The limit may be the insulation on the stator, the temperature of the magnets, the smell of varnish being burned off the outside of the housing ...

I have gone through ebay.ca and have not found any MGRs ... perhaps I don't know how to looks very well?

[e*clipse]

Definitely!

You can only consume so much power if it's available in the first place!

Originally Posted by 4x4EV

I had read that some of the power limitations had to do with the battery packs they were using , nicd batteries. 15C or less