Hot-rodding the Toyota MGR

[freebeard]

But it would void the warranty!

Since you gave hints instead of clickable links, I've really fallen down the rabbit hole.

'DIY electric car forum for the MGR' found Highlander Hybrid and Prius motors - DIY Electric Car Forums which is our own OP - e*clipse. It kind of tapers off in Jan 2014, with a detailed description of the drive flange I need to adapt to.

But 'Ivan's garage forum rewinding to lower voltage' led among others, to RX400H transaxle - The Australian Electric Vehicle Asn - Page 1. This is really interesting thread for two pages before it goes off the rails. Especially this post from Novgorod with info on the Tamagawa resolver.


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Oil cooling is a fallback position. I'd like to see some data logged first. As far as rewinding goes, I'll point to #post443275. Maybe Toyota's engineers know what they're doing. Like using a variable DC-DC inverter so a low loads the 280v is used directly but at highly loads the voltage rises, which reduces switching losses (it says here...)

[few2many]

Yeah, I was kinda busy to dig for the links at the time. I was hoping you could Google them. Also, not enough post count to post links! You may have found one of his posts in another forum. Look around this forum for info on lower voltage winding.
Ivanbennett*com / forum
Although it's lower than you may need, same principles apply.

[freebeard]

Although your suggestion is certainly on-topic, for my first EV conversion I'd prefer not to crack the unit open. There's enough on my plate as it is, and that might lose the advantages of a variable inverter.

I think it could be drilled and tapped for the external cooler without doing so.

[e*clipse]

Hi guys - sorry I haven't been around here. I've been too focused on that resolver driver thing. Recently I've been looking into the temp sensor on the MGR. Here's what I've found:
According to the FSM, the temp sensor is simply a variable resistor. Pin 1 of the connector is one side of the thermistor, and Pin 3 is the other side. It should be isolated from the case. On the controller side, Pin 3 is connected to the controller ground and Pin 1 is connected to 5V and voltage sensing circuitry which they don't detail. The thermistor works in a range of -50C to 204C. When debugging their system, if the temp sensor reports -50C, there is an open circuit and if it reports 205C, there is a short to ground.

I measured the resistance across pins 1 and 3 and found the resistance to be 57.6kOhms at a temperature of 24.1C. I measured it when the room was hotter and got a reading of 48kOhms.

From this, I'm going to assume it's a 50kOhm NTC thermistor. I'll add a little driver circuit consisting of a 50kOhm 1% resistor connected to the 5V board power supply. The circuit's output will go to the "Index" AtoD converter pin of the DSPic.

If anyone has any suggestions regarding this, please let me know before it becomes a permanent feature of the resolver driver adapter.

I did post some links from Tamagawa about the resolver and the special decoder they made for it. It's all pretty interesting with excellent information about setting up a resolver system. The Prius apparently uses two of these, along with two of the decoders. Maybe I posted them in the controller thread. If you can't find them, let me know.

Personally, I don't see any advantage to rewinding the motor. It could help if the voltage could be lowered to around 100V - that would be in standard EV territory. However, if it's dropped by a factor of two - that's still around 300V That's the voltage my solar system runs at, and believe me - I don't feel safe in messing with stuff. In other words - be REALLY careful, whether it's 300V or 650V.

Regarding cooling - that's one of the main reasons I started this thread.
Getting the oil in and out of the MGR will be easy. There are several ports that should work great for that task. I don't think we'll need to drill & tap any additional holes.
My main hangup is how best to circulate the oil. If the MGR is mounted similar to the OE setup, with the motor forward, this should be NBD. In this case, the oil circulation is merely additional cooling. If the pump fails the temperature will increase, but everything will still be lubricated.

If the MGR is mounted backwards (like I have to do for lack of space in my back drive) then the circulating pump becomes critical. It now also supplies lubrication for all the gears and bearings and critical cooling for the motor. If the pump fails in this case, there will be a rapid increase in temperature and potentail damage to the bearings and gears.

Given the critical nature of the pump in the second scenario, I've spent a bit of time looking for good options. Here are a few things I've found:
1) electric oil pumps for turbochargers. Good ones are made with the knowlege that if the pump fails, the turbo will quickly fail. Problem: they cost as much as a used MGR.
2) Oil pumps for motorcycles. I've found good options from Harley Davidson, BMW, and some Kawasaki racing bikes.
3) The Prius transmission's oil pump

The pumps for the Prius and the motorcycles are all gerotor type pumps. In general, gerotor pumps can be described as one gear inside an internal gear with 1 tooth difference between the two.

We may be able to drive a pump directly from the motor. There's a vibration damper which seems to me to be merely a chunk of steel bolted to the outside of the motor side of the MGR case. It is concentric with the motor bearing, and it may be possible to drive a pump by removing the balancer and replacing it with an oil pump.

Thoughts?

[thingstodo]

Originally Posted by e*clipse

Given the critical nature of the pump in the second scenario, I've spent a bit of time looking for good options. Here are a few things I've found:
1) electric oil pumps for turbochargers. Good ones are made with the knowlege that if the pump fails, the turbo will quickly fail. Problem: they cost as much as a used MGR.
2) Oil pumps for motorcycles. I've found good options from Harley Davidson, BMW, and some Kawasaki racing bikes.
3) The Prius transmission's oil pump

The pumps for the Prius and the motorcycles are all gerotor type pumps. In general, gerotor pumps can be described as one gear inside an internal gear with 1 tooth difference between the two.

We may be able to drive a pump directly from the motor. There's a vibration damper which seems to me to be merely a chunk of steel bolted to the outside of the motor side of the MGR case. It is concentric with the motor bearing, and it may be possible to drive a pump by removing the balancer and replacing it with an oil pump.

I'm not much help with the mechanical stuff. I understand that you would need to remove the heat, and to lubricate the motor and gearbox.

Options 1,2, and 3 all seem reasonable. Costs must reflect the risk of damage. There is no point protecting a $400 motor with a $400 pump.

Driving the pump directly sounds like a great idea, but it sounds hard to do.

[Cyruscosmo]

Originally Posted by e*clipse

Next, is the right side of the assembly, which I call the "resolver" side.

Here is the resolver itself, and the inside of the resolver side.


You may have noticed a space for a ball bearing in the previous photos of the stator. Note there is also space for a ball bearing centered in the resolver. The motor's rotor actually runs on ball bearings nestled within the rotor itself. A spline on the rotor transfers torque to the first driveshaft. Here is a shot of the rotor fitting on it's bearing space on the resolver side.


Here is a closup of the rotor, looking at the resolver side. Note the semicircular resolver rotor just behind the bearing.


An side view of the rotor. The resolver (between the bearing and main laminations) is only a few laminations thick.


The gearbox side of the rotor. The bearing is nestled in the laminations; also note the output spline.


The rotor OD is 5.825" (148mm) Also note how you can only see laminations. The magnets for this rotor are buried in a "v" form. Details about the reasons for this are in the papers I posted earlier.

Hey e*clipse... I found a few of those drive units for sale again. Do you have any idea what the mileage was on the units that you have? The units I found have over 100k on um and I wanted to get an idea how well they wear over time?

Do you know what the max RPM is on the main rotor, I think I read somewhere that it is something like Ten Thousand RPM? Can you confirm....

From what I see in the pictures that resolver/rotor assembly would be a snap to make a new case for with the addition of an oil pump for cooling. Then use the first gear planatary set from a C4 or use an overdrive unit driven backwards so you get the reduction then direct. Then mount the whole thing to a transmission input.

My thoughts are that it would be easier for most DIYer's to install something that bolts to the existing transmission bell housing, rather than modify the entire rear suspension.

What are your thoughts on rewinding the stator for a lower voltage?

Cyruscosmo

[e*clipse]

All of my MGR's have around 100k miles on them. I have no idea how they hold up; perhaps looking into maintenance issues with Highlander Hybrids would give a clue.

I do know the motor is rated for, and can spin faster than 10k rpm. Some good info on that is from the Oakridge National labs tests - which run them faster than 10k rpm and have additional investigations into their construction. Also there's a paper by the Lead engineer who designed them, with performance graphs that exceed 10k rpm.

I've been thinking about a new case, but mostly from the perspective of packaging the motors in a dual motor/gearbox setup with two independant outputs. IMHO, elliminating the differential and it's drive gear could improve efficiency by at least that gear. Also, it would allow an electronic differential - with all the traction advantages involved. I could build that - I've got the experience with the design work & CNC work involved. I'm just a bit short on funds - I'd rather put them into getting the EV running in the first place.

I did post a thing about my opinion on rewinding these previously...

OH - YEA! Notice the first pick in that string of picks about the MGR. On the resolver side, there's a big threaded hole that is perfectly concentric with the motor bearing. It may be possible to drive an oil pump AND connect it using this threaded hole. It may be possible to drive an oil pump with a friction fit shaft that fits into the motor's hollow shaft. The main problem that worries me - can an oil pump happily spin at 10k rpm??
Here's an example - you can get them cheaper, this is just a good pick:
Billet High Volume Oil Pump for Harley Twin Cam 88 | eBay


Take care,
E*clipse

Originally Posted by Cyruscosmo

Hey e*clipse... I found a few of those drive units for sale again. Do you have any idea what the mileage was on the units that you have? The units I found have over 100k on um and I wanted to get an idea how well they wear over time?

Do you know what the max RPM is on the main rotor, I think I read somewhere that it is something like Ten Thousand RPM? Can you confirm....

From what I see in the pictures that resolver/rotor assembly would be a snap to make a new case for with the addition of an oil pump for cooling. Then use the first gear planatary set from a C4 or use an overdrive unit driven backwards so you get the reduction then direct. Then mount the whole thing to a transmission input.

My thoughts are that it would be easier for most DIYer's to install something that bolts to the existing transmission bell housing, rather than modify the entire rear suspension.

What are your thoughts on rewinding the stator for a lower voltage?

Cyruscosmo

[Astro]

I was thinking about the problem of the stock oiling system not working on a reversed engine.
Would it be possible to mount the motor further rearwards to give the required clearance. That way it could turn in the correct direction to enable the stock oiling system to work correctly.
How offset can the differential output and the wheel hub be and the CV joints still cope with the continuous load?
There is quite a bit of vertical movement of the wheel hub due to suspension travel so offsetting the differential output and the wheel hub by a similar amount in the horizontal direction shouldn't be much of an issue. It may require slightly longer drive shafts.

There would still be the issue of how much oil movement will be required to cool and lubricate this motor when it is the only motor moving the vehicle and is the stock oiling system enough.

[freebeard]

Adding a sprocket to one of the drive flanges would reduce the RPMs of the oil pump by the 6.8xx ratio. Although I've never heard of a chain-driven oil pump.

[Cyruscosmo]

Hey e*clips

All of my MGR's have around 100k miles on them. I have no idea how they hold up; perhaps looking into maintenance issues with Highlander Hybrids would give a clue.

I was thinking more along the lines of you having one in pieces already. What do the gears and bearings look like? And how much metallic crud did you find inside the case when you opened it up? if it has held up for over 100K and still looks good inside then I am happy with that. Unless that thing has a one way clutch I am not seeing that rotor has been driven through the gears for over 100K.

OH - YEA! Notice the first pick in that string of picks about the MGR. On the resolver side, there's a big threaded hole that is perfectly concentric with the motor bearing. It may be possible to drive an oil pump AND connect it using this threaded hole. It may be possible to drive an oil pump with a friction fit shaft that fits into the motor's hollow shaft.

Yes... I was wondering about that bolt head and fat washer that can be seen on the outside of the case in that position. Do they rotate with the rotor shaft? If so then replace that fat washer with a toothed belt sheave and there is your oil pump drive. Plumbing is as easy as tig welding on a couple fittings for the oil ports. If you are going to use a positive displacement pump then don't forget a pressure relief valve and you may as well mount an oil filter and cooler.

I noticed in a few pictures that I found that the oil in those gear boxes looked like transmission fluid? Is it that thin? If so a battery powered pump would work and you would only need a couple places to put case fittings. If don't have a tig welder you could use hydraulic through bulkhead fittings with O rings like this. JIC/AN Bulkhead Straight-SS-2700| Stainless Steel Fittings .com| Online Fittings Store

Damn... someone bought the drive unit I was looking at and the shipping will cost almost as much as the two I see on e-bay.

Cyruscosmo