[Swing]

Hi all,

Sorry that this is not a 100% EV question, but I already drive an EV (Bolt/Ampera-e) as a daily. And my classic petrol car (Toyota MR2 1985) is now slower than my daily driver
I already have knowledge about motors and battery systems, however, I am doubting how you could add a small system to an existing petrol car.
Converting to full EV is somehow easier because you bolt on the electric motor with a plate.
Making a hybrid of a rear wheel drive or 4x4 gives you some options on the axles.
However, with an FF or MR layout (and a 4 cilinder in a small car), there are very little options to add a motor to add power to the drivetrain.
You cannot do anything with the axles, and there is usually very little space to do anything on the timing belt side of the engine (in my car there is no space)

I can think of some ways at this point and I am hoping to see some examples. Or something I hadn't thought off.

1: Remove alternator and place a (small) electric motor there. Maybe some nice small motor at 48 or 96v, that goes on the belt drive.
This would make an easy conversion, but the downsides are that size and power is very limited. How much could you do over a belt drive? probably 10kW is already to much and break belts really easily?
It would already allow you to start the motor via the added electric motor and do some nice regen, but it is only a small boost in power.
Ditching the alternator and the starter and possibly the 12v battery, it wouldn't really increase the weight, so that is nice. (we are talking about a very small battery pack of maybe 5 kWh or so)
Would make things more efficient with only small boost in performance.

2: Remove starter motor and add an electric motor there.
Would allow for more power, but it is probably very limited what you can do with such a tiny gear?
Motor cannot be to big as it will stick out to much from the ICE engine.

3: Try to get a gearbox for a 4wd version of the same car, and connect the output to the electric motor.
(in my case a corolla 4wd gearbox?)
This is already getting complicated and needs quite some work.
Also, because of the ratios, it is probably hard to match it on RPMs for an electric motor.
And you have to weld the 4wd center diff, which is usually some kind of viscosity coupler, when talking about older cars (without electronic guided 4wd)

4: Try to drive the front wheels with electric motors. This would make it 4wd and has some grip advantages.
However, even though it might grip better, I want it to remain a (mainly) rear wheel drive car because that is why it drives so nice.

5: Similar to point 1, find some space to fit an electric motor parallel to the petrol engine and use chain or other drive to connect electric motor to crankshaft pully.
In the MR2 that is possible, sacrificing trunk space. This would allow for some beefy electric motor putting down some power.
As engine can move in the rubber engine mounts, will the crankshaft location not move to much so that chain drive to fixed electric motor will work?
Downside is cutting the body, and it would be nice to be possible to revert all these changes to original.
Would allow for a 100kW motor if chain drive can do that, doubling the power of the car.

6: Go the Prius route. This would probably work out in term of drive axles since Toyota reuses a lot. Lots of work, but quite a power boost.
But it would ruin the driving experience if it would be the CVT operation. Even if CVT is faster.

I am afraid that only option 1 is not too intrusive for the car, and it somewhat of a small project that wouldn't take too long.
Of course at the same time it allows for the least amount of power.
Options 3, 4 and 6 I am probably never going to do.
Option 5 is an option if I feel confident about driving the crankshaft with a chain or other system. However, I know very little about chain and belt systems, so I am not very confident. Probably should talk with some motorcycle guys for that.

Thanks in advance.

 

[brian_]

1: Remove alternator and place a (small) electric motor there. Maybe some nice small motor at 48 or 96v, that goes on the belt drive.
This would make an easy conversion, but the downsides are that size and power is very limited. How much could you do over a belt drive? probably 10kW is already to much and break belts really easily?
It would already allow you to start the motor via the added electric motor and do some nice regen, but it is only a small boost in power.
Ditching the alternator and the starter and possibly the 12v battery, it wouldn't really increase the weight, so that is nice. (we are talking about a very small battery pack of maybe 5 kWh or so)
Would make things more efficient with only small boost in performance.

There is a system of describing parallel hybrid configurations based on the electric machine (motor/generator) location, in which this is called a P0 or P1f hybrid, and I think this is a good summary of the characteristics. It is commonly used for "mild" hybrids, and currently used by the Ram eTorque and GM truck eAssist system. The 12 volt battery is still used, but is not normally used for starting so it can be smaller.

 

[Swing]

There is a system of describing parallel hybrid configurations based on the electric machine (motor/generator) location, in which this is called a P0 or P1f hybrid, and I think this is a good summary of the characteristics. It is commonly used for "mild" hybrids, and currently used by the Ram eTorque and GM truck eAssist system. The 12 volt battery is still used, but is not normally used for starting so it can be smaller.

Nice. What is the source of this naming convention?

Anyway, it seems like same conclusions. With transaxle being more limited.

I guess the question is how much power you can apply or take (regen) on such a belt system for alternators and waterpumps. For P0 or P1f, alternator route.
20kW is probably to much, but it would be fun though and make the conversion worth while. As it would be noticeable on the low weight and current power of the car.
The car doesn't need much to keep driving at continues speed (lets say 100 or 80kph) but you have to go through the petrol engine with all its losses. So an EV only mode is probably not achievable.

Probably max of 10kW is more realistic?
Anyway, if a cheap motor can be found, it would be a nice little project that is overseeable in terms of time and cost.

 

[Swing]

Hi all, this is still waiting approval to be publically seen after a week? How does that work?

 

[brian_]

I guess the question is how much power you can apply or take (regen) on such a belt system for alternators and waterpumps. For P0 or P1f, alternator route.
20kW is probably to much, but it would be fun though and make the conversion worth while. As it would be noticeable on the low weight and current power of the car.
The car doesn't need much to keep driving at continues speed (lets say 100 or 80kph) but you have to go through the petrol engine with all its losses. So an EV only mode is probably not achievable.

I agree - 10 kW seems more reasonable; the Ram eTorque system runs up to 12 kW. The practical limitation with a belt drive is likely torque, rather than power. Regardless of what is technically possible there's no point in a high-powered P0/P1 hybrid because the vehicle is never driven by only the electric motor.

EV mode is not possible with any P0/P1 hybrid because turning an engine which is not running is not viable.

 

[Swing]

I guess the easiest way could be to source such an alternator of a mild hybrid. Could be the eTorque or something of an Audi or something.
As far as I know there are no Toyota mild hybrids only full hybrids.
And then do the motorcontroller yourself. But having a good sized motor already on a alternator mount might be good.
I guess there is not only the benefit of the extra power, but also to remove the drag the alternator is causing and possible other accessoires.
You could top it of with running an 48v electric turbo like the Torqamp, and you have a much quicker car running mostly on regen power from braking.

 

[brian_]

I guess the easiest way could be to source such an alternator of a mild hybrid. Could be the eTorque or something of an Audi or something.
As far as I know there are no Toyota mild hybrids only full hybrids.

Current mild hybrids include Ram eTorque, GM eAssist, and Ford (on some cars, not the F-150 PowerBoost); there have been several others. As far as I know you are correct - Toyota has never done a mild hybrid.

I guess the easiest way could be to source such an alternator of a mild hybrid.
...
And then do the motorcontroller yourself. But having a good sized motor already on a alternator mount might be good.

Unfortunately it's more complicated than that. Even if a powerful enough alternator/motor is mounted, the usual belt drive is not sufficient, especially if it also replaces the starter.

I guess there is not only the benefit of the extra power, but also to remove the drag the alternator is causing and possible other accessoires.

I don't see how replacing the alternator with a larger alternator reduces drag. Perhaps I have just misunderstood the proposal.

You could top it of with running an 48v electric turbo like the Torqamp, and you have a much quicker car running mostly on regen power from braking.

Yes, a mild hybrid is a good combination with an electrically assisted turbocharger. Unfortunately Torqamp isn't a turbocharger, because it doesn't have an exhaust turbine; it's an electrically-powered centrifugal supercharger. That takes a lot of power to be useful. The Torqamp has a 5 kW motor (and a roughly 300 Wh buffer battery with 500 W charger, so they intend it to be used for less than 4 minutes at a time and less than 10% of the time). If used with a ~48V mild hybrid, the Torqamp battery (or "Power Box") wouldn't be needed, although I don't know if their control system would allow that.

By "running mostly on regen power from braking" I assume that you mean most of the energy used by the 48 V components would come from regenerative braking. In typical driving I'm not sure that would be true - there just isn't that much braking - especially if trying to run the Torqamp.

 

[brian_]

There is a system of describing parallel hybrid configurations ...

Nice. What is the source of this naming convention?

In that discussion that I quoted, I linked to an article (Mild Hybrid Electric Vehicle (MHEV) – architectures) which describes the naming convention. I've seen it from multiple sources, but I don't know where it originated.

 

[Swing]

Current mild hybrids include Ram eTorque, GM eAssist, and Ford (on some cars, not the F-150 PowerBoost); there have been several others. As far as I know you are correct - Toyota has never done a mild hybrid.

There are some Kia / Hyundai as well, and in recent years also Audi.

Unfortunately it's more complicated than that. Even if a powerful enough alternator/motor is mounted, the usual belt drive is not sufficient, especially if it also replaces the starter.

Well there is a supercharged version of the motor, including some pulleys. I don't know how much kW it takes though.

I don't see how replacing the alternator with a larger alternator reduces drag. Perhaps I have just misunderstood the proposal.

Yes, a mild hybrid is a good combination with an electrically assisted turbocharger. Unfortunately Torqamp isn't a turbocharger, because it doesn't have an exhaust turbine; it's an electrically-powered centrifugal supercharger. That takes a lot of power to be useful. The Torqamp has a 5 kW motor (and a roughly 300 Wh buffer battery with 500 W charger, so they intend it to be used for less than 4 minutes at a time and less than 10% of the time). If used with a ~48V mild hybrid, the Torqamp battery (or "Power Box") wouldn't be needed, although I don't know if their control system would allow that.

Torqamp will come with a version for external battery/power source. And it is significant power draw. It is not a real turbo indeed.

By "running mostly on regen power from braking" I assume that you mean most of the energy used by the 48 V components would come from regenerative braking. In typical driving I'm not sure that would be true - there just isn't that much braking - especially if trying to run the Torqamp.

It would be a combination of charging and regen power. Long highway drive it is not going work, and the petrol engine will just need to do the work.
But I expect some spirited driving, which includes regen, and a cooled battery, that is charged before you go, to have a nice effect.

An electric motor instead of an alternator will reduce drag in that it is brushless, and that it will not charge during acceleration. Unless of course battery is flat and you want to drive the Torqamp, like an indirect electric supercharger.

 

[brian_]

An electric motor instead of an alternator will reduce drag in that it is brushless, and that it will not charge during acceleration. Unless of course battery is flat and you want to drive the Torqamp, like an indirect electric supercharger.

I hadn't thought about brush drag, but any drag from the brushes of a conventional alternator will be insignificant. The brushes are small, carrying only the excitation (field) current of a couple of amps rather than the alternator output. A synchronous permanent magnet motor has no brushes, but it will have a cogging effect when idling; I note that GM uses an induction motor in their eAssist system... but induction machines are less efficient than permanent magnet synchronous machines.

There are existing brushless alternators, but they're generally a really awkward design which inductively transfers power to the field. They're use in some trucks for very long life.

Any alternator will only generate when its field is excited. With a common alternator, you could turn it off during acceleration if you want, based on a wide-open throttle switch, for instance.

I agree that the Torqamp is an electric supercharger, and that when the battery is low the alternator and the Torqamp's motor form an expensive and inefficient (but variable-speed) drive alternative to a belt.

 

[Swing]

Yes in the end it is about skipping alternator drag during acceleration, and instead of drag, use the newly added motor to add power during acceleration. If the battery is not empty.
Brushes drag is probably insignificant, probably your right. What is significant, well for a 120hp engine, is that the alternator is inefficiënt and still working while accellerating. Turning it off during acceleration is probably sufficient, I agree.

I guess in the end it is a lot of work for some solution that will still be limited by some pulleys and a belt.
In the end, adding front wheel electric drive (with existing parts) will be the best solution, but it is very unlikely that I will do that.

If I want to maintain how the car drives, with rear wheel drive only, I guess I should just find some 50kW motor (or something like that) and bolt it in the engine bay, and try to add chain drive to the crankshaft pulley. That will be a hassle with the chain but will provide decent results that are worth the effort.

 

[86elco]

Yes in the end it is about skipping alternator drag during acceleration, and instead of drag, use the newly added motor to add power during acceleration. If the battery is not empty.
Brushes drag is probably insignificant, probably your right. What is significant, well for a 120hp engine, is that the alternator is inefficiënt and still working while accellerating. Turning it off during acceleration is probably sufficient, I agree.

I guess in the end it is a lot of work for some solution that will still be limited by some pulleys and a belt.
In the end, adding front wheel electric drive (with existing parts) will be the best solution, but it is very unlikely that I will do that.

If I want to maintain how the car drives, with rear wheel drive only, I guess I should just find some 50kW motor (or something like that) and bolt it in the engine bay, and try to add chain drive to the crankshaft pulley. That will be a hassle with the chain but will provide decent results that are worth the effort.

Why use a chain, plenty of motorcycles run belts with more power than that, high HP superchargers use more power with their belt drives also. Chains require cleaning, lubing and adjusting, belts are mostly trouble free.

 

[Swing]

You are probably right, anyway I would talk to some motorcycle fabricating guys of which I know one with mechanical engineering background.

Anyway, it means adding a pulley at the crankshaft and putting the motor somewhere else.
It will be the only way to add some significant power, but putting some serious strain on the battery pack, high C discharge rating. But yeah that is inevitable, the car cannot ger much heavier.

At this point it seems more complicated than at the beginning. I had another idea which is to wait for a cheap (broken) GS450h and mess around with that (has been reverse engineered to quite some extent). I prefered the MR2 project as being more simple and already having the car. But I may be wrong, because of all the mechanical work included and modifications to the car, while trying not to increase the weight too much because the car is only 1000kg. Hah, we will see.

Thanks for the feedback everybody, I think I have a better idea of the options and the work involved now.

 

[brian_]

I had another idea which is to wait for a cheap (broken) GS450h and mess around with that (has been reverse engineered to quite some extent). I prefered the MR2 project as being more simple and already having the car. But I may be wrong, because of all the mechanical work included and modifications to the car, while trying not to increase the weight too much because the car is only 1000kg.

If you are interested in experimenting with a production hybrid, then any Toyota transverse-engine hybrid system can potentially swap into an MR2. With the first-generation MR2, you would want the more compact 4-cylinders, such as a Prius. If you also want to try AWD, then a RAV4 hybrid system could go in an MR2, with the electric "rear" drive unit in the front - this is similar to the current Acura NSX configuration. Yes, it's going to gain weight...

 

[Swing]

Yes the Prius transmissions with an engine would be great for MR2s, and although I havent researched it, I am pretty confident it will connect up nicely. Since a lot of stuff is shared on Corollas and MR2s so also Prius and Auris axles.
Better yet, keep the engine and manual and add fwd electric power.
However both options would kill how the fantastically drives now, with manual and MR layout. Also the weight is increased.
And it is becoming more and more of a classic collectors car that you don't want to ruin.

That is what is fun about an older GS450h. Lots of potential for weight reduction even though you are aslo adding batteries, and there is no classic driving experience to be ruined.
Anyway, it would be a project mainly focussing on battery side and figuring out how to get the most power out of the drivetrain (using open inverter boards etc). Quite different from improving a standard petrol car.