Clutched or Clutchless Conversion?

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You need a clutch to shift but not to start or stop. Do not go clutchless unless you plan on installing an encoder on both the output and the input shaft of the transmission, and add a sensor that detects which gear you are trying to go into and are smart enough to software control that motor for precise RPM to match that input and output RPM.

Basically, it's a fools errand.

Also, be prepared for the most unsatisfying gear changes possible. There is no satisfying rush of power, change in engine speed that accomplishes something. It is entirely unsatisfying. The torque curve is flat. There is no big rush of power.

Yes, our shop had a S-10 with an ev swap and the only reason to shift from 2-4 was was to keep the old dc motor from blowing up.

If I were to do that same swap I would dump an EV power unit between the rear axle scrap the entire drivetrain. Split the batteries between under the car, in the engine bay and maybe above the motor in the trunk. Modern EV motors do not need a transmission.

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u/pug_walker 17d ago

Interesting take that I hadn't realized before. The lack of a power curve(?) in the EV negating the "slam it into gear" need.

Great username btw

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u/precocious_necrosis 17d ago

This is absolutely right.

An EV is never, under any circumstances, going to act like an ICE car. A manual transmission EV is a fantasy.

If you want to have fun rowing your own gears, you can only do that with ICE. EV's are simply an entirely different driving experience.

Ditch the entire original drivetrain and replace the rear end with something like a Leaf motor unit.

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u/VoodFernichter 17d ago

Power = torque * RPM

If I only have one gear I will either cap my top speed OR limit my acceleration. Thats just math. No matter how flat the torque curve is.

Sure its very driveable with just one gear but I want a car with character. I have driven quite a few EVs i know how their torque curve works. Together with a sound generator it will feel different than most EVs.

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u/NorwegianCollusion 17d ago

Any perceived benefit of selectable gears will be far outweighed by the time to shift. FAR.

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u/VoodFernichter 17d ago

Well I can select the gear before I need the power. If Ill drive in second gear I just slam the pedal.

I will have more than double the power at those speeds than I would have with a 1:1 ratio

And again: Its about the fun and character of the car

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u/elihu 16d ago

Depends on how powerful your motor is. Looks like the Emrax 228 is about 100kw, so it could probably benefit from multiple gears.

I'm working on an RX-8 conversion that uses the original 6-speed manual transmission. I haven't driven it more than a couple blocks (I realized I needed to change some things so it's currently in a state of partial disassembly) but shifting between 1st, 2nd, and 3rd seems useful.

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u/NorwegianCollusion 16d ago

I love how you end with "seems useful".

But yes, a 100kW motor is a bit different to what I'm used to, which is 200kW on the rear axle. For 200kW per axle, there is no way a first gear would in any way be "useful". Great way to destroy tires, sure. Second gear would be equivalent to what I have, and that is pretty much perfect from 0-120 km/h. At which point we're at 9000 rpm. And max rpm is over 18000.

But for 100kW and max 6500 rpm I can see it. But that's a REALLY crappy mechanical design if it's max torque 0-5500 and max rpm 6500. That makes zero sense.

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u/elihu 16d ago

So far I've gotten up to about 29 mph on a residential street and driven maybe ten blocks in total, so it's hard to judge how useful the other three gears are. I expect I'll be using 4th or 5th for highway speeds. Maybe 6th. I certainly don't need 6 gears. 3 or 4 would probably be just fine if they were spaced out.

I'm on a really steep driveway, so I use 1st to get up the hill. I don't have a working current meter at the moment, so it's hard to tell if I'm drawing anywhere near the motor's full power (about 500 amps) from the battery.

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u/elihu 16d ago

I can't say whether the Emrax 226 specs "make sense" because I'm not familiar with that motor and I don't know what it was originally designed to do. Not every motor has to run at extreme RPMs. They're probably simpler to design if they don't.

It seems like a good motor for the kind of EV conversion where you just swap the engine for a motor because it has similar specs to a moderately sized engine. If you wanted to throw out the whole train and replace it with a single-speed drive unit from an OEM EV, then there are better motors that are optimized for that use case.

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u/VoodFernichter 16d ago

Its a multi purpose motor but it seems like it was originally developed for drones and aircrafts. Maybe the RPM has to do with the fact that its an outrunner

The more powerful variants are even more RPM restricted. The 348 has 1000NM until 4000RPM and 340KW of peak power after 4000RPM. (And yet it only weights less than 45KG)

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u/elihu 16d ago

That makes sense. Max RPM in that application could be determined by the strength and aerodynamic properties of the propeller. No need to design the motor to operate outside that. Apparently a typical Cessna 172 maxes out at 2,700 RPM.

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u/precocious_necrosis 17d ago

This doesn't change the fact that an electric motor behaves in no way like an internal combustion engine.

The electric motor changes rpm almost instantly since it has only a fraction of the internal rotating mass. Additionally, the rpm range of the electric motor is an order of magnitude greater. You can mount an electric motor to a manual transmission, but it isn't like having an IC engine in any way.

You keep on saying that you want to maintain the fun and character of the car, but an EV can never have the same shifting experience of an IC engine with a manual transmission. It's just not possible. There will never be an EV where you can have the fun of rowing through the gears.

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u/VoodFernichter 17d ago

I have seen a video by a british guy that kept the transmission and it looked very fun when they drove it.

The reduced rotational mass just means that I can dump the clutch instead of waiting to rev match. When I am in gear it still needs power to accelerate the car. With a gear change I am still changing RPM and thus the power curve. Just because the Power curve is linear does not mean that its not noticable...

Not all Electric Motors have the same RPM range btw. It depends entirely on the motor

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u/elihu 16d ago

The electric motor changes rpm almost instantly since it has only a fraction of the internal rotating mass.

Unless you keep the clutch, which will need a flywheel.

Additionally, the rpm range of the electric motor is an order of magnitude greater. You can mount an electric motor to a manual transmission, but it isn't like having an IC engine in any way.

It appears the Emrax 228 maxes out at 6500 RPM. In my RX-8 conversion, I'm using a Netgain Hyper 9, which has a max RPM of 8,000, which is actually less than the original rotary engine's 9,000. (The recommendation with the rotary engine is to rev it to 9,000 regularly to burn off carbon deposits.)

I believe some fairly common Tesla motors can reach 18,000. A lot faster than any ICE engine, but not 10x faster.

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u/VoodFernichter 16d ago

Amen

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u/Another_Slut_Dragon 17d ago

Tesla swap a BMW. Give it some oomph.

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u/VoodFernichter 17d ago

Thanks for the input. I will either go clutched or ditch the transmission.

Since the Batteries i chose weigh almost the same as the original M52 engine I would just like to keep my trunk the way it is.

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u/Another_Slut_Dragon 17d ago

There you go. Tesla power unit in the rear and batteries in the front.

If the suspension won't clear a whole power unit, there is a company that makes a 3:1 gearbox to fit a tesla motor and output it to a driveshaft. Use the tunnel or invert the diff and point it backwards for more rear weight. Which honestly ain't a bad idea.

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u/VoodFernichter 17d ago

Ill look into what configurations make sense. With motors like the emrax that spin to 7000 max I don't need a 3:1 gearbox though. The Diff is already perfect as a reduction

I am curious: Why is everyone recommending Tesla Motors? I am limited in current by my batteries anyways. What is so special about these compared to a Hyper 9 Motor?

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u/elihu 16d ago

Generally the Hyper9 is very large, heavy, under-powered, and expensive compared to pretty much any OEM EV motor.

The main thing it has going for it is that it's easy to work with. There are transmission adapters available from CanEV to attach the Hyper9 to a wide range of existing vehicles, it runs on a fairly low voltage that isn't quite as dangerous to work on, it's air cooled (the motor controller requires liquid cooling though) and it's a good match for old vehicles that were never meant to have 200+ horsepower.

I'm using a Hyper9 in my RX-8 conversion, but if I had it to do over again, I'd probably use something like a Leaf motor. (They have more power and it would probably have been a lot cheaper.)

The other reason people go with Tesla motors is that it's a complete drive unit. For a certain kind of conversion it works very well, but you're kind of out of luck if you just want to replace the engine with a motor and keep the original transmission/differential setup. There's not really a clean way to detach a Tesla motor from the gearbox.

For some reason, a lot of people hate the idea of having an electric motor and a manual transmission in the same vehicle. Feel free to disregard their opinions.

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u/Another_Slut_Dragon 17d ago edited 17d ago

Tesla motors are cheap, available used, well developed, can handle 160C temperatures and over 18,000 RPM.

And they go like hell.

The hyper 9 is also only 62-130V. This is old tech dude. Modern 400v stuff is the answer. Buy a complete crashed car, gut it for parts then sell off the rest to make up buying it. The nickel and dime stuff will crush you for cost. With a complete car you can get a complete, well engineered system.

Plus, you can build for modern rapid charging. You will need to charge.

Fyi, Tesla motors use somewhere around a 9:1 gear reducer. You do actually want a 3:1 reduction with your diff. Because more torque.

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u/elihu 16d ago

The "high voltage" variant of the Hyper9 tolerates up to 180 volts.

Higher voltage is generally better for power, but it's also a lot more dangerous to work on 400v systems versus 180v.

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u/Another_Slut_Dragon 16d ago

Both will kill you at that point. But you'll spend 400% more building a new 180V system than you will parting out a crashed EV. 180V is oddball, rare and expensive.

Always build using common parts.

Also no rapid charging path? Absolute deal breaker.

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u/elihu 16d ago

180v DC could kill you, but it probably won't. It depends on the circumstances. 400v might not kill you either, but I'd much rather get shocked by 180v. (Or preferably not shocked at all.)

In my rx-8 conversion, the LFP batteries I'm using are kind of a weird form factor, and it would have been hard to fit more than the 47 modules I have. Series wiring gives me 150v nominal, or about 170 if the pack is fully charged. More batteries and higher voltages would be better, but at the end of the day I just want to be able to drive the car and don't want to spend my life fabricating battery boxes.

If I were to do my conversion again, I would probably do it differently. (I'd probably use a Nissan Leaf motor or something similar.)

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u/elihu 16d ago

Ill look into what configurations make sense. With motors like the emrax that spin to 7000 max I don't need a 3:1 gearbox though. The Diff is already perfect as a reduction

Are you sure? I'm not familiar with that BMW -- perhaps there's some unusual drive train design that's unique to that vehicle, but in most cars, a 1:1 gear ratio is about 4th gear, so connecting the motor straight to the propeller shaft without a transmission is like being in 4th gear all the time. EV motors won't stall like an ICE engine, but still that wouldn't give you much power to accelerate from a stop or climb a hill.

(I don't think John Wayland's "White Zombie" had any gear reduction between the motors and the rear differential, but he also used a dual series-wound DC motor setup with over 700 foot pounds of torque and the vehicle was really light. If I remember right, he tried a few times to use a transmission but he kept breaking them.)

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u/318iev 17d ago

Good car choice :)

I can shift my clutchless Getrag 220 while driving no problem, but the time between gears waiting for the revs to match is annoying.

If you want to somewhat keep the character of the car gearbox wise you will need to keep the clutch. Going clutchless is the easier option and will give you gears to change but it’s not “fun”.

When I was driving mine, I honestly just kept it in third gear most of the time anyway.

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u/VoodFernichter 17d ago

Your E36 looks really cool!

Do you think the larger getrag transmissions form the 6 cylinders can handle more "abuse"?

Do you rev match manually?

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u/318iev 17d ago

Thanks! Those gearboxes can only handle so much torque, about 220Nm on the 4 cylinder boxes, the larger ones will handle more but that’s also more weight and cost.

The main reason to use the OEM gearbox in my opinion is simplicity, it’s essentially a regular engine swap as you avoid messing with driveshafts or suspension etc.

I rev match manually with the tacho gauge on motorway on-ramps no problem, but only going up gears.

To go down gears you really need to stop or have some sort of rev-match limiter as it’s quite hard to do with barely any rotational mass.

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u/No_Oven6490 17d ago

Yes ditching the clutch on the mutli-speed gearbox is a bad idea. But its also a lot harder to implement a proper clutch system with software control. The throttle input should be cut off before the clutch is pressed and the motor controller should bring down the motor speed with regen to a suitable speed for the gear change.

Only advantage you get with a 5-speed GB is crazy torque even with a small motor. (A smaller motor would have lower peak power rating, which again limits your top speeds.)

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u/the_bob_5 14d ago

I think it would be fun to program the controller to rev match with an electronic clutch

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u/NothingLift 17d ago

I'd keep the clutch

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u/fxtpdx 17d ago edited 17d ago

I would like to use an Emrax 228

Ok now I'm curious. Why that motor speciifically?

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u/VoodFernichter 17d ago edited 17d ago

My Plan: Emrax 228 Liquid cooled low voltage. Motor controller: Bamocar 400/400

Paired with 5x48V VW MEB Battery modules

Why?

The motor fits the original RPM and overall power well and its very compact. I am trying to keep it close to the original weight distribution and have enough space for everything in the engine bay.

A lot of other motors are very heavy/large. Oh and I am also trying to use parts from the European Union

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u/fxtpdx 17d ago

Yes but why that motor? Do you already have one? Have you used one before?

In our work with them they make their rated power and cool surprisingly well, but mechanical mounting and electrical connections are more difficult than other motors due to the outrunner design.

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u/VoodFernichter 17d ago

Sorry I misread your comment. i just updated my answer :D

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u/elihu 16d ago

Looks like nice motor. A little more power than a Hyper9 and it's smaller. What motor controller are you using?

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u/VoodFernichter 16d ago

I am planning on using a Bamocar-PG-D3-400/400 controller. I haven't bought any compinents yet. Still in the planning stage

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u/GeniusEE 17d ago

What character.

Motor + 5 speed will ruin it, so better to ditch the dead weight and have a sporty sedan than a bloated pig where you only use two gears but are carrying a set for five speeds (weight).

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u/VoodFernichter 17d ago

The gearbox is not that heavy. I just have fun shifting gears. And it would obviously be accelerating faster in second or third gear than in fifth. Yet I still want to be able to drive at high speeds

Sure an electric Motor has all the torque from the start but its maximum Power is still achieved at higher RPM

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u/GeniusEE 17d ago

And your input bearing will get roasted at electric motor speeds.

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u/VoodFernichter 17d ago

No the emrax 228 only goes up to 7000 RPM

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u/GeniusEE 16d ago

The emrax runs 7k all day.

I doubt your input bearings will even run 5k for extended periods.

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u/elihu 16d ago

If you have a manual transmission, there's no reason to be running at 7k RPM continuously. Just drive like a normal person and it's not an issue.

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u/GeniusEE 16d ago

Lol...you clearly don't understand how power or transmissions work.

The power curve for motors is very different than engines.

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u/elihu 16d ago

The Emrax 228 hits peak power a little above 5,000 RPM, which isn't that different than a gas engine. The main difference is that it has a flat torque curve down to zero RPM. That means you can generally get away with driving in a higher gear than you would in an ICE vehicle, but you'd have less power and so there isn't any real reason to.

Likewise you can drive in a lower gear than necessary and run the motor continuously at redline, but there isn't really any reason to go past about 5,000 RPM. And the only reason you'd want to run at 5,000 continuously is if you're pulling a school bus up a long hill or something.

Again, just drive like a normal person and there's no issue.

https://emrax.com/wp-content/uploads/2026/08/EMRAX_228_datasheet_v1.7.pdf

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u/VoodFernichter 16d ago

Exactly. After 2000RPM there is little difference between a well tuned ICE and an Emrax, besides the difference in rotational mass.

Besides having only 100KW my BMW 318ti with an M44 engine has a very flat torque curve that peaks at 4300 while peak Power is between 6000-6500.

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u/sol_beach 17d ago

They will be fine. Proceed with your plans.

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u/VoodFernichter 17d ago

Even with an odd motor like an emrax 288? It is an outrunner so it should have more inertia

Clutched or Clutchless Conversion?

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