Building a Smart ForTwo in a different way…

Hey guys,

so I work in manhattan and free street parking is damn near impossible, the only chance of finding a spot with a car within any reasonable amount of time is with a smart car, it's only 8.8' long and fits in 1/2 car spots...

I had an electric smart and it was cool, instant torque and super low COG means it was quick enough to be fun, not exactly fast by any means, but zippy enough for a road warrior commuter to zip around without being slow enough to be annoying, was basically a street legal go cart...

The car wasn't worth much because it was hit when I got it and I only half repaired/patched it up and it was good enough. well that car died because of a known fault in Mercedes BMS, bricking the battery and making it worthless, so I bought another newer one. Didn't want to take another gamble on an electric so I bought a turbo 5 speed, figured it would do, and it does, but it's sluggish compared to the old one, basically I have to beat the E36 M3 out of it to get it to go and then it barely goes, pretty wimpy...

ive tried to sell the old smart for parts but no one wants them, they are basically "unrepairable" disposable cars so I decided to resurrect it with a drivetrain swap...

Now we've all seen the hayabusa swaps and if you do any digging at all you'll see plenty of other swaps too, anything from honda Vtecs to Mitsubishis, VW's and Toyota engines, pretty much all shoved into the rear where the original engine was...

This was not something I really wanted to do because the weight balance of the smart is already pretty horrible, something like 64/36 rear have weight distribution, an engine swap would only make this worse, and that combined with a super short wheelbase and a narrow track width would mean an end result that's only good for Hooning and YouTube content, but NOT a good car to actually drive... 

I want to build an awesome driving smartcar, not looking to drift or do wheelies but to maybe track at an SCCA even here or there eventually but main goal is a nice driving and handling little commuter with balls...

So I started searching around for possible candidates, came close to pulling the trigger on a honda 2.0 JDM K swap but the drivetrain alone was ~$5K and I want to keep this thing budget, not to mention this would probably put me at least 70/40 weight distribution, no wonder they wheelie so easily 😊

I did consider the popular Hyabusa swap but they're not exactly cheap either, and stock they are not much to lust over, a turbo Busa would need a budget north of $10K and is a rabbit hole for rich men... this is a garbage car, not looking to go there...

So I found this BMW touring bike, wrecked with no tittle for cheap... it's a BMW K1600GT, it's a 6 cyl shaft drive bike with 160 HP but the real gem is it makes 130 FT#'s of torque @5,200 AND it makes 70% of that torque from like 1,500 RPM's.

A Hyabusa or any sport bike engine for that matter would be pretty bad if you tried to just drive it "normal", try letting the clutch out at just off idle and it will be so low in torque that it will stall. Sport bike engines are made to rev high and make power up high but are not going to be so hot when you throw them into a vehicle that weighs 3-4 times the vehicle it came out of... this BMW 1600 on the other hand comes from a bike with an almost 1,200 pound load rating.. with any luck I'll only be a few hundred #s over the stock vehicles intended load... this means it will be able to accelerate normally, instead of aggressively launching it each time just to not stall...

so now that I have this bike, and this car, now comes the look/measure/plan part...

so this thing is a shaft drive, and it's very compact... first thought is, can I fit it in the front? This would pretty much solve the horrible weight balance of the car, and if I swap out the front and rear subframes for Miata units I can upgrade the suspension and widen the track at the same time. So a tape measure and a sawzall and some back of the napkin math says I think I can make it fit if I move the firewall, peddles and seating position back just a bit, I'm short enough for this to work so,sounds like a plan 😊

So the first thing I did was strip the bike, I wanted to try to keep it all intact and running outside of the bike itself, half the battle with an engine swap is having everything needed to run it, getting a complete running bike was a definite plus here. I've built my fair share of cars over the years but no longer have a shop or even a garage ATM so I have to build this thing in my driveway and back yard 

https://youtu.be/CdSbnb90OSo?si=9BtcfFQU_9B3SfiE

This should be interesting!

As a new member I can only post once an hour so this is going to take a few hours 😊 also couldn't go back and edit the typos in post 1 

so this is my driveway, where the car sits is where it's going to be built 😊 it has a nice downward slope just to make it a little more interesting 

So now next step is to strip the car, the nose is very shallow, there's just enough room for a radiator and the steering up here, plus the little HVAC cowl ducting that's already removed here...

Speaking of the steering, that's the first problem. Because they never intended on putting an engine in the front there was no reason to snake the steering around anything, so it runs right down the middle of the car. That's not going to work, that's where the Miata subframe comes in to play, by using a Miata subframe and rack that goes around an engine so let's see how that works... test fit the Miata subframe... looks ok, going to need some sawzallin' it needs to go up a good 6 inches from where it is but it'll fit. The right side rail was already crushed from the accident before I bought it, I just pulled it and ran with it but now I'm going to have to cut the front frame rails off and redo them anyway, finally I'll have a straight frame after driving it like this for so long,  so yeah there is that 😊

The K1600 looks like a very Smart choice.

I'll show myself out.

See if you can now post more often. I just changed your incept date. 

Thanks for joining us and thanks for sharing. 

I was so excited to see you doing this on a street in NYC! Glad you have a driveway for safety though. Very cool. You may be able to replace that bricked BMS with orion if you still have the electric one.

The K1600 turns out to have been a really great choice, really nothing like it.

The inline 6 is a good engine configuration being inherently balanced by design and BMW builds some of the best inline 6s but i6's are usually a pretty long configuration

This engine was built by them for there flagship new grand touring machine and has a lot of unique things that happen to make it perfect for this build.first is the crankshaft has nothing on either end of it, there is no output end, the whole block is only as wide as it needs to be to contain the 6 cylinders and the timing chain. The transmission is driven from a gear on the crank inbetween 2 of the cylinders in the center of the block. They did a lot of things to make it very narrow where a riders feet would be, or in my case, where my frame rails are 😊

its 1600cc 160hp 130tq revs to 8,500, naturally has a sequential 6 speed box with quick shift up and down but a surprise I didn't even realize until after I got it is, it actually has a dry sump!

Yeah that's a big problem with bike engines in a car normally is oiling. 

bike engines are designed for the centrifugal forces that a bike see's, that a car doesn't.

A car instead sees side loads, which a bike doesn't.

What this means is a bike engine in a car will have oil starvation issues when pushing the g's through turns, long sweepers can actually starve it long enough to take the motor out... ideal setup is a dry sump but big $$$ normally... at a minimum I was planning an Accu sump or custom oil pan maybe but then come to find out this one has a bmw factory engineered dry sump built into the engine and has the reservoir contained within the engines wasted space. They did this for a flat oilpan for a low COG,

the whole motor is designed specifically for compactness and low COG... oh and light weight with hollow camshafts with composite lobes and magnesium case covers, they engineered this thing pretty cool when you really start to dive into it

ok so now the point of no return, gut it and start cutting...

ok let's see how the motor fits in the opening...

oh another thing about an electric car is, it is kind of like building an old school car, something like a 69 Camaro or 57 Chevy or something, in that it don't matter what you decide to put under the hood. do whatever you want, there are no restrictions really unlike most modern cars, where you can't just do an engine swap on anything and expect it to actually pass inspection, but that's where the other good thing about this car is, because its electric it has no emissions, so it's EMISSIONS EXEMPT from birth 😊

now being a bike engined car I'll be adding an electric reverse, no reason not to add electric forward and reverse while I'm at it, just to keep it all 100% legal and super easy inspection, I mean I could add a small motor and battery with very limited capacity and not too much weight, maybe something just powerful enough to drive a few blocks at maybe 15-20 mph would do it. Then legally it's still an electric car, only with a gas powered "assist" 😊
 

I love it when a new member shows up with a bonkers project like this. I am very much looking forward to this.

This is just getting better and better.

Ok so now I see the engine fits the car, but how does it fit the subframe?
 

im not opposed to redoing the headers and of course the cooling and anything else but since this is a low resource build if I can make it work as it already does and as it came from the factory, at least until I have a running driving hunk of a thing,then why not? I mean I can always go back in later and haltech it, upgrade to a torsen, etc etc but I'd like to initially just get it done,

the biggest danger with a project like this is it never getting done, this isn't my first rodeo and I know all the pitfalls, 

tying my hardest to avoid as many as possible. That's why I'm starting with Miata subframes instead oftrying to build my own suspension, start with a running bike,  I'm going to try to build it initially with the factory ECU and factory dash from the bike... very doable and good enough until it's a complete running driving car. At that point I'll be able to assess exactly wtf I've built and what it is or isn't actually good for 😂 

if the build goes well enough and I like the end result, then I can go on to phase 2 and start throwing some money at it, etc etc... but there is still a TON of work to be done before that point, right now my goal is to keep it as simple and direct as practical and get it done. With winter coming that's going to slow down quite a bit now too, I'd love to have it moving by sometime next summer maybe, see how it goes...

ok, so engine, subframe, right, so I don't have a lot of shots of mating the 2, I don't have an engine hoist or a place to store one anyway so it's a bit tricky working around that,

but the engine fits close but not really, I mean would take quite a bit of hacking of the subframe... kind of like the Miata guys do when they swap LS's into them... I need that much extra room ideally, so it's a good thing I happen to have a Miata LS subframe from my 91. Was trying to get away with the stock junk frame but not worth all the extra work, again rule #1 keep it simple get it done.

so I used a pretty accurate 6line laser level, leveled out the car then transferred symmetrical cut lines on both sides of the rails for the subframe to raise into the body. Using lasers, plumbobs and tram gages I will be able to get this thing straight as an arrow.

I'm going to build all of the frame extensions with 4130 chromoly to match the high strength steel of the factory rails and of course this subframe will remain removable with the 6 bolts.

so this is pretty much where I'm at now... trying to get an hour here and an hour there in on it while the weather is still holding out...

still a E36 M3 ton of work, haven't even spoken about the fact that the driveshaft rotates opposite direction as most any car engine, meaning if I just run the driveshaft from the motor to a diff I'll wind up with 6 reverse gears, so that won't  work 😊

This is a fun one!

To solve the 6-reverse problem, I'd suggest simply swapping the seat and steering wheel 180 degrees. Ezpz. Plus, then you have forklift steer, which should be great for agility. 

And they say nothing good comes from Jersey... (I'm assuming location). 
 

awesome stuff, hope you don't mind my stalking!

https://m.youtube.com/user/turbocad6

In reply to bbbbRASS :

Not on this car. Everything is proprietary MB CAN buss linked, and these have not been cracked and open sourced like say a leaf or a Tesla, that's why they're disposable.

For about a grand someone in Germany can supposedly reflash and reset the BMS but then there's another component in the battery that usually fails and is not sold, someone came up with a work around for that but that's another $6-700 and these $'s of course don't include needing a new battery still. in the end was going to be thousands just to attempt it not  to mention also needing a MB Star computer adds almost a grand just to be able to talk to it, at that point I would have just swapped everything out to a leaf drivetrain which was a consideration and would have been cool but still $$$

a budget leaf donor is a few grand and then that's not going to have a good battery at that $ so add a few grand for that even building it yourself, then another $500 for an open source controller for the leaf... still would have been $$$

instead I bought this bike for $1,100 and it comes with a lot of what I need to complete this thing. I winded up going this way mainly out of being cheap but in the end it's going to maybe turn out better than if I spent a lot more and went with a more conventional swap like everyone else 😊

actually I'm still considering and debating exactly how much electric assist I'm going to add back into this thing. If i wasn't so weight conscious on this build I would consider adding a forklift motor that I already have and really upping the torque with a hybrid drive. Then this thing would launch like an animal 😊 and I would have regen to avoid having to plug it in, just a small high amp battery enough for like I said, very minimal range not even a mile is necessary but then again depends, I'm not sure what I'm going do with the electric assist yet, options are anything from a starter motor for reverse only, or a healthy e-bike go cart style electric drive to have foward and reverse limited speed all the way up to the 60HP shot of adding the forklift DC motor I have.

its a little heavy but not like warp 9 type heavy, think its in the 70ish # range

So now about this whole reverse thing, and the driveshaft output being opposite rotation...

there are some commercially available reverse gearboxes made specifically for BEC's but they are all designed again more for the sport bike engined guys who are starting out chain drive. There intended straight through rotational strong direction is still opposite mine.
I spoke to quaife and they said if I used the box as reverse being forward it would overheat and destroy the box, so that's not really an option 

one way to deal with this is to flip a diff., by mounting it upside down it would rotate backwards, meaning forwards for me but that has a few issues... one being the ring and pinion is now operating reversed  on its weaker coast side vs the drive side that was intended so weaker gears... other problem with diff flip is oiling....

there are ways around both of these things, among some are using reverse cut gears from a front differential and there are ways to deal with getting oil to the front pinion bearing when flipped too. Really I'm not making that much power so a strong diff like a mustang 8.8 even if flipped and running on its weaker side would still be more than strong enough, some 4X4 guys run these and corvette diffs on there monster off road things... reason this applies is because front diff rotates opposite direction like my motor does but even a front diff would still need the flip and oiling issues still

i was pretty much set on going the flip diff route but was still wishing I could find a reversing gearbox that would work for me. Even if it isn't a full forward/reverse solution, as long as it changes the rotating direction and allows me to use any old standard diff that's good enough, I can still add an aux electric drive, but can't find anything off the shelf...

I considered building my own, there are very crude ways of doing it, something like a chain drive and jack shafts but that's not a real solution. Building my own gearbox from scratch could be a huge rabbit hole and could go against my rule #1... imagine building everything around this home made gear box, only to find out after that it's not good enough, then what?

If I build a gearbox it has to be right the first time. Something made to handle the loads, helical cut perfect gear mesh and designed in the correct loaded direction of rotation so the thrust loads of the helical gears is all right, it's simple but then again it has to be right

so while I was thinking diff flip most probable that didn't stop me from still considering building a reverse rotation box. I did a bunch of research on typical gearboxes and looking at what to start with to gut some gears from when stumbled into something that would work great for this and it's half done already...

what I'm talking about is using a rear tail shaft housing from a Subaru 6 speed. What they do is reverse the rotation for the output shaft that runs to the front diff right before it exits to the rear driveshaft. What this gives me is a precision cut gear set that's made to handle way more torque than it's going to see here, it's loaded in the right direction of rotation it's spaced correctly and the half of the housing included is more than strong enough to build the rest of the gearbox from.

it's not exactly a done deal though, building the rest of the housing and good anti twist mounting is easy, shortening that output shaft and redoing the end bearing not so bad, the complicated part is the input short stubby spline, that needs a connection and it needs bearing support on top of that, the way it interfaced to the rest of the Subaru tranny isn't so useful here so this is a little bit of a project but seems like a real good shot. I have to interface that stub from this gear to the output from the BMW bikes driveshaft which I am going to attempt to use here, then the output from this box is a Subaru rear driveshaft front yoke

As complicated as this all sounds if it eliminates ALL custom rear diff crap and let's be just throw a cheap complete Miata rear subframe in as-is it's a worthwhile thing

Oh boy. OH BOY! This is good stuff. I'm happy to send you Headway cells for a small battery if that helps ya, or spotweld you a high current 18650 pack. I figured there was someway to code into the BMS if it has CAN buss, and Orion can pair with that but it does get pricy quickly. If you want to get ride of the Smart cells or motor I may be interested.

Wish I had someway to convey what is in my head properly to solve the cap, seal and bearing issue. Only issue I see is how to shim the output shaft if it was cut down. Using a couple layers fo 1/2 plate aluminum could work for mock up to have it machined or run as is. Plus a air vent and drain and fill access. Easy peasy. 

For the electric assist side, what about the 48v starter/generator from a BMW "mild hybrid"? They're driven/drive via a 7pk belt with a neat built in floating tensioner, the air cooled one is about 7hp, water-cooled is 10hp (from memory). Much more compact than the forklift motor, but your have to come up with a way to run it off the bike motor.

Honda used reverse rotation engines for a long time. I think there were some AWD/ RWD vehicles at that time, like some of the civics. Possible source for an easy diff solution?

I might have a set of the Subaru parts if you need them, I converted a split case 6-speed to 2WD. 

In reply to bbbbRASS :

I do want to get rid of all the electric crap, only thing I was considering salvaging was a few contactors in the battery I dont have the patience or desire to start breaking this pack down to salvage cells, make me a ridiculous offer I want it gone anyway tbh...

initially I tried to individually charge the cells back up, I got a lot of them to eventually come up and hold charge after days of micro amp trickling I even got the center bank up to over 90 volts and somewhat even over 3v each cell but then some were resistant and rose slower some would drop from 3v back to below1v in a few days... I didn't even bother playing with the third bank, at that point I gave up on the OE electric it's just sitting in the back yard trying not to get wet atm 😊 

The motor and all the other electric crap is still in the car, can't touch the rear now because of the driveway slope, if I try to jack the rear off the ground with the front on stands the car is going to roll back and fall of the stands, right now both wheels and emergency brake are what's keeping it stable on the slope

Apprently reverse rotation diffs are a thing in the off-road world and were used in the XJ from the factory for a while. I don't know any more than that but it would be interesting to check out. 

In reply to Gammaboy :

I'm open to ideas and I'll look into it. This is the forklift motor I have with the controller and a 2 way 90* gearbox, I bought it to build an electric bike originally but never got that project off the ground.

it's rated to 144v and it can take huge amounts of short bursts of amperage, I checked it's around 80 pounds motor alone, that controller is an old style so it's huge and heavy too... it's a great drag race type motor being DC and al, but not ideal in DC when it comes to regen I think.

I haven't researched the electric stuff in years, have to refresh my knowledge there when I get to that but the electric drive is pretty low on the list of priorities atm, I'd be happy to get it running initially with no electric assist then added it as an add on maybe. Not sure right now my only real hard focus is on front frame rails and getting the motor mounted to the subframe, front stuff... then I'll move on to mid and rear stuff 

oh and BTW Dave I still can't post more than once an hour 😂

And yeah I've looked at the off road stuff, I spend a lot of hours reearching and got a lot of insight but nothing that will directly bolt in as a great solution. A lot of straight axle heavy Dana type stuff there, when it comes to a relatively light weight aluminum pumpkin type setup it gets limited. One option was GM 2500 front dif with of course custom axles and mounts, or similar for certain year navigator or f series with ford 8.8's but off road and heavy truckers don't give a E36 M3 about weight. I don't want a heavy iron Dana or ford rear,

now the honda B series reverse rotation stuff I also looked into but the honda stuff don't help for a few reasons, 1 they just  swapped the gearbox side to side to make up for the reverse crank and then the diffs are either the ones contained inside the tranny fwd style or little wimpy secondary diffs like the CRV type stuff..

. I'd hate to build a whole lot of custom one-off fabrication around something fragile, I mean a Miata 1.8 torsen diff should be strong enough and not excessively heavier than necessary and make the whole rear a 123 almost drop in bolt up easy type deal, axles and all, vs having to make custom mounts, custom axles, I'm really looking for the path of least resistance here I think, this gearbox is going to make everything else so much more straight forward and easier all around, worth the minor engineering challenge I think,

and yeah Kieth that's what this rear housing is from I think, a 6 speed 2wd conversions left overs but I don't have anything other than what's in the picture, what I need is something that has the splines on it, which is the center diff I think, plus there's a skinny shaft that goes through the diff, don't have any of that don't really need much but something with the splines would help a lot If you have that I could definitely use that 😊

I was going to buy a whole Subaru tranny originally but space issues, plus would be a whole lot of stuff I don't need, pita and mess of taking it all apart, was easier to just get the tail piece to start with to see if this could even work but now I think it will I need something for that spline interface

In reply to Turbocad6 :

I'll dig through my pile of leftover Subaru parts and see if there's anything that might be useful. Feel free to remind me.

Have you contacted a gear manufacturer about just buying reverse cut gear for the Miata diff?  They are available for Dana 30-60 ford 8.8 etc. for about $200.

Have you seen the rear diff in an AWD Subaru, they are pretty small maybe perfect for this.

$150 on Fleabay.

In reply to akylekoz :

It takes a bit of effort to design and set up to cut reverse gears, not so bad when doing this for a market where once this work is done there is potential to sell at least several if not many, but to have this done as a one-off would be very cost prohibitive and there is no market at all for something like this so nothing readily available for a reverse cut Miata gear as far as I know.

i think the Subaru rear is no different from any other automotive diff, meaning the ring gear is still on the left side of the pinion. This would still give me reverse rotation to the direction I need so no benefit with a subby diff really. If I do not reverse the rotation then I need a diff that has the ring gear on the right side of the pinion while sitting at the right position in the car, hence the reason for the diff flipping part in the first place