# 1995 BMW E39 Conversion



## brian_ (Feb 7, 2017)

175 Nm of torque, multiplied by the 4.1:1 final drive ratio, divided by the 0.324 m tire radius, means 2215 N of drive force. With a 1320 kg curb weight, that's about 0.17 g acceleration. "Sedate" would be a generous term for this.

The stock engine puts out up to about 280 Nm of torque, and is multiplied by the lower transmission gears, so this is a small fraction of the stock performance.

The motor can run up to 8000 rpm and can't produce its full rated power until 3000 rpm, but that gearing means those correspond to 238 km/h (@8000 rpm) and 89 km/h (@3000 rpm). So in normal driving, the motor is rarely given a chance to perform properly. The motor is just not well suited to driving the final drive directly, without an extreme final drive ratio. If you could get an 8.22:1 final drive (and you can't), you could get twice the acceleration up to 45 km/h, without losing any performance above that; you would have a 120 km/h top speed due to the motor speed limit, but you won't be able to reach that in a reasonable time anyway.

A typical production EV with a motor of similar speed specs (and usually much higher power) runs at least 6:1 overall reduction.


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## boznz (Aug 22, 2018)

Thanks for the feedback, 

This is about the same as the 0-100KM in 18 seconds I calculated, slow, but faster than the 24 seconds I've been timing myself at up to that speed. My commute is a flat/quiet country road with some small town driving and I barely see another vehicle until town. I also based the choice of direct drive on the fact that a lot of the EV conversions's of similar weight and power seem to happily start off in 3rd gear with no apparent issues and I really would like to do a direct drive if possible.

You are right however in one sense, that is most people who do ride in an EV now expect much better performance than the ICE equivalent, and I may not be up-selling the idea to many people if I run a snooze-mobile. So I will have a think on this, I have a few months before the car goes under the butchers knife.

Food for thought as they say.


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## Emyr (Oct 27, 2016)

Have you watched @jackbauer's YouTube vids about his 5-series conversion?


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## brian_ (Feb 7, 2017)

brian_ said:


> 175 Nm of torque, multiplied by the 4.1:1 final drive ratio, divided by the 0.324 m tire radius, means 2215 N of drive force. With a 1320 kg curb weight, that's about 0.17 g acceleration...





boznz said:


> This is about the same as the 0-100KM in 18 seconds I calculated, slow, but faster than the 24 seconds I've been timing myself at up to that speed.


Accelerating at 0.17 g for 18 seconds would result in 100 km/h, but that rate of acceleration is only at the instant of starting from a standstill. As soon as the car is moving it has drag, which will take some of the power (and more as it speeds up) resulting in significantly lower acceleration, so even 24 seconds to 100 km/h seems very optimistic to me.


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## brian_ (Feb 7, 2017)

boznz said:


> You are right however in one sense, that is most people who do ride in an EV now expect much better performance than the ICE equivalent, and I may not be up-selling the idea to many people if I run a snooze-mobile.


I don't think it's realistic expectation to expect "much better" performance from an EV. Tesla cars are quick, but so are all $100,000 cars; the rest of the worlds available EVs have modest performance, not better overall (and often slower) than engine-driven cars of similar size and type. Single-speed EVs respond quickly to the accelerator pedal (no need to shift to a lower gear), and usually have good low-speed acceleration, but they usually lag before highway speeds; they just don't have enough power. The pre-2018 Leaf is a good example: everyone likes the low-speed acceleration, but 80 kW (107 hp) just can't keep up with lighter (due to the lack of the big battery) cars with at least 50% more power.

The performance likely with this planned project isn't just not "much better" than the gas engine car... it's much, much worse.

On the other hand, most cars have far better performance than they need, and much more than people use. I'm sure that most drivers have never used the full power of the car they are driving.


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## boznz (Aug 22, 2018)

Hi Brian

So I would need something like this ? http://rodyne.com/wp-content/uploads/2018/10/ev-reduction-gear.jpg


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## boznz (Aug 22, 2018)

Emyr said:


> Have you watched @jackbauer's YouTube vids about his 5-series conversion?


Been ploughing through some of Damien's videos over the past few weeks, the guy makes it all look so easy, however he didn't have much success with auto boxes, I would have liked to see him try the auto box without the torque converter, everyone says its unnecessary but I cant find any reference to anyone who has done it! Manual is not an option as the wife and daughter cannot drive them and refuse to learn and as you can see from my first post I'm no speed demon.


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## brian_ (Feb 7, 2017)

boznz said:


> So I would need something like this ? http://rodyne.com/wp-content/uploads/2018/10/ev-reduction-gear.jpg


Yes, a reduction gearbox like that would match the motor to the required operating speed range. One challenge with that design is that it offsets the motor, so it can be hard to fit in a limited space (such as the transmission tunnel). It does appear to meet the torque and speed requirements.

Another option is the ev-TorqueBox, which is well suited to this vehicle configuration, but has more capacity than required (it was designed for pickup trucks) and is expensive.


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## brian_ (Feb 7, 2017)

boznz said:


> ... he didn't have much success with auto boxes, I would have liked to see him try the auto box without the torque converter, everyone says its unnecessary but I cant find any reference to anyone who has done it!


There have been lots of ancient Powerglide transmissions converted for EV use, including some without the torque converter. They are commercially available... but they're also expensive and massive: Powerglide 2 Speed Direct Drive Transmission for EV Motors - EVGlide. Removing the torque converter and keeping the transmission functional might be more difficult with more complex transmissions.


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## boznz (Aug 22, 2018)

brian_ said:


> Another option is the ev-TorqueBox, which is well suited to this vehicle configuration, but has more capacity than required (it was designed for pickup trucks) and is expensive.


Thanks, the torqueBox looks bullet proof and may be preferable to the Chinese copy or "welding out" the torque converter. I got in touch with the company in China anyway just to see the price.

On a brighter note, my Salvaged Leaf turned up this morning, I put the charger on the 12V battery and lots of red lights but it drives! Battery says its low so I need a mains charger then going to have to source an older ODB2 bluetooth adaptor to get leaf spy and some diagnostics going to see how the battery is, but looking good so far. Lots of learning to do!


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## Duncan (Dec 8, 2008)

Hi boznz

If I was you I would sell that motor on

You have a much better motor and final drive in the Leaf you just bought!

Fitting it in the front of the BMW would be easy but drive the wrong end - I would try and put it in the back

That would give the whole engine bay and transmission tunnel for your batteries

And some people are extracting 300 hp from that unit

On a different note
Have you contacted your certifier yet? - I have a feeling the only one on the Mainland is in Dunedin

Have you got a copy of the NZ Hobby Car Manual ? - AKA "The Bible"


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## brian_ (Feb 7, 2017)

I wondered why not use the Leaf motor, given the use of other salvage Leaf components. The Leaf motor has twice the continuous power rating of the proposed motor, although it would need the entire Leaf battery pack to reach the voltage required for full power over the full speed range.

The assembly of motor and transaxle (reduction gears and differential) is sometimes called a 'drive unit'. The problem with putting the entire Leaf (or similar from another EV) drive unit in the back of the car are that:

the small space for the suspension and final drive unit is far from large enough (in height) for the motor and transaxle, especially if you keep the inverter on top of the motor; and,
the E39 rear suspension is a multi-link design which is not designed to accommodate an engine or motor and does not have a lot of width available between the control arms, so the drive unit (which places the motor transversely) is probably too wide to fit in.
In this particular case, the rear suspension subframe is a massive aluminum structure - it doesn't look really friendly to massive DIY modification.

We've seen a few people try to put drive units in the back of cars which started as rear wheel drive, using the car's original suspension. There has been if any little success other than with Tesla drive units (which place the motor behind the axle, unlike the Leaf) and semi-trailing arm suspensions (like the E34, not the E39).


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## MattsAwesomeStuff (Aug 10, 2017)

> We've seen a few people try to put drive units in the back of cars which started as rear wheel drive, using the car's original suspension. There has been if any little success other than with Tesla drive units (which place the motor behind the axle, unlike the Leaf) and semi-trailing arm suspensions (like the E34, not the E39).


Is there a particular place that describes this thought process and the common constraints of motor mounting with respect for suspension types and OEM EV orientations?

I feel like it's sort of a common question people have been having and it doesn't seem to be something very well described anywhere so people keep describing things for their one situation.

In my head there's a little "I dunno I'll just make it work" placeholder that skips over this whole topic entirely, especially with respect to what kind of donor car I might look for and what different things might limit me to. RWD with a forklift motor up front is a pretty universal solution, but perhaps the least elegant especially with all the OEM options available nowadays.

Like, if I'm going to spend $5-10k on a conversion, I wonder if I'm going to regret "saving" $1000 on a cheap motor and the simplest solution rather than go with something fancier.

Anyway, it seems like the kind of thing that could be written thoroughly, once, and updated maybe once a year and get everyone 95% of the way to navigating this part of their build decision-making process.


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## Duncan (Dec 8, 2008)

Hi boznz

My tuppence worth

Get the complete Leaf front subframe and suspension with the motor drive unit in it

Sit that down - chocked so it sits "right

Get the arse of the BMW high in the air
Unbolt EVERYTHING that unbolts -

You will be left with 
some visible "hard points" that all the BMW bits bolt onto
Some structural "rails"

And a lot of sheet metal

get some cardboard boxes and mock up the Leaf drive unit 

Try and convince yourself if it is a forlorn hope or if you have a chance of it fitting 

Think of how much you love your BMW

At this point you can
Give up the Leaf idea
Bite the bullet and Cut the sheet metal - cutting away the rails and hard points only if necessary

Go and get another old BMW shell to experiment on and leave yours until after you have made most of the mistakes

The ideal situation is when you can cut away the sheet metal and get the Leaf unit in there then make a subframe (or several) to go from the Leaf Subframe to the hard points on the BMW


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## brian_ (Feb 7, 2017)

MattsAwesomeStuff said:


> Is there a particular place that describes this thought process and the common constraints of motor mounting with respect for suspension types and OEM EV orientations?
> 
> I feel like it's sort of a common question people have been having and it doesn't seem to be something very well described anywhere so people keep describing things for their one situation.
> ...
> Anyway, it seems like the kind of thing that could be written thoroughly, once, and updated maybe once a year and get everyone 95% of the way to navigating this part of their build decision-making process.


There isn't a single location or a general treatment that I know of. There is the Wiki section of this forum, which is supposed to be reference material, but it isn't managed in a way that makes it useful... topics just dissolve into disorganized conversation.

I doubt a stable reference is a practical goal, and consensus is unlikely. If anyone wants to produce their own, host it elsewhere, and link to it when the topic comes up in discussion, that would be one way to maintain one point of view on the subject in a rational manner.



MattsAwesomeStuff said:


> In my head there's a little "I dunno I'll just make it work" placeholder that skips over this whole topic entirely, especially with respect to what kind of donor car I might look for and what different things might limit me to.


I think a lot of people do that. There result is stalled projects, and projects that throw away the original components and get very different ones. There are also "interesting" results, such as the 8-series BMW downgraded from a modern multi-link suspension to semi-trailing arms to make the drive unit installation feasible.

It would help in planning if people just had the key dimensions of the drive units that they are considering, and access to the bottom of their potential donor while holding a tape measure. Some imagined installations are pretty clearly unworkable with just the basic dimensions considered.


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## brian_ (Feb 7, 2017)

Duncan said:


> Go and get another old BMW shell to experiment on and leave yours until after you have made most of the mistakes


I like that idea. 



Duncan said:


> The ideal situation is when you can cut away the sheet metal and get the Leaf unit in there then make a subframe (or several) to go from the Leaf Subframe to the hard points on the BMW


That leads to either using the Leaf suspension (which might be feasible, but consider that it has McPherson struts to accommodate), or custom-building a suspension (hopefully with mostly parts original to the base vehicle).

It isn't a Leaf drive unit, or a BMW car, but an example of one extreme of this sort of adaptation is this project which inserted a Tesla drive unit and complete subframe with Tesla suspension into a Nissan Skyline:
Tesla Powered Nissan r32 skyline
The builder had been planning to use a Leaf drive unit in the rear of the car with the original Skyline suspension (which would be similar to putting a Leaf drive unit into the BMW with the original BMW suspension), but he decided that was not feasible so he used a lot more of the Tesla Model S. This involved building a tubular steel structure to connect the Tesla subframe to the Skyline body, and mounting the Tesla struts to the body as well.


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## brian_ (Feb 7, 2017)

boznz, if you are considering putting a whole Leaf drive unit in the back (rather than mounting a motor in the transmission tunnel), you might be interested in this project with a 1973 BMW 2002:
Mounting leaf motor gearbox ideas

That car is much older, and has the old semi-trailing arm suspension; your E39 has a very different suspension which is also a poor fit for the Leaf drive unit, but in a different way. They don't have much in common other than a BMW badge and rear wheel drive. The point of linking to it is mostly that the Leaf drive unit and subframe are shown, and the dimensions discussed.

One positive note is that, the E39 has four subframe mounting points which are much more like the Leaf subframe mounting points than the 2002.


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## boznz (Aug 22, 2018)

Duncan said:


> Have you contacted your certifier yet? - I have a feeling the only one on the Mainland is in Dunedin


No, I was told he comes to Blenheim from Christchurch once a month, the certification is the reason I would like to keep the original BMW gross-weight/brakes/steering/suspension and avoid welding, I will contact him before I execute whatever plan I decide on.



Duncan said:


> Have you got a copy of the NZ Hobby Car Manual ? - AKA "The Bible"


No, I will look out for it now I know about it.

Brian/Duncan. Thanks for the links and advice I must admit, using the leaf motor sounds a good option if I can get it to work, I do have a "spare" BMW and I will have access to some much better tools when I get my workshop built, bit early yet, but I will look at all these options when everything is dismantled and I can get some pictures and measurements to work on.

On another note Leaf is from August 2015 and has 12 bars showing but its displaying 2 bars of charge and a low bat warning, it is going to be idle for 2-3 months so what is better for the battery health, if I charge it up? or should I leave it as is? Would hate for its health to decay due to lack of action.


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## Duncan (Dec 8, 2008)

Hi boznz

You are going to build yourself a shed first?

Have a look at getting a Two Post hoist - they are incredibly useful and nowadays they are dirt cheap - $2500NZ - for everything!

I'm well chuffed with mine


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## boznz (Aug 22, 2018)

Duncan said:


> Hi boznz
> 
> You are going to build yourself a shed first?
> 
> ...


Yip, one of those is on my christmas list


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## toper (Jul 12, 2018)

I'm extremely interested in how this project progresses, especially around the electronic spoofing bits. I am working on an '02 325xi conversion, and those are areas where I am a little more concerned. 

The mechanics make sense, but making the car happy with its new components seems more difficult, especially with the AWD system. I hope your project goes well, these are great cars to work with


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## boznz (Aug 22, 2018)

*Re: 1998 BMW E39 Conversion*

Hi

We are lucky in that a Lot of this work has been done already.

If you look at the beemer forums or watch Damien's BMW conversion videos it seems that once the ECU (and TCU if an automatic) have been ripped out and the remaining immobiliser circuit (if any) removed or bypassed you are then left with a working car with a few red/yellow lights and non working instruments on the dashboard; It should however be driveable and brakes/ABS, steering, lights, etc will work but may report errors that the instrument console picks up, all these warning lights and the speedo will have to work correctly however if you are certifying it for road use in most countries.

The orange alpha-numeric display on my E39 instrument clusters suffer from the normal dropped pixel problem, My goal is to get all the dials working and mapped to there EV equivalent, but I will be replacing the character display or blanking it off as the information will be available on a bigger center screen,

I did some CAN bus spoofing about 11 years ago when I got an MP3 player working on the original head unit on my Rover 75 (which used a lot of the E39 CAN systems) and there are much better information and tools out there now than back then so I am hoping it wont be too hard.

I really don't want to de-ICE my BMW on a gravel driveway with no cover but I am getting impatient and the weather is warming up nicely here so I may start early.


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## toper (Jul 12, 2018)

*Re: 1998 BMW E39 Conversion*

That makes sense, I was wondering if that was going to be the case. I have toyed around with the idea of either heavily modifying the dashboard to communicate with the electric motor systems, or even replace the dials with a screen and make my own digital dash. 

When you mentioned that the information will be available on a 'bigger center screen', what exactly are your plans with that? Do you mean it'll be shown in an infotainment system or something along those lines?


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## boznz (Aug 22, 2018)

Hi

its probably not worth doing a custom instrument cluster for a 1 off conversion (if 10 people were converting E39's it would be different), I had the instrument cluster off yesterday and while it is easy to remove it is a pig to dissemble. So keep it simple and spoof/re-purpose the dials currently there and blank off the lights and displays no longer used, eg

Blank off the alpa-numeric display except the mileometer. (or the testing stations will freak out)
Speedo KPH/MPH -> KPH/MPH
RPM -> Motor RPM/Torque or Amps (not sure if RPM is any use on a direct drive as it would just mirror the KPH/MPH)
Fuel -> EV Battery Charge (volts)
Temp -> Max of controller or motor or battery temperature
MPG Meter -> Motor torque or Amps or calculated MPG/KPL
ENGINE Fault -> motor/controller Overheat?
LOW Fuel = Low Battery
Maybe re-purpose the dials and some other LEDs when charging
etc

The instruments would then also make sense to non-EV people. 

I noted it was easy to power the cluster up on the bench and there seems to be enough information to make the dials work and re-purpose other leds so i will concentrate on that for now. I also measured the 20 char alpha-numeric display dimensions in the high-line cluster and a generic 4-wire 40x2 LCD display such as this, would fit snugly, however this is definitely a "nice to have" at the end of the project and dissembling the display risks damaging the dials due to the horrible mechanical design so I would rather try this with a spare unit off eBay. I also considered a PCB shaped to fit the whole cluster with black solder mask, with LEDs, and LCD dials in place of the existing, could look good but also goes in the category too much of a distraction and too little gain for a 1-off

Same with the center entertainment unit. CD Changer and tape deck will definitely go, but I do like the retro feel of the old unit so it would be good to see if I could change/re-purpose the crappy display and integrate bluetooth and MP3 behind the scenes. I do also have a whole Nissan leaf head unit and instrument cluster which I doubt I will be able to use but might be worth a play, otherwise if everything fails a android head unit with a custom app should work.

Again priority is on getting the car driving, everything else is a bonus.


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## boznz (Aug 22, 2018)

I cant find my notes but it looks like all the systems for the E39 have already been thoroughly hacked and documented since I last looked eg the i-bus here and here

Popping a micro in series with the buses will allow me to easily pass, block or generate new messages as I need, and, as it looks like all the buses converge in the instrument cluster (IKE), any customisation circuit would probably go between the 3 cables connecting it.

The other system buses and inter-connects seem just as well documented so I am pretty sure there wont be any road blocks on this side of the conversion it also means basically I can re-use the existing cabin interfaces for everything I need, so, assuming I can re-use the auto selector, the inside will look the same as it does now. 

The Instrument cluster is now on the bench to play with.


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## boznz (Aug 22, 2018)

*Re: 1998 BMW E39 Conversion*

Quick Update Ref Reduction Gearbox on page 1 of this thread. link picture here and diagram here 

Specification is:

Max Rotate Speed 9000r/min
Max Input Torque 280N.m
Max Output Torque 600N.m
Speed Ratio 2.2
Dimensions(L*H*W) 254*311*336mm
Net Weight 18Kg
Oil Type Recommend 75W-90/GL-4

I got a price back of US$240 for a sample gearbox qty=1, delivery was US$360 from China to NZ (ripped off on shipping as usual!) but all in all US$600 still seems a good price to me for something that should fix my gearing problem so I ordered one to check out...

She will definitely be screaming at 100KMh


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## ArtbyLander (Jan 26, 2019)

How's this going?


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## boznz (Aug 22, 2018)

Very Slowly.. Moving to my new workshop later this month, will pick up the project from there. Stay tuned.


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