# BMWs and ECUs



## Richard Wood (Jun 27, 2008)

I am trying to get a quick fix on the complexity of my chosen vehicle - a 95 BMW 318ti (E36). Does anyone know if I will be needing the ECU and needing to do tricky things to fool it. I'd like to keep my conversion real simple. I intend at the moment to dump the automatic transmission and go AC direct drive. Also does anyone know if the ECU is anything to do with central locking, antitheft system?


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## E30_Dave (Apr 19, 2012)

Hi Richard,

Apart from the visually obvious, electrically and mechanically, the E36 differs little from the late E30s, therefore the electrical hurdles which we both face are not dissimilar from each other. 

As regards BMW anti-theft systems of the period, they were all fitted as options, and therefore are self contained - they merely cut the power supply to certain elements of the car... eg. fuel pump, starter motor and engine management.

There were two or three types: The OBC (if fitted) has a key-code immobiliser, whereas the others are slightly modified versions of Serpi Star / Gemel (which BMW called the G3 - two button remote control) or possibly Sigma aftermarket alarms, and should therefore require alteration only to two of its' three immobiliser circuits.

As regards then engine management ECU, I suggest you unplug the wiring loom from it, then switch the ignition on, and see what works (ie Speedo, fuel gauge, temp gauge & warning lights etc.).

Thankfully this is not a car where every decision the driver makes has to go through a **&*(&^&)* computer (!), so no CAN-BUS etc - it should be relatively easy.

Which alarm do you have ?

Cheers

Dave


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## esoneson (Sep 1, 2008)

Richard Wood said:


> I am trying to get a quick fix on the complexity of my chosen vehicle - a 95 BMW 318ti (E36). Does anyone know if I will be needing the ECU and needing to do tricky things to fool it. I'd like to keep my conversion real simple. I intend at the moment to dump the automatic transmission and go AC direct drive. Also does anyone know if the ECU is anything to do with central locking, antitheft system?



I will be following this closely. I am converting a 1995 BMW 318i and have the same questions about the ECU.

Well, of all the E36 vehicles to choose for a direct drive system, the 318ti with automatic tranny is the best choice. 1) lightest of them all and 2) the rear diff ratio is 4.44:1.

Hopefully you will be able to find an AC motor/controller that will be able to push you along with your existing differential and no tranny.

Good luck with your efforts.

Eric


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## CrunchTime (Feb 13, 2009)

Richard Wood said:


> I am trying to get a quick fix on the complexity of my chosen vehicle - a 95 BMW 318ti (E36). Does anyone know if I will be needing the ECU and needing to do tricky things to fool it. I'd like to keep my conversion real simple. I intend at the moment to dump the automatic transmission and go AC direct drive. Also does anyone know if the ECU is anything to do with central locking, antitheft system?


For my 1995 328i, I pulled the ECU, then basically removed anything from the loom that connected to it or the ICE. So far I haven't found anything that doesn't work as expected.

It moves (up and down the driveway ), but until it's actually certified/on the the road I suppose I could still find something...

BTW - I found the Electrical Troubleshooting manual a great help in deciding what was/wasn't required in the loom...

I assume you'll be going lithium - I couldn't get the theoretical weight down to anything reasonable using FLA - the GVWR didn't allow more than two people (driver, passenger), even after replacing my electric seats with manual etc...


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## Richard Wood (Jun 27, 2008)

Hi E30_Dave 
Thanks for this information. The approach of my build is that where there are choices, I'll keep it simple. I might just leave all the anti-theft and ECU stuff there and if removing the engine causes some other issue through the ECU then deal with that specific issue. What are the three immobiliser circuits you mention? Are you saying there is one that still relates in an EV arrangement. 
I don't think the car has an alarm. There are no beeps or sirens apparent. I am guessing it is transponder immobiliser only, with the two-button key controlling central locking.

Hi esoneson
Yep, it's the AC motor/controller decision that seems crucial with tradeoffs over costs, capability, weight and cooling approach. I get the impression a water cooled combination has more chance of delivering the top speed and the acceleration at low speed in direct drive but I guess it means retaining the radiator, which I wanted to dump. Perhaps an air cooled motor combined with a specialised 2 speed transmission would give me the bottom end acceleration I need and keep it simpler over all. I am attracted to the EVGlide system in that respect although there is a cost to it.

Hi CrunchTime
Great to hear no issues with the ECU out. So all the speedo, warning lights, ABS etc still works fine? Where do you get the Electrical Troubleshooting manual? Sounds useful. Definitely going non-lead. I'll see what the best batteries are when I've finished. I don't have great range requirements - 30km daily commute (so thinking 50% or so more than that) so am expecting to get under GVWR relatively easily. I might switch my electric seats too for lighter manual ones as they are in pretty poor condition visually anyway. 
I see you are in Lower Hutt. I'd love to come and see your car.

Cheers
Richard


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## E30_Dave (Apr 19, 2012)

Hi Richard,

Simple is the best way - it's where I believe EV conversions score over OEM Evs, and certainly over IC cars.

As regards leaving redundant parts in situ: It all adds to dead weight, which obviously has an impact on performance and range.

The immobiliser could certainly have an on-going function. The BMW G3 alarm has two or three immobiliser circuits - one is a heavy duty circuit to isolate the starter motor, there will be one which isolates the engine management system, and another which isolates the fuel pump. ...and remote central locking is great!

The BMW G3 looks like this:


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## CrunchTime (Feb 13, 2009)

Richard Wood said:


> Hi CrunchTime
> Great to hear no issues with the ECU out. So all the speedo, warning lights, ABS etc still works fine?


Like I say, I haven't gone on oad yet, so I'm still nervous about the ABS, but yes, the speedo and warning lights are fine. I've got an EVWorks FGD+ to drive the fuel gauge (and the tach as an optional Ammeter).

Definitely going non-lead. I'll see what the best batteries are when I've finished. I don't have great range requirements - 30km daily commute (so thinking 50% or so more than that) so am expecting to get under GVWR relatively easily. [/quote]

With Lithium it's easy 



> I might switch my electric seats too for lighter manual ones as they are in pretty poor condition visually anyway.


I do have a set of gray E36 manual seats for sale (~$100 - what I paid for them), but they're in really bad shape (split driver's seat, etc).



> I see you are in Lower Hutt. I'd love to come and see your car.


You have PM...


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## ACEVS4US (Jul 21, 2011)

Damn, the world is a small place. I live in Wellington too and am also starting a BMW 318 conversion (there must be something in the water). I'm using liquidated stock from azure dynamics. 

I am using the Siemens 1pv5135-ws14 and DMOC combo with vacuum pump, water pump and AC pump. All this is CAN controlled so there is a small amount of work to get it going, but it should be fairly easy. 

I figured regen would be kind of good in Welly with all the hills. 

Can you guys tell me which certifier you are using?


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## Richard Wood (Jun 27, 2008)

Have only talked to a very helpful retiring certifier so far. The list is maintained here: http://www.lvvta.org.nz/contact.html#certifier
Keen to connect at some point and see what you are up to.


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## Thaniel (May 25, 2008)

CrunchTime said:


> Like I say, I haven't gone on oad yet, so I'm still nervous about the ABS, but yes, the speedo and warning lights are fine. I've got an EVWorks FGD+ to drive the fuel gauge (and the tach as an optional Ammeter).


I converted a '93 E36. Removed the DME (ECU) entirely. ABS works fine (Yes I have tested it's function. Not just relying on lights). IT was not integrated into the ECU. The ABS also has it's own warning light. IF it goes off then it's ok. 

One word of warning. If you run the car on the jackstands the ABS light WILL come on (how woud I know that? ) It sees the wheel speed between the front and rear wheels are different and figures there is a fault. Running the car on the ground turned it back off for me. 

If you have a version of the E36 with traction control there may be a few more things to keeping all the warning lights off.

P.S. Can bus is nothing to be afraid of. My next conversion will be an E46.

Thaniel


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## ARti (Oct 27, 2008)

I've got a 97 US 318ti 5speed. It's a great ride, if your batteries have the juice for it. Mine's very simple, with a 9in DC setup from EVA. One of the great things about these E36s is that they're very modular. The ECU is an entirely separate unit from the "Body Computer" that regulates door locks, windows, etc. ABS is it's own black box as well. 
I left the ECU in place, and as a result, still have lots of lights on the dashboard. But I don't mind; I sort of get a kick out of the admonition to "Check Engine."

Regarding Instruments, the Speedo is driven by a sensor in the transaxle, so it still works fine. Somewhere, I've got a schematic for the fuel gauge that someone at 318ti.org sent me; I'll add that to the thread as soon as I dig it out. It's a simple voltage divider circuit. I didn't bother with a Tach signal. It's on the "someday" list.

That's the bottom line with the ti's: They're well built, but were designed as simply as possible to try to keep the cost down. That makes them easier for us to work with.

Have fun,
Phillip


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## ARti (Oct 27, 2008)

Here's a link to the thread on Tachometer and Fuel Gauge from 318ti.org's forum:
http://www.318ti.org/forum/showthread.php?t=29504


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