CAN bus info for engine swaps

Posing this question could open a whole can of worms (and makes me realise how little I actually know), as well as broadcast to everyone here just how little I know

I'm trying to research engine swaps, specifically, a newer BMW engine (such as an M52 or M54) into an older E28. Forgetting for the time being about fitment issues, I've been trying to learn about CAN bus systems.

I get the basic concept of different modules constantly communicating, and each responding/acting as needed, when it interprets a certain code sent from another module. I don't think I need to get too bogged down and bother learning the exact coding particulars. My question is this: how does one get a newer engine, controlled by an ECU/PCM which talks with the rest of the car's electronics via CAN bus, run in an essentially isolated situation, without most of those additional modules? I see guys like jakeb (fellow GRM board member) who runs classicdaily.net swapping newer engines into older vehicles and they make it look quite achievable.

How much of the CAN bus system can you do without? What are the essential modules that need to remain (I'm guessing PCM and gauge cluster?), and which can you remove (Body control module? ABS module? DSC module?) and the system still stays happy and allows the engine to run? Anyone here have experience with this?

I think that depends on the vehicle in question. Some engines require the gauge cluster, some don't. They all need the PCM They may require the ABS module, they may not. You're going to have to find out more about the PCM that you're using.

Or, setup a megasquirt/standalone engine management. Then you just need power and ground and the engine + management is a pretty isolated system.

I'd just run a standalone EMS like Megasquirt or RusEFI. Although you will need to dyno tune the EMS for maximum power, it's a much simpler route than trying to swap a whole harness. That said, there are people who have put these newer engines in E30s.

In some cases the transplant engine and parts are hooked up to the original wiring and computer as well. Properly sized injectors and such should all need the same kind of signal to squirt and sparking one 4-cylinder is the same as another.

For the ones suggesting running a standalone module- some modern engines are not able to run on those- many of modern BMW engines use the variable cam system as the throttle. I don't think you can run that cam system with MS or Russefi. Many stand alone systems can't run electric throttle, and none can run direct injection.

To the OP- Keith is spot on- it depends. The ABS/Traction control interface is pretty important with many modern engines for proper torque inputs- some can still run with errors, although many get vehicle speed from the ABS module. Thefts systems are really important- that's a go/no-go input.

Europeans will be worse than Americans, who will be worse than Aisans, I think. My specific experience is with Volvo, and they are probably as bad as anybody. They have a high speed network for the important stuff- engine, trans, abs/tracs, and that sort of stuff. The low speed is windows and sound systems and alarms and awd and on and on and on. The tricky part is the central electronic module. Its the hub for both networks, and transfers the info needed from one network to the other. An example- The awd control module is on the low speed net, but the wheel speeds come from the abs, which is on the high speed. That data goes from one to the other through the cem.

Communication issues are surprisingly not that common, considering the amount and complexity of everything. As long as the module you remove is just removed, and doesn't contribute something critical, you will just have a "no comm with ddm" type of code stored. The bigger problems come when you have a bricked module, or a corroded connection either powering or grounding the comm line. I had a XC70 that would intermittently not start. Finally traced it to a bit of green in the connector on the differential electronic module. Ground out the comm line, ecu can't get permission from the upper electronic module which includes part of the alarm system, no start. Another, the charge light was on. Car was charging adequately, but since the low speed was down, it didn't know the outside temp, so wouldn't charge at full rate. That one was due to a bit of contamination in a plastic insulator going to the drivers door, where the comm line was next door to the main door ground wire...That one was fun, particularly since that comm wire was a new addition that wasn't shown on the wiring diagram...

Its all do-able, but I'd hesitate to do it at home with a German car, without some expert help. Honda, I'd probably attack it.

Thanks for the responses guys.

Keith Tanner wrote: I think that depends on the vehicle in question. Some engines require the gauge cluster, some don't. They all need the PCM They may require the ABS module, they may not. You're going to have to find out more about the PCM that you're using.

What sort of info would you be looking for, if you were in my shoes?

rcutclif wrote: Or, setup a megasquirt/standalone engine management. Then you just need power and ground and the engine + management is a pretty isolated system.

alfadriver wrote: For the ones suggesting running a standalone module- some modern engines are not able to run on those- many of modern BMW engines use the variable cam system as the throttle. I don't think you can run that cam system with MS or Russefi. Many stand alone systems can't run electric throttle, and none can run direct injection. To the OP- Keith is spot on- it depends. The ABS/Traction control interface is pretty important with many modern engines for proper torque inputs- some can still run with errors, although many get vehicle speed from the ABS module. Thefts systems are really important- that's a go/no-go input.

It would be awesome if this option was possible, I hadn't thought about a Megasquirt system. And I'm guessing that MS would be able to put out a normal tach signal that an old E28 tach could recognise. However, I doubt MS could run a BMW vanos system, so that probably limits it to only the original ECU.

Any good reference sites for this sort of stuff?

Yeah, if MS can't do it, berk it. Find a different car.

I'd be going to a BMW expert if I were planning this. It's easier to put a CAN engine in a non-CAN car than vice versa, though. You could also start with a happy, running car and start disconnecting modules to see what happens. A copy of a wiring/diagnostic manual can also help, as they'll sometimes tell you what the error behavior is if a particular module cannot be contacted.

Yes, definitely look at a wiring schematic for engine sensors and outputs.

GM controllers are very very nice in this regard, they put everything engine related through the PCM and then the PCM sends the data out by CAN. The instrument cluster probably gets all of its gauge info from the PCM by CAN. Mind you, this makes it difficult if you are going the other way, putting a standalone in a GM car.

Ed: the m52 runs ECU only, looking only for the ews sensor output from the chipped key. This can be disabled easily by anyone who reflashes these ECUs - Google ews delete m52b28. Mail them the ECU and they'll delete ews, rear O2 feedback and a few other things if desired.

The m52 is a great, cheap ($600ish) motor, and fits with little difficulty using an e34 oil pan and pickup ($150ish). The e30 guys are a great resource for the electric side of this swap, but it is EXTREMELY straightforward, since bmw uses a separate harness for the engine to ecu. M3 (s52) cams and m50b25 intake (with the appropriate tune since you're reflashing it) really wake it up. Or megasquirt it, use arp head studs, flex fuel sensor for e85 and add boost: the iron block m52s are stout. Megasquirt can be setup with flex fuel adjusting fuel/timing/boost for percentage ethanol.

Anything that goes in an e30 goes into an e28 in exactly the same way.

The m54 is trickier, requiring a custom oil pickup and some oil pan work, but ms will indeed control dual VANOS using ms3. He's posted on e30tech and r3v for years. http://m54megasquirt3.blogspot.com.au/?m=1

http://www.r3vlimited.com/board/showthread.php?t=297172&page=2

And yes, I've spent WAY too much time on this.

edwardh80 wrote: It would be awesome if this option was possible, I hadn't thought about a Megasquirt system. And I'm guessing that MS would be able to put out a normal tach signal that an old E28 tach could recognise. However, I doubt MS could run a BMW vanos system, so that probably limits it to only the original ECU. Any good reference sites for this sort of stuff?

MS3 will do variable VANOS just fine on the current code. It currently doesn't have a drive by wire option for the M54, but the easy option there is to put on a cable operated throttle body. One good starting point is here:

http://www.msextra.com/manuals/

The M52 and M54 are before Valvetronic or direct injection, so you're safe there.

These guys will probably have all the answers:
Bimmerforums Engine Conversions

alfadriver wrote: For the ones suggesting running a standalone module- some modern engines are not able to run on those- many of modern BMW engines use the variable cam system as the throttle. I don't think you can run that cam system with MS or Russefi. Many stand alone systems can't run electric throttle, and none can run direct injection.

Agreed, but OP mentioned M52 and M54, which are both newer than the e28, but neither is really that 'new'. As mentioned above, the M52 is old enough that is basically is a closed system needing the ECU only already.

To the OP - I have wanted to motor swap an e28 for a long time. I'd really be looking long and hard at the M70 though. Not really a power leader or price leader (if you want that, then SBF or SBC, or turbo the snot out of the current mill), but the awesome factor would be large in my mind.

And if you do go M70... I want to watch!

The M70 is pretty awesome, but not really that powerful for the amount of work it would take. I swapped a M62B44 V8 into my '71 Bavaria, the V12 would be similar in effort, probably easier actually. I don't recommend swapping the V8 either, not worth it. I was facing the same dilemma as you and went with megasquirt. If I did it again, I would have converted to OBD1 or had the OBD2 ECU reflashed to remove the requirement for the other modules. Megasquirt is a lot of work and if you're just running a mostly stock engine, not worth it. The benefit of megasquirt is you'll learn a ton, more than you wanted to. Megasquirt is never going to run as well as the stock ECU.

The V12s had two engine computers, yeah?

It actually has three ECU's, one for each bank ignition and the third that controls fueling.

bmwbav wrote: It actually has three ECU's, one for each bank ignition and the third that controls fueling.

Yep, the m70 is essentially two m20s joined at the crank. two ecus, two distributors, two sets of sensors (MAF, O2, crank, etc), and one more computer to keep the two engines working together.

I feel this thread derailing.... sorry OP.

Cool! Lots of info to digest now, thanks guys!

If I could swap any engine, I'd really like an S62 V8 from an E39 M5 - around 400hp, no turbos to worry about, V8 goodness - but since E28's didn't come with a V8, I'd imagine a six cylinder swap would allow easier fitment.

Yes, much easier to do the inline swap, go that direction. My v8 swapped e3 is cool, but its a lot of work. If you want a V8, I would go with an LS swap, there are some out there already. It's much smaller than the S62

Sia over on the mye28.com board has an e28 with an S54 out of an M coupe in it: http://www.mye28.com/viewtopic.php?f=7&t=108450 He had the work done at The Stance Factory in Toronto: http://www.stancefactory.com/ If I were to do a swap on my car, I think this is the way I would go. There have been a bunch of engine swaps into e28s - LS series Chevys, BMW V8s, even a couple BMW V12s, but a six will be a lot easier; the brake booster and steering gear tend to get in the way on V engines.