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Engine Transplants - just how difficult and thoughts?

  • 29-06-2010 1:53pm
    #1
    Matt Simis
    Registered Users, Registered Users 2 Posts: 8,718 ✭✭✭


    I cant really post this on the car specific forums as Id be murdered. I would love to put a modern diesel (yes diesel, sacrilege I know) into an e31 BMW (ie 1990 to 99 8 series). Now I already have a limited run 850CSi, I wouldnt of course be using that, Id get an older/tired/damaged lower spec 840i or 850i for a couple of grand in the UK.
    The goal would be a fast'ish old school 8 series with good economy and ideally BioDiesel compatibility. DPFs, Cats etc would be removed.


    8er as a donor car:
    Has a massive engine bay as it was designed for V12s
    Is designed to support high torque and heavy engine weights
    Has a lot of electronics, but none of them advanced by todays standards
    Has awesome suspension (its a heavy car that doesnt feel it)
    Has a 210mm Diff Case, which I assume is the same as the e60 gen BMWs?
    I have a fully working one, so familiarity and I really, really like them \o/

    Negatives:
    Old electronics tend to have corroded wiring and somewhat weird ways of doing things
    850i has 3 ECUs as its a twin engine bank design, starts to sound complicated, 840Ci is like a 540i mechanically however
    ABS and TCS hard to get working in a normal model
    Engine bay may be wide and long, but its not very "tall", may require Mad Max style bonnet mods.
    Others arent familar with them, limited resources and skillsets


    Diesel engine options:
    2000 era M57 / 530d - under 200bhp, smokey and old, but cheap
    2003 era M57 / 530d - 218bhp - not really that cheap, still smokey and old
    2007+ era M57 / 530d - 235bhp, latest evolution, tunable to near 300bhp, not that much more expensive <- The preference
    2005+ 535d/335d - 265-285bhp, tunable to 350bhp, most expensive and lowest economy, twin turbos is twice the failure chance etc.
    1999 era BMW V8 Diesels - not sold in the UK/IRE, low BHP compared to the I6s above
    Non BMW Diesels - Audi V8 TDis - lots of power, but expensive, possibly harder to fit and maybe RWD vs FWD/AWD issues.


    Now I have some help here in work from those that did transplants with US engines (which seem to be sold for transplants over there) and online but anyone here?
    Things Im curious about:
    - Better to get ECU from Donor car too (assume yes)?
    - Understand with diesel engine swap the Diff needs to be changed to a much shorter ratio for the lower RPMs, but is new transmission needed too?
    -Auto box would be the preference, both vehicles came with them, does this make them easier? ECU control of Auto box?
    -Diesel fuel pump vs Petrol, Diesel fuel tank vs petrol, some people say these are issues, others that have done such swaps say not?


Comments

  • #2
    v300
    Registered Users, Registered Users 2 Posts: 356 ✭✭v300


    You are really into "suck and see" territory here. Best bet is to buy two vehicles, the 8 series, and a whole complete running diesel car to rob parts from.

    Try to make sure both are manuals unless you are going for a full loom swop over, which may stop a lot of the 850 bits working, as getting a 8 series gearbox ECU to run an auto box from another BMW would be a no-no. There is no plug and play cross-compatibility designed into these components.

    Basically it's a nightmare job, with a large potential to be very uneconomical to complete regarding labour and custom fabrication costs. Little things like subframes, engine mounts gearbox mou8nts, exhaust routing away from interfering with the steering rack etc.

    1- Better to get ECU from Donor car too (assume yes)?
    Yes.

    2 - Understand with diesel engine swap the Diff needs to be changed to a much shorter ratio for the lower RPMs, but is new transmission needed too?
    Yes. The diesel torque will eventually strip the teeth off of most of the gears in a petrol gearboxes, or at the very least have a vastly reduced lifespan.

    3.-Auto box would be the preference, both vehicles came with them, does this make them easier? ECU control of Auto box?
    Only if using the gearbox designed to be used with the chosen transplant engine.

    4.-Diesel fuel pump vs Petrol, Diesel fuel tank vs petrol, some people say these are issues, others that have done such swaps say not?
    Diesel pumps operate at vastly different pressures and are lubricated by the diesel. They fail when used with petrol. Best bet is a swap over of all the components as some of the fuel system pipes and materials are not compatible with the "wrong" fuel being used.

    Now, if you can buy a pre-engineered kit for this job, or send the car to a recognised expert in this activity ie he has done an 850 diesel conversion before, then go for it. To attempt to do it in your backyard would be planning to fail I fear. Also consider the UK in your quest to get this done. I know a chap down here (County Clare) and he loves this sort of stuff and gets these conversions done and is very reasonable, but he's as rough as a badgers árse.


  • #3
    L-M
    Registered Users, Registered Users 2 Posts: 23,694 ✭✭✭✭L-M


    A friend of mine put a Nissan 200 engine into an E30 (it's a drift car).

    It's doable, but he used the whole suspension set up from the 200 as well, so it involved cutting and welding in turrets. I've seen an attempt fail of putting the engine out of a VZR Pulsar into an Primera due to wiring, in the end a lack of, and a requirement of, immediate funds resulted in the project becoming a failure.

    Tbh, risk of twin turbo fail aside, the 535d is the only engine that I'd put into the likes of an 8 series. I'm assuming you would still have massive gains in MPG over the 5.0 petrol.

    It's a big, big job. Could be worth it, but the money you'd spend on it would get you alot of petrol and more smiles per miles in the 5.0.


  • #4
    Matt Simis
    Registered Users, Registered Users 2 Posts: 8,718 ✭✭✭Matt Simis


    Forgot to come back here to check for an update, thought you guys were ignoring me!
    Limerick man wrote: »
    Tbh, risk of twin turbo fail aside, the 535d is the only engine that I'd put into the likes of an 8 series. I'm assuming you would still have massive gains in MPG over the 5.0 petrol.
    It's a big, big job. Could be worth it, but the money you'd spend on it would get you alot of petrol and more smiles per miles in the 5.0.
    The 535d engine would be ideal, but its expensive and I think a little more "custom" than the 530d (ie it has a specific auto box). A 2007+ 530d is a lot nicer than the older models and compares well onpaper to the 2005 535d.
    Dont worry about smiles per miles, I have the 5.6 petrol for that!

    v300 wrote: »
    1- Better to get ECU from Donor car too (assume yes)?
    Yes.
    How about Immobiliser in the new ECU + Engine, what do people do to get around that?
    I found a company that will have an m57 ECU out soon, could go completely aftermarket:
    http://www.bodylogicuk.com/90265/info.php?p=10
    Only problem there is I suspect the price is £2700 for the ECU alone..
    v300 wrote: »
    Yes. The diesel torque will eventually strip the teeth off of most of the gears in a petrol gearboxes, or at the very least have a vastly reduced lifespan.
    The 4speed (yes 4 speed!?) Auto box (a ZF 4HP-24) in the early 850s is a designed for high torque V12 applications (ie 350 to 400ft/lbs, more been put through it by aftermarket). I dont think the diesel torque will be an issue, mating it up (m57 uses a GM box, the 850 a ZF box) seems doable.
    The problem with sticking to manual (my preference) is a 6sp Manual 850 is £12k and a 4sp Auto is £2-3k. Thats an astronomical difference in price.
    v300 wrote: »
    3.-Auto box would be the preference, both vehicles came with them, does this make them easier? ECU control of Auto box?
    Only if using the gearbox designed to be used with the chosen transplant engine.
    Ive seen many examples of random engine with X auto box online. Doesnt seem like this is too big a concern in the US.
    I also found this, an aftermarket TCU for using the 4HP-24 with low RPM diesel, High RPM diesel or V8 Gasoline engines:
    http://www.ashcrofttransmissions.co.uk/index.php?act=viewProd&productId=18
    People are doing all sorts of conversions with that.
    v300 wrote: »
    4.-Diesel fuel pump vs Petrol, Diesel fuel tank vs petrol, some people say these are issues, others that have done such swaps say not?
    Diesel pumps operate at vastly different pressures and are lubricated by the diesel. They fail when used with petrol. Best bet is a swap over of all the components as some of the fuel system pipes and materials are not compatible with the "wrong" fuel being used.
    Thats probably not a big deal.. the fuel lines on 850s tend to go to $hit after a while and need to be changed anyhow and I assume the average fuel line replacement hose is both diesel and petrol safe. Fuel pump can be taken from a scrapped 530d.


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