Running with no front subframe - discussion.

Thread in 'Technical Questions' started by willirl, Aug 24, 2013.

  1. willirl

    willirl Member

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    Hi all,

    Now the title definitely makes it sound an awful lot worse than it really is, so please read in full before posting! This isn't something I'm looking to do, more so discuss the theory as to why it would or wouldn't work.

    We were discussing in the garage today the pros and cons of fitting an M60 or 62, to an E36 or 46, and naturally the sump to subframe clearance issues where the main point of discussion. We wondered if the subframe could be removed, the engine mounted to the chassis and the steering rack given its own mounting frame, and that the subframe be replaced with a custom frame and/or braces in locations on the front chassis legs that provided clearance for the sump.

    Now I am by no means a chassis engineer, and it's not something I would say I have great knowledge on, outside of my own basic research, so I would like some input from someone who has experience in this area, if possible!

    Anyway, I don't see why it wouldn't be a feasible option (and I could well be wrong here). From my understanding, the principle function of a subframe as an engine member is to 1) spread the load of the engine over a larger area, 2) dampen vibrations to the cabin, and 3) reduce production costs.
    Now points 2 and 3 I would take as being null and void seeing as I am talking purely about a track only car. Which leaves the issue of spreading of the weight of the engine over a larger area, which I'm sure could be overcome quite easily with correctly designed chassis mounted engine mounts that dissipate the load correctly?

    In terms of suspension, it provides a tie between the chassis legs with provides stiffness, and on an E36/46, mounts for the front wishbone inner balljoints. Now, would I be correct in thinking that bespoke mounts to the chassis for the balljoints could solve that issue, and also x-bracing or similar between the chassis legs could replace the stiffness?

    Now I'm sure there's many other variables like different loads placed on the chassis legs etc etc, but more so is there anything I'm missing, or is my theory sound?

    Again, I want to re-iterate that this isn't something I'm planning to do, and I understand it would involve a lot of fabrication! But I want to see if my theory correct, and would it be feasible to do.

    Thanks,

    Will
     
  2. Matt G40

    Matt G40 New Member

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    something else to add: its not just engine weight but load going through a subframe, the intial tourqe say from a bmw v8 going through a paddle clutch at a 5k clutch kick will be something to think about.

    Nice discussion :)
     
  3. willirl

    willirl Member

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    Good point dude, definitely one to add to the list!
     
  4. tathan

    tathan Member

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    There are lots of cars that the engine bolts straight to the chassis so with thicker load bearing members it's no problem. The torque fatiguing the sheet metal along the load path is going to be main failure mode I'd have thought.

    The suspension mounting is probably more difficult as you don't want it to move, at all, so you're essentially going to end up just fabricating a different subframe to link both legs and the suspension pick up points. At which point you'll wonder why you don't just put the engine mounts on it too ;)
     
  5. Will.

    Will. Come at me bro

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    If the standard subframe is giving you grief and you can't modify it for whatever reason, a custom tubular subframe would probably be your best bet. Whatever you go with, it sounds like a lot of hassle.
     
  6. Mike@TDSW

    Mike@TDSW Active Member

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    Use an e30 subframe and modify to get everything else in the right place would be my idea.
     
  7. spaniel

    spaniel bigballs small brain

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    I have been trying to think of a better way of getting a v8 in my e36.
    I was thinking couldnt you modify the original subframe so it comes round the front of the sump? The problem is then you would have to move the steering rack forward which i dont know if it would effect the steering. I was thinking at worst it would put more preasure on the track rod ends.

    Or as said above modify one from an e30, havent really looked at one yet so i dont know what they are like.

    Good thread will definately keep reading:thumbs:
     
  8. spaniel

    spaniel bigballs small brain

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    I still reacon modifying a subframe would be easier
     
  9. brennon

    brennon Active Member

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    Bmw can sell you a sump to fit the v8 into e36 chassis as alpina made one. Given it may well be pricey but its a bolt on solution.
    I heard rumours that the x5 sump would also fit but I can't confirm.
    Bmw will also sell you engine mounts etc to fit.
     
  10. Mike@TDSW

    Mike@TDSW Active Member

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    The alpina v8 has a different sump and oil pump I believe not subframe.
     
  11. brennon

    brennon Active Member

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    That's what I said, is it not?
     
  12. MJG

    MJG Active Member

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    Would work fine, just keep the rack as close to "between the hubs" as possible and make sure every load is considered from suspension and engine. At worst, your car will fall apart.
     
  13. spaniel

    spaniel bigballs small brain

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    I know you can buy a sump to fit but you still have the expensive problem of the oil pump.

    Im taking out an engine on an e36 soon so gonna have a look and see about making mounts for the wishbones and engine to the chassis, then tie the chassis together in front of the engine. The only problem really is where to put the steering rack?
     
  14. Khmer

    Khmer Guest

    tl;dr

    go tube subframe for sump clearance.
     

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