Midmounted R17 turbo
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  1. #1
    Fellow Frogger!
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    Default Midmounted R17 turbo

    Hi all,

    was having a few beers with a mate (as you do over the holidays..) and was lamenting the fact that although I have front wheel drive renaults- i really miss the RWD thrill. Anyway- long and short of it is I have a r17 body- rough but salvageable- already stripped of motor and box. I also have the running gear from a r18turbo+5spd. I was originally going to just put this motor and box into the car - as it's a straight bolt in job. However- it got me thinking (and I realise this is by no means a simple/straight forward scenario) what it I put that same setup - into a midmounted arrangement. Same motor and box- but mid mounted to try and get as close to 50/50 weight split as possible.

    So whilst I am about 50% serious about this at this stage- I was wondering if users here had some thoughts as to the major pluses/minuses to doing this conversion.

    Some initial thoughts I had were;

    -fuel tank + battery in front to aid weight dist (accident risk?!)
    -intercooler and radiator to front for good fresh air.
    -remove rear seat and tank and there is plenty of room( roughly 60cm wide, engine bay it comes from is 42cm wide)
    - front end brakes and A- arms can stay as they are (probably want to slot them to make them camber adjustable though)
    -rear end- get A-arms custom made to suit- both top and bottom- costly + difficult?
    -half shafts- if I can use the standard R17 halfshafts with R17 discs should be pretty straight forward.
    -exhaust, will have to be custom made- due to the very short overall length.

    long, long build time due to the complexity and possible horrendous cost. Still, I like the R17- my other car has a mild fuego GTS motor(1647cc) + 5spd with carbs/exhaust etc etc . This one I have now has cost me nothing, and would make for quite a different machine....

    Keen to hear your thoughts- like I said above- am about half way through convincing myself about it, want to hear good/bad what you think the major stumbling blocks to something like this working(and not being a pig to drive with a shocking handling and wt distribution!) would be...

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    Cheers Ben.

  2. #2
    Fellow Frogger!
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    This sounds to me like an excellent project. You will have to cut big holes in the floor and inner guards, so the body will need reinforcing. You will also need some pick-up points for your rear suspension. A tubular subframe could solve both these problems.

    Fabricating the new wishbones is the least of your worries. If you incorporate rod ends/spherical joints, your cutting doesn't even have to be very accurate - you can adjust any inaccuracies out when setting up the suspension. However, why not just use another R17 or similar front suspension, on the back? Everything will line up beautifully - all you have to do is provide the pick up points for the suspension, gearbox, and engine mounts, which is where the subframe comes in.

    Conceptually, it's pretty easy, and could make a great hillclimber, or similar.

    Tim

    I am assuming the R18 has the gearbox behind the engine? Otherwise it will definitely have handling problems........................
    Last edited by tcusack; 7th January 2011 at 01:33 AM. Reason: Question

  3. #3
    Fellow Frogger!
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    Hi Tim,

    yes the R18/fuego motor is north/south configuration -with the gearbox in line behind it. I had thought abuot using the hub/brakes etc from the front of the R17 too- but like the other point you make- if you locate the motor and box - then worry about attaching it to the wheels later - and make up the suspension pickup points etc
    I was assuming that the whole thing will need a very serious rollcage- throughout the entire car- and would hopefully be tying this into suspension pickup points etc too

    I will measure the total length of the motor/box in my R18 turbo- and the distance from the halfshafts back to the front of the motor later today. Which then presents the next issue - if the motor stays the same i.e north/south with gearbox behind it- how do you get the gear linkages to do their thing- underneath might be too low, and over the top would be too high?

    Cheers Ben


    Quote Originally Posted by tcusack View Post
    This sounds to me like an excellent project. You will have to cut big holes in the floor and inner guards, so the body will need reinforcing. You will also need some pick-up points for your rear suspension. A tubular subframe could solve both these problems.

    Fabricating the new wishbones is the least of your worries. If you incorporate rod ends/spherical joints, your cutting doesn't even have to be very accurate - you can adjust any inaccuracies out when setting up the suspension. However, why not just use another R17 or similar front suspension, on the back? Everything will line up beautifully - all you have to do is provide the pick up points for the suspension, gearbox, and engine mounts, which is where the subframe comes in.

    Conceptually, it's pretty easy, and could make a great hillclimber, or similar.

    Tim

    I am assuming the R18 has the gearbox behind the engine? Otherwise it will definitely have handling problems........................

  4. #4
    Fellow Frogger!
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    Default Of course you can do it!

    Just get into it Ben. You would have it finished before a certain 12 gets mobile!
    Gear linkage is a readily solvable, I will give you a contact off line. He has done the same with a PRV V6 and box in a VW Baja off roader.
    Just get out the cut off wheel and go for it!

  5. #5
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    Hey Rhys,

    yeah I hear ya- was hassling Mark about progress on his 12 motor the other day- seems his motor builder doesn't make much progress unless he hassles him about it....

    On the 17- the guy with the baja conversion sounds interesting- I am stumped as to how to get the gearbox on the back and the linkages to the gearshift to work properly- I haven't had the experience of one of them 'funny' renaults with the gear in the back!

    I figure if the box is mounted in line with the rear axle- the main part of the motor will be sitting squarely in where the back seat used to be- and not far from the drivers left ear! However should not be too different from the sort of setup you have to 'endure' in a R5 mid mount...

    My major concern is around the weight distribution- anyone got some cunning ideas as to how to assess this before cutting/welding begins? I am just talking about a way to determine if the wt split will be 54/55 or 70/30 with some rough backyard calcs?

    Cheers Ben

  6. #6
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    I think that the 50/50 weight split might be harder to achieve than you think. Easiest way to get a rough idea would be to get your current chassis set up with some scales under each wheel and at least try and work out what you currently have without engine, and then find the weight of the 18 engine, gearbox, drive shafts etc and make up a dummy to that weight using a bag of wheat and some weights etc and have a fiddle with that to get an idea of whether you are in the ballpark.

    It is maybe going to be easiest to make up a subframe that mounts engine, gearbox and suspension, and this then bolts into the stripped out rear of the 17. You could look at a lotus Europa or the like for ideas re gear linkages. It would also be a good idea to measure up where the front of the engineis going to end up when it is installed to make sure that you are going to have room! Best bet would also be to look at designing things around a 4 stud wheel hub to start off with so that you have a good choice of wheels to use. Me thinks there will need to be a fair bit of guard pumping at the back to get everything in.

    You will need to go to a coilover arrangements for the front suspension, but even then you are going to have some issues with getting the front end set up low enough and with enough negative camber. You could look at a coilover double wishbone arrangement for the rear as well, mounting off your subframe. I reckon there would be some kit cars that have a good template for how this could be done.

    The fact is though that you are moving a lot of weight back and there is only so much you can bring forward. You will need to weld in a floor to the front and a radiator pushed a long way forward along with the battery and the fuel tank somewhere forward (but remember your steering) will get you to a point, but I would be interested in knowing what the weight distribution is without any of the mechanicals - get them scales out!

    I dont know what the deal is in NZ re registering something like this, but I reckon that getting some research done re how this could all work and getting an engineer to hve a look re what would need to happen for approval would be a smart move before you started doing too much if your aim was to get the thing on the road.

    Have fun!!!

  7. #7
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    Thats the way you do it - Ginetta G12
    Attached Thumbnails Attached Thumbnails Midmounted R17 turbo-g12_dare_duratec.jpg  

  8. #8
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    Quote Originally Posted by oldnago View Post
    Thats the way you do it - Ginetta G12
    I am currently working on an R5 Turbo built originally by Bob Watson. It has a mid mounted 16TX motor turbo boosted to 15+ psi.
    This project done in 1980 cost $20000+ and a considerable amount of effort and labour, so go into this project with your eyes open and also your credit card full.
    Rob Sealey

  9. #9
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    Hi all,

    forgot to mention- I was assuming that this car would be used only for hillclimbs/racing from now on. I'd obviously want it to be safe etc- but the cost of engineering something like this to a standard fit for road use - is beyond me (for at least the next 10 years!)

    Cheers Ben

    ps- the ginetta picture- they have basically fabricated the whole rear end of the car and then will be clothing it in a body later. Is this the better way to do it- i.e cut away the suspension tops etc and start from scratch, with a new 'subframe' in the rear that everything attaches too- i.e motor, gearbox, suspension points etc

    Also - another point about battery/fuel cell/radiator- you'd HAVE to mount these far forward in the engine bay wouldn't you?

  10. #10
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    The Ginetta is a full spaceframe chassis with a fibreglass body. It is just an illustration re how you really need to approach things.

    What I was really getting at was that the whole process is incredibly complicated and as Rob has pointed out expensive. 20k for the 5 30 years ago needs to be looked at in the context that you actually had a factory racer to copy to some extent, where you are very much going it alone with the 17.

    If you build a competition only lotus 7 type car, for as cheap as you could, I think it would be both cheaper and quicker than a mid mounted 17.

    Without wanting to rain on the parade, the complexity of calculating spring rates and setting up just the front end geometry wth the engine gone would do most peoples heads in before you even got to how you get the engine in there etc.

    The compromise might be to look at a kit car that could use the renault 18 turbo engine in a mid mounted form. There are a number of UK companies that do a mid mounted spaceframe chassis.

  11. #11
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    Quote Originally Posted by oldnago View Post
    The Ginetta is a full spaceframe chassis with a fibreglass body. It is just an illustration re how you really need to approach things.

    What I was really getting at was that the whole process is incredibly complicated and as Rob has pointed out expensive. 20k for the 5 30 years ago needs to be looked at in the context that you actually had a factory racer to copy to some extent, where you are very much going it alone with the 17.

    If you build a competition only lotus 7 type car, for as cheap as you could, I think it would be both cheaper and quicker than a mid mounted 17.

    Without wanting to rain on the parade, the complexity of calculating spring rates and setting up just the front end geometry wth the engine gone would do most peoples heads in before you even got to how you get the engine in there etc.

    The compromise might be to look at a kit car that could use the renault 18 turbo engine in a mid mounted form. There are a number of UK companies that do a mid mounted spaceframe chassis.
    No problem- this was what I was really after- kick the pluses and minuses around with some like minded people. At the end of the day the replacement of the std motor (in the front) with a worked r18turbo motor will still be quite a lot of fun- will just be easier to buy another(don't tell the wife-) rear wheel drive car to get my RWD jollies at some stage. (always did like the idea of a 504 with a hot PRV v6 in it too.)

  12. #12
    1000+ Posts HONG KONG PUGGY's Avatar
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    This was for sale on e-flogg a few years back
    Attached Thumbnails Attached Thumbnails Midmounted R17 turbo-r17draglhs.jpg   Midmounted R17 turbo-r17dragrhs.jpg   Midmounted R17 turbo-ultimate17.jpg   Midmounted R17 turbo-ultimate-seat.jpg   Midmounted R17 turbo-ten04qtr-eng.jpg  
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  13. #13
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    Default R17 Mid Engine !!

    The best way to make it a lot cheaper is to get the entire front subframe and graft it into the back of the car.

    This means you do not have to re-engineer a car, just specific measuring and aligning. The rear spring rates will need to be upped about 15-20% because of weight transfer to the rear. An R12 subframe would probably do as the floorpans are very similar with geometry. The R5 Turbo had a similar thing done on the prototype versions, until they realised the need for special suspension to homologate the car for motorsport. That subframe is very similar to the 16TS.

    Ray geckoeng.

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