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Author: Subject: rear engine 4x4 maybe mid engine
chimney sweeper

posted on 15/1/12 at 08:21 PM Reply With Quote
rear engine 4x4 maybe mid engine

Hi guys this is my first post and I have a project idea in my head so here goes.

I want to make a chassis that is rear engined and 4WD.

I have wondered about 90s subaru engine in the back with gearbox facing forward but fliped upside down so I still have forward gears, the prop would then go forward to the rear diff that would be mounted in the front of the car but again upside down so the wheels turn the correct way.

I have seen flipped diffs running in all kinds of 4x4 off roaders and racers and it does not seem to give them a problem but i will be building a road car with maybe a little track time as well

I am sure I will be missing something with this set up or maybe a better set up so any advice or ideas welcome

I intend to run as much subaru suspention and steering as possible to keep costs down, I would mount this in a tube back bone chassis with parimiter frame to mount the body.

I would think that Audi 4WD could be used in the same way as well unless you guys tell me diffrent.

[Edited on 16/1/12 by chimney sweeper]





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coyoteboy

posted on 15/1/12 at 08:29 PM Reply With Quote
It's an interesting concept and one I'd panned around in my head but decided against for reasons of purpose more than anything - to me this sort of car should be light, fast and scary - 4wd really only contributes to that in 1 way. But I still think it's a viable option and would be great fun to drive. Flipping the box and diff would be fairly simple, the only issues being what's the correct oil level when upside down (might be a different volume than when upright as it may not cover the driven parts sufficiently, or if pumped, may need the pump extending) and sealing up the various vents and shifter holes. I've never tried sealing up a shifter shaft system, might be a piece of cake!

Keep us informed as to how you get on, this would be a really interesting project.

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zilspeed

posted on 15/1/12 at 08:53 PM Reply With Quote
Now think of the weight distribution.

Loads at the back.

Sod all at the front.

I wouldn't.






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JoelP

posted on 15/1/12 at 08:54 PM Reply With Quote
Do you really want the engine behind the rear wheels? Surely a mid engine setup would be better, which admittedly is difficult with the scooby lump. However, if you used a donor with seperate front and back diffs, you could leave the gearbox the right way up, and just flip both diffs. The diffs would still be turning forward. Being upside down doesnt change that, it just makes the wheels turn the other way.

I cant off the top of my head think of a light and powerful longtitudinal engine that has seperate diffs! Maybe just something like s2000 with a proper transfer box (ie full time, not part time).





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chimney sweeper

posted on 15/1/12 at 09:23 PM Reply With Quote
I have a covin 911 turbo shell without chassis that is why I do not want mid engine.

Do not want to go beetle box and air cooled engine along with the rubbish suspention that brings.

If you fit the subaru lump in the back of a covin the front goes light from the extra weight in the back, the 4WD system will add some weight to the front to counter that and also make an intresting project.

I will have front mounted rad, oil cooler, battery and a few other bits up front to also counter the weight





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nick205

posted on 15/1/12 at 09:39 PM Reply With Quote
I'd have thought a Subaru flat 4 motor would be an ideal fit for a mid-engine RWD set-up in a 911 profile body. Engine hieght shouldn't be an issue and the 4WD gearbox should be easily modified to drop the existing RWD output.






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britishtrident

posted on 15/1/12 at 09:43 PM Reply With Quote
A lot of trouble for little for no gain 30%-70% weight distribution becomes 10%-90% under hard acceleration.





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chimney sweeper

posted on 15/1/12 at 09:44 PM Reply With Quote
I would like to keep the small rear seats so rear engine only for me in this build.

If I went mid engine I would have to do a 911 speedster rep but have other plans for this one





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JoelP

posted on 15/1/12 at 09:53 PM Reply With Quote
quote:
Originally posted by chimney sweeper
I would like to keep the small rear seats so rear engine only for me in this build.

If I went mid engine I would have to do a 911 speedster rep but have other plans for this one


Fair enough, sounds like a mega project though flipping the gearbox!





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bi22le

posted on 15/1/12 at 10:37 PM Reply With Quote
quote:
Originally posted by britishtrident
A lot of trouble for little for no gain 30%-70% weight distribution becomes 10%-90% under hard acceleration.


a lot of car projects are done to solve a challenge not to make a gain.

its all about the chase, not the kill!





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owelly

posted on 15/1/12 at 10:48 PM Reply With Quote
Wasn't there a VW van synchro? Use that running gear with a Scooby motor. Unless I'm talking out of my hoop?





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owelly

posted on 15/1/12 at 10:59 PM Reply With Quote
Thus...







http://www.ppcmag.co.uk

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zilspeed

posted on 15/1/12 at 11:03 PM Reply With Quote
Being a Covin puts a different slant on things.

Go with Owelly's suggestion sould be my, err, suggestion.






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Ninehigh

posted on 16/1/12 at 01:57 AM Reply With Quote
Porsche already do a 4x4 911 don't they? Would it be worth hunting in a scrapyard for the right diffs and gearbox?






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v8kid

posted on 16/1/12 at 03:59 AM Reply With Quote
quote:
Originally posted by britishtrident
A lot of trouble for little for no gain 30%-70% weight distribution becomes 10%-90% under hard acceleration.


Very true but under braking it would be nearer 50/50. Still would possibly need huge rear tyres in acceleration mode

How would the front suspension be set up? What would the front/rear roll stiffnesses be? Caster camber trail all these configurations would be quite different from "standard" IMO.

Challenging Project even apart frI'm the workshop skills required.

Good luck

Cheers!





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coyoteboy

posted on 16/1/12 at 01:42 PM Reply With Quote
The only real issue I see is that you'll effectively be driving the metaphorical dumbell.
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blakep82

posted on 16/1/12 at 01:52 PM Reply With Quote
can't work out what flipping the gearbox upside down would acheive?





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v8kid

posted on 16/1/12 at 01:59 PM Reply With Quote
More forward gears than reverse





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blakep82

posted on 16/1/12 at 02:18 PM Reply With Quote
quote:
Originally posted by v8kid
More forward gears than reverse


well, no, surely you'd just have an upside down gearbox?

or are we talking about a transaxle? with diff built in to the gearbox? that could work, but if just a gearbox, it wouldn't make any difference. they only way it can is if the diffs are upside down. not familiar with subarus stuff.





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coyoteboy

posted on 16/1/12 at 02:43 PM Reply With Quote
quote:
can't work out what flipping the gearbox upside down would acheive?


Scooby 4wd boxes are like Audi quattro boxes, they contain the front diff in the box, meaning to reverse the direction you need to flip the box completely upside down. And deal with the fact that the diff is now at the top of the box, and the oil is trying to fall out of the breathers and selector, and the oil is trying to stay away from the diff where it's normally kept bathed.#

Lower C of G though I guess! (assuming you can lower the engine and box to keep the driveshaft angles sensible

[Edited on 16/1/12 by coyoteboy]

[Edited on 16/1/12 by coyoteboy]

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blakep82

posted on 16/1/12 at 03:26 PM Reply With Quote
i see. i'm old school, i still think of a gearbox with transfer box, 2 props and seperate diffs lol
when i got my vauxhall engine with fwd gearbox still attached, ithought they shared the same oil, like the mini used to...





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chimney sweeper

posted on 16/1/12 at 07:49 PM Reply With Quote
Hi all thanks for the replys so far.

I have just got back from a long day that has involved 7 hours round trip with a days work in the middle, anyway whan driving I tend to think to much so have been wondering about mid engine 4WD, I want to make it 4WD just to make life harder I think I am becoming obsesed with it in this project.

So I was thinking sierra xr4x4,

Turn the engine and box round so the engine is in the mid position with the gearbox facing the middle of the car. The front diff of the sierra that is in the sump would now be the rear diff still in the sump, flipped again for forward gears. The prop would then go forward to the sierra rear diff now in the front of the car but flipped.

This would make the car mid engined with the gear box close to the center of the chassis. It would lose the small rear seats but leave enough room for the front seats.

I was thinking of the sieera as it is the only 4x4 car with this layout that I can think of. The main problem with this plan that I have thought of is I do not want a 2.8 v6 boat anchor in the middle of my car, I have thought of the 2.9 24v out of the grany cosworth but would be intrested to here of any better engines I could use.

Sorry for all the questions and posts but I want to start this as soon as I have finished building my race car so want to have the detail in place before i start





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zilspeed

posted on 16/1/12 at 10:07 PM Reply With Quote
quote:
Originally posted by chimney sweeper
Hi all thanks for the replys so far.

I have just got back from a long day that has involved 7 hours round trip with a days work in the middle, anyway whan driving I tend to think to much so have been wondering about mid engine 4WD, I want to make it 4WD just to make life harder I think I am becoming obsesed with it in this project.

So I was thinking sierra xr4x4,

Turn the engine and box round so the engine is in the mid position with the gearbox facing the middle of the car. The front diff of the sierra that is in the sump would now be the rear diff still in the sump, flipped again for forward gears. The prop would then go forward to the sierra rear diff now in the front of the car but flipped.

This would make the car mid engined with the gear box close to the center of the chassis. It would lose the small rear seats but leave enough room for the front seats.

I was thinking of the sieera as it is the only 4x4 car with this layout that I can think of. The main problem with this plan that I have thought of is I do not want a 2.8 v6 boat anchor in the middle of my car, I have thought of the 2.9 24v out of the grany cosworth but would be intrested to here of any better engines I could use.

Sorry for all the questions and posts but I want to start this as soon as I have finished building my race car so want to have the detail in place before i start


Sorry, can't follow your logic at all here.

If the gearbox ends in the middle, the engine's at the back with your plan.
Cologne V6 at the back, surely not ?






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chimney sweeper

posted on 16/1/12 at 10:16 PM Reply With Quote
sierra has a diffrent lay out to subaru.

front diff of sierra is in the front of the engine sump so in my set up the rear most 2 cylinders of the v6 would be in line with the rear axle line with the rest of the engine in front of the rear axle line and the gearbox towards the center of the chassis. A drive shaft comes out the side of the box on the sierra and goes to the front diff, this would be the rear drive shaft on my set up, hope this makes more sence.





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Livio

posted on 17/1/12 at 07:30 AM Reply With Quote
Do the flipped Subaru engine rotates the same direction as the Porsche boxer in original? If not, you can't even use the Subaru engine with the original powertrain. If yes you could use the scooby 4x4 powertrain with a Porsche engine also.
I suppose the minimum requirement of flipping the gearbox upside down is an adapter plate also.

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