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]
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.
Now think of the weight distribution.
Loads at the back.
Sod all at the front.
I wouldn't.
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).
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
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.
A lot of trouble for little for no gain 30%-70% weight distribution becomes 10%-90% under hard acceleration.
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
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
quote:
Originally posted by britishtrident
A lot of trouble for little for no gain 30%-70% weight distribution becomes 10%-90% under hard acceleration.
Wasn't there a VW van synchro? Use that running gear with a Scooby motor. Unless I'm talking out of my hoop?
Thus...
Being a Covin puts a different slant on things.
Go with Owelly's suggestion sould be my, err, suggestion.
Porsche already do a 4x4 911 don't they? Would it be worth hunting in a scrapyard for the right diffs and gearbox?
quote:
Originally posted by britishtrident
A lot of trouble for little for no gain 30%-70% weight distribution becomes 10%-90% under hard acceleration.
The only real issue I see is that you'll effectively be driving the metaphorical dumbell.
can't work out what flipping the gearbox upside down would acheive?
More forward gears than reverse
quote:
Originally posted by v8kid
More forward gears than reverse
quote:
can't work out what flipping the gearbox upside down would acheive?
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...
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
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
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.
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.
The flipping of gearboxes is common in mid-engine land, particularly for GT40’s and the like, commonly done with Porsche units such as the G50 as they
are the strongest ‘reasonably’ priced units available. So I would be surprised if the Subaru unit would not work acceptably in this config. Of
course an adapter plate will be required, which’ll stuff up the use of the standard flywheel I expect.
Refer to www.gt40s.com and search in the transmission section for help on the above.
Only the drive train is fliped not the engine.
Some one told me that honda engines spin the oposite way to other engines? if that is true I would not have to flip diffs and boxes with eather drive
train would I.
No, but you'd be having 5 reverse gears......
Looking at it B,D and H Honda motors spin the other way so no diff flipping needed with the above mid or rear engine set ups, May make things easyer
quote:You might want to read up on axial thrust in helical gear sets before you think too much about running a whole gearbox/drive train backwards. It would destroy itself eventually because all of the thrust didirections are reversed.
Originally posted by chimney sweeper
Looking at it B,D and H Honda motors spin the other way so no diff flipping needed with the above mid or rear engine set ups, May make things easyer
Yup, running it in reverse will trash it in a matter of miles.
I kn ow alot of the 4x4 of road racer guys do it with out a problem but I have wondered about it.
Have also seen an MGB with honda engine and fliped rear axle that had done over 30,000miles without problem. I am sure I could find plenty of people
who have had a problem as well, this is the reason I am posting on here.
quote:
Originally posted by chimney sweeper
I kn ow alot of the 4x4 of road racer guys do it with out a problem but I have wondered about it.
Have also seen an MGB with honda engine and fliped rear axle that had done over 30,000miles without problem. I am sure I could find plenty of people who have had a problem as well, this is the reason I am posting on here.
Very true never thought of that, rules out the Honda engine then
Couldn't the gearbox be slightly modifed to reverse the direction at the point where the engine enters the box?
I suppose you could interface a simple 1:1 reversal box right off the crank to get it back to gearbox input direction, but you're adding complexity, weight and failure modes left right and centre.
I'm thinking that on the input shaft, thus no need to add anything more than one shaft, the 1:1 gears and the fittings to hold said shaft down
How about a FWD engine, gearbox and driveshafts, turned through 90 degrees so the driveshafts run fore/aft, connected to 2 more diffs for the front and rear axles? Ratios might be a problem...?
Ruled that idea out due to your last coment, I want to use this car alot not top out at 6000rpm at 55mph
[Edited on 17/1/12 by chimney sweeper]
quote:
I'm thinking that on the input shaft, thus no need to add anything more than one shaft, the 1:1 gears and the fittings to hold said shaft down
In your 'thinking/driving' post you mention now losing the rear seats and going midengine.
In which case I think I'd go back to the Scooby scenario, & going 2WD, i.e losing the original rear prop output and using the transaxle to
drive the rear wheels (if you follow)
2WD is an option but think it would be easyer to go with Audi engine and box as I think an Audi 2WD box would be easyer to find so would not have to
spend time and money modding a Subaru box, I aim to build it for as little money as posible but be a good looking semi daily driver.
I could hunt down a passat vr6 like the cheep one that I just missed on EBay for engine and box, then I just need to think about front and rear
uprights, I have an old BMW 728i on the drive that no one wants to buy so I could use the uprights of that if not going 4WD and I have some BMW PCD
wheels tht i want to use as well.
http://www.members.iinet.net.au/~ttriebler/
you can get reverse cut ring gears for the subaru box, simplifys everything.
I'm planning on doing an all wheel drive beetle eventually.
Will have to find the price of reverse gears for the subaru box, will more than likely be over budget especially with shipping as this is a budget project like all my past projects
Just don't under-estimate the cost of screwing around with the rest of it though, or the cost of not having what you want. I like to make everything, but sometimes you can't beat paying a bit and not having to mess about endlessly.
I know what you mean mate I like to do everything myself but have had to pay someone to do some welding on my race car because in the run up to xmas I
have no time and did not want the project to stall, also want it finished by the first race in April.
You do have to weigh up cost and time
I doubt you need to pay $1500 for that reverse ring gear. Look on HPC gears website, maybe call their technical line, im sure if you can send in the original then they can make a mirror image (assuming thats all it is).
We've been looking at a small project involving an off-the-shelf worm and gear system for low torque use (around 12Nm) and the cheapest quote we have so far is £100 delivered, for a couple of bits no more than 3" diameter.