Rear-engined AWD?

I've often thought of buying the reversing ring/pinion for a Subaru transmission so that I could stick the WRX engine in a Karmann Ghia. The problem is that the suspension, steering and brakes would then be inadequate for the task, so the obvious next step would be to reinforce the pan with tubing and put in the rest of the Subie driveline - reversed. I know that it's doable, and certainly high on the cool scale, but performance-wise, does it make sense? Clearly when accelerating one already has most of the power where one wants it - over the rear wheels. Is the ability to pull the nose around worth adding more weight, friction and the polar moment change? Porsche didn't sell many rear-engined awds so the market has already sounded off...

I think this is totally dependent on your intended use of the vehicle. How much time is it going to spend on loose surfaces? I've yet to drive an AWD car that handled better than an RWD one on dry pavement, regardless of configuration (though an Evo with yaw control might change my tune on that, it doesn't sound like you'd go that far).

Even on loose surfaces, I'm not sure a rear-engine AWD setup is so great. Getting good turn-in response often requires deliberate weight transfer to the nose, even with a front-engine AWD car. That's going to get a lot worse with the weight over the back axle. Coming out of the corner though...

Buy a Previa.

I would skip everything but the subie engine. For the cost of machine work, welding, and fabrication, you could save money by just adapting a Porsche 915 (or g50) transmission to the Subaru engine and bolting that into the back of your Ghia. You would then have money left over for brakes and suspension while keeping the car lightweight and simple

kreb wrote: Porsche didn't sell many rear-engined awds so the market has already sounded off...

What? About half the 911's I see around here are Carrera 4 models. I was drooling over a '99 model the local Lotus dealer had a couple of years ago.

In reply to mad_machine:

I think Kennedy Engineering has what you need for this

914Driver wrote:

That is cool

Karmann Ghia awd would be nuts.

Thanks for the feedback, guys. I'm not sure what to make of the van references, although finding an uber-rare supercharged, manual transmission, awd Previa is a unicorn of interest - but not relative to this potential project.

I suspect that for this car's intended use (mainly dry pavement) the AWD wouldn't be of much benefit. It's more of a "wtf, let's go all-out" thing.

you would need to tube chassis the ghia to make this work. All the strength in the aircooled cars is in the backbone.. to cut that out to run a Driveshaft through it would destroy the car. I would just run a Porsche transaxe bolted to the suby engine. Easier is better

I'm thinking along the lines of a RWD version of this:

It's designed to allow an Audi v8 to be mounted amidships. Widen the backbone and you should be able to run a driveshaft through there.

You are very right about "easier is better". AWD in this instance is a classic example of scope creep, OTOH, a 250 HP Ghia would be practically unmanageable unless you're going to upgrade the entire package. If you're going to stay normally aspirated, the stock chasis with better brakes and more modest upgrades would sufice.

The thing is, I'm not sure how much AWD will really help you outside of just being a cool accomplishment. Will the weight and complexity offset the performance gains? Also, the execution of the AWD could totally make or break the idea. Are you going to run a Torsen center, LSD rear, open front? All open? Lockers? Poorly implemented AWD sucks balls and can destroy an otherwise good car's handing, like the early AWD Volvo "R" cars that would just sloppily throw all power to the rear at a moment's notice.

If it were me, I'd just stay RWD and run a LOT of tire.

AWD will be more difficult to execute well, but assuming equivalent setups...

To impress at car shows and on the internet: AWD > RWD

To turn the absolute fastest time at the track: AWD ≥ RWD

To maximize driver enjoyment and reward skilled drivers: AWD < RWD

Porsche 996 Carrera 4 was waaay easy to handle on track. But it still pushed under power. That was a totally stock car; suspension tuning would probably have helped.

However, note that all the 911 GT3 versions are RWD only. Just sayin'...

David

Ian F wrote:

kreb wrote: Porsche didn't sell many rear-engined awds so the market has already sounded off...

What? About half the 911's I see around here are Carrera 4 models. I was drooling over a '99 model the local Lotus dealer had a couple of years ago.

Isn't it a somewhat popular mod to convert them to 2wd for weight savings?

Kenny_McCormic wrote:

Ian F wrote:

kreb wrote: Porsche didn't sell many rear-engined awds so the market has already sounded off...

What? About half the 911's I see around here are Carrera 4 models. I was drooling over a '99 model the local Lotus dealer had a couple of years ago.

Isn't it a somewhat popular mod to convert them to 2wd for weight savings?

People have done it, but it isn't popular in any sense because it is pretty difficult and requires chopping up some pretty expensive Por$che parts to leave you with a worthless non-OE mishmash. It is cheaper just to sell the C4 and buy a C2.

http://forums.rennlist.com/rennforums/964-forum/481810-dollar-amount-for-c4-to-c2-conversion.html http://forums.pelicanparts.com/porsche-964-993-technical-forum/553244-964-carrera-4-fwd-converion-who-has-done.html

That being said, the people that do go through the trouble have 10/10ths track cars and do it for the handling improvement, so take that for what you will...