advice on a crazy dream

Well, lets start with: what do you want to do with it?

What is the budget?

Build timeframe?

Are you or someone else building it?

Will the resulting car be street legal in your area - have you checked to confirm?

kb58 said:

Well, lets start with: what do you want to do with it?

What is the budget?

Build timeframe?

Are you or someone else building it?

Will the resulting car be street legal in your area - have you checked to confirm?

street car/ capable track car

as much as i need to get it done

2 years

i am building it

will be street legal

It'd be easier to use a Porsche transmission than a Subaru, since the Subaru would need a reverse-rotation gearset that costs almost as much (around $2k IIRC) as the transmission will cost used (about $3k), and there are bolt-upable options for any engine under the sun to Porsche transmissions thanks to the kit car community.

The other advantage is that, since STIs are rear drive biased, the Subaru transmission would be front wheel drive biased, which is a great thing to have when your weight bias is in the 66/34 range, not so good any other time.

Definitely 911 drivetrain would be the way to go. The 991 generation wheelbase is within a half inch of the C4 so you wouldn't even need a custom driveshaft. Or the 996/997 wheelbase is only 4" shorter which might not be too hard to deal with.

My first thought was to use C5/6 parts since it uses a T56 transaxle at the rear, but since you're basically sitting on top the rear diff in a C4, that would put a block in your lap.  I'm trying to picture it, but it might be hard to actually do it as a mid-engine since there isn't much distance between the back of your seat and the pinion.

So, yeah.  Porsche.

Audi transaxle. 

As short as you can get. But yeah, what Curtis said...

Any chance you can do a sketch of what you have in mind and a quick resume to give us an idea how far in the deep end you are diving?

Audi transaxles have offset pinions, meaning you can't just flip the diff like in an ACVW to make it reverse rotation.

Excuse the bash but this idea is DOA.  But just because we all have questionable ideas pick the car/drivetrain with the desired features, cut the body off and glue on a vette body.  

I've touched a tube frame car where I live (at the gas station I frequent) with an Audi manual transmission and a  mid engine Chevy V8 with an adapter plate between the two pieces. What you want can be done. Go check out the project cars forum on this site. We enable crazy weird things. Heck if some of us are local to you there's a good chance we'd be happy to come work on it with you and have some knowledge to help you through the project. Times I've seen an idea poo-pooed on this board? Zero. Times I've seen insane projects completed by these guys? Every time the work gets put in. Don't forget to start a project thread so we can encourage and enable you.

Pete. (l33t FS) said:

Audi transaxles have offset pinions, meaning you can't just flip the diff like in an ACVW to make it reverse rotation.

Way I see this playing out is that "Mid" engine does not mean the engine has to be behind the seats. Leave it up front and shove it back for a 50-50 weight distribution and use Audi bits to make it 4wd. Or maybe even just drop a vette boddy on a peeled Audi. 

NOHOME said:

Pete. (l33t FS) said:

Audi transaxles have offset pinions, meaning you can't just flip the diff like in an ACVW to make it reverse rotation.

Way I see this playing out is that "Mid" engine does not mean the engine has to be behind the seats. Leave it up front and shove it back for a 50-50 weight distribution and use Audi bits to make it 4wd. Or maybe even just drop a vette boddy on a peeled Audi. 

Spec is rear engine, not mid engine, so the engine is hanging out behind the rear axle.

When I see an FC RX-7, I want to jam a 911 drivetrain under the hatch. It looks like there is just enough room between the axle centerline and rear bumper cover outline to make it happen.

NOHOME said:

Pete. (l33t FS) said:

Audi transaxles have offset pinions, meaning you can't just flip the diff like in an ACVW to make it reverse rotation.

Way I see this playing out is that "Mid" engine does not mean the engine has to be behind the seats. Leave it up front and shove it back for a 50-50 weight distribution and use Audi bits to make it 4wd. Or maybe even just drop a vette boddy on a peeled Audi. 

Where does the word "mid" appear in the OP? Honestly for wanting AWD, rear engine is going to be the "easiest" (least extremely difficult) option. There's a million reasons why this is a terrible idea and it's never going to happen, just gaming out how it would be done. You are onto something though, the simplest and most effective thing would be to just graft the body onto a 991 Carrera 4 chassis. Then you just have to relocate the interior to match the Corvette.

Reason I see this playing out as a mid engine is because a rear engine vette would only be good for doing wheelies and spinning off the road into trees. Not that those activities don't have some appeal, just not my idea of a good time.

The budget is missing and the time frame for a 3000 hour project is unrealistic unless this is a full-time job $$$ is no object.

NOHOME said:

 

Reason I see this playing out as a mid engine is because a rear engine vette would only be good for doing wheelies and spinning off the road into trees. Not that those activities don't have some appeal, just not my idea of a good time.

 

The budget is missing and the time frame for a 3000 hour project is unrealistic unless this is a full-time job $$$ is no object.

 

 

Porsche would like a word with you.

Just need to flare the rear fenders and stuff 335 width tires back there and a set of 225's in front. 

He's kind of right. If you were able to just plop an engine in the rear of a Corvette, that's about what would happen. You'd need to totally reengineer the suspension (or just steal it from porsche) to make it actually work decently.

We're also starting with a car that has an almost perfect weight distribution from the factory.  51/49%.

I'm afraid a rear engined 'vette wouldn't steer where you point it unless you had a fat guy super glued to the hood, and that would totally ruin the clean lines of the C4 design.

In reply to Curtis73 (Forum Supporter) :

Bring her sister along maybe?

I'll take a different angle on this than powertrain/drivetrain, suspension/chassis is the biggest challenge with this premise. The differential in the C4 contains half of the rear suspension mounting points. The half shaft act as an upper control arm in many regards, the leaf spring mounts to the diff but this can be removed easily, the rear wheel toe control is attached to the diff and so is the lower control arm which controls camber.  The differential is a very integral part of the C4 chassis and is also directly connected to the transmission with the PPF.

A C5 or C6 however has an aluminum subframe where all of the rear suspension components attach. You can basically discard the drivetrain on either of these cars and still have a rolling chassis.  You could drop a V8 and Audi transaxle onto one of these subframes and then just have to figure out packagaing, axles and mounting rather than re-engineering the full suspension.

Olemiss540 said:

NOHOME said:

 

Reason I see this playing out as a mid engine is because a rear engine vette would only be good for doing wheelies and spinning off the road into trees. Not that those activities don't have some appeal, just not my idea of a good time.

 

The budget is missing and the time frame for a 3000 hour project is unrealistic unless this is a full-time job $$$ is no object.

 

 

Porsche would like a word with you.

Just need to flare the rear fenders and stuff 335 width tires back there and a set of 225's in front. 

Porsche engineers got to be extremely good at chassis dynamics as a result of trying to make rear engined cars handle well.

In reply to RacetruckRon :

No matter what you will be throwing out the front and rear suspension, in any vehicle.  The front suspension/subframe will not cotton to having a diff and axles put in there.

I do not think anybody makes a reverse rotation ring and pinion gear for Audi units to convert them to rear engine, not when Porsche transaxles are right there.

Pete. (l33t FS) said:

In reply to RacetruckRon :

No matter what you will be throwing out the front and rear suspension, in any vehicle.  The front suspension/subframe will not cotton to having a diff and axles put in there.

I do not think anybody makes a reverse rotation ring and pinion gear for Audi units to convert them to rear engine, not when Porsche transaxles are right there.

Not sure what you are trying to get at in the first paragraph there. No one is arguing that changing the weight bias drastically isn't going to have other vehicle handling consequences.

As for your second paragraph like NOHOME I see this playing out more like a rear-mid engine. More Monzora, less 911.

Have you guys seen a C4 corvette? Where does the driver go when the engine is occupying the space where the driver's seat should be? Meanwhile they appear to actually have more rear overhang than a 911. And the plug and play drivetrain already exists.

RacetruckRon said:

Pete. (l33t FS) said:

In reply to RacetruckRon :

No matter what you will be throwing out the front and rear suspension, in any vehicle.  The front suspension/subframe will not cotton to having a diff and axles put in there.

I do not think anybody makes a reverse rotation ring and pinion gear for Audi units to convert them to rear engine, not when Porsche transaxles are right there.

Not sure what you are trying to get at in the first paragraph there. No one is arguing that changing the weight bias drastically isn't going to have other vehicle handling consequences.

As for your second paragraph like NOHOME I see this playing out more like a rear-mid engine. More Monzora, less 911.

The front suspension from the starting chassis will be thrown out. You MIGHT be able to use C5 uprights but the subframe is in the way of axles, by recollection.

Remember that AWD is one of the goals.

There is no such thing as "rear mid engine". Rear engine is engine behind the rear wheels, mid engine is engine between passenger compartment and rear wheels, front engine is engine ahead of passenger compartment.

Pete. (l33t FS) said:

RacetruckRon said:

Pete. (l33t FS) said:

In reply to RacetruckRon :

No matter what you will be throwing out the front and rear suspension, in any vehicle.  The front suspension/subframe will not cotton to having a diff and axles put in there.

I do not think anybody makes a reverse rotation ring and pinion gear for Audi units to convert them to rear engine, not when Porsche transaxles are right there.

Not sure what you are trying to get at in the first paragraph there. No one is arguing that changing the weight bias drastically isn't going to have other vehicle handling consequences.

As for your second paragraph like NOHOME I see this playing out more like a rear-mid engine. More Monzora, less 911.

There is no such thing as "rear mid engine". Rear engine is engine behind the rear wheels, mid engine is engine between passenger compartment and rear wheels, front engine is engine ahead of passenger compartment.

Ok I guess I know nothing. I'll let you be the expert here what do I know about bastardizing Corvette suspension.