Porsche flat 6 mid mounted in kit cars?
Discussion
This may be incredibly stupid, but in the absence of anything worthwhile to focus my brain on at the moment I found my self wondering if anybody has used a Porsche flat 6 in a mid-engined car?
We know that the gearboxes can be inverted to prevent ending up with 5 reverse speeds, could it then be re-attached with minimal effort to a 911 engine to give a much better layout?
Personally have a soft spot for boxer type engines, it's not as though it's lacking pedigree or performance - even the smaller Boxsters put out a fair amount - and it would obviously be excellent for keeping a very low centre of gravity.
so what say ye? Should I boil my head to try and clear it of such stupidity?
We know that the gearboxes can be inverted to prevent ending up with 5 reverse speeds, could it then be re-attached with minimal effort to a 911 engine to give a much better layout?
Personally have a soft spot for boxer type engines, it's not as though it's lacking pedigree or performance - even the smaller Boxsters put out a fair amount - and it would obviously be excellent for keeping a very low centre of gravity.
so what say ye? Should I boil my head to try and clear it of such stupidity?
Edited by Davi on Thursday 8th November 11:40
Davi said:
....I found my self wondering if anybody has used a Porsche flat 6 in a mid-engined car?
We know that the gearboxes can be inverted to prevent ending up with 5 reverse speeds, could it then be re-attached with minimal effort to a 911 engine to give a much better layout?
Why bother converting a 911 engine/gearbox? There are plenty of bent Boxters in the breakers yards these days...We know that the gearboxes can be inverted to prevent ending up with 5 reverse speeds, could it then be re-attached with minimal effort to a 911 engine to give a much better layout?
Depends how much power you need, I guess. The Boxster/Cayman put 295bhp through the gearbox, presumably with a comfortable margin of reliability.
No doubt a 480bhp current Turbo engine would kill it pretty quickly, but I'm not at all convinced that a competently designed sportscar needs that sort of horsepower for anything except bragging rights down the pub.
No doubt a 480bhp current Turbo engine would kill it pretty quickly, but I'm not at all convinced that a competently designed sportscar needs that sort of horsepower for anything except bragging rights down the pub.
Sam_68 said:
Depends how much power you need, I guess. The Boxster/Cayman put 295bhp through the gearbox, presumably with a comfortable margin of reliability.
No doubt a 480bhp current Turbo engine would kill it pretty quickly, but I'm not at all convinced that a competently designed sportscar needs that sort of horsepower for anything except bragging rights down the pub.
If I was doing it then "competently designed" wouldn't form part of the equation No doubt a 480bhp current Turbo engine would kill it pretty quickly, but I'm not at all convinced that a competently designed sportscar needs that sort of horsepower for anything except bragging rights down the pub.
You are correct on the BHP, there is a point where it becomes a bit, well pointless, but for me torque is important - top end doesn't interest me anywhere near as much as the feeling of being kicked in the back by an elephant, if you see what I mean.
Davi said:
from what I've read while digging up info for the gearbox on my own mid engined car, the Boxster gearbox isn't that strong if you wanted to push the engine performance.
The base 2.5 engine is mated to an Audi gearboxThe later S versions have a stronger Porsche gearbox
I don't know how the S Boxster box compares to a 911 unit though.
Something points that might be relevant:
Just how big are the advantages of a flat engine?
Height
Surely there can't be much in it. You can't mount it too low because of the exhaust being under the block. Then ther's all the intake stuff on top. Has anyone ever measured one up and compared the whole package to another layout, say using a Duratec on an Audi gearbox?
Or put it another way, if I built a car with identical gearbox positioning would the bodywork be any lower for a flat engine?
Width
Disadvantage. Tricky to get a spaceframe with decent triangulation around something short and wide. Doable but it's never going to be as neat as with a narrower choice.
Centre of Gravity
Always the reason touted for using this layout. However you can never mount the engine as low as another layout due to having to keep some ground clearance under the exhausts and having to put a lot of stuff ontop won't help either. How much lower is it really?
Power potential/cost
Apart from turning up the boost on Subarus do flat engines look good on a pound per bhp basis? There are Boxster units with boxes on ebay for 3K. That sounds pricey but a colleagues kit cat zetec cost him circa 1.5k by the time he'd fitted the induction system (Webbers) and bits to make it actually work and it supposedly gives 165bhp. That's about 9 quid/bhp. The boxster units come complete so are 15-12 quid/bhp depending on the engine.
I suppose I'm really just padding out the first post question a bit! The Subaru and Boxster engine and gearbox units do look like interesting choices for a home built mid engined lightweight. Is there some reason why kit makers don't use them more often?
Just how big are the advantages of a flat engine?
Height
Surely there can't be much in it. You can't mount it too low because of the exhaust being under the block. Then ther's all the intake stuff on top. Has anyone ever measured one up and compared the whole package to another layout, say using a Duratec on an Audi gearbox?
Or put it another way, if I built a car with identical gearbox positioning would the bodywork be any lower for a flat engine?
Width
Disadvantage. Tricky to get a spaceframe with decent triangulation around something short and wide. Doable but it's never going to be as neat as with a narrower choice.
Centre of Gravity
Always the reason touted for using this layout. However you can never mount the engine as low as another layout due to having to keep some ground clearance under the exhausts and having to put a lot of stuff ontop won't help either. How much lower is it really?
Power potential/cost
Apart from turning up the boost on Subarus do flat engines look good on a pound per bhp basis? There are Boxster units with boxes on ebay for 3K. That sounds pricey but a colleagues kit cat zetec cost him circa 1.5k by the time he'd fitted the induction system (Webbers) and bits to make it actually work and it supposedly gives 165bhp. That's about 9 quid/bhp. The boxster units come complete so are 15-12 quid/bhp depending on the engine.
I suppose I'm really just padding out the first post question a bit! The Subaru and Boxster engine and gearbox units do look like interesting choices for a home built mid engined lightweight. Is there some reason why kit makers don't use them more often?
Thanks for all the thoughts. Cymtriks has expanded quite nicely on it - it's after consideration of these some of these points that I began pondering on it in the first place -
Height - I believe there is a reasonable saving overall here, though this is based on the VW flat 4 engine rather than the later Porsche as I've not had the opportunity to study a Porsche unit in depth. Putting a type 2 or 3 engine and a straight 4 of similar capacity side by side it's quite obvious. There really isn't much above the upper flange of the gearbox.
Width - definite disadvantage, although with the height triangulation can be formed above it.
Centre of gravity - as per height, not a lot up top, the c of g of the engine isn't much above the centreline of the gearbox.
Power / potential costs - One area I've only touched on, but I've seen 25k mile Boxster engines for £1800 with guarantees... compare that to the prices I'm being quoted for the Audi V8 and it starts to look like a bargain!
As to why they are not used more often.... that's something I'd like to know
Height - I believe there is a reasonable saving overall here, though this is based on the VW flat 4 engine rather than the later Porsche as I've not had the opportunity to study a Porsche unit in depth. Putting a type 2 or 3 engine and a straight 4 of similar capacity side by side it's quite obvious. There really isn't much above the upper flange of the gearbox.
Width - definite disadvantage, although with the height triangulation can be formed above it.
Centre of gravity - as per height, not a lot up top, the c of g of the engine isn't much above the centreline of the gearbox.
Power / potential costs - One area I've only touched on, but I've seen 25k mile Boxster engines for £1800 with guarantees... compare that to the prices I'm being quoted for the Audi V8 and it starts to look like a bargain!
As to why they are not used more often.... that's something I'd like to know
Edited by Davi on Thursday 8th November 22:27
cymtriks said:
The Subaru and Boxster engine and gearbox units do look like interesting choices for a home built mid engined lightweight. Is there some reason why kit makers don't use them more often?
The Alfa and VW flat 4 engines used to be very popular choices for kit cars, of course. I had an AlfaSud powered Raffo some years ago; the overall height of the engine was significantly lower than an inline 4 and while I never actually measured the CG height, from a purely visual assessment I'd say that it would be a worthwhile advantage.Width wasn't as bad a problem as you might think... the width of the engine was comfortably less than the width of the cockpit bay in front of it (and the width of the rear cockpit bulkhead tends to define the width of the front end of the engine bay on a mid-engined car, of course) and the low height of the engine installation meant that the Raffo had been able to provide removable triangulation over the top of the engine bay from the rollover bar to the rear suspension/gearbox mounting bay on the spaceframe without impeding general maintenance access in the slightest (you needed to remove the bracing to take the engine/gearbox out, but not for any other operation).
As to why the Porsche and Scooby engines aren't more popular, I'd suggest that it is cost (of components, not just the initial donor engine) for the Porsche and lack of an easy ('donor') gearbox installation for the Scooby.
The Scooby engine is extremely compact and would be a very tempting option for a lightweight mid-engined car.
Sam_68 said:
As to why the Porsche and Scooby engines aren't more popular, I'd suggest that it is cost (of components, not just the initial donor engine) for the Porsche and lack of an easy ('donor') gearbox installation for the Scooby.
The Scooby engine is extremely compact and would be a very tempting option for a lightweight mid-engined car.
Surely there have been front drive versions of the Subaru? I've just checked their website and they are all four wheel drive now but I'm certain there used to be 2wd variants.The Scooby engine is extremely compact and would be a very tempting option for a lightweight mid-engined car.
Even if they are too rare to consider there's still Audi boxes or modified 4wd Subaru ones.
There's a homebuild Subaru powered car at blastautomotive.com so it's certainly do able.
Davi said:
Height - I believe there is a reasonable saving overall here, though this is based on the VW flat 4 engine rather than the later Porsche as I've not had the opportunity to study a Porsche unit in depth. Putting a type 2 or 3 engine and a straight 4 of similar capacity side by side it's quite obvious. There really isn't much above the upper flange of the gearbox.
Dunno, it was said the unusually wide vee on the engine that powered the winning Ferrari F1 cars was partly responsible for their very low centre of gravity. Certainly C of G height in general is well worth obsessing about from a vehicle dynamics point of view...... make the car as light a possible, as low as possible and (within reason) concentrate the mass as centraly as possible and you've given yourself a very good headstart.ricola said:
Davi,
There is a team in the US that race a 911 turbo powered Ultima, they have a fairly decent website which you should be able to find fairly easily, if not, I'm sure I've seen references to it on the Ultima forum.
Rich
Rich, do you have any further details on this - searching under all the logical terms give you 000's of results because of the G50 gearbox use!There is a team in the US that race a 911 turbo powered Ultima, they have a fairly decent website which you should be able to find fairly easily, if not, I'm sure I've seen references to it on the Ultima forum.
Rich
More I look at this the more I like the idea of it as something different with distinct advantages.
http://www.millerteamracing.com/
Maybe not a TT though...
Other than that, there is a lot of info about putting later 911 engines into 914s. Patrick motorsports specialise in conversion parts for that.
Rich
Maybe not a TT though...
Other than that, there is a lot of info about putting later 911 engines into 914s. Patrick motorsports specialise in conversion parts for that.
Rich
Edited by ricola on Tuesday 13th November 10:00
Edited by ricola on Tuesday 13th November 10:02
It's not nice - but it does have a Porsche flat six.
Graham
http://www.oldtimermanchester.com/details.asp?carI...
Graham
http://www.oldtimermanchester.com/details.asp?carI...
Cheers Rich & Graham, like it. Definitely going to be looking into this further. I'm convinced the C of G would be lowered enough to make this a worthwhile avenue, coupled with the fact I've seen three times as many porsche engines for sale as I have from RS4's, at considerably less cost.
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