RCR 917 motor options
- Thread starter Gulf GT40
- Start date
I have looked into that engine and it certainly has the potential for high power; but the subaru 6 must be the tallest flat engine ever created. Unlike a Porsche engine which is dry sumped, the subaru has an entire lower assembly containing a wet sump AND a water pump with its passageways.
Jeff Perrin of Perrin Performance has a great build project doucmented in pictures of a 800hp monster subaru 6 cylinder...
The 917s used a flat 12 rather than V12....the type 912 engine in either a 4.5 or 4.9 diplacement.
That's a good idea taking the displacement out to 3.5 on the 930 (3.0/3.2) block for some extra hp although I believe that mod is quite expensive requiring some machining of the block and, obviously, new pots and matched heads. Extra Porsche hp doesn't come cheap....
Incidentally, I think an all alloy 331 SBF with quad 48IDAs would be a smokin' engine choice for a 917 replica....
My bad, Cliff. I know the 917's engine is flat but the "V" somehow slipped in there.
Standing back and looking at the reality of a 917 replica, is the car more designed for long circuits with very high speeds? Most of our circuits now seem to favour highly manoeuvreable cars with not so many opportunities for opening up on very fast straights Bathurst being an exception).
Standing back and looking at the reality of a 917 replica, is the car more designed for long circuits with very high speeds? Most of our circuits now seem to favour highly manoeuvreable cars with not so many opportunities for opening up on very fast straights Bathurst being an exception).
flatchat(Chris)
Supporter
Dalton, it isn´t your bad at all.
Hans Mezger, designer of the 917 engine, gave many lectures about his engine at universities, engineering societies etc. and correctly described his engine as a 180 deg. V 12 with two rods sharing one crankpin just like all other engines in "V" configuration (possible exceptions proving the rule).
Your usual "flat" engine has one rod per crankpin, also commonly known as a "boxer" layout because of two rods looking like "boxing" each other.
Best,
Marcus
Hans Mezger, designer of the 917 engine, gave many lectures about his engine at universities, engineering societies etc. and correctly described his engine as a 180 deg. V 12 with two rods sharing one crankpin just like all other engines in "V" configuration (possible exceptions proving the rule).
Your usual "flat" engine has one rod per crankpin, also commonly known as a "boxer" layout because of two rods looking like "boxing" each other.
Best,
Marcus
Gent's
If I were to do it. I would go with a 4.7 Litre M20/19 used in the 928 mated to a 930/G50. Put a Porshe engine in a Porshe. Cost wise no more than a flat six, more horsepower. Just the water cooling to work out. He has the room. If he wants more horsepower he can go to town on the engine, I think it would be a nice combo.
Dave
If I were to do it. I would go with a 4.7 Litre M20/19 used in the 928 mated to a 930/G50. Put a Porshe engine in a Porshe. Cost wise no more than a flat six, more horsepower. Just the water cooling to work out. He has the room. If he wants more horsepower he can go to town on the engine, I think it would be a nice combo.
Dave
I believe the 917 only had a 90" wheel base, about the same as a cobra; though, the 917 being a bit wider. I always figured with the car being so short and wide that the handling characteristics would be 'quick'.
Having flown a Cobra - I can tell you that it's not a desirable trait!!! :stunned:
With regards to the 915 gearbox in a lightweight 400hp car, you'll have no problem. You'll have so much tire in the back it'll be interesting to see how acceleration from a start is.
If you look around a bit you can find a later 915 with a factory built in aux cooler (euro 911's in the early to mid 80's-1986) and that with a lsd should be good for most any 917 build without turbos.
As for a turbo install, the factory motors are quite reliable and when coupled with a light car are much more fun than in their original chassis. I drove an RS rebodied 1987 with a g50 gear box, carbon front bodywork and doors, stripped to RS interior with no ac and a shoehorned 993tt which was stone stock below a modified rs ducktail. Fun but absolutely untractable below 40mph. Above 40mph felt like it would whip a 997 based GT2 (which it might have). Interestingly he could get another 150hp easy and cheap but he was happy to say it was good enough. And it was. Still wouldn't sell it though I put my name on the call list if it ever becomes available cause then you'd be done as far as 911's go.
If you look around a bit you can find a later 915 with a factory built in aux cooler (euro 911's in the early to mid 80's-1986) and that with a lsd should be good for most any 917 build without turbos.
As for a turbo install, the factory motors are quite reliable and when coupled with a light car are much more fun than in their original chassis. I drove an RS rebodied 1987 with a g50 gear box, carbon front bodywork and doors, stripped to RS interior with no ac and a shoehorned 993tt which was stone stock below a modified rs ducktail. Fun but absolutely untractable below 40mph. Above 40mph felt like it would whip a 997 based GT2 (which it might have). Interestingly he could get another 150hp easy and cheap but he was happy to say it was good enough. And it was. Still wouldn't sell it though I put my name on the call list if it ever becomes available cause then you'd be done as far as 911's go.
Mark,
I can't sleep because of you !!!!!! :drunk:
I had a chat on pelican parts about your project....
and one guys make a good remark.
don't you think that the chain would be better placed on the other side of the engine. (the best is on the middle like original 917 engine)
Thus, you are limiting torsional effect on both crankshaft and camshaft.
maybe it's better to do like the original flat6.... you divide the load on each side of the crankshaft....
Any engine specialist to answer that question which makes me an insomniac....
In answer to some questions about my earlier post about the perfect 917 engine for a replica:
I evaluated many many different options for the engine layout including a close replica to the original, cam drive in the middle with chains, and SOHC with cam drive and power take-off on the ends of the engine.
If one is not concerned with cost, the optimum solution would be the replica DOHC engine with central power take-off.
If cost is a concern, then the SOHC engine would be quite a bit less expensive. Figure at least US$ 50,000 ea for a small run of 5-10 engines vs. US$ 100,000 for the DOHC version.
I could never work out all the problems with driving the cams from the center of the engine using cam chains, mostly because of space contraints. Since that approach still had the very epensive crank with central power take-off, it would have been quite a bit more expensive than the end driven apporoach.
The torsional issue with the long Crank and Camshaft are a bit more of a problem. It would be my intent to add a harmonic dampener to the front of the crankshaft, such as on most production cars, and to increase the diameters of the journals on the crank to make it stiffer. Also, since it is a not a boxer engine, with individual throws, the crankshaft is an inherently stiffer design.
The torsional stiffness of the camshafts could also be increased by making it slightly larger in diameter, between the lobes. I believe it is possible to increase the torsional stiffness of the 12 Cyl camshaft to nearly double the 6 cyl, so that they both would behave in a similar fashion in their respective applications.
These changes would add some weight to the engine, but unlike Porsche, I am not trying to win races, just have some fun.
Mark
I evaluated many many different options for the engine layout including a close replica to the original, cam drive in the middle with chains, and SOHC with cam drive and power take-off on the ends of the engine.
If one is not concerned with cost, the optimum solution would be the replica DOHC engine with central power take-off.
If cost is a concern, then the SOHC engine would be quite a bit less expensive. Figure at least US$ 50,000 ea for a small run of 5-10 engines vs. US$ 100,000 for the DOHC version.
I could never work out all the problems with driving the cams from the center of the engine using cam chains, mostly because of space contraints. Since that approach still had the very epensive crank with central power take-off, it would have been quite a bit more expensive than the end driven apporoach.
The torsional issue with the long Crank and Camshaft are a bit more of a problem. It would be my intent to add a harmonic dampener to the front of the crankshaft, such as on most production cars, and to increase the diameters of the journals on the crank to make it stiffer. Also, since it is a not a boxer engine, with individual throws, the crankshaft is an inherently stiffer design.
The torsional stiffness of the camshafts could also be increased by making it slightly larger in diameter, between the lobes. I believe it is possible to increase the torsional stiffness of the 12 Cyl camshaft to nearly double the 6 cyl, so that they both would behave in a similar fashion in their respective applications.
These changes would add some weight to the engine, but unlike Porsche, I am not trying to win races, just have some fun.
Mark
Here's a crazy idea that might have some appeal.... How about a 928S engine? Roughly 5 litres (the later ones), nice valve train, good hp and torque. Lots of these laying around in scrap yards for a couple thousand bucks. It's a nice engine, sounds good, some easy performance enhancements are available. And, of course, you'll have a good kraut engine in back instead of something from a different continent.
A properly set up 928 engine will give you more hp/tq than a basic 3.0/3.2 911 engine for the same or less money.
No doubt you could make a 930 turbo motor work but as others have wisely pointed out you'll have to engineer cooling and intercooler layout which could be difficult.
That's a fun project!
A properly set up 928 engine will give you more hp/tq than a basic 3.0/3.2 911 engine for the same or less money.
No doubt you could make a 930 turbo motor work but as others have wisely pointed out you'll have to engineer cooling and intercooler layout which could be difficult.
That's a fun project!
AA/F dragsters routinely coupled two BBC's or Mopar Hemi's during the '70's......I would like to see what could be done with two of the Subaru WRX boxer motors :idea: .....crazy HP from one, two might be just insane :shocked: !!
I mentioned this before
A Ferrari Testarossa engine is a 180 °V12 with exactly the same layout as the 912 type engine just liquid cooled. Haven´t looke at it closely , but may be taking the f engineblock , remachine it to put on some aircooled barrels ( dont know if the spacing would be sufficient) plus 2 combined 6 cylinder head banks.
Would be a project and also a challenge for some of our KIWI friends
TOM
A Ferrari Testarossa engine is a 180 °V12 with exactly the same layout as the 912 type engine just liquid cooled. Haven´t looke at it closely , but may be taking the f engineblock , remachine it to put on some aircooled barrels ( dont know if the spacing would be sufficient) plus 2 combined 6 cylinder head banks.
Would be a project and also a challenge for some of our KIWI friends
TOM
Trond
Lifetime Supporter
Hi
Check out this:
917 Replica - Dual 3.0 liter engine -> flat 12 - Pelican Parts Technical BBS
This guy has buildt his own Porsche flat 12 based on two 3L flat 6 merged together!
Regards
Trond
Check out this:
917 Replica - Dual 3.0 liter engine -> flat 12 - Pelican Parts Technical BBS
This guy has buildt his own Porsche flat 12 based on two 3L flat 6 merged together!
Regards
Trond
