Campeck

dead straight

nine-44

First off, extensively lighten all of the moving parts, valvetrane and rotating assembly. Go full standalone for optimization of the RPM band as far as fuel and ignition. Do alot of R&D for your intake and exhaust and match them to a custom set of cams, I'd say that pulse tuning along with some valve overlap will help with airflow in a quick spinning motor. Without the pulse tuning on intake and exhaust and some overlap, I don't think you'll get enough flow to keep the cylinders full. With big or huge ports, you loose air velocity, that hurts flow and low end. Pulse tuning will be the best key.

xsboost90

there was a guy talking about tuning headers at the tour today. He was talking about running large ports w/ a steped down section then back up to the same size to momentarily slow down the flow to allow for pulse tuning. This is supposedly done for most race cars, factory on the new 997, and nascar. Sounds like it makes sense, although i couldnt tell you any specifics.

inactiveuser92616

since these cars have hyrdaulic lifters; you may have to address "Pump up" of the valves; on some engines the lifters just cant respond fast enough and essentialy reach an equilibrium point and stand there. I know this was an issue on the isuzu 4xf1 engines (a powerplant of my last car); limiting them to ~6.5-7k on a stock head. To get higher RPM people would swap in compatible solid lifter heads.

Tom Carson

per Mumzer...you do want "custom dowel pins for block and girdle" to keep the bottom end together

NineMeister

Thanks for all the replies guys. After re-reading my post I guess that I should have been more specific. As somebody touched on, we are on the case of head/cam/spring/intake/exhaust design and we are confident that we can make the engine work at whatever revs we like. The unknown issue is how to stop rods appearing through the side of the block.
I know that custom lightweight pistons and rods will be required, so I suppose my question is more like has anyone actually wound any 944 engine to more than 7500 and how have they gone about modifying the bottom end to cope? If nobody has specifics I'll talk to John Milledge & Bob Norwood and let you know how I get on.

Zero10

I think with cross/perp drilling, lightened pistons, and forged rods, you would be fine in the bottom end. Although the stresses would go up from the increased revs at a rate proportional to the angular velocity of the crankshaft squared, decreasing the weight at the end of the rod (i.e. piston), you should be able to bring the stresses on the rods down to workable levels. I wouldn't count on ever making a 944 engine rev over 10,000rpm though. But I do think that 8500 is reasonable.

If you could cut down the weight of the pistons/rods by 50%, then you would be alright if you increased the oiling on the rod bearings.

Predator

Makin' her spin to 8500 rpm and making horsepower at 8500 rpm are horses of two different colors!

hosrom_951

Guys, anything is possible if:

1) You got LOADS of green $$$$$$
2) You have lots of parts and time in handy (incase anything goes wrong, which is a fact during R&D)
3) Do LOTS and LOTS of research..........

BTW, you never mentioned if reving to 8,500 would be for track or street, assuming track because if you do eventually get a 'safe' 8,500 reving engine like ours, the power and torque rangines would be very high and 'non-streeable'.

BruceWard

Colin,

Huntley Racing marketed and I believe even built a few high end 968 engines. I believe they were hitting the RPM numbers and HP / TQ numbers you are looking for.

Huntley is no longer in business but their website it archived at http://web.archive.org/web/200304301...le_engines.htm

inactiveuser92616

de-stroke it!

NineMeister

Thanks Zero10, I guess that is all I needed to know.

W.R.T. high revving engines and streetable, from my own experience with our 993 3.82 race engine the two requirements are not mutually exclusive provided that the design is right.
To use the 9m 103mm bore race engine as an example, this has 320 degree cams, will start, idle and drive from cold at zero throttle and has more torque than a factory 993RS road car from 3000rpm upwards. Peak torque is 411Nm and it has over 400Nm from 4000 to 7000rpm, revs to 8000 and has peak power of 392 bhp at 7300 on stock 993 headers.
Like I said, I am confident that we can get the top end right but I was unsure of the bottom end.

Danno

"If you could cut down the weight of the pistons/rods by 50%, then you would be alright if you increased the oiling on the rod bearings."

Colin, you and zero10 got the right ideas. If you can destroke to get better bore-to-stroke ratios for high-RPM along with the longest rods possible, that will reduce the secondary harmonics by quite a bit. I know of two "tuner" outifts that turbo'ed 968 engines and they both broke the stock 968 forged rods. The mass of the pistons is a major problem here (as is the pins) and I'm sure you know the difference between H-beam vs. I-beam rods. Have fun

Duke

Very interesting project!
It's obvious many people here don't know anything about this company...

Regarding efficiency, it is quite possible to have over 100% VE.

And about 8500 rpm not being streetable.... tell that to Honda

The outcome I'm most keen on from this project is how the valvetrain design will end up.

BC

Well, the 928 head (32V) is similar to the 968 head. I think some nice big valves and some heavy springs, some more lift and duration, and some lightweight components, would do the trick?

Acura gets 300 out of a 3.5L V-6. And its pretty damn torqey.

With that adjustable cam, you guys could do wonders with an aftermarket EFI.