Kevin

I had a person that offerend me monies that I couldn't refuse to sell the heads and rotating assy.
With that said, as soon as I finish my 996TT version of this build I'll get back on this project.

chris walrod

Damn Kevin, I was eagerly following this thread from way back. Hope to see more builds like this in the future!

TB993tt

I personally cannot see a 911 turbo engine for the street being reliable over 8000rpm, there is so much more going on at these high revs.

The article below gives a superb insight into how Sportec developed their 8000+rpm SPR1 engine and the detail and testing which seems to have gone into it is absolutely mind blowing. One can only guess at how much $$$$$ went into the R&D. I hear anecdotally that these engines are not "sorted" and still have intrinsic issues affecting their reliability....

My favourite line in the article is " the oil started flowing in a different direction at 8000rpm compared to 7600rpm" !!!
http://www.sportec.ch/files/document...851cf9f2fa.pdf

The holy grail must be the 800hp, 9000rpm twin turbo flat six with Honda vtec smoothness and reliability but I just can't see it

Kevin

Toby, GT3 engines are run over 8000RPM's everyday. It is a well known fact that a turbocharged engine is actually easier on the connecting rods vs a NA engine. The first Sportec engines did not have the developed crankshaft and engine case oiling systems. The mods that I have done with my engines have been taken directly from 935 and 962 engines.

sfl993t4

I agree that the GT3 revs to over 8000 happily and so why shouldn't a turbo engine, but I'm not sure that I understand why a turbo engine is easier on its conrods than and NA (most likely this is my misunderstanding).
If I change gear at 8000rpm, I completely come off the throttle. At this point shouldn't the turbo engine see the same cylinder pressure as the NA and if so shouldn't the net conrod forces (mainly due to the engine speed/reciprocation) be the same?
I'm still learning about engines.
Steve

Kevin

The the forced induced engine actually dampens the rods vs a NA engine if everything was the same RPM and HP within reason. Now things get out of wack when you are comparing a 700HP turbo engine vs a 400HP NA engine. Apples to apples the turbo engine HP for HP is easier on the rods and rod bearings. There are articles written on this subject.

Basal Skull

I'm actually quite ignorant about these things but I have noticed that off boost/coasting after throttle/ when you let your foot off the throttle, I get a significant amount of vaccum with my new turbos cf before/stock. I've wondered what this means. (I get 50 cm Hg or more). If the cylinder pressures have anything to do with conrods as you suggest at off throttle, I think there may be significantly more vaccum in a turbo engine vs NA...

Jean

TB

I absolutely agree! Even using GT3 heads and gear, a turbo engine with 800hp and going to 8k rpms will put more damage than any N/A car. They cannot be compared.

Rod damage is not a function of torque alone, RPMs play a bigger role in the tension on the rod and potential damage. On a turbo engine revving to 8k RPMs, not only you have to deal with RPMs like the NA car, but also with more torque and heat than the N/A car at those levels => high torque at high RPMs is simply much more damaging, nothing that a N/A car will ever see.

As to turbos being nicer on rods than N/A cars, I have a different opinion, the reason is rather that the N/A car spends much more of its life at high RPMs, and RPMs are what cause most of the strain. Our turbo engines were designed to live at rather low RPMs during most of their life, hence are nicer on the rods, also the fact that the compression is much lower when off boost than a N/A car help a lot. On a modified 993TT engine, there is usually a higher redline (7-7400 RPMs) and higher torque going on together, resulting in damage to the stock rods/bolts.

As to the SPR1, the damage is not in the case or oiling but the top end, in the car that I test drove at least, and also in the car that was at Nardo similarily. Most likely cause? High RPMs with high torque. Those cars are a wonder in R&D, the quality in the slightest detail of the build is absolutely amazing, there were only a handful produced, 4 or 5 if I recall correctly and they all come with warranty so at least the owners got taken care of the damage without spending yet an arm and a leg.

I guess that the day we see high revving monster porsche cars on the street being driven for many thousand miles flawlessly, the theory will become practice.

Shige

Hi,
Probably everyone saw this youtube but just reminder I love this High Rev Air cooled Turbo sound.

Thanks

PiB993

Someone asked it a few years ago and I would like to ask it again. Could that flat fan arrangement SpezialMotorer be put on a stock setup 993 Turbo or is the intercooler and or other things in the way?

Basal Skull

Probably not enough space, the 935 had horse shoe shaped intercooler/intakes as you probably know that went around the flat fan. Wonder if the flat configuration was much more efficient in cooling?

Random thoughts about the engine fan:
https://rennlist.com/forums/showthre...ferrerid=28499