Red rooster

Geoffrey,

The RSRs that I saw back then were running a totally different inlet system ( Jumbo Vario style + throttle per cylinder + tps mapping ) with a well defined , long intake cone with definitive diameter power restrictor.
This was to make the car fit with power regulations .

Thats the only reason I mentioned to be cautious in accepting that the performance numbers were the best that could be acheived.
When the cars moved into non National series then all sorts happened ,
especially on the intake area.

All exciting stuff !! I will shut up now !!

Geoff

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KS400200 , the oldest 964 on Rennlist , unless you know differently !

Geoffrey

Red, I'm not sure I understand you correctly. I know of the factory RSR have individual throttle bodies sitting on the head with an aluminum "manifold" with a dual port resonance tube with electronic flap. With this manifold, there were several options that provide for the different restrictors used in the various series. Are you referring to this manifold, or was there another that is like the 993 varioram intake?

I also don't think the published 350hp represents the best these engine ever did. I know the sprint engines had larger valves, more agressive camshafts, slide valves rather than ITBs under the "manifold", higher compression, different ECUs, different exhausts, and no restrictors. These are the engines reported to produce 408-412hp on PMNA's engine dyno with dyno sheets provide by Porsche.

Jean

Geoffrey,

I will need to get back to check some of this info, but it does seem in line with what I have. The only caveat are the sprint engines producing 410BHP which I have never read about, doesn't mean they don't exist though. If you have an engine dyno sheet can you please read the torque number, which I don't think improved beyond 380NM but I would love to know more... The rest is a bit over my head technically.

Sprint engines are what I was talking about, not the endurance engines. Some of the race teams like Freisinger really pushed the envelop with R&D and testing of different ECU systems, intakes and valve sizes and cams.

Regardless though, I think it is very far fetched to think that any of those engines can match and exceed one of the new factory race engines , watercooled, 4V etc.. I would doubt even they could get close to 80% of their efficiency.

Thanks for the info.

Geoffrey

Jean, I agree with you on the aircooled vs watercooled engines. My engine produces similar power with slightly more torque than the several 2001 GT3 Cup engines (335-337whp) we've tested. I need to get the graph file off the dyno in order to post the comparison. The 03-later Cup engines are in the 365-370whp range. In contrast, the last GT3 RSR in UNRESTRICTED form, reflashed by Porsche Motorsport to the unrestricted engine configuration was 505whp at 8.8k RPM. However, several laps into running an aircooled engine the power will begin to drop off as the engine is heated up. The watercooled engines are more consistent. This can be seen with disassembly where the aircooled engine cylinders begin to oval where the watercooled cylinders look very good after 80 hours.

NineMeister

Geoffrey,
We talked about the results I had seen with the 4 litre engine so here they are as corrected rear wheel hp dyno plots (since you have alresdy posted rear wheel curves).
The first graph shows the difference between the long and short intake air horns on the 13mm lift 9m Race camshafts showing the improved top end and area under the curve of the short horn engine as discussed.

The second graph illustrates the results of the 15mm high lift engine shows the difference between a conventional header set with a parallel collector against another similar length set which have a proper venturi style tuned collector.

The final graph is a comparison between a stock GT3RS and the best result from the high lift 4 litre with the extractor exhaust.

Enjoy.

Jean

Geoffrey,

Your flywheel torque on your RS engine shown is approximately 333 fw ft.lbs whereas the 996 watercooled 4V 2001 Cup car was 273 ft.lbs, that’s 60 ft.lbs more or about 22% more, not a small number.

I understand all the great modifications you have done but I do not really see major differences vs the factory RSR setup, other than 9M heads that "could" justify a 5% increase in BMEP vs the 964 RSR.

The 997 GT3RSR is rated at 485BHP@8500RPMs with the restrictors and 321 ft.lbs of torque, I can see how an increase of about 25-40 BHP without the 30mm restrictors (to 500+ FWHP) is rather likely, but surely not 115BHP (your quoted 505whp)??

In any case the 30mm restrictors should do little in limiting the torque numbers since they limit mainly airflow at highest RPMs, I am staying away from HP to avoid RPM interference in the numbers, the BMEP efficiency numbers that I am comparing are torque driven, not HP.

As I said I am not too hang up about the max HP numbers, but to understand how good numbers are, one needs to compare to a known benchmark, in this case the factory engine dyno numbers, for any really meaningful comparisons. Otherwise it is all a moving target.

Jean