Geoffrey

After nearly a year, I had some time to put the engine back on the dyno and map it for running open pipes. Previous to this I had been running a "Lime Rock" muffler setup which allows the car to pass an 89db noise limit. The system that is on the car is from Peter Dawe and consists of some cheap mild steel headers and a custom mufflers with the mufflers weighing 33.6lbs alone which is nice to remove from the rear of the car. I do have some nice stainless steel headers to try, but that is another project for another day.

The engine was out of the car and serviced over the winter with the leakdown on all cylinders between 2-3%, best to worst. This is still running 93 Octane street fuel with no knock sensors and MoTeC with a near 12.0:1 compression ratio.

Here are two graphs, the first is the comparison of the engine with and without muffler, with the solid line being the open pipe version of my engine on both graphs. The 80ft/lb torque drop at 4250 is gone, having moved lower in the RPM range and there is significantly more area under the curve everywhere. While I only gained 10rwhp peak, there is close to 20rwhp more at redline with a much flatter torque curve across the board. In talking with Colin this morning, the shape of the curve is similar to his 4.0l engine but obviously with less torque and hp. This is good to know since I have the 9M heads and similar camshaft (pre 9M high lift setup) and intake setup. He suggested a minor modification to the intake to perhaps gain some additional power from 6000 and up which I'll try when I get a chance. I am extremely pleased with the heads from 9M, they are fantastic.

The second graph is of a factory 993RSR engine built to PMNA Sprint configuration specifications running 110 octane race fuel. I had it on an engine dyno and it produced 410hp. My engine is only slightly less than the sprint engine by less than 10hp, but has a much better area under the curve. I suspect that with the better headers I have and the minor intake modifications, I should be able to match or exceed the PMNA Sprint engine.

38D

very cool

puma1824

Nice. BTW can I use some of your pics on my site?

See: www.964tech.com

Thanks,
Puma

TB993tt

Geoffrey
Nice curves Can you work out what BMEP is for your engine -for comparison to others ?

DrJupeman

Sweet

Geoffrey

Anyone is welcome to use any of the pictures of my car that I have posted except for the 1 or 2 that show copyright Josh Brown who is the gentleman who took the pictures for the total 911 shoot.

Toby,
I have the BMEP numbers based from an estimated Flywheel number based from this chassis dyno. This, based on the above shown factory RSR sprint engine I did on an engine dyno 410hp and same chassis dyno 349hp. The factory RSR sprint engine is known to be 408-412 on PMNA's dyno, so I feel good that I have the same numbers. Maybe Jean can forward the formula he is using and I can plug my number in.

Jean

Geoffrey, here is the formula based on torque:

Max. TQ= (BMEP X displacement)/150.8 x Absolute pressure
The calculated BMEP = 220 psi assuming 283 lbs. ft of torque at the wheel, which at 15% (?) loss becomes 333 lbs.ft of flywheel torque.

The factory 3.8 RSR engine was calculated at 175 psi BMEP, about 26% less.

Geoffrey

When you say 175psi BMEP, which factory 3.8 RSR configuration are you using? They ran restrictors in some series and I think were rated at 360hp. There were numerous other endurance and sprint versions over the years. The differences were among others, some with slide valves, some without, some with Bosch ECUs, some with Theilert ECUs, and some teams like Alex Job Racing used MoTeC, some with lighterweight higher compression pistons, some with the standard endurance ones like mine, some with 54mm intake valves, some with 51.5mm intake valves, some with Porsche camshafts, some with Theilert of which there are at least 4 different grinds. The factory RSR engine above is a sprint version with the Theilert sprint camshaft, factory intake manifold and ITBs, latest version Porsche Motorsport header design, sprint pistons, 54mm valves. I know this configuration was 408-410 on PMNA's dyno and I saw 410 on the one I use. The slide valve engines were more like 412.

I think mine with the works Porsche headers I have in a box, and some intake tuning will match the RSR Sprint engine shown above.

Jean

Geoffrey

The factory 964 3.8 RSR had 325HP and 360NM of torque per factory ratings. The highest reported output was in fact non official by R&T, of a sprint engine with 375PS unrestricted. Torque was still 360-370NM (around 280lbs.ft at the flywheel).

On the 993 based RSR they added a resonance intake electronically controlled by a flap valve, higher lift camshafts, increased compression, and no catalyser, this was only for the 993RSR Japanese GT3 Class, and saw a maximum output of 340PS..

But this formula is worked out based on torque, since HP can vary depending on which RPMs they are running the cars, torque on all these different cars was about the same.

It does not really make a difference here, this engine is showing a very nice and beefy torque curve, the numbers are however on the high side by about 15% on torque, I don't know what dyno PMNA has or how they used it, but if you are getting the same numbers than the RSR, then it is an achievement already, regardless of the final number. .

Jean

Chris M.

Very cool. That engine in your 2100# car must be quite a ride.

Geoffrey

Jean, thanks. If you look at the RSR curve, you can see at 5000 where the torque increases due to the resonance flap. I spent a lot of time with the factory engine on the dyno to determine where best to open the resonance chamber which does help the engine on top end considerably. I had assumed that with the longer runners of the intake system it would have provided for better low end torque that I could have hoped for with ITBs.

I think the broad torque curve is due to the 9M intake port design in the head and the fact that I'm using only 50mm intake valves compared to the 54mm in the RSR Sprint engine. With the higher velocity I measured on the flow bench, I think the cylinder filling is much more optmized.

When you say that the 993RSR has increased compression over the 964RSR, do you know by how much? My understanding is that both of the engines use the same 11.5:1 compression pistons. I am aware that there were other pistons available from Porsche later in the 993RSR model series, but were only used in some of the sprint configurations. I believe they were in the 12.5:1 range.

Over the course of the lifespan of the 964RSRs, they were fitted with the 993 style RSR intake with the electronically controlled resonance flap. The two Roock cars for instance had the later engines.

From a design perspective, the factory RSR pistons are a disaster.

Red rooster

Geoffrey,

Well done with the RSR type motor. I had some small involvement with the Bosch system variants and one factor that was very significant was the primary intake restrictor .
That makes power/torque comparison between various national uses of that
motor quite difficult to assess.

Are you using the seriously enlarged Vario and six throttle body system ?

Geoff

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

Geoffrey

I'm running individual throttle bodies. Here is a picture.

Jean

Geoffrey

ITB setups are very sexy!

As far as compression ratios, there were 11.3:1 versions, and as you rightly mentioned, some with higher compression ratios, the 993 moved to 11.5:1 I believe as well as higher exhaust lift cams..

I am on the move so I don't have my data with me now, but from memory, Roock (driven by Alzen), Weheimer(sp) and another couple of teams that were factory backed (Maybe Konrad?) were running sprint engines between 325- 340BHP. Freisinger had a high compression version and high lift cams as well with 340BHP.

I hate to be contradicting these numbers honestly, but I don't see the heads doing that much difference vs. an already outstanding factory sprint RSR engine with advanced intake system, ITBs, compression, hundreds of hours of programming on the factory bench etc, especially on the torque department.

These efficiency levels we are talking about are 5% higher than the latest all out race engine from Porsche Motorsports, the watercooled 997RSR and 25+% improvement vs the factory RSR sprint engines. A 5-7%% is what the revolutionary watercooled vs aircooled 996 vs 993 improvement was with all the variocam changes, 4V per cylinder and watercooled heat reduction measures.

Anyway, I just wanted to answer the efficiency question, outstanding engine that I would love someday to test, the throttle response must be fantastic.

Geoffrey

Jean, I agree that we can be caught up in the numbers which is why I compared my engine to a factory PMNA built engine on the same dyno using the same tests with a similar MoTeC ECU and the same tuning methodologies.

Next time you are in the US, look me up.

I am interested in some of the technical infomration you have because I think the 3.8RSR M64/04 engine is confusing with all of the variants and documentation or lack of documentation on some of them. For instance, in one place for 1993 it is listed as 325hp in ADAC GT regulation which ran 40mm restrictors (engine numbers 701-715). That same engine without restrictors is listed at 350hp (engine numbers 727-730) and a third one with 48.2mm restircotrs (engine number 716-726). I have only seen the engines listed at 11.5:1 compression in the factory manuals, but the Porsche Sport book lists it at 11.4:1. Bruce Anderson's book shows 11.3:1 but 350hp for the 93 M64/04 version, nothing for the later 993 version. These were all endurace engines as delivered from the factory. The Sprint engines may have been something that PMNA produced with the help of Weissach, I don't really know and I'm sure the Theilert engines were something PMNA did on its own. I'd like to be able to fill in some of the blanks I have with this engine and this period of time.

In honesty, the RSR engine was not all that advanced by today's standards, and the programming of the engines from what I've seen is not all that good except for wide open running which is one reason PMNA went to the Theilert system in an effort for more power in the IMSA GT series. In all, the engine tolerances were wide. For instance, the connecting rods could be within 4 grams where mine are all the same within .5grams. The pistons can be within 5 grams, mine are all balanced to under 1 gram. The pistons themselves have a design flaw with the deaxising of the wrist pin.

Here is the high compression sprint piston (I think). Notice the thinner skirt and larger intake pocket compared to the endurance pistons in my engine.