964 C2R

Hi fellow racers and happy 2008!

I was think how many of you who have made any power tests of your 964 3.6 normally aspirated engines (lately)?

Figures that I love to see is:

*What powerfigures @ what rpm
*What torque @ what rpm
*Highest rpm
*Finally what modifications the engine had at the time of the test


If nothing else it would be interesting to see how these engines hold up over the years since they left Porsche Platz 1!

I have a stock C2 engine (late-91) with good leakdown figures and updated symetrical headers, K&N air filter, racecatalysts that I am gonna run on the dyno so I would like to see the real difference (improvement?!!).

Cheers,
Daniel Saxlid

kgorman

Christer

Well this is mine, but it is highly modified.....and as I am posting only an 'after dyno' my car clearly only makes 250hp....

Steven C.

RWH somewhat modified. It can do better

TR6

Steve, where is LG motorsports? Would you recommend them to dyno my car? I'm planning to dyno mine as soon as I clear 1000 miles break in and was looking for another option besides that place in Lewisville we met at last time. Not that I don't have confidence in their work....

edit: just looked them up on the web. Looks like they are in Wylie which is the other end of the world from me.

964rh

Max BHP - 250.0
Max Torques - 238.5

Standard (when this was done) apart from a cat bypass and g pipe

1990 C4 with 124000 miles. Topend rebuilt at 102k (iirc)

964 C2R

Thanks a lot boys, I knew I could trust you to come up with something really useful. Especially nice to see that the engines hold up quite nicely over the miles.

"Christer" & "Steven C.", what mods where done on the engine at the run?
Were there any adjustments done in the software at these runs or was it power tests?

"Steven C." I also appreciate the lambda graph in your diagram.

Was it never tempting to run higher than 6700 rpm? On the other hand, both graphs tend to suggest the power curve has started its decline @6500ish.


"robh" at what rpm´s were your figures recorded?


Keep the figures and beer flowing!


Cheers,

Daniel Saxlid

Christer

Hi Daniel

The dyno graph is slightly incorrect in displaying data when it comes to RPM - the rev limiter cuts in at 7200 on mine...the graph is not correctly calibrated.

I cannot even begin to list the mods that has (allegedly) got me to 371hp and 462nm torque, but if you search on a thread called 'car needs good home' or something like that (I started it) then I list the mods in there...

964russ

252.6 bhp with 74,000 miles

N51

Christer,

Could you post your previous dyno/build? From memory, it appears Colin has found some additional hp/tq. Curious as to where it came from. What exhaust are you using? Same?

Thanks,

Pesty

Im not posting mine up I got too much stick last time. Dyno charts are somewhat controversial on this board

Christer

Yes, there is approx another 10hp and 15tq, and Colin has speculated that it is a change from the 3.8 Cup pistons and cylinders I used to use, and the 9M items now used....he talked about things like 'squish' and slightly increased compression....bbut it may also be down to the fact that he is used to using those pistons and can generally find something more because it is known variiable? Perhaps he will chime in.

The car is not tuned to the max, it has a margin for safety, plus of course the knocklink so that the detonation side of things will never be an issue again...unless the driver is blind of course...

Christer

p.s. nothing else has changed, but I did spend a bit of extra money on mapping so that the car is quite easy tolive with...bearing in mind the state of the tune...

Geoffrey

The Mahle pistons, both 100 and 102mm, while working well in the 964 are really not performance pistons. They have several issues and aftermarket pistons like 9Ms address these issues (although have other considerations to work out that the Mahles don't).

1) The factory pistons are extremely heavy 625g for 100mm and 540g for the 102mm pistons. Weight is an enemy, it limits the RPM the engine can run at since the force exerted on the connecting rod grows exponetially with RPM. An aftermarket racing piston can be in the 380-400g range depending on how it is designed and how large a skirt is used.

2) The factory pistons have shallow valve reliefs. This limits the amount of lift and the acceleration rate of the ramp angle that can be used on a pefromance camshaft.

3) The factory 102 pistons have the wrist pin deaxised 1mm, however, they are deaxised all the same way which means that on one side of the engine they are on the thurst side and the other they are on the compression side. The engine is not running equally and I see air fuel differences between the banks when using these pistons. To optimize the engine the fuel needs to be trimmed on one side of the engine compared to the other due to the efficiency difference between the banks.

4) The pistons have a production open skirt design. The aftermarket performance pistons (should) have a boxed skirt design which strengthens the piston and keeps it from flexing at higher RPM. A stock piston should not be revved past 7000rpm, it damages the wrist pin boss and flexes the stock connecting rod.

5) The factory pistons have a 23mm wrist pin, a proper light weight piston with a proper boxed skirt design can run a 22 or even 21mm wrist pin which allows the compression height to be shorter and therefore you can run a longer connecting rod which helps the rod to stroke ratio. A longer connecting rod will slow the acceleration rate down and increase the piston velocity which builds torque. It also changes the crank angle where the maximum piston speed occurs because the piston travels a different distance in the bore with a longer connecting rod. All of these things help to build torque in an engine.

6) The stock pistons have a net dome volume that does not meet the advertised compression ratio. I have measured stock 3.6 engines as low as 10.5:1 and as high as 10.8:1 compression. Machining of the components is require to get 11.3:1 compression as Porsche advertises.

7) The 9M piston specifically has an optimized squish area which increases the efficency of the combustion. The engine therefore, requires less ignition timing than a comprable engine with factory pistons, and therefore will build more torque.

8) The aftermarket pistons can be designed with different ring packs which allows the use of smaller rings for compression and oil control. The smaller rings have less friction on the cylinder walls and therefore there is less fiction loss in the engine and the engine makes more power.

And that is just the piston...

N51

Geoffrey,

I'm swimming it. :-)

My best,