Dave White

What are you using, and what are your problems, if any?
I am in the middle of a rebuild, mechanic says that I have a lot of pitting on one of the cams. I am going to 3.8, want a street-able (no stalling) cam that would give me a boost. This would be a street car, but don't plan on going past 6800rpm. Lumpy idle fine, as long as it doesn't want to stall. The 2 that I have read about are 964ss, and 964rs spec cams. Any specific thoughts on these and where they make more power would be appreciated.

Geoffrey

There is no 964RS spec cam, only a different part number due to not having any power drives off the back of the cam for accessories. The profile is the same as a street car. I always have a camshaft made to my specifications based on application, but I don't think that is what you are asking. Since you are going to 3.8 and will require ECU reprogramming, I think you'll want to stick with a cam / piston combination that someone has a chip for. Steve Weiner has a chip for a 3.8 and 993RS camshaft which is probably your best bet even though the camshaft grind isn't that great. Don't forget to set the installed height of the valve springs to the force requirements of the new camshaft profile and valve masses. The stock 964 installed height with stock springs and retainers will not be enough for a performance camshaft.

Dave White

Not arguing, but when I see a factory 3.8 rs(r?) engine upgrade kit, it comes with the P&C's, the new intake system, chip, and new camshafts. Wouldn't that mean they are different? Also, is there a difference in a euro RS cam? I wouldn't know what to ask for in a custom grind, not willing to risk an unknown quantity for drive-ability issues. Will look into springs, thanks for the other tips. Not my expertise, just asking questions so I can learn, and make a good decision. Thanks for all responses.

Geoffrey

The 964 RS is the same engine as a 964 Street car with minor differences such as no power steering. The only 3.8l 964 engine was the 20 street 964 RS 3.8 and 50 race cars 964RSR. These engines were ITB engines with race style camshafts The kits you see advertised are an entirely different engine than the 964 3.8 engine. The kits have the 993RS street car internal parts P&C, and camshafts. People like Steve W have been able to have a chip produced that will work with the factory 964 ECU, intake, and exhaust system.

Bill Verburg

just to clarify
964 and 964RS(both3.6) use the same cams except that RS don't have the power steering drive, both have the same Motronic w/ barn door air meter.

964 3.8RS uses race cams and can do so because pistons have valve pockets and itb's can handle the intake manifold air fluctuations that give the street Motronic air metering fits

993 use a hotwire air measurement w/ cams similar to 964, 993RS uses a slightly hotter cam than its normal sister w/ the same hotwire air measurement The RS does have valve pockets in the pistons but is still limited wrt cam timing by the air measurement system which does not handle intake manifold air fluctuations well.

Geoffrey and Ninemeister have done some remarkable things w/ Motec engine management and the elimination of either of the 2 types Motronic air measurement systems and using TPS and MAP sensors. Their intake is just a big ole tube and w/ proper pistons can run some very aggressive cams and still be streetable.

Dave might want to look through the archives for notes on Geoffrey's race engines and shokem's engine built by Geoffrey

here's one link to get you started

I'd love to hear more about the latest engine that Geoffrey did for Jeff

race911

Ultimately, what do you hope to accomplish. As I posted last week, car-to-car acceleration at Laguna exit of T11 up the front straight to braking for T2, the difference between my yellow 3.8 car and my stock 140K RSA was AT MOST two car lengths.

The 3.8 was built by Steve, and though it had a stock exhaust (damned Laguna sound police), dyno'd at 315HP. A 140K 964 3.6? Your guess is as good as mine.

(Note: the 3.8 car has revised gearing, and I was shifting into 5th. The RSA has stock gearing.)

Geoffrey

It was just a budget race engine that used some of the parts from my original engine with custom pistons, replated stock cylinders, ITBs, 7.25" clutch and the same M48 unit we use on the street cars.

NineMeister

..... that made 20hp more at the tires than a factory RSR?

You're too modest for your own good, Geoffrey.

Dave White

Thank you all for the clarification on factory parts. Ideally, I just want a quicker street car, and while it's apart, want to replace with better parts, if available, within a reasonable budget. Motec, ITB's are not reasonable at this point, but a mild cam could be since I need it anyway. I can always add the external stuff down the road. I have chatted with Steve W and might be going that route if no other options surface. The P&C choice is Mahle Motorsports, by the way.

Bill Verburg

For a budget street car w/ stock Motronic you cant go to wild on the cams, I know several people w/ the 3.8RS hydraulic cams in 3.6, w/ a 3.8 it's an obvious choice. The mechanical equivalent of the 993RS is the SS cam which also works well

993 Super Sport(mechanical)
lift .490I/.456E
Advertized duration 260/248
duration at .050" 240/230

993RS(hyd)
lift .490I/.446E
Advertized duration
duration at 1mm 243/232

Webcam 20/21
lift .485I/.452E
Advertized duration 258/246
duration at .050" 238/226

993 stock
lift
Advertized duration
duration at 1mm 240/230

Super C2 248/236 duration @ 1mm
.475"/.455" valve lift

Sport 964 254/236 duration @ 1mm
.490"/.455" valve lift

284/274 254/244 duration @ 1mm
.490"/.460" valve lift

All of these grinds work well in the 3.6 litre and up engines and the choice depends on your mods and driving style.

The sport 964 is a little more than the 3.8 super cup cam. and the 284/274 is another step up.

I also recommend Steve Wong for a chip for these engines, he will work w/ you to get it right. I have several of his chips and am very happy w/ them.

Paulie964

If your looking for a little bump in performance and money is tight, I would talk to Dima at Elgin Cams in CA ... He did a hard weld/regrind for me for like 400 bucks ...

might be a decent solution for you ... plus, I hear nothing but good things about him from people in the industry around here

Rob 97 993c2

im confused. Why does a Euro-RS or 964cup have a 10hp advantage over the standard 964?
is this due to motronic chip?

NineMeister

Blueprinting + chip

Rob 97 993c2

sorry to be dense, what does 'blueprinting' mean?
is the chip basically the same as a steve wong or autoauthority chip?
are the cams the same on a euro-rs or cup?

Geoffrey

Different engine than you are thinking about Colin. That one I just completed was a factory RSR engine with your 9M cylinder heads, custom pistons and camshaft and produced +20 over the PMNA Sprint engine we started with.

The engine Bill is referring to made the same as a power as a factory RSR sprint engine but about 7t/lb torque less. However, it has a much broader torque range and better under the curve features and ran on 93 octane fuel. 3.6l vs 3.8l


I would not agree with your assessment. The Webcam 20/21 cams are CIS cams and are awful on an injected engine. Furthermore, you are missing the lobe centerline information which has a lot to do with the characteristics of the camshaft. From the spintron testing I've done, the Porsche camshafts have slow openeing ramps and are very hard on the valvetrain with high harmonics. I think this is a funamental reason why custom camshafts with similar lift and duration outperform a Porsche camshaft.

FWIW, it has been my experience that very little is gained from a 3.8l conversion (3.8RS pistons, RS cams, and a chip). I don't know how much the motronic programming limitation is the cause or simply the heavy Mahle pistons and poor squish. I am about to install a MoTeC system + the 9M USA Sport 2 camshafts on an engine with the 3.8l RS pistons. We'll see what happens. The baseline showed 254whp where the 3.6l with the same cams and MoTeC showed 301whp. (basically the car you rode in Bill). It will be interesting to see the difference.

Technically speaking the 964 RS/Cup engines are not blueprinted. The parts for the engine are hand selected and have tighter tolerances in weight and sizing. If you simply install an RS ECU into your stock street car, you get the +13hp the RS engine has. So, yes, it is all the Motronic programming.