Thanks. Don't the factory X51 cars also have enhanced cylinder heads?

 

The X51 heads have a stiffer exhaust valve spring and some port clean up, that's it.

Dave

 

Interesting...

Here's what I've previously read:

• New cylinder heads with flow optimized intake and exhaust ports
• Exhaust ports and exhaust valves with larger cross section and stronger exhaust valve springs
• New exhaust manifolds/headers with larger cross section and optimized flow behavior. New cast aluminum intake manifolds (Plenum) with modified cross section.
• New larger throttle body. (Previously 76mm on the 3.8, now 82mm)
• The 'X51 Kit' for the 911 also includes a new carbon fiber air cleaner housing with dual intake ports.
• Modified DME/ECU maps.
• Increased engine RPM limit.

If this is accurate, it appears the exhaust valves and ports are also larger than stock and the DME/ECU is remapped to better utilize all the changes.

I've also read that the camshafts have more aggressive profiles...perhaps it was for the Club Coupe???I'll try to remember where I saw it and dig it up.

 

Here it is:

http://autojunkie.blogspot.com/2005/...lub-coupe.html

This article was in Excellence if I remember correctly.

 

Actually the article was incorrect, as the X51 uses the OEM cams. I have the full part list as well as the TSB and it doesn't mention any cams. Not to mention in the X51 instructions it even mentions how to remove the stock cams and reinstall onto the X51 heads. I talked to several people in europe regarding the X51 heads and the concensus were that the heads were just cleaned up on the exhaust ports along with a stiffer exhaust valve spring to accomodate the 7450 rpm rev limit. Something to think about as well, the OEM non X51 head has to flow very well to make almost 100hp per litre at under 7k rpm. Even though you can rev it higher than 7k rpm it plateau's out before this. If the heads weren't good to begin with we wouldn't be making as much power as we are now. There is a diminishing return on such head work...really to get more power than what the kit provides is going to require more rpm..ala GT3.

Even on PorscheNA's website doesn't mention anything about cams..

http://www.porsche.com/usa/accessori...hideintro=true



Dave

 

Yes makes sense, as you read I was skeptical about the cams too that's why I wanted some feedback. I am still curious about the larger exhaust valves (cross section or as Porsche says "modified geometry) and the remapping of the DME and ECU (or as Porsche says an uprated engine management system).

 

Does anyone know how difficult of an install the intake manifolds would be?

 

I heard it could be done on a coupe without dropping the engine. I don't know, I looked in my cab and I highly doubt it.

 

I hope you are not doing this kit by yourself, if you find a good P-shop they shouls know how to install that for you. How come you didn't do some research before you buy this X51 kit?

 

This is interesting...seems like the 996 powerkits had different cams but mostly the same other parts; so I wonder how they got about the same % power increase for the 997's without the cams?

http://www.parkplacestores-porsche.com/capo.html

The Carerra Powerkit provides a substantial increase in power output from 320 to 345 hp on Manual gearbox 911 Carerra models 2002 & up (from 08-2001 production date). Modifications include: 1. New alloy induction manifold system with modified cross-section 2. New inlet pipe support adapters 3. New exhaust manifolds with larger cross sections & optimized flow patterns 4. New cylinder heads with optimized CNC-milled intake ducts 5. New higher performance camshafts with larger valve stroke on inlet sides & modified inlet & outlet timing 6. New inlet valve springs adapted to the enlarged valve stroke 7. Revised engine management software (DME). Enjoy greater performance on board with the peace of mind that comes from knowing your Porsche was properly modified by the engineers who designed your car in the first place. 2-year Factory warranty when installed by our authorized Porsche technicians. (Installation pricing below).


000-044-100-15Regular price: $8,540.00Sale price: $8,490.00

InstallationTurn key installation by Factory trained technicians.

installation$3,750.00

 

I think it is because the 997S engine is already in a higher state of tune than the 996 Carrera (i.e. it probably already has the mildly warmer cams). Whilst the standard 996 Carrera at 320 BHP has 88.9 BHP/litre, the standard 997S 3.8 at 355 BHP has 93.4 BHP/litre - very close to the 345 BHP 996 X-51 at 95.8 BHP/litre. Flow the heads on the standard 997S, leave everything else alone and the specific outputs would be close on identical to the X-51 996 (as would the engine spec).

To go to the 100BHP/litre the 997S X-51 achieves, also needs the bigger valves, new inlet plenum / runners etc. in addition to the cams (that it already has as standard).

Ian

 

Makes sense, thanks Ian.

 

Has anyone put after market cams on there 997s, I wonder why this isnt a popular mod, besides for being a bit pricy.

 

Thinking the same thing...in the old days we used to do it all the time with our 911/930's.

 

i don't want disappoint anyone here but i have a 2007 997 s with headers, milltek mufflers softronics plenum and air intake and i have just put it on the dyno last week and all we got was ..........293hp at the rear wheels, so i dont know how you guys up there get 380 or 400 at rw.
please let me know how you get more power.
andre