RadioActiveMotorsports

Hi fellow GT3 followers,

Need some help here... I need to know the technical difference between GT3 cylinder heads, specifically:

996-104-002-94 (I'm told a standard GT3 head)

996-104-002-96 (I'm told an RS GT3 head engine code m96. 76/79)

I would like to see pictures and any technical information you guys have on these parts since I am considering replacing my 04 GT3 heads (7500 race miles) with RS heads, but at twice the price, I need to know exactly what the difference is or is it all hype...

Any help is greatly appreciated, Rennlist rocks!!!

Sincerely frustrated with dealers who have no clue,

Jeff

911SLOW

In the standard GT3 the cylinder heads are manufactured from extreme temperature-resistant light alloy.
The intake and exhaust ports are surface machined to improve the charge cycle and thus power output. The combustion chambers are designed as spherical cups, the two intake and two exhaust valves of each cylinder have a diameter of 41 mm and 35.5 mm respectively around the valve disc.
The are arranged in a “V” at an angle of 27.4°. The exhaust valve stem is hollow and filled with sodium to improve heat dissipation.
Owing to the power-oriented valve timing and the associated high forces, double valve springs are used to close the intake and exhaust valves.
This ensures the speed stability of the high-speed designed engine.
The diameter of the flat-base tappets is 28 mm.
The contact areas between tappets and cams are cambered.
Valves have a shank diameter of 6 mm, which creates excellent prerequisites to achieve top placement regarding power exploitation on naturally aspired engines.
The chain drive runs with plastic guide rails and hydraulic chain tensioners located at the un-tensioned end of the chain. A driving flange for the oil suction pump is attached to the input side of each exhaust camshaft.

The engine of the 911 GT3 is used in the 911 GT3 RS in model year 2004 but the geometry of the inlet ports in the cylinder head have been optimized.
Sadly I do not have the exact information as they were never published in the Service Information Technik of the PIWIS.


John

aussie jimmy

iirc didn't the rs use different spark plug arrangement?

911SLOW

Yes

https://rennlist.com/forums/8187109-post11.html

RadioActiveMotorsports

Hi John and thank you for your analysis of the standard GT3 cylinder head. I was wondering if you have access to pictures of GT3 heads versus GT3RS heads? I'm sure the readers would be very interested as I am!!!

The word "optimized" comes up often with the RS, yet, I find no specific information any where. Any ideas where we might find some?

Thanks again,

Jeff
RadioActive

911SLOW

Yes contact member DanH and ask him to take his RS engine apart for our viewing pleasure..



PS. I will try to find some photos as I am curious too, but no promises.

DanH

oh sure I'll just strip my engine for you now!

RadioActiveMotorsports

Hey DanH,

Appreciate the offer to tear down your RS engine, lol. But, so long as its work'n, no sense in hurt'n that pretty car!

Butt... if you know an RS owner who's get'n some work down, I would luv to see pictures of the cylinder heads...

Thanks,

Jeff
RadioActive

FFaust

I'm surprised that you would have to purchase a different head. I would have thought that various high-end tuners (RUF, Manthey, Sharkey) might have their own optimization programs (porting, valve size, etc.)

DanH

No, most of these guys do little more than a remap and exhaust for your 10k USD. If it weren't so ridiculous it would be funny. Having said that, I don't think there are any easy gains to be found, these engines are pretty optimised from the factory.

DanH

I don't know anyone with an RS who has had to open the engine. In fact don't know of any GT3 in the UK except for a 996 mk1 about 7 years ago which had a problem after a bad remap. So odds are not high for you, sorry!

911SLOW

You are not being fair to the tuners.. for 10kUSD they do add a panel filter and a sticker..

911SLOW

DYNO RESULTS (stock engines/same dyno (SP))

2004 996 GT3 392.4PS / 395.7Nm
2004 996 GT3RS 381.2PS / 388.1Nm
2003 996 GT2 487.6PS / 590.2Nm

aussie jimmy

not all engines come off the production line the same. alot of freaks out there. gotta be lucky...also doesn't the rs add more power once the ram get's some real air into it?

911SLOW

Average output of a 04 GT3 and GT3RS was 390PS for both, according to a tuner that tested a fair amount of these.

True about the ramair something like 10PS is correct.. Porsche didn't quote a number back then but from various sources and from people involved in the development of the GT3, it is something like 10-15PS above some klm/h..

The official quote for the 6RS was:

"The engine compartment lid is as on the 911 GT3, model year 2004. On this,
the large carbon look rear wing is mounted, along with a plastic air intake scoop
for ducting the intake air."