FFaust

So John, you got one of those "scoops" for sale?

RadioActiveMotorsports

Hi guys,

Thanks for comments to date, and here is a little back ground for the need.

I have been racing a '04 996 GT3 since 2004. Freddy Baker and I (Jeff Amos) developed the car and help Porsche develop the ABS on the car (explain later) which was horrible in '04, also we help Hawk brake develop the first aftermarket brake pads for the GT3 and ultimately the DTC 70 which works great.

SCCA the best we could do is a close 2nd at the Nationals in '04, the 9th in '05 (rules favoring the Vettes), then the Vipers in '06, had my chance in '07 but a flat tire put an end to that. Blah, blah...

NASA last year lead in the points, took pole for the German Touring Championship race at Miller Motorsports Park, lead the entire race until the last lap when a coolant fitting let go and ended my race!

Ok so why did I make this post, well.. my GT3 has 7500 race miles on the engine, in '04 we had 373 rwhp with 120 miles on the car, by the end of the season in 2010 the car had 350 rwhp. The tranny had been rebuilt twice (syncros & LSD), and with the heat build up and injestion of coolant every expert says to put new heads, rings and bearings on the engine.

So... with 1400 GT3's in America give or take there are only (2) two standard cylinder heads in the USA. Germany has only (12) RS cylinder heads for the world for twice the price of the standard head, tough to swallow when no one in the public world can tell me with absolute certainty what the difference and pictures to prove it!

Porsche wrote a paper explaining the volumetric efficiency of the RS head compared to the Standard GT3 (84.7% vs. 77.4% respectively), and there has been PR notes that the heads were ported and polished on the intake side, yet no pictures, no real proof.

So, any help or leads on getting to the bottom of the mystery on GT3 cylinder heads will be greatly appreciated.

RadioActive

DanH

Well I don't think it makes any difference to power and the RS does have a map of its own, so my feeling is its probably not going to make any difference... I guess it depends how much we are talking as to whether I'd risk paying the extra...

aussie jimmy

cylinder heads should be expensive, the difference may be at least $5000....

so, the 996 had coolant-loss issues as well?

FFaust

Thanks for sharing the info Jeff. Interesting read.

RS heads are double, but double of what? Yeah no help I know, but I am curious.

I don't doubt that porting, polishing, and flowing a head WILL provide some benefit, but from the numbers posted by Slow, it doesn't seem to be earth-shattering.

Now, wonder if you could spot some differences by looking at the PET? Diff P/N for valves, springs etc (diff sizes). Might be worth a look and might yield some clues.

RadioActiveMotorsports

Hi Jimmy and Dan

To answer Jimmy's question:

The RS has 15 more HP than the standards GT3, stated all over Porsches PR campaign lit. It has been explained to me but not proven that this was due solely to the cylinder heads and the work that was done to them by no other than... Porsche Motorsports AG, hmmm.

To answer Dan's question:

The cost for the 15 extra HP, well... the dealer price for the standard GT3 cylinder head is $2,500 USD, for the RS GT3 mkII Cylinder head is... $4500 per head. So for $4k divided by 15 equals... $267 per HP, ouch!!! Now I have been taught that an acceptable number is roughly $100 per HP, so once again look for explaination to the holy grail of cylinder heads...

RadioActiveMotorsports

[/IMG]

Coolant lines in all 996's especially GT3 & Turbo's have fittings which I intially thought were sudo pressed in and glued. Well... the are only glued in and with significant heat cycles they come loose. Lots on Rennlist with pictures of guys 996's blowing coolant all over the track. Also Excellence has a great article in their Feb issue of those fittings which I learned there are no less than eight just like the one attached here that can come loose over time. Come to find out there is a class action lawsuit againist Porsche about this issue, should be interesting to see how that works out...pun intended, lol.

[IMG]http://http://forums.rennlist.com/upload/ps_coolant_line_gt31.jpg

FFaust

Care to elaborate?

996FLT6

Whatever lawsuit they have hopefully it works out in our favor. I was surprised that cupcars have the same press fittings. Mike

DanH

Not ever seen that claim about the RS engine. In europe it was marketed with same power as standard GT3 although Preuninger did say the ram air duct gives approx 10hp at 100mph. Nothing was mentioned of the heads in anything I saw, although he said the map had more agressive fueling to take advantage of the light weight fly wheel.

On track I've never seen a noticeable difference really between GT3 and RS, at least not beyond the delta in driver ability.

Also if you look at European tuner mods, they never made higher claims for their kits on the RS. So it all seems a bit dubious to me. May be the head is just a homologation part which was useful for the RSR but would require the RSR plenum/induction etc to take advantage of.

Were it my money I'd probably not bother...

jrgordonsenior

No comment on the head issue.....

Have you leaked the motor and if so, what were the results?
You probably have about 100 race hours on the motor (7500/75) which isn't unreasonable for these motors. Cups are known to go up to 200 hours brefore losing enough to require a rebuild though most tear them down around 120-150. A leakdown will confirm the need....

PS: I was looking forward to competing with you for that GTS4 title but my motor didn't want to play anymore....

Apex996

Perhaps try grabbing a copy of issue #009 of:
RACE ENGINE TECHNOLOGY 009
JULY/AUGUST 2005

If I recall there are a few articles in that issue about the boxer's evolution... w/ cool photos of the motorsport CNC porting.

996FLT6

Now I know the 6rs had the rear airscoops did it also have a different crankcase breather? 15 hp is plausible at the upper end. Mike

coryf

It sounds like the RS has the 997 cup heads. The difference in the 996 and 997 is the 7 has the smaller 12mm spark plug's and more porting to the intake side. I think the cup heads would be the same as the street heads. I believe we have both at the shop. I will try to take some pictures to show the difference. The intake runners are also port matched to the slightly larger opening.

The extra porting gives more power at the top of the rev range. On the same dyno, a 997 cup will make 15 or so more over 7200 rpm than a 996 with the same exhaust and mapping. The later dual resonance intake (like on the 997 street and 08 and later cup) will make even more gains up top.

IPguy

Can the 997 intake system be fitted to the 996? I would imagine so since the engines are nearly identical, but have not been there done that.