GT3 engine question

[blue72s]

Hello,

Is GT3 engine partially or fully watercooled? I'm confused because GT3 uses bottom end from the 964/993 which were fully aircooled..

I read that 997 and Cayman engine blocks have integrated oil and water channels with no external hoses, and integrated dry sump. But GT3 no?

If 964/993 block is much better, then why are Porsche using different and less reliable blocks for 997 and Caymans?

[PorscheGuy79]

I believe that the GT3 is an air cooled with water cooled heads...but I dont know much.

[Bill Verburg]

cylinders and head are the parts that are water cooled, just like on all other water cooled engines.

The GT3 uses a dry sump bottom end developed from the air cooled 911 engines. That is the design feature that is unique to GT3 and late turbos.

The normal 996 and 997 is water cooled and wet sump

[randywebb]

... despite P AG's claim that they are not wet sump, but are instead an "integrated sump"....


Bill, is the case design stronger also?

[Bill Verburg]

I suspect so but really have no idea. The 996 rear main area is said to be very flexible and the source of at least some of the 996 RMS problems that have been reported.

[blue72s]

Originally posted by Bill Verburg
cylinders and head are the parts that are water cooled, just like on all other water cooled engines.

OK thanks.

Specification of the latest GT3 engine from Excellance mag:

The motor that answers the call is once again based on the race-proven Hans Mezger-designed GT1 block. All previous GT3s have used the same 3600-cc displacement with a 100-mm bore and 96.4-mm stroke, but connecting-rod lengths varied between each generation. Without changing bore or stroke, Porsche AG stretched the connecting rods between the 1999 and 2004 GT3s from 128.5 mm to 130 mm. Why? To reduce their thrust angle. The latest incarnation of this motor features a further reduction in thrust angle for the even higher-revving 997 GT3 motor, with the light and incredibly strong titanium rods now measuring 131.5 mm.

The matching pistons are even shorter and lighter than before and use a new ring system to keep them stable in the bores. The piston-crown shape has been modified slightly to bring the compression ratio up from 11.7:1 to an incredible 12.0:1. The crankshaft benefits from a re-profiling of its counterweights, but its main bearings are identical to those in previous GT3s. At the top-end of the motor, the camshafts are hollow to save weight. The hydraulic lifters have been upgraded for higher valve-lift and higher-rev capability, while the tops of the bucket tappets spread to make the travel of the cam lobes longer, thereby reducing forces on the valvetrain. An all-new resonance intake system uses two separate throttle flaps to create three different intake lengths to enhance power and torque — dependent upon rpm and load. The GT3’s throttle body has been increased in diameter from 76 to 82 mm to get more air into the motor, faster.

Doing the same is a refinement on the ram-air rear engine lid concept found on the European 996 GT3 RS street car. The 997 GT3 lid’s aerodynamics were honed through hours of work in Porsche’s wind tunnel. Two scoops, rather than the single scoop used on the GT3 RS, promote a ram-air effect to the air-filter housing, which uses the same filter element. The effect of the air pressure between the wing and engine cover in the single scoop on the old GT3 RS promoted a 15-hp increase at high speeds. This is now closer to 20 bhp in the new car. Preuninger says the airflow created between the two halves of the new, Gurney Flap-equipped rear spoiler further increases over-pressure on the twin intake slots of the new GT3.

“We had between 20 and 25 millibar of over-pressure on the GT3 RS, and now we have between 25 and 30 millibar,” he explains. “The exact figure depends on the angle of attack set on the top wing, where the first position is set for road use and top speed and the second for track work with maximum downforce.”

More intake air and improved combustion efficiency meant a better exhaust system was needed to take full advantage of the changes. The engineers designed a totally new, three-chamber exhaust system with 8.5 liters more internal volume across two longitudinal silencers and one laterally disposed. Besides its weight savings, this new system boasts 25 percent less back-pressure.

The Bosch Motronic engine management has been mapped to suit, with more aggressive ignition timing than before. The GT3 is designed to run on Europe’s 95-octane fuel, but Porsche admits that optimum performance requires Europe’s 98-octane gas. With the right fuel, the GT3’s numbers are spectacular: 415 bhp at 7600 rpm — well before a redline set at 8400 rpm. This means a specific output of 115.3 bhp per liter, one of the highest numbers ever for a tractable, street-legal, normally-aspirated engine. Maximum torque is 298 lb-ft at 5500 rpm.


How much is a new complete GT3 engine ?

[PorscheGuy79]

Originally posted by blue72s

How much is a new complete GT3 engine ?

Top Gear mentioned something about 40 grand...

[blue72s]

GBP or Dollars?

[tshih]

If 964/993 block is much better, then why are Porsche using different and less reliable blocks for 997 and Caymans?


Porsche has decided to earn money first by selling cheaper to manufacture products. They probably feel (correctly) that the new Porsche owners will not be racing the normal 911, Boxster lines, or even Cayman derivatives. They figured that the true hardcore racers will be satisfied by the GT3 and since the number of those are much smaller percentage of the market then the best strategy is to sell a cheaper 911 variant with all the marketting image earned from history and keep the company financially successful (#1 most profitable car producing company).