[old worker]

Picked up a 964/993 car that ran GT1R. I replaced the turbo with a 3.6 964 engine ( cup flywheel / chip ) 2556 pounds. would it run in GT3?

thanks

[Dr K]

I'm not sure, but let me take it out at Summit Point this weekend, and I'll tell you what I think

Sounds like a blast at 2556 lbs!

[good hands]

Seems pretty simple to figure out.

Classes GT-1 through GT-6

GT cars will be classified by calculating a “performance index.” The performance index applies the same principle of classification as

used for the stock classes, which is weight/horsepower. The formula is:

Performance Index [PI] = (Weight/[Displacement [D] x Horsepower/Liter for engine type] [T]) x 100

Transposing terms when you know your engine and the class you want to run in gives this:

Minimum weight for your car in your class = (minimum class PI x D x T) /100.

There are 16 engine types. Displacement in the formula is the exact displacement of the engine to the nearest thousandth of a

liter. The weight in the formula includes car, driver and driver gear. The table below provides the HP/L for your engine type to

calculate the Performance Index or minimum class weight for your car:

Engine Type (T) HP/L

4 cyl air cooled 90

4 cyl air cooled turbo 150

6 cyl air cooled 110

6 cyl air cooled turbo 210

4 cyl 2 valve water cooled 100

4 cyl 2 valve water cooled turbo 185

4 cyl 4 valve water cooled 115

4 cyl 4 valve water cooled turbo 230

6 cyl 986-based (M96 engine, any chassis) 135

6 cyl 987-based (M97 engine, any chassis) 140

6 cyl GT3 with single throttle 165

6 cyl GT3 with six throttle bodies 175

6 cyl water cooled turbo (any chassis) 240

8 cyl 2 valve 90

8 cyl 2 valve turbo 145

8 cyl 4 valve 100

8 cyl 4 valve turbo 165

Classification is as follows:

Performance Index (PI) Class

425 and below GT-1

426 to 550 GT-2

551 to 675 GT-3

676 to 825 GT-4

826 to 975 GT-5

976 and above GT-6

•

It is permissible to add ballast to change one class only. Ballast is defined as removable weight bolted into the car solely

to achieve a target weight. Ballast may be placed anywhere in the car so long as it is appropriately and adequately

secured.

•

Cars not on DOT or equivalent approved tires must add an additional 50 pounds to their formula based minimum class

weight.

•

GT class, engine displacement, engine type and minimum weight must be written in the car’s log book on the inside

cover.

2014

[Carrera51]

Depending on the power to weight ration, PCA 3S or 4S. There a plenty of 3.6 powered cars in 4S. Dyno it, weigh it, and go from there.

[good hands]

Originally Posted by Carrera51

Depending on the power to weight ration, PCA 3S or 4S. There a plenty of 3.6 powered cars in 4S. Dyno it, weigh it, and go from there.

No more S and R any more. Tires are free. One GT class now.

[Vicegrip]

Dyno it?