richard glickel.

Hey Geoffrey,

I think Jason managed to get the weight of his car down to approx 2500 lbs. At roughly 350 rwhp +/-, that would mean a power-to-weight ratio of about 7.14! His "at the crank" HP would, of course, be higher (like close to 390) and result in an even lower power-to-weight ratio, something like 6.4.

I need to take a look at the new PCA classifications.

Ciao!

BBailey

3.0L 8V turbo gets a 200 hp/L multiplier in the GT classes next season, so he'd slot in at an index of approximately 4.46 which classifies him in GT2, assuming car and driver at 2675 lbs.

He can shed another 120 lbs or so off the car and remain in that class, any more than that and he'd get bumped up to GT1.

Jason Judd

How much weight would I have to add to move up to GT3?

How does one compute that?

Thanks,

Jason

BBailey

A LOT unfortunately

Indices are as follows:

GT1 - 4.35 and below
GT2 - 4.26 to 5.50
GT3 - 5.51 to 6.75
GT4 - 6.76 to 8.25
GT5 - 8.26 to 9.75
GT6 - 9.76 and above

To figure the weight for your car for any class, take the power output per liter of displacement (in your case thats 200 hp/L for an 8V 4 cylinder Turbo) and multiply it by your displacement. Then take that number and multiply it by the corresponding index number (assuming you want to be at the top of GT2 its 4.26, at the top of GT3 its 5.51).

So for GT2 you get 600 * 4.26 = 2556 lbs
And for GT3 you get 600 * 5.51 + 3306 lbs

And thats car plus driver weight.

I'm thinking 3.0L 16V normally aspirated 4 cylinder 968 in GT4 with a fully built engine for myself. Will be nice to actually be able to competitively race a 4 cylinder normally aspirated Porsche with PCA in the GT classes for a change.

richard glickel.

Geoffrey/Brian,

I don't understand how this works at all. Let's use my N/A 968 for example. The car weighs approx. 3050 lbs. with me aboard (me = 185 lbs) (I have removed all ballast that I ran with this past season). Car was dyno'd @ 218 RWHP. I can run in SP3 (944 spec class), or what was "E" if I add the passenger's seat. How would I figure the proper GT class at 3050 lbs (w/ driver) & 218 RWHP?

Thanks.

Russ Murphy

Sounds like 3.0l*125hp/liter (for a 4 valve 4cyl. water cooler)=375 potential power output.

3050/375=8.133 Performance Index. Looks like you would slot into the bottom end of GT-4 currently.

Looks like you could run as light as 2535lbs and stay in GT-4

BBailey

Russ has it exactly right.

Actually power output is irrelavent. It's potential power output based on the guidelines in the rulebook that matter.

Eric_k

Another option would be to add 50lbs and run at the top of GT5 (3100/375=8.26). Then of course mod the crap out of the motor.

Geoffrey

Richard, the performance index is not based on the actual output of your engine, but rather the theoretical maximum HP/L for your engine type. So, you can change the displacement and add or subtract weight to move in and out of about two classes per car. Add weight to run in a lower class, remove weight to run in a higher class. Add displacement to run in a higher class or reduce displacement to run in a lower class.

You could for instance, reduce your displacement to say 2.8 by installing a shorter stroke crank and run at a weight that would allow your 968 to fit in GT4.

richard glickel.

Russ,

What exactly is "potential power output"? Certainly 375 isn't the potential HP for a normally aspirated 968 4 cylinder/3.0L engine. Is PPO simply a number arrived at through applying the formula for race ccar classification?

richard glickel.

Okay guys, I read the new rules and now I've got it. My car is borderline GT-4 or GT-5, depending upon the weight with driver. At 3050 lbs (w/driver) the car's index is 813, which is GT-4; add 50 lbs of ballast and the index becomes 826.6 which is GT-5.

But, how does one determine the relative benefits of running in any one of 3 different classes, viz., stock class, SP3 (944 class) or GT class?? E.g., in 2006 I raced in PCA "F" stock. Last year I participated in PCA SP3 (1 race only) and mostly ran in 944 SuperCup (NASA/PDA/EMRA). With a passenger's seat I could have run in PCA "E" stock in '07.

GT, SP3 or stock class; which would you choose?

993944S2

Hi Richard;

What class to run in?? I think the answer lies more in who do you want to drive against, what venue's do you want to run at, and what your schedule allows. If you have the ability to do 10 races each year then your I guess your question is more important.

Don

BBailey

I'll be running GT4 with my to be purchased 968. Will be nice to race a normally aspirated 4 cylinder water cooled Porsche with PCA in the GT classes and actually have a real shot at competitiveness.

So how hard do you think it'll be to get 375+ bhp out of the 16V 3.0L?

Jason Judd

So how hard do you think it'll be to get 375+ bhp out of the 16V 3.0L?
______________________

Brian,

To quote you from before...."A LOT unfortunately"...I think that's about what I put out with a turbocharger strapped to my 968.

Jason

Geoffrey

Richard, I don't think anyone knows yet as this is brand new. I think you can start with some assumptions, like running in a class with a performance index near the bottom is probably not as good as running with a performance index near the top. Changing weight is easy, changing engine displacement requires a committment, and at this point the competition is not known. You also need to look at your potential competition, for insance, in GT4. A 3.0l 911 running at 2250, a 3.4l 911 running at 2600lbs. You have to ask yourself, "do I think I can be competitive with those cars". Look back at some of the PCA race results and see where you'd fall in line. Personally, I think you'd be more competitive adding weight and running in GT5.

You'll definately have to rev the engine to get the HP.