PCA SDR

In the 2012 rules the primary determinant of base points is the ratio of pounds per horsepower.

I have done some math, and have come to the conclusion that the four-tenths (.4) mutliplier for weight reduction is excessive.

Comparing apples-to-apples: (using PCNA chart supplied in the rules)

2004 996 C2 is 3020 lbs, with 320 hp. This is 9.44 lbs per hp. Base points 440.
2004 996 GT3 is 3043 lbs, with 380 hp. This is 8.01 lbs per hp. Base points = 530.

If I wanted to strip weight out of a C2 to get down to 8.01 lbs/hp of a GT3, I would have to remove 460 lbs from the car. That comes out to 170 points, for a total points 600 – 2 classes away from GT3 base points.

Can a stripped down, but otherwise stock 996 be considered on par with a GT3, let alone 2 classes above?

Or, a 2011 Boxster Spyder versus a 2001 Boxster S
2001 986 S is 2850 lbs, with 250 hp. This is 11.4 lbs per hp. Base points 385.
2011 987 Spyder is 2811 lbs, with 320 hp. This is 8.78 lbs per hp. Base points = 515.

To get my ’01 Boxster S to 8.78 lbs/hp of a Spyder, I would have to remove 650 lbs from the car. That comes out to 240 points, for a total points 625 – also 2 classes away from Spyder base points.

And for apples-to-oranges:
To get my ’01 Boxster S to 8.01 lbs/hp of a GT3, I would have to remove 850 lbs from the car. That comes out to 320 points, for a total points 705 – 3 classes away from GT3 base points.

Basically, I would take a much bigger points hit to get my ’01 car to new Boxster Spyder specs than if I simply bought a new Spyder (I wish).

I think a .2 factor would be more appropriate.

This graph shows the problem -- http://www.flickr.com/photos/59095370@N07/5414591550/

X-axis = lbs/hp. Y-axis = points.

Blue diamonds: All cars listed in the rules are plotted as blue diamonds. The blue line shows the general population slope of lbs/hp versus points.

Red squares: My 986 S points for weigh reduction at @ .4 points/pound.

Green triangles: My 986 S points for weigh reduction @ .15 points/pound.

The difference in the slopes of the red and blue plots is quite dramatic. I would take a much bigger points hit to get my ’01 car to new Boxster Spyder specs than if I simply bought a new Spyder (I wish).

By, adjusting the penalty factor to .15, the slope/rate at which my points change more closely resembles the plot of the general population. However, since we don’t allow for adding weight to reduce points, we can only look at the data to the left of the intersection of lines. A two-tenths (.2) factor would bring the points assessments much closer to blue base points on the left side of the graph.

Mark, you have valid questions. The short answer is... it's complicated. For example: if you were to remove 850lbs and add a set of tires to your 2001 Boxster S it would easily destroy a stock GT3 on an AX course as this 99 2.5L has done many times:
http://www.6speedonline.com/forums/atta ... 1270507051
Even though your stripped 2000 lb car and the GT3 would have the same hp/wt ratio, you would weigh 1000 lbs less. A huge performance advantage. Weight reduction improves acceleration, braking distance, and cornering speeds. A hp increase only improves acceleration.

Agreed that cars with similar running weight AND similar hp/wt ratio should be classmates regardless of how they got there (weight reduction, motor transplant etc.). Develop a formula you think will work, test it with AX results over the next 6 months and present your findings to Z8 rules committee. Rules guys love real world data.

Mark

You are leaving out one huge factor.
When you remove 460 pounds from a C2 you are effectively making the engine, brakes and tires a minimum of 15% larger (more effective) and you have left this out of your equation. It is just physics, everything from the tires to the brakes to the suspension has 15% less work to do.

But you bring up another interesting topic.
Why is it the same point penalty to remove 400 pounds from a 3500 pound 928 as it is for a 2000 pound 912?
The 928 gets an 11% reduction and the 912 gets 20% for the same point penalty.
(Weights are off the top of my head for the iterest of making a point-close but not actual)

Just throwing another log on the fire...

Thanks for bring this one up

What I have been looking at for a proposal for 2012 would be to utilize the same formula for basepoints to determine your weight modification points.

Instead of using the PCNA weight, you would use your own (lower) weight in the equation and the difference between this number and your model's basepoints would be your modification points.

This would solve several issues people have brought up. Lowering your weight 200# in a 912 has a much greater impact on performance than the same 200# in a 928 or 996.

The details I am still looking at are how your weight is to be determined and how granular to make the point scale.
I think we now have it too complicated by allowing you to put back your tools, spare, fluids, etc. Very hard to enforce or measure well
I think your weight should be with a full tank of gasoline and ready to go to the track.

Instead of the free 50#, I would look at not having to take points until you reached 10 and then rounding down for each 10 point gap. This would allow some scale error without affecting points too much.
Have not tried playing with real numbers yet, but I think the concept is a much better way to go.

Greg

I disagree, our basically stock racecar weighs about 2650 dry, add the 50 pounds free, the ~35 lbs for spare tire, tools etc, 125 lbs for full tank of gas, that makes 2860 with a curb weight of 2905. So we don't have to take hardly any weight points and I just don't see a problem with that

Oh and yes, a 2500 lbs 996 will destroy a stock GT3 at most tracks.

Greg Phillips wrote:...What I have been looking at for a proposal for 2012 would be to utilize the same formula for basepoints to determine your weight modification points.

Instead of using the PCNA weight, you would use your own (lower) weight in the equation and the difference between this number and your model's basepoints would be your modification points.

Greg, sounds very interesting, but could you clarify the weight calculation approach you have in mind? Didn't quite follow it. Difference between track weight and basepoints?

Don Middleton wrote:

Greg Phillips wrote:...What I have been looking at for a proposal for 2012 would be to utilize the same formula for basepoints to determine your weight modification points.

Instead of using the PCNA weight, you would use your own (lower) weight in the equation and the difference between this number and your model's basepoints would be your modification points.

Greg, sounds very interesting, but could you clarify the weight calculation approach you have in mind? Didn't quite follow it. Difference between track weight and basepoints?

OK, maybe more than you were asking for: Here is the formula used for base points and the explanation from the GGR website where it was developed.
Step 1: Assigning "Initial Basepoints"
"Initial Basepoints" are assigned based on a formula using the car's power to weight ratio, model age and the width of its standard‐equipment wheels. A car's power to weight ratio (PW) is calculated by dividing the PCNA published curb weight (lbs.) of the model (equipped with a manual transmission) by its PCNA published horsepower. The calculated PW ratio is then used to determine the appropriate Initial Basepoints using the following formula:
(4000 / PW) + (year of model introduction ‐ 2010) + (5 x (width in inches of one front + one rear standard‐equipment wheel ‐ 12 )) = Initial Basepoints
Explanation: This formula takes the inverse of the PW ratio and multiplies it by 4000 (creating a steepening curve that assigns progressively higher and higher basepoints for each incremental improvement in PW ratio, then subtracts one point for each year since the model's introduction prior to 2010 (to grant a modest discount for age and, in future years, assign one additional basepoint per year for models introduced after 2010), and then adds 5 points for each inch greater than 12 of the car model’s standard‐equipment wheel‐widths (this serves as a rough proxy to capture design and performance advantages inherent to models that were engineered to utilize wider wheels, and conversely the limitations of vehicles designed to use narrower wheels).

For the weight points, decreasing the weight would only change the PW or power to weight ratio, so the difference between the basepoints and the greater points with a better PW number would be your weight points penalty.

Assume a 911 SC with 172 hp and 2552 # PCNA weight, this would give a PW=14.8. 4000/14.8= 270
Since the rest of the equation will stay the same this is the only part of the equation we need to deal with.
Now if you have your weight down to 2408 then your PW would =14 and 4000/14= 285.7 So 285.7-270=15.7 points attributable to your weight loss, depending on how much rounding we might consider from 10-20 points as the weight penalty.

As an aside and another related topic, a similar method could be used for stock engine swaps, but instead of changing to a lower weight, you now would have a greater amount of power which would also change your PW in the calculation.
Again taking the SC, if you put in a stock 964 3.6 with 250 hp, your PW would be 2552/250= 10.2 4000/10.2=392 392-270=122 points for your engine swap penalty.

Greg

Jad wrote: stock racecar

??? I've never seen a "stock racecar" wasn't that car in a professional race series in a previous life?

davidsq wrote:

"stock racecar"

BUMP

I will only give that he has a crate motor with stock internals and a stock transmission.
The rest has been modified slightly, although he may still have a license plate somewhere

Not sure the Koni Challenge completely qualifies for a professional series.

Greg

OK, so the irony may have been lost on some, but weight reduction is really the biggest mod in our car, though the current system penalizes the aero, springs, shocks and swaybars more. I am not opening the tire can of worms, but feel tire points should be about double what they currently are.

I never understood the free 50lbs or the put the spare, tools etc back. It should be, how does your car compare to the stock weight. Keep it simple, otherwise, what about 997 without spares? What about the 100 lbs steel truck tire I use as a spare, or the awesome set of lead tools that came with the car......

While this may not help our 'stock' car, I do think the weight should be more of a penalty when we have removed virtually everything to reach our current weight and other stripped cars should also be penalized.

By the way, compare my time at the last TT in a stock 996 with aero, springs, shocks and swaybars to the GT3's to see how the cars compare....

I am just curious here, can someone tell me if the curb weight of my 04 GT3 at 3043 lbs, does that include a full tank of gas? Steve? Greg?

Angela

The weight you posted for the GT3 sounds like a low fuel weight, sans tool kit etc.

Aavitt wrote:I am just curious here, can someone tell me if the curb weight of my 04 GT3 at 3043 lbs, does that include a full tank of gas? Steve? Greg?

Angela,

The 3043 lb. figure is what the 2012 rulebook declares as the "curb weight" for a 996 GT3. Curb weight is defined as the weight of the base car as listed in the chart in Section XVIII Appendix C. It is what you use to calculate any modification points you need to take for weight reduction. The first 50 pound reduction in weight is zero points. Beyond that, points are determined by multiplying the reduction in weight by .40 and rounding up to the nearest multiple of 10. The rules state: "For weighing, the car should be ready to drive with all fluids (gas, oil, etc) full, tools, spare tire, jack, etc in the car but no driver. These items do not have to be in the car or fluids full while participating in the event. Anything removed for purposes of Section XIII Part M may be replaced and all fluids may be topped off, as needed, before weighing."

Thus, the "target" number to avoid any mod points for your car is actually 3043 - 50 = 2993 lbs. If you put the spare tire in, w/ tool kit, jack, fill up all fluids, and the car weighs more than 2993 lbs. (without driver), you do not need to take any points for weight reduction. Anything less, and you do (calculated according to the formula above). When running in the event, those items can be removed, and you can run with a 1/4 tank of gas if you want, so your "on track" weight can actually be considerably less than 2993 and be perfectly legal without taking any weight reduction point penalty.

Hope that's clear enough,
TT