Can You Shed Some Light On The BRI For New Classes?

[brilliantrot]

So I was looking over the BRI for the new classes as my new car fits into the newly created OM class and I am left a bit confused. All of the mod (M) classes still flow into AR1 and then AR2 yet these are the BRI correction factors listed.

Class Autocross Time Trial
AR1 (1.130) (1.182)
AR2 (1.155) (1.222)
OM (1.165) (1.202)

Anybody else see the issue with this? I hope is it just a typo of some sort but if not sure would make a good excuse for needing 20 more points in mods so I can correct out better .

-Evan

[ttweed]

Ya, Evan, that looks like a mistake. When classes get added each year and cars reshuffled, the BRI often gets modified as an afterthought. Something must have happened too quickly without adequate review, because there should be a steady progression upward with improvements. It doesn't make sense that a lower class should start higher than a class it merges into when improved further, so the BRI for OM is an anomaly in the current listing.

TT

[Otto]

Tom:

You are correct Tom. The most advanced classes AR1 and AR2 should have the highest factors. Can you suggest corrected factors looking at the overall situation? You are very knowledgeable about the cars involved and the BRI philosophy.

[tb911]

When new classes are created, and cars are shuffled around, I generally look at the old numbers, where those cars used to be, where they are now and as necessary do some interpolation between the classes to come up with the new numbers. Certainly doesn't mean I get it right. Especially as Porsche keeps popping out new models. Appreciate the heads up that their may be an issue here, I'll go fuss with the numbers again. Of course, all of this is so rough, one must remember that this is just fodder for conversation, as is stated on the BRI page. It isn't realistic to expect these numbers to truly equalize the classes across the board.

Case in point, the Time Trial numbers have never been adjusted since their first inception. Other than my tweeks for class changes and new car models, they have not changed since day one. In contrast, every other year or so, the autocross team does a performance analysis of the last few seasons and tries to adjust the numbers to improve the system based on our actual event results. Again, don't expect to much from all this, but at least on the autocross side things are evolving based on our experience.

Again, thanks for the heads up, I'll see what I can do.

[brilliantrot]

Just though I would see what the case was, and I appreciate you looking at it. I am well aware that it is rough estimate and was on the receiving end of a good correction factor with my last car (AI 914). Having come from sail boat racing I am fairly used to the handicap format and even there, it is never quite right because there are just too many unknowns and manufacturers that try to get good ratings for their boats . Another couple of classes that might warrant a review are RP and QI as they currently have the same or higher correction factors than AR1 for autocross.

Thanks for being so on top of it,
Evan

[tb911]

I think I see what has happened over the years. When we first started the BRI (2002) base classes only went up to N. Since then we've added O, P, Q and now R.
Each time we added a base class, as I said above, I just whipped out my calculator and added what I thought seemed the right amount to go from NSS to OSS to PSS to QSS and now to RSS. After moving up, I'd have to move right. From OSS to OS to OP to OI, etc. I just kept adding up numbers and plopping them on the chart.

It all seemed reasonable from the point of view of the new cars. After all, a new GT3 blows the doors off of a 964, and so on. So I went up the left side and across the top, but what slipped my mind was that the chart goes back down on the right side, as you move towards AR-1 and AR-2. So the numbers in the higher classes got closer and closer to the BRI for AR1 and AR2. And they in fact passed them, and not this year either. It was last year or maybe even earlier (I didn't try to find the history of when it first happened.)

You are just the first to notice. I think that is because most cars with more than 20 points and especially with more than 40 points, are older cars. 911 E, T, S, SC; 914, etc. In other words, it didn't matter, as no newer cars where playing that game.

And like I said, the autocross team has been periodically adjusting the numbers to fit the results we see at our events. The last time they did this was January of 2009. As of then, the BRI numbers actually fit the race results we were seeing, even if they seem skewed when looking at the chart. Consequently, until we see 996, 997, Boxsters and Caymans running in AR-1 & AR-2, I'm not sure I should change anything. Fixing the BRI to handle them will place the older cars in AR-1 and AR-2 at a real disadvantage. Actually, we probably need an LR-1 and an LR-2 anyway. Separate the old from the new. After all, even if they are both in AR-2, a 90 point 911S and a 90 point GT3 are never going to be equal cars....

(Also keep in mind that other than my adding new classes, the Time Trial BRI is identical to the first time we used it. No re-evaluation has ever been done since it's initial creation.)

In summary, I think we need to let another year pass to get some experience with the new classes and then maybe the autocross team will re-evaluate the BRI. Until then, I don't know if anything really needs to be changed.

Thoughts?

[ttweed]

Actually, we probably need an LR-1 and an LR-2 anyway. Separate the old from the new. After all, even if they are both in AR-2, a 90 point 911S and a 90 point GT3 are never going to be equal cars....

I think this is probably true, Tom. As the newer cars depreciate and people are willing to hack them up and modify them further, the R class should probably be split. The older torsion-bar cars would have to start with many points worth of mods (a tube frame and sophisticated coil-over suspension to start) just to get close to the same beginning platform of the modern cars. Of course, the newer cars would have to have 3-500 lbs. stripped out of them to get to an equal starting weight, so that might make up some of the difference, if the weight reduction rule remains as it is.

My first reaction to this discrepancy was that the OM index was set too high, but it may be that we haven't raised the AR classes sufficiently as well, to reflect the possible development of cars from the newer classes.

TT

[LUCKY DAVE]

TB, how about posting the old/new BRI chart so we can easily see what the changes are?

[tb911]

TB, how about posting the old/new BRI chart so we can easily see what the changes are?

Done

Check it out here: http://www.pcasdr.org/porsche_events/track_events/bench_racers/index.php

In doing this little project, I did notice that the Time Trial BRI was updated in 2006. Not as long ago as I thought and mentioned previously. Sorry for the misinformation.

[LUCKY DAVE]

Thanks, Tom.
I guess my rating hasn't changed after all. The mind is the second thing to go.......

[gocart]

tb911 wrote:Actually, we probably need an LR-1 and an LR-2 anyway. Separate the old from the new. After all, even if they are both in AR-2, a 90 point 911S and a 90 point GT3 are never going to be equal cars....


I think this is probably true, Tom. As the newer cars depreciate and people are willing to hack them up and modify them further, the R class should probably be split. The older torsion-bar cars would have to start with many points worth of mods (a tube frame and sophisticated coil-over suspension to start) just to get close to the same beginning platform of the modern cars. Of course, the newer cars would have to have 3-500 lbs. stripped out of them to get to an equal starting weight, so that might make up some of the difference, if the weight reduction rule remains as it is.

This brings up a point that has annoyed me, and I'm sure the owners of most older cars. That is, one can put 30 to 40 points into an older 911 (one older than '78) and still only be equal in performance to say a "stock" 911 SC. You'd be in modified before you could be on equal footing with a 3.2 Carrera.

For example, to get my '71 911's motor up to 180HP costs TEN points. FIVE points for PORTED heads!

Then the penalty for weight removal. My car is 175lbs lighter, that's EIGHT points! Heck, that's just the weight of a passenger.

On the other hand, exhaust is free. That doesn't help an older car with it's already efficient exhaust, but on a 3.2 Carrera headers make a noticeable improvement.

If I was starting new, the 3.2 Carrera would look like the sweet spot.

Sorry to hijack, maybe this should be another thread...

... and why isn't there an FM?

[mrondeau]

[

... and why isn't there an FM?

There is. It's the dial thing above the slot for your 8-Track player.