Rule Change #4: Touring Class Vehicle Base Class Adjustments, FT86

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Rule Change #4: Touring Class Vehicle Base Class Adjustments, FT86

Post by Dtangard » Wed Nov 21, 2018 6:56 pm

Touring Class vehicles receive a Showroom Assessment, aka “base classing”, based on the vehicle’s power-to-weight ratio (using factory-advertised horsepower, torque, and curb weight specs). In addition, a subjective Performance Adjustment Factor is included. This adjustment factor compensates for any cumulative non-power-to-weight advantages or disadvantages (e.g., aero properties, chassis dynamics, drivetrain, driver aids, etc.) related to potential on-track performance. Because power-to-weight is calculated and non-negotiable, the subjective Performance Adjustment Factor is the only way to adjust for unbalanced potential vehicle performance in the Touring Classes.

Since the Touring Classes launched in 2013, rarely have any vehicles been “way off” – exceptions are typically limited to newer vehicles, which were added after the Touring Class vehicle Subjective Performance Assessments were directly translated from CASC, a well-established professional racing organization in Canada. Many 1990’s to 2010’s sports cars that are popular at COMSCC events have a performance adjustment that range +/- 4-7 point, typically between +0.0 and +10.0. It can be helpful to get a sense for assessments across a range of relatively popular and competitive, yet non-controversial vehicles:
• -5.0 Ford Mustang Fox Body
• -3.3 Honda Civic DX
• -1.7 VW GTi Mk4
• +0.0 Nissan Sentra SE-R
• +1.7 Mazda NA/NB Miata
• +3.3 Mini Cooper S
• +5.0 Lotus Elise
• +6.7 Porsche Cayman (base or S)
• +8.3 BMW M2
• +10.0 C5 Chevy Corvette Z06
• +11.7 Porsche 911 (997) GT3 RS
• +13.3 C7 Chevy Corvette Z06 (non-aero pack)
• +15.0 1st Generation Nissan GT-R

Another helpful tool is the laptime-per-touring-class-point approximation. In 2017, when overhauling the Touring Class Tire Compound assessments, a benchmark was used that is still helpful and has proven to be a good measuring tool: Touring classes vary in performance potential by ~2.5% per class. This works out to just under 2 seconds per class at NHMS, or about 0.2 seconds per point. At Watkins Glen, the spread in-between classes is between 3-3.5 seconds, or about 0.33 seconds/point. Similarly, relative point values can be considered in terms of a hypothetical weight penalty. All things being equal, 1 point is equivalent to a 1.5% change in weight relative to the factory curb weight – this works out to 36lb/point for a 2,400lb car, 47lb/point for a 3,100lb car, 57lb/point for a 3,800lb car, etc.

With that said, there are 2 Touring Class vehicles that stood out in 2018: FT86 (BRZ/FR-S) and BMW 3-series (e90/92/93) non-M. The first thing to note is that one of the flying 86s and the e90 were both on RE71R tires, which are subject to the proposed +2.0 bump mentioned above.

In regards to the FT86, the top 2 T40 competitors were driving at a high-level all season. Tight finishes, nearly identical platforms, and seriously competitive attitudes combined to produce one of, if not the most impressive 2-competitor Class Championship battle that I’ve seen in my 10 seasons with the club. Sash is an established competitive karter and now avid all-around racer, and he has taken full advantage of learning and development opportunities at events…more than any other driver in the club. Club members who have been around for a while already know Dan as a gifted driver. He is probably the fastest COMSCC driver ever that no one’s heard of because he’s always driven clapped-out POSs on bad tires…until now. Dan is also one of the only instructors who regularly takes advantage of driver development opportunities within the club. In my view, the 2 hardest working, gifted, and overall fastest drivers in T40 took the top 2 spots in 2018.

However…the margin of victory ahead of veteran T40 competitors and relative laptimes compared to T50 merits another look. Using the example of me versus Dan at NHMS-2: I drove a 59+ point NB Miata in T50 and finished with a 1:19.7. Dan’s official TT result is slower because the 3rd lap was dropped due to a shortened Time Trial. However, Dan’s 3rd lap was actually a 1:19.8. Given the general metric that Touring Classes should be ~2 seconds apart at NHMS, how is it that a T40 car has essentially matched a T50 car?
• The first factor is driver. I spent a good amount of time driving near Dan on-track in practice, and it looked like he was getting everything out of his car all day, just like he was a few weeks earlier at Watkins. He was also abusing his instructor privileges and driving in every group on Sunday morning to get up to speed for the TT. I would consider Dan a peer in ability and believe his TT performance on that day was as good as anything I could produce. On that same day, however, I’m pretty sure I left 0.3 – 0.5 seconds on the table in my own TT due to overheated the tires with a couple big mistakes on lap 2.
• The next factor is quality of setup– Dan’s car is brand new and has street tires that are always in the sweet spot of grip. Given that he comes in at 49.9 points, I would consider his setup 100% optimized to the rules. Mine is not – my car has well-used shocks, I’m using SM spring rates instead of taking advantage of stiffer springs for 0 points, my car is still bent from Watkins (I can get over 4 degrees negative camber in the back if I’d like), and I’m using R7 tires that, while still “good”, were not new. All-in-all, for a Miata none of these makes a huge difference, but I’d guess this resulted in ~0.5s a gap off of an “optimal” setup.
• That doesn’t account for everything… Between leaving some time on the table with my drive and the setup, and assuming the track remains just as insanely fast as it was that weekend with cool weather and good grip…I believe a high 1:18 is theoretically possible in T50. If you assume just under 2 seconds per class at NHMS, then T40 should just be breaking into the 1:20’s, and Dan’s setup put him into the 1:19’s, about 1.0 seconds faster than the theoretical benchmark.
So overall, if Dan’s BRZ is ~1.0 seconds “too fast”, how many points should be added? According to the NHMS laptime/point conversion, 5.0 points should be added to Dan’s total setup. If the RE71R rule change passes, 2.0 points will already be added to the setup. This means that ~3.0 points should be added to the car in order to bring the entire setup back into line. A final note, Dan’s BRZ includes the Performance Package and Sash’s does not. Based on the upgrades included in the Performance Package (Car and Driver’s write-up does a good job of laying them out: ... ive-review), it seems that a small differentiation in base class between the base model and Performance Package is warranted.
Currently, the FT86 has a Subjective Performance Assessment of +3.3
Proposal 4: Change the Subjective Performance Assessment of the FT86 base model to +5.0, Performance Package to +6

Combined with the proposal to add 2 points to the RE71R, 4.7 points would be added to Dan’s setup, and 1.7 points would be added to Sash’s. At the final NHMS event, Dan was 1.0 seconds faster than Sash - the 3 points net penalty added to Dan’s car would theoretically close that lap time gap to 4 tenths.
#01 T40
1995 Miata


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