Rule Change #5: Touring Class Vehicle Base Class Adjustments, BMW e90/92/93 3series non-M

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Dtangard
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Rule Change #5: Touring Class Vehicle Base Class Adjustments, BMW e90/92/93 3series non-M

Post by Dtangard » Wed Nov 21, 2018 6:57 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.
Next, the BMW 3-series e90/92/93, particularly Serv’s setup, was noted to be particularly fast, grabbing victories against long-standing COM winners at Tremblant and Watkins. In looking at the base class list, there actually appears to be an oversight: the e46 3-series non-M has a performance adjustment of +3.3, but the e90 only has +1.7. While the e90 non-M isn’t necessarily a more capable chassis than the e46, it is certainly no less of a platform.
If the e46 and e90 non-M platforms were made to be equivalent (adding 1.7 points to the e90 to bring the Performance Adjustment up to +3.3) and if the RE71R adjustment passes (another +2.0 points), then Sherv would have 3.7 points added to his setup. Based on the laptime benchmark, this would be ~1s at Tremblant and ~1.2s at Watkins. In terms of weight penalty, this would be about 200lb. With these changes, Sherv would have likely finished just behind Lemoine at Tremblant and Watkins, and in both cases and would have fallen even further behind at the New England tracks.
To me, the addition of 3.7 points already feels about right, maybe even a tick heavy, especially given that the driver deserves some recognition. Sherv was one of the most active participants, and a competitive finisher, in the COM Winter iRacing league. Combined with soliciting advanced coaching at every event, Sherv is working his way up the steep part of the learning curve on iRacing, and his best finish of the winter season was a podium at Watkins Glen in a field of over 20 racers. Sherv lost at the local twisty tracks. At some longer tracks the heavier, higher hp cars are going to walk away, but at other shorter tracks (especially the ones that make up the majority of the COM calendar) they’ll never be able to hang. In COM, this debate has ebbed and flowed over the years (probably indicating that we’re not that far off) between “street cars are no match for lightweight race cars with cages” and “no way my little momentum car can keep up with something that fast in a straight line”.
Currently, the BMW 3-series e90/92/93 non-M has a Subjective Performance Assessment of +1.7
Proposal 5: Change the Subjective Performance Assessment of the BMW 3-series e90/92/93 non-M to +3.3
Derek
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1995 Miata

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