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AFT's Traction Control Era Begins

Indian's total dominance of the AFT era of pro flat track dates back to round 1 of the 2017 season. In that time there have been 69 AFT Twins/ SuperTwins races. Of those 69, Indian has won 62, a win percentage of 90%. Kawasaki has won 4 races (3 of those were TTs); Yamaha have won 2 (both TTs), Harley has won one (Carver's Texas HM on a private XR750).

Such has been the FTR's dominance that AFT has introduced the Production Twins class to, among other considerations, give other manufacturers a look in, and now, after lobbying, we're told, from the Estenson Yamaha SuperTwins team, they have introduced traction control. The new rule states:

Engine Control System/Electronics/Traction Control

a. Production (Street Bike) Engines:

i. Wheel, transmission or countershaft speed, chassis attitude or location sensors that provide information to the ECU are permitted.

b. Race-Only Engines: c. Vehicle speed, chassis dynamic or location sensors to include but not limited to wheel, transmission, countershaft speeds, GPS or other sensors that provide information to the ECU to facilitate any means of electronic control of engine output or brake systems are prohibited. The Engine Control Unit (ECU) that comes on the homologated motorcycle or engine may be used. The use of non-standard/aftermarket ECUs must be approved in writing by AMA Pro Racing. Approved non-standard/ aftermarket ECUs will be listed on the Approved Engine Controller List on the AMA Pro Racing website.

d. Only OEM engine sensors may be used to provide input to the ECU unless otherwise approved.

e. The software in ECUs may only be modified to affect spark and fuel table control, as well as data logging.

Another section of the AMA AFT Rulebook states:

vi. Production (Street Bike) Engines: any type of electronic throttle control or fly-by-wire, secondary throttle plates or other such induction controlling devices is permitted.

vii. Race-Only Engines: in all cases, any type of electronic throttle control or fly-by-wire, secondary throttle plates or other such induction controlling devices are prohibited. The rider must have uninterrupted mechanical connection via traditional cables from handlebar to the induction components.

With Volusia's test day today, we have had our first glimpse of the systems, thanks to contributor Sammy Sabedra.

This photo and the one at the top of the post show JD Beach's Estenson Yamaha MT-07. The small discs bolted to the hubs are read by a sensor, seen behind the wheel spindle. Why it has two, we're not yet sure. The rear wheel will have another sensor to allow front and rear wheel speed to be compared. The blue component, that looks like a car hatchback damper strut, is a potentiometer that measures fork extension.

In very simple terms, the bike's engine management system compares the front and rear wheel speeds, using the data from the blue potentiometer to determine if the front wheel has slowed down due to a wheelie. It also takes in throttle position data, then compares the information to decide if it should cut power to the rear wheel because it's spinning up and breaking traction and adversely affecting the lap time.

The team has to programme the system to know the difference between the spinning the rider wants, and is helping him turn, and the wheelspin he doesn't want, because it's spinning up off the corner, because the revs has risen to quickly and the rear tyre can't find traction, so the bike isn't driving down the straightaway. I'm guessing it'll be clever use GPS positioning and track maps, but I have no idea how that could be programmed in, especially as track conditions differ through the race, never mind through the day-long event.

JD Beach has extensive road race experience, so he'll be more conversant with traction control (T/C) that any other rider in the paddock, perhaps barring James Rispoli.

My question is, how do the systems know when a rider is deep in the cushion, looking for another line, or hard on the gas, turning the bike up the inside of another rider? How does it determine when it should or shouldn't second guess his throttle commands? In a sport rooted in spinning and sliding it seems a tricky thing to sort, but not impossible, MotoGP has solved it. They too spin the rear to turn, and have T/C that riders rely on, but tarmac is different to dirt. Even Florida dirt is different to Ohio dirt is different to Illinois dirt...

This image is interesting for a few of different reasons. One, it's Gauthier's bike, and it has T/C, but Gauthier was confirmed as a Production Twins rider and that class isn't allowed T/C. So is Gauthier riding SuperTwins now?

Also, Sammy, who took the photos, says the T/C sensor disc is a mountain bike brake disc (though I'm not sure. It looks a lot like a road motorcycle ABS sensor to me).

Only road bike derived engines are allowed T/C, to give them some advantage the FTRs don't. We spoke to a highly-respected former team owner and he told us that he was sceptical about T/C making much difference to the FTR's win rate, and that the FTR's advantage comes from its comparatively large crank weight and inertia, giving it superior drive off the corners, compared to the lighter, revvier, road bikes engines. It's not just the weight of the crank, but also its diameter that helps. This weight and diameter of crank flywheels is a fundamental of the design that was shared by the XR750 and the Honda RS750.

This photo shows Gauthier's 79 on a black plate Production Twin and a white plate SuperTwin. The final entry list hasn't been confirmed so we don't know if this is just for testing or what, but it is intriguing.

Are AFT going to allow riders to race two classes, at the last minute, after recently changing their rules to limit all riders to just one class? We might find out tomorrow, Volusia H-M, AFT 2021 round one.

All photos: Sammy Sabedra and not for use with permission.


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