Turbocharged cars competing in IMSA’s WeatherTech SportsCar Championship will no longer rely solely on sonic air restrictors to manage power levels. In place of the physical restrictors that governed turbo power and torque through 2015, IMSA is switching to the ACO/FIA’s preferred method of electronic boost mapping for the cars that run under ACO/FIA technical specifications.

With boost mapping, IMSA can tailor boost pressure throughout a turbocharged engine’s rev range – and in each gear – to achieve specific power and torque output. The new electronic management system should allow IMSA to increase parity with non-turbo cars by limiting the torque and top speed advantages offered by turbo motors.

“For 2016, and in following and adopting the ACO/FIA technical regulations, we’ve gone away from sonic restrictors for boosted cars in GT Le Mans and in GT Daytona with GT3 cars,” IMSA technical committee chairperson Geoff Carter told RACER. “We will run those cars sans restrictor, and will be issuing, as part of the BoP (Balance of Performance), RPM-specific boost limits. Those will be monitored with an independent, IMSA-mandated scrutineering logger. That will be announced in the next week or so.”

Some turbocharged cars in IMSA’s Prototype category, which do not necessarily comply to every level of ACO/FIA governance, will also switch to the electronic power management system.

“We’ll do the same with Prototype on some cars; the Mazda still has a restrictor, but will use RPM-specific boost table and could go away from its restrictor at some point,” Carter continued. “The Honda turbo is a little bit different, and doesn’t require sonic restrictors, so it will run without them at the next test we have planned. We’ll do an RPM-specific boost table there, too, and gather data.”

In a final note of interest, IMSA has discontinued the use of “Adjustment of Performance” (AoP), and will use the standardized “Balance of Performance” (BoP) going forward.