IMSA’s balancing act

July 5, 2016

IMSA’s balancing act

July 5, 2016


The toughest job in motorsports isn’t making the call on whether to pit or stay out, or fending off a quicker rival late in a race. It is making the technical rules and establishing what competitors grumblingly refer to as “Balance of Performance” (BoP).

It is certainly a thankless job and, as Geoff Carter, IMSA WeatherTech SportsCar Championship Senior Series and Technical Manager, explains – this is not your father’s “BoP.”


What is BoP, or “Balance of Performance?” What is the purpose?

Our Balance of Performance programs started 10-12 years ago to allow different platforms and equipment to compete on a more equal basis.


gtlm_carsWhat is the process?

We test the cars before they begin competition. The GT Le Mans cars are also tested at Ladoux, the Michelin technical center in France where ACO does its tests. All of the GTLMs also went to the Windshear wind tunnel in North Carolina to assess aero lift over drag.

We also took engines from each GTLM and GT Daytona manufacturer to the NASCAR R&D dyno to measure power and torque. We try to adjust to make all cars the same weight and have comparable power and torque.


What levers can you use to adjust performance?

Our main tools are vehicle mass, air restrictors, different aero, RPM and RPM specific boost levels.


Do you have a target range of performance?

For the GT cars our target is to get the cars within 0.3 percent, so on a 100 second lap they would be within 3 tenths of a second. We also look for a stratification between the classes.


What can you see now that surprised the teams?

If teams try to give themselves a “push to pass” capability we can see that in the sector times and the exhaust gas temperatures.


Porsche North America, Daytona 24h

How do you factor the differences from track-to-track?

We rate tracks as low-, medium- and high-speed or high-downforce tracks. We basically take every lap from the green flag at Daytona in January to the checkered flag at Petit Le Mans at Road Atlanta and make that into one very big lap. That helps us see the similarities in tracks.

Except for the elevation changes, Long Beach is very much like Monterey. Daytona and Road America have very similar percentages of full throttle laps. We don’t balance for each track. That would be very time consuming and produce micro-balancing.


Do you bring the fast guys back to the field or speed up the others?

It depends on the situation. Is it on the low end or the high end? We try to determine where the “outlier” is. Speeding cars up costs money. It is a difficult balance.


How do you manage turbocharged cars in different weather and elevations?

We set the turbo boost based on atmosphere and elevation. We set the final boost on the afternoon before the race based on atmospheres.


If a team has an especially quick driver, does it impact the adjustment?

We don’t balance the drivers, we balance the cars, but cars don’t drive themselves.


How does the 2016 BoP process compare to prior years?

Years ago, the BoP was not very well understood from the Competitor/manufacturer standpoint. It wasn’t transparent. It appeared to be working from a black hole with the only data being from timing and scoring. One person was overwhelmed trying to do it all. Now, with series-mandated scrutineering loggers, improved analytic programs, better communications and transparency; the phone rings 80 percent less. We now have six people, plus support from Bosch.


How do you gauge success?

One team principal said that if we walk into a room and there is a negative buzz and everyone is a little bit unhappy then you are probably about right.

You learn to deliver “bad news,” meaning that we are adjusting someone’s performance.


sandbagsAt the Daytona tests earlier in the year, there were reports of widespread sandbagging. How do you detect and deal with sandbagging? Do teams have tricks to try to mask their performance?

We found some teams not using full throttle, running full fuel loads, varying tire pressures well beyond normal ranges, short shifting, braking early, and using “lazy” acceleration. Some guys ran the “wrong” gears to limit RPM. We saw 10 or 11 different mechanisms. GPS can tell us the line the driver took. Some guys at “The Roar” ran the entire test without hitting an apex. Some just rolled into the corners.


What was the most obvious example?

In NASCAR Turn 4, coming onto the front straightaway there were cars where the driver had completely lifted and the throttle position was zero! Of the 52 cars at the Daytona test, all showed some “performance management.”


How did you catch them?

In the past, the only tool that we had was a timing and scoring lap analysis with some very limited vehicle data. Now we have sophisticated data loggers that can overlap with lap times and the timing and scoring loops. After the race at Daytona, our analytics guys had over 100 gigabytes of data. We spent more than 40 hours in Committee meetings reviewing all of this information with the IMSA Technical Committee in order to make BoP recommendations before the next event. In this case it was the Sebring winter test.


In single-make or series with virtually identical cars, organizers come up with gimmicks to permit passing. Do you consider the ability to pass slower class cars in setting the adjustments?

We are a multi-class series. From a car standpoint, we have two Prototype classes and two GT classes. From a driver standpoint, we have two “Pro/Pro” classes and two “Pro/Am” classes. It’s like a 3D chess board in terms of how to manage the interactions. We try to have 4 percent stratifications between each class. We often see less than that, somewhere between 2.8 and 3.5 percent.

We set the measures based upon the Pro drivers.


Where do you think things are now?

Our process is much more refined than it was even a year ago. We do the analytics and get our BoP recommendations sent to the manufacturers after each race. The next day, we have a class specific WebEx call. We show them the table and give all of the OEMs the opportunity to comment. On the first calls we spent 90 minutes talking about IMSA, now the calls take 20 minutes and the manufacturers are asking each other questions. The process is much more transparent. We communicate more. We’ve added a lot of data analysis and we can simulate the impact of proposed changes. The only thing that skews the picture is inferior or imperfect data.


Is it difficult to manage when you have cars – like the Porsche and Corvette in GTLM that have been developed over a span of 2-3 years – competing against new cars still being developed like the Ford GT, BMW M6 and Ferrari 488?

With the new rules for 2016, the Corvette and Porsche are basically “evos” of the last year’s cars so they have changed, too.


Front Row
Simon Hodgson, Vice President, Competition
Geoff Carter, IMSA WeatherTech SportsCar Championship Sports Car Series Senior Series and Technical Manager (Committee Chairperson)
Mark Raffauf, Director of Series Platforms

Second Row
Rob Elson, Technical Manager, IMSA Mazda Prototype Lites, Lamborghini Super Trofeo Porsche GT3 Cup
Scott Raymond, WeatherTech Championship Senior Technical Engineer
Jeff Mishtawy, IMSA Continental Tire SportsCar Challenge Senior Technical Manager
Matt Kurdock, IMSA Manager, Technical Systems

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