Marshall Pruett's Tech Mailbag for March 7
Can you explain how teams plan fuel strategy, specifically how they adjust when yellows come out and such. I have heard mention that you want to be, ‘The first guy to make the last stop,’ which makes sense, but teams seem to push that a lot. Also, do they use software to help plan or is it all manual?
MP: In a general sense, they work backward from the final lap to determine their fuel windows. They will also look at historical data for the race, when possible, to look for trends on how many yellows, the length of those yellows and when they tend to happen. If we were going back to Baltimore, you’d pencil in “every start and restart” for when to expect yellows…
The adage about wanting to be ‘The first guy to make the last stop’ comes from creating options. If you’re in early, you’re out and lapping hard to the finish and have more time to improve your position. You’d rather be the guy to pit early in your final fuel window than to wait, hope for a yellow, fail to get it, and then risk having to fall down the running order or get back up to speed while the rest of the field is lapping on hot tires. For the teams with nothing to lose, taking that gamble might pay off if a yellow falls at the right time, and other teams with multiple cars might split their strategy to improve the odds of a team win, but you’ll find most of the top teams stick to a pretty basic formula for strategy.
Almost every form of racing that has pit stops/refueling and allows on-board data systems will also have software that helps engineers and strategists to determine their fuel windows. Telemetry comes across, gives MPG info, remaining fuel info, and calculates how many laps are left to run on each tank.
For series like NASCAR where data/telemetry isn’t allowed, teams manually input expected MPG data into their software and how much fuel went in at each stop to come up with approximations on how far a car can run. With telemetry, teams can get down to incredibly low fuel levels before pitting – within a few tenths of a gallon, and the margin is wider without it.
I've read that some in IndyCar believe speeds at Indy will approach 230 this May. That sounds like a sizable increase in horsepower, and I'm skeptical. If the engines started at 550 and topped out at 219 mph on practice days and race day, but 224ish during qualifying with extra turbo boost, what kind of horsepower are we looking at this May at Indy with normal boost and then added boost for qualifications?
MP: That’s a great question no one will answer! I’ve heard power increases from 2013 to 2014 could be in the 20-25hp range, but it’s pure speculation. Drivers have said they can feel the extra power, so we know it’s there, but putting a number on it is impossible until Chevy or Honda want to disclose that information.
We saw some 229mph laps in high boost during qualifying last year, and with the extra power, along with IndyCar’s desire to see the 230mph threshold broken, all it takes is for IndyCar’s Derrick Walker or Will Phillips to set the boost level where it will happen.
What do the IndyCar Honda drivers need to do differently in their driving style to transition to the new twin-turbo, if anything? Do they notice a difference in throttle response, lag, power band, etc.?
MP: Alan, I asked Badass, AKA Dale Coyne Racing’s Justin Wilson, who recently drove Honda’s twin-turbo for the first time to answer this question for you:
“I really didn’t notice the change very much from one turbo to two. Honda’s done a great job on the drivability; you have more instant power available, but it’s very similar to the single-turbo I used the last two years. There’s a little less turbo lag with the twin, but it wasn’t a big change. It didn’t turn the car upside down or make me think I needed to drive any differently or be more gentle on the throttle. You almost drive it like a naturally aspirated engine, and as a driver, you find you just instantly adapt.
They’ve done a great job on the engine mapping right out of the box. There aren’t any gaps or holes on the power band, so really, the best I can say is it isn’t much different for me to drive. And I thought there was a bit more power, too. It’s not the 1000 horsepower we’re wanting, but it’s a nice change.”
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