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Written by:
Marshall Pruett
05/17/2008 - 12:57 AM
Tooele, Utah
Audi's twin-turbo diesel V-12 has a few attributes that aid it in Salt Lake City's thin air. (Photo: Marshall Pruett) » More Photos
Turbo-Diesel’s on a Restricted Oxygen Diet at Altitude
At 5050 feet above sea level, Miller Motorsports Park provides a very unique problem for engine tuners to solve. Being almost one mile in the air, the mountainesque race track is a spectacle to view, but provides less air than the engines are accustomed to at lower altitudes.
Racing teams have long been forced to alter the air/fuel mixture to work best in the presence of reduced oxygen. Turbocharged engines have enjoyed advantages at altitude, with the turbochargers forcing higher volumes of air into their engines than the naturally aspirated powerplants are able to draw in without assistance, but the topic of tuning a turbo diesel road racing engine in high altitudes was something I’d yet to see explained. Thanks to our friends at Audi, we now have a basic understanding.
“The real problem is,” said an Audi engine specialist, “exist in many of the same ways with an NA engine but there are differences. The more we learn about air restrictors--we learn about the way they affect things, whether they are in a turbo diesel or otherwise. They universally all work in the same order. And we had the same issues that you have with a gas engine, where you have the turbos run over speed or up on the limit up on their rotational limit quite easily because you don't have the dense air to balance the turbine on the cold side of the turbo housing.
“The one thing that diesel does have is that, here at this altitude, the engine drivability is good because with the diesel you don't have any reversion with the turbine. The throttle never closes. So you never back up the air. You never have this big column of air moving one way and then you close the throttle on it; it bounces off and goes the other way. You don't have that. Since diesels don't have throttles, you don't have that sort of reverse the flow through the restrictor. It's a little bit more predictable and it's a little bit more of a limiter, I guess, is the word to use for that.
Aha—so the first main difference between gas and diesel turbos at altitude is a diminished reversion of turbocharger intake reversion. Got that? In more simple terms, with a gas turbo engine—all that use a throttle that opens and lets air into the engine, when a driver lets off the throttle, the high pressure air that’s being forced into the engine by the turbo is allowed to go in the opposite direction—back out of the engine, which impact throttle response when the driver wants to get back on the throttle. With no throttle bodies in a diesel, this lack of boost problem ‘off throttle’ is diminished in the thinner air.
“It's probably better than a petrol engine, although I haven't seen what a petrol engine would at this altitude. The altitude is a wildcard here; we have to watch that quite closely. We must make sure that you're not getting yourself really set up for a big problem and we've seen the density altitude change as much as 500 millibar a day and that's a huge sweep. If you were getting ready to take off in your single-engined airplane, you would alter your flight plan based on making sure you could get up to speed in time before running out of runway. So that part is very interesting.”
There are surely more small gains the Audi Sport engineers have found, but beyond the design and operational differences between the gas and diesel motors, the air restrictors all of the cars are forced to run severely governs the amount of air the engines receive at any altitude. At 5050 feet, it’s apparently worse, but not as bad as I’d originally thought. “We tried to figure out ways to trick it (the air restrictor) up here and it's very difficult. Up the air, you can't make the power, no matter if it is diesel or NA, but we are somewhat more fortunate.”
Farnbacher-Loles Burns Up the Anytime Minutes
Dino Loles, a man of many anytime minutes. (Photo: Marshall Pruett) » More Photos
The Farnbacher-Loles team has yet another weekend where their racing operations are split between two events. With the single-car ALMS GT2 entry for Alex Davison and Marc Basseng in Utah, Dino Loles gave me details on how hectic life becomes when they’re also fielding a multitude of cars at Laguna Seca on the same weekend.
“We start planning for these dual weekends at least six months in advance. Our shop gets split, with different transporters, cars, and equipment to support running in two different series. I’d guess that we have a total of fifty people spread between two events, and I know that for me, I’m on the phone constantly to check in and see how things are going.”
For Loles, a dual race weekend has him married to his cell phone. “So it can be pretty funny sometimes—I’m calling to check in over there, they’re calling to check in on things over here, and sometimes we have other team members or drivers on hold as we’re bouncing around getting everything coordinated. It’s a good thing I have an unlimited minute plan…”
De Ferran’s New Ride, New Team are Right at Home
de Ferran keeps a relaxed on on his new team--he's the owner, driver, and his crew's biggest cheerleader. (Photo: Marshall Pruett) » More Photos
As Gil de Ferran walked out of his de Ferran Motorsports trailer this morning, it was the first time if five years he’d stepped into a garage as a driver. Since his retirement from a twenty year career as a professional racer, de Ferran had guided the HondaF1 team prior to his departure last season. Now at the helm of his own team, Gil carries the weight of delivering results for Acura both on and off the track, but the Brazilian is game for the challenge. His warm personality should motivate and inspire his team’s progress faster than one might expect.
How de Ferran interacted with his crew was the most telling aspect of his return; while he’s now officially unretired as a pilot, he made a point to seek out each crew member, stop them, share a genuine smile, and shake each one of their hands.
For a man about to embark on a massive new chapter in his life, de Ferran carried the calm and ease of someone who was at peace when most expected him to working frantically to wrap up last minute detials.
Gil now carries with him the added responsibility of being a team owner, but you’d never know it from one of the questions his crew asked him.
“You nervous, Gil?”
(De Ferran looks back at the mechanic as if he’d been asked if he was from Moon) “Am I nervous? Are you kidding me? This is my home, man!”
‘Nuff said. Welcome, Gil.
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