JIM COVEY, ENGINE TECHNICAL DIRECTOR, GM RACING, DISCUSSES THE DEBUT OF UNLEADED FUEL IN NASCAR NEXTEL CUP SERIES COMPETION AT CALIFORNIA SPEEDWAY IN THE AUTO CLUB 500. WILL THE MANDATED SWITCH TO UNLEADED FUEL AFFECT FUEL MILEAGE FOR OUR CHEVY...
JIM COVEY, ENGINE TECHNICAL DIRECTOR, GM RACING, DISCUSSES THE DEBUT OF UNLEADED FUEL IN NASCAR NEXTEL CUP SERIES COMPETION AT CALIFORNIA SPEEDWAY IN THE AUTO CLUB 500.
WILL THE MANDATED SWITCH TO UNLEADED FUEL AFFECT FUEL MILEAGE FOR OUR CHEVY TEAMS? "Yes. It is my understanding that they are going to have to add more fuel with the unleaded fuel than they do with leaded fuel. How much? I can't exactly say. That will be a question for each individual engine builder. From a performance standpoint, there is not a big difference."
BASICALLY, WHAT HAVE OUR NASCAR NEXTEL CUP CHEVY TEAMS HAD TO DO TO PREPARE FOR THE SWITCH TO UNLEADED FUEL? "The biggest challenge is the reliability and durability of the valves and valve seats. Leaded fuel has lubricity; unleaded fuel does not. Therefore, with the unleaded fuel they have experienced wear issues with the valves or valve seats."
HAVE OUR TEAMS HAD ENOUGH ADVANCE NOTICE TO WORK THROUGH THESE ISSUES IN PREPARATION FOR THE CHANGE? "Yes, but it hasn't been a seamless transition. They haven't been able to take an engine that ran 500 miles on leaded fuel and get it to live for 500 miles on unleaded fuel without modifying the valves or the valve seats. They ran some with the Busch and Truck engines last year and certain combinations of materials in the valves and valve seats would live for 300 miles but they wouldn't live for 500 miles. And so over the winter they have had to do quite a bit of extensive testing to find out what will let it live for 500 miles.
"During the race, these engines turn as much as 9500 rpm, which means the valves are opening and closing more than 75 times per second. Leaded fuel provides a cushion, whereas unleaded fuel does not. So there is a tremendous amount of wear on the valves and valve seats. That has been the biggest challenge to overcome.
"There is no common solution for the teams because each team has its own combination of valve material and valve seat materials. Each team has had to learn on it's own. For example, you can't take what is learned at Hendrick Motorsports and necessarily apply it at Joe Gibbs Racing or RCR or DEI.
"The other thing that affects the wear is that the valve motion controlled by the camshaft is different from engine to engine and from team to team. Therefore, it might react differently from one team to another.
"If the teams can get through today's race -- given the stress 500 unrestricted miles puts on an engine anyway -- they will feel more comfortable going to a (track like) Bristol or Martinsville. Of all the tracks on the circuit, California Speedway is the toughest race track on an engine. If they can make it here, there shouldn't be any concerns at the other tracks on the tour."
WILL FANS NOTICE ANYTHING DIFFERENT WATCHING A RACE? "No, they won't. The performance difference is negligible within a percent or two so fans won't see or hear anything different."
-credit: gm racing