GM Racing Q&A: New 3.0L Chevy Indy V-8
Bowtie Bullet Points: Chevrolet Notes for the Indy Japan 300
Twin Ring Motegi, Motegi, Japan
Round 3 of 16, Indy Racing League IndyCar Series
Saturday, April 17, 12:30 p.m. (Japan time)
TV: ESPN2 (live), April 16, 11:30 p.m. EST
* Farewell to the 3.5-Liter Chevy Indy V-8
The Indy Japan 300 marks the 40th and final race for GM's 3.5-liter IRL IndyCar Series engine. In accord with the IRL's initiative to reduce speed and enhance safety, a new 3.0-liter version of the Chevy Indy V-8 will be introduced at the Indianapolis 500.
The downsized Chevy racing engine had its initial track test at Indianapolis Motor Speedway on April 3 in the hands of Panther Racing's Tomas Scheckter and Red Bull Cheever Racing's Alex Barron. All Chevrolet-powered teams will use the new 3.0-liter Chevy Indy V-8 in the upcoming pre-Indy 500 open test at IMS on April 27-28
* Backgrounder: IRL Engine Evolution
GM is the only manufacturer that has competed continuously in the IndyCar Series since the introduction of the naturally aspirated engine formula in January 1997. The first engine developed by GM Racing for IRL competition was the 4.0-liter Aurora Indy V-8. While not a "stock-block" engine, the Aurora Indy V-8 was based on the architecture and technical specifications of the production 4.0-liter Aurora V-8.
Limited to a maximum of 10,500 rpm by IRL regulations, development of the 4.0-liter engine package reached its zenith in 1999 when GM Racing's "kit engine" used by 31 of the 33 Indy 500 starters delivered 730 horsepower. Maximum engine speed was subsequently reduced to 10,000 rpm for the remainder of the 1999 season.
In order to keep racing speeds in check, engine displacement was reduced to 3.5 liters and the rev limit raised to 10,700 rpm at the start of the 2000 season. As engine development continued and speeds climbed again, the maximum rpm was lowered to 10,300 rpm in 2003. The engine rules also were revised to allow smaller, lighter purpose-built racing powerplants with technical features not shared with a manufacturer's production motors, including gear-driven camshafts and two fuel injectors per cylinder.
The reduction in displacement from 3.5 to 3.0 liters required for this year's Indy 500 was achieved by shortening the Chevy Indy V-8's crankshaft stroke from 64.4mm (2.53") to 55.1mm (2.17") and making complementary changes in the connecting rods and pistons. The cylinder bore diameter was unchanged at 93mm (3.66"). Per IRL regulations, the major engine components (block, sump, cylinder heads, etc.) were not altered. Development of the 3.0-liter Chevy Indy V-8 is focused on optimizing the camshaft design, tuning the intake and exhaust systems and recalibrating the electronic engine management system that regulates the fuel mixture and ignition timing.
* 3.0-Liter Engine Q&A
In the following Q&A, GM Racing IRL program manager Joe Negri discusses the transition to the new 3.0-liter specification and its impact on key engine characteristics: horsepower, torque, tractability, fuel economy, reliability and availability.
Q: What are the effects of the change from 3.5-liter to 3.0-liter displacement on horsepower and speed?
Joe Negri: The rule of thumb says that when you change displacement from 214 cubic inches to 183 cubic inches, engine output will be reduced by approximately 100 horsepower. The unanswered question is how much of that loss can be overcome through development.
It's not just the displacement that is changing, however. The IRL required the use of vented air scoops in the first three events of 2004 as a temporary measure to reduce performance with the 3.5-liter engines. With the change to 3.0-liter engines for Indy, the scoops will again be sealed. The supercharging effect of the air scoop at high speeds will restore about 15 horsepower.
The overall impact on speed remains to be seen, since the chassis, aerodynamic package, tire performance, track surface and weather conditions also affect the maximum speed. The stated goal of the IRL rule revisions was to produce a pole qualifying speed in the low 220-mph range. Based on the initial track test with the 3.0-liter engine and the new aerodynamic devices, it appears that goal will be achieved.
Q: How will the reduction in displacement affect torque and throttle response?
Negri: The new engine's torque curve is flatter and it doesn't reach the same peak as the 3.5-liter version. The effect of the reduction in torque will probably be most noticeable at the Speedway in the short chutes between Turns 1 and 2 and between Turns 3 and 4. The key for teams will be to set up the car and chassis to maintain as much momentum as possible because with less torque available the car won't accelerate as quickly. Drivers who are accustomed to the 3.5-liter engines may perceive that the 3.0-liter version is not as responsive because it has less horsepower and torque.
Q: What's the expected impact on fuel economy?
Negri: The 3.0-liter engine produces less horsepower and therefore uses less fuel. The IRL regulations reduced fuel cell capacity from 35 to 30 gallons at the start of the 2004 season, which cut the number of laps between pit stops. The improvement in fuel economy with the 3.0-liter engines will offset this reduction in fuel capacity to some extent. All of the manufacturers are still developing their 3.0-liter engine specifications, but I expect that there will be about the same number of pit stops in this year's Indy 500 with 30-gallon fuel cells as there were in previous years with 35 gallons.
Q: What about engine reliability with the new components?
Negri: The new engines are producing less horsepower with the same basic components as the previous engines, so the Chevy Indy V-8's excellent reliability record should be even better. We've decreased the crankshaft stroke, which reduces piston speed, and the mechanical loads on engine components are also lessened. The IRL rules mandate the minimum crankshaft weight, so there isn't an incentive to build engines with superlight components that might have reliability issues.
One area of concern is the valvetrain because camshaft profiles used with 3.0-liter engines will tend to be more aggressive. Faster valve acceleration increases stress on the valve springs and other valvetrain components, so this is an area that will require significant development.
Q: How many 3.0-liter engines will Chevrolet have available for the Indy 500?
Negri: Our goal was to have the capacity to supply Chevy Indy V-8 engines for 10 cars at the Indy 500. So far we are on schedule to meet that objective. Currently we have eight confirmed Chevrolet-powered entries: two from Panther Racing, two from Red Bull Cheever Racing, and single entries from Dreyer & Reinbold Racing, Robby Gordon Motorsports, Patrick Racing, and Beck Motorsports. We are in discussion with other teams as well.
* The Air Force
The IndyCar Series has also developed a new aerodynamic package for the Indy 500. GM Racing chassis and aerodynamics specialist Kevin Bayless commented on the first track test:
"The new aero package appeared to work very well. The conditions during the test were quite windy and the teams were understandably cautious getting up to speed.
"Along with the reduction in horsepower with the 3.0-liter engine comes a corresponding reduction in the amount of downforce that's required. With less horsepower, the cars don't carry as much speed into the corners, and consequently they don't need as much downforce to run quickly.
"In fact, the speed reduction produced by the change to 3.0-liter engines more or less offsets the downforce that was lost through the rule changes. As a result, it appears that the teams will be running similar setups and wing angles for the Indy 500 as they did last year."
* Racing Around
Chevrolet is competing in four major American motorsports events this weekend. In addition to the Chevy Indy V-8s competing at Twin Ring Motegi, Chevy Monte Carlos will race in the NASCAR Nextel Cup event in Martinsville, Va., Chevy Silverado pickups will run in the NASCAR Craftsman Truck Series race in Martinsville, and Chevy Pro Stock Cavaliers and Monte Carlo Funny Cars will compete in the NHRA Spring Nationals in Houston, Texas. Chevy races to win across the spectrum of motorsports, and is the only manufacturer that currently competes in NASCAR Nextel Cup, the NASCAR Craftsman Truck Series, the IRL IndyCar Series, NHRA drag racing and American Le Mans Series road racing.