USAC Sets RPM Limits For Midgets
by NSSN Staff
Brad Kuhn (17b) battles Caleb Armstrong earlier this season during Indiana Midget Week. USAC has mandated an RPM limit in its USAC Mopar National Midget Series. (David E. Heithaus Photo)
INDIANAPOLIS — USAC has mandated an RPM limit for engines competing in the midget division beginning next season. It has also approved the Esslinger EST as a sealed engine platform available for USAC competition.
While the move may not be popular with all competitors and all engine builders, USAC, which has seen car counts for some of its national midget events in the low teens, is clearly making an effort to reduce the costs of maintaining a midget racing engine.
According to the USAC statement, “RPM limits were achieved due to an extensive and ongoing program of data acquisition and analysis commissioned by USAC for Ilmor Engineering throughout 2010.
“Data was derived from a large number of comparable chassis dyno power curves representing the most efficient platforms, along with racing data acquired from a large variety of racing venues, including big and small ovals, dirt and pavement.”
USAC has set varied RPM limits for different types of engines:
-8,700 RPM for push-rod engines (166 c.i.)
-8,800 RPM for crossflow engines (174 c.i.)
-9,800 RPM for single overhead cam (161 c.i.).
According to USAC, these limitations result in a performance difference of less than four percent.
Additionally, the Esslinger EST has been approved as a sealed engine platform eligible for competition at all USAC midget racing events beginning with the 2011 racing season. The Esslinger EST is sealed and approved with a factory RPM limit of 9,400 RPM.
NSSN readers will recall that the 2.65-liter Esslinger EST engine was previously approved by the United States Speed Ass’n for competition next season. The engine is expected to produce 320 to 340 horsepower and sell for $22,000.
USAC will continue to monitor and evaluate RPM limits throughout the 2011 racing season, with several review points planned.
USAC personnel are currently working with the ignition suppliers (MSD and EFI) to ensure that additional costs are not incurred by midget owners for RPM controls and an easy solution for validation is provided to USAC and other sanctioning bodies for trackside evaluation.
Ilmor Engineering will conduct a seminar of their findings for interested midget teams and suppliers during the December trade shows, the time and date to be announced in the coming weeks.
“USAC has done its diligence on studying RPM limits through the Ilmor Engineering analysis,” says Dan Esslinger, president of Esslinger Engineering. “The timing is right for controlling RPM as a means to help contain cost escalation in midget racing over the years.”
http://www.nationalspeedsportnews.co...et-rpm-limits/