HINDSIGHT – DIESELS AT INDY
was despite the fact that, thanks to magnesium components, the engine weighed around half that of a production version. There was also the fact
that a crude turbocharger had been installed. Although this was sometimes referred to as a supercharger it was in fact the first turbo to be used in the Indianapolis 500. Little was known then about the science of matching a turbocharger to a specific engine, and wastegates were not generally used. The turbocharger / compressor combination was selected to give peak boost pressure at peak engine rpm, with the pressure
“The first
turbo to be used in the
Indianapolis 500”
trailing off at lower speeds. A large turbo unit was used giving 20psi boost at 4000rpm engine speed, which resulted in an output of almost 400bhp. However, the boost was a mere 11psi when the throttle was opened out of the turns and it took between three and five seconds for the turbine to speed up to around 15-20psi down the straights. Unfortunately, because its air inlet was just inches from the track, the turbocharger also acted like a vacuum cleaner and sucked in dirt. It would be another 14 years before this technology returned to the Speedway.
POWER PROTESTS The respected Agabashian was concerned that the diesel’s massive power could lead to protests being made so, in initial practice, he kept his speed down and there were those who wondered if he would even qualify. But with Don Cummins personally directing the operation, the main object of the exercise was to find the most effective method of weight distribution. In over 400 practice miles, Agabashian did not exceed 135mph. Then came pole day, and he let the car off the leash. The result was one of the biggest
upsets in the history of the Speedway. His average speed was over a mile an hour faster than the four-lap qualifying record that Andy Linden had just set with his Offy-powered Kurtis. The jubilant crew members, having suffered weeks of toil, lifted Agabashian on to their shoulders. The Cummins’ right rear tyre, though, was in shreds, which did not bode well.
Dave Evans raced this four-cycle Cummins diesel-engined car in 1934, while team mate, H W Stubberfield, drove an experimental two-cycle engine
BORROWED TIME In the race, Agabashian ran fourth for many laps before the turbocharger became blocked with lumps of rubber and detritus. Although it was for this reason that the car retired, it was discovered many years later that the crankcase had a crack running from the second crankshaft journal to the sixth, so even if the turbocharger intake had remained unblocked, the Cummins Diesel – which now resides at Cummins headquarters in Columbus – was running on borrowed time. Don Cummins was aware
Freddie Agabashian competed in 11 Indy 500s. On five occasions he qualified in the top four, but 1952 was his only pole position
that pressure from other competitors would probably result in a reduction of permitted engine capacity for diesels if his company was to return and a loss of any competitive advantage, so he called it a day after this momentous achievement, content in the knowledge that Cummins had demonstrated the potential of the diesel engine. As their business was not racing anyway, and its truck sales had increased dramatically, it was a case of job done. And job done well. Three-time Indy 500 winner
The 1950 Kurtis-Kraft diesel on display at the Indianapolis museum. Although green was considered unlucky in American racing, the colour was chosen in tribute to Arsenal Technical High School, Indianapolis where driver, Jimmy Jackson, had had been a standout at football
“The result was one of the
biggest upsets in the history of the Speedway”
28
www.racecar-engineering.com • May 2012
and the track’s then general manager, Wilbur Shaw, remarked in his autobiography that he was ‘itching’ to drive the 1952 Cummins Diesel. A few days after the race he had his chance to test the car. ‘Even though I didn’t put as much pressure on the throttle as Fred had applied, it was a perfectly wonderful feeling to be back on the track and running at high speed,’ he wrote. Despite Shaw’s enthusiasm for the then unlikely technology, and the fact that they had proven to have both the speed and frugality to make them a sensible choice for racing, diesels were never to return to The Brickyard.
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