When the Diesel came to Indy…

Some of you may remember Ryan’s great post on the 1952 Indianapolis 500 line up a few years ago. That got me thinking a little more about the fantastic and innovative #28 Cummins Diesel-powered Kurtis Kraft piloted by Fearless Freddie Agabashian. The car was an Indy first in many ways: First sideways mounted, modern diesel, first turbo charger, first aerodynamic tested body, which proved to be a real slip stream. A mere 23 inches off the ground, with the headrest only slightly taller than the tires. It was wide, low, and had a great advantage in a lower center of gravity than the other cars.

The Cummins team looked hard at the Indy racing rules, which were written to encourage some drivetrain diversity, allowed for standard gasoline engines of up to 274 ci, but supercharged engines were only allowed to displace 183 ci. To level the playing field a bit, a diesel was allowed to displace 401 ci, whether it was supercharged or not. Cummins engineers took full advantage of the rules. With the new Kurtis chassis & body, and the 6.6 liter, 380 horsepower beast, breath taking test laps left Fred to declare ” We’ve got a rocketship here…”

The team kept the car low profile until qualifying, for fear that the officials would change the rules on them, but what the #28 Cummins Diesel Special car did in those four qualifying laps shocked the racing world. Fred completed the first lap in 1:04.70 for an average speed of 139.104 mph, and the next three laps at 136+. That first lap was a single-lap Indy 500 record; the four-lap speed of 4:20.85 also produced a four-lap record of 138.010 mph. The cat was out of the bag, and the other teams, track officials, and press all went nuts.

On race day, 5,000 Cummins employees & fans from Columbus had come by charter bus for the event. The diesel was sluggish at the start and never led the race, but it ran strong. “Once he got going, he was cruising along and ran fifth for quite a while.” And then, all of the sudden, it was over. At lap 70 the car began to belch black smoke, and the #28 car made a pit stop at the 175-mile mark. The engine was overheating. The experimental car was taken into the garage and withdrawn from the race, officially due to turbocharger failure.

What happened? Chunks of rubber from other racers tires (marbles) had been sucked into the non-filtered turbocharger, and shut it down. The design mistake of putting the turbocharger inlet down low behind the car’s grille led to the failure.

Despite hopes and speculation, the car never returned to Indy again. Why? Don Cummins said “We knew we had this huge engine. A lot of people weren’t very happy about us. We were convinced they would change the rules the next year. We caused such an upset by being on the pole.