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Cummins vs. Dragstrip Part One

Fast Times With Our 1989 Cummins-Powered Dodge Diesel

Text By , Photography by , Justin Fivella

The idea seemed simple. We planned to take Project Rust Bucket, a 972-rwhp Dodge Ram diesel, and hit the dragstrip to show what our March ’12 cover truck could do. We’d make record-setting times and write a story about how we were faster than all the Camaros, Corvettes, and heck—maybe even a Ferrari or two. As it turns out, drag racing is a lot harder than making power on the dyno, especially in a high-strung, two-wheel-drive pickup.

While we weren’t entirely successful in getting our Bugatti Veyron-beating numbers, we did at least get the truck up to the Camaro SS level—plus we still have about 300 hp worth of nitrous left to go. Here’s our story.

Toyota Speedway, Irwindale, California (Eighth-Mile)
Run Number One
We used our first pass down the eighth-mile track just to check the truck out. We left the line with the Cummins at idle and shifted through all the gears using the speedometer as a reference. We locked the transmission’s torque converter in Third, just as the truck’s street tires finally hooked up. For that run, everything went perfectly, and Rust Bucket ran a 10.0-second eighth-mile at 82 mph. The engine had nosed over at the top of Third gear when the injection pump hit its mechanical governor as the truck crossed the finish line. Our 60-foot time was a laughable 2.7 seconds—something we really hoped to improve upon.

Run Number Two
We were having trouble spooling our 5.9L engine with the injection-pump timing so advanced, so we used a 0.032-inch jet of nitrous to leave the line at 10 psi off the transmission’s transbrake. Though we’d swapped our street tires for a set of 33x10.50-15 drag slicks, the boosted launch resulted in instant tire smoke. We recorded a 2.9-second 60-foot time—our worst yet. The truck went 9.76 seconds at 84 mph in the eighth-mile, which was worse than the 9.6-second run we recorded back when Rust Bucket had 300 rwhp.

Run Number Three
This time we launched the truck off the footbrake with the engine making 10 psi of boost. We locked the torque converter in Second gear and hit the nitrous again in Third. We actually short-shifted Third gear and pedaled the throttle when the turbo began surging in order to finish the run. A 2.1-second 60-foot time and an overall eighth-mile time of 8.63 seconds at 86 mph was right on par with the Camaro SS that ran an 8.81-second pass at 84 mph that same night.

Although the run wasn’t perfect, it was close, considering our traction issues. Our 60-foot times were still horrible, and the fact that our Duramax-powered Project Sleepermax ran an 8.31 at 83 mph in four-wheel drive indicated that once the traction was there, we should be able to drop at least half a second off Rust Bucket’s time.

Auto Club Dragway, Fontana, California (Quarter-Mile)
We made it to a quarter-mile track with the truck a few days later during a street-legal test and tune session at Auto Club Dragway. The unfortunate part of the equation was that nearly 400 other vehicles also showed up. Despite our best efforts, most of our time was spent waiting to get in or waiting in the tech line. After eight hours of work, we only got to make two passes.

After opening up our Cummins’ external wastegate, we were ready to make a full-nitrous run with one stage (a 0.135-inch jet) of spray. Our plan was to leave the line at about 10 psi of boost, shift to Second and Third, lock the converter, and hit the button.

Run Number One
On the first run, our plan worked pretty much like we imagined it would, but the fact that the boost was limited to 35 psi (instead of 60 psi) meant a much slower eighth-mile time. At a little before half-track, with the converter locked, the nitrous was hit, and boy, did the truck start moving! For a second or two, it felt great, and then the truck nosed over. Oops, we forgot to hit the button on the floor to shift our manual valvebody 47RH into Overdrive. Coasting through the traps, the truck still ran a 13.7 at 98 mph despite the bad start and missed shift.

Run Number Two
On our last run of the day, the truck actually shifted through all the gears and went down the track cleanly. With the transmission in Third and Fourth, the nitrous felt great, boosting the truck up from about 350 rwhp to more than 600 rwhp. The truck was pulling hard and went 8.94 at 89 mph in the eighth-mile—our best speed yet—which is faster than any stock ’12-model-year diesel truck can run in the quarter-mile. On the back half of the track, the truck picked up a whopping 29 mph and ran a 13.1 at 118 mph.

At those speeds, the wind noise was deafening, and our windshield wipers were fluttering all over the window as the 20-year-old Dodge tried to cope with 120-mph speeds. Our time was somewhat impressive, but our speed is the real success. Considering supercharged Shelby GT500 Mustangs can run 12.4 at 116 mph, our trap speed indicates the truck is really making some power.

So What Now?
Our truck’s 60-foot times were horrible. Thanks to the stock differential in the Dana 70 rearend, even slicks couldn’t fix everything. Once the traction is there in the form of a locker and suspension work, we should be able to drop at least half a second off our truck’s time. Rust Bucket is also way too busy on the inside, with the driver having to manually hit the nitrous and torque converter lockup, engage Overdrive, and shift through all the gears. Some automation with our nitrous setup ought to help bring on the power before the eighth-mile.

Finally, we’re going to retard the engine’s injection timing so we can spool the engine at the line without the spray, leaving our first stage open for a bigger jet. Then we’ll start dipping into the more than 300 hp worth of nitrous we have on tap and see what we can really do.

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