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The Bosch P7100 Pump: Scheid Diesel’s 16mm Plunger

For years, the Bosch P7100 pump (most commonly found on ’94 to ’98 Dodge Rams) has dominated diesel pickup horsepower and can be found in the nation’s top drag racers and sled pullers. The simple design of the pump, along with its excellent fueling and rpm capabilities led to 160-hp rated Cummins engines making 1,000 horsepower within a decade of the ’94 Ram’s introduction. Now, it’s nearly twenty years later, so we wondered, what’s the latest and greatest?

THE BASICS: HOW A 12MM P7100 PUMP WORKS

The function of a P-pump is relatively simple, although it may take a few readings to understand. The pump basically acts like a small engine, but instead of compressing air, the rotating plungers compress fuel to thousands of pounds per square inch needed for diesel injection. These plungers ride on a camshaft, which controls the rate of injection as well as the total lift. While the cam profile remains constant through the rpm band, the pump rack rotates the plungers to supply more fuel through the injection lines and into the injectors.

THE EARLY DAYS: A “QUICK CAM” 13MM PUMP

By looking at the P7100’s basic operation, we can see that there are two basic parts that are very important to fueling: the pump cam, and the plungers. It wasn’t long before performance pump builders found out they could run larger 13mm plungers in a bored-out P7100 body to increase the amount of fuel the pump could produce. Also, even among stock pumps, certain cam profiles were “hotter” than others (injecting more fuel at a quicker rate, again leading to more usable fuel production).

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WELCOME TO 2016: THE SCHEID 16MM PUMP

As time progressed, so did the sport of sled pulling, and the popularity of this no-holds-barred sport lead to radical advancements in mechanical injection pumps. We stopped by Scheid Diesel in Terre Haute, Indiana, to get a glimpse of the latest in modified P-pumps and were surprised to learn that they were now custom building 16mm plunger pumps, which could produce more than 1,500cc of fuel and spin more than 7,000 rpm, which is just nuts. While we’d heard of 14mm pumps before, 16mm pumps were new to us, so we were eager to see how they worked. Luckily for us, owner Dan Scheid was nice enough to walk us through how these awesome units are built.

CUSTOM PARTS, COATINGS, AND CONSISTENT PERFORMANCE

The heart of a big pump build starts out in a fairly simple place: normal 12mm core pumps. From there, a lot of work is done to integrate the 16mm plungers into a system that was originally designed for 12mm units, with virtually everything inside the pump being machined or modified. The plunger diameter increases the rate that the fuel is injected, which also increases power. With so many custom parts that could be seeing 6,000 to 7,000 rpm engine speeds, the camshaft, plungers, and a number of other parts use Scheid’s proprietary coatings for increased durability. For those looking for a clean-sheet effort, Scheid can also build the larger P8600 pump, as long as it’s within the rules of the class.

THE FUTURE OF P-PUMPS

With the rapid progressing of P7100 and P8600 pumps of the past few years, we wondered, what did the future hold? “We’re already working on a 17mm unit that should be available by the time you read this,” noted Dan Scheid. “We’re still making horsepower by leaps and bounds, and picking up hundreds of horsepower on pulling engines, even in the top classes,” he continued. “I don’t know where we’ll end up ultimately, but we’re not there yet.” With what we’ve seen over the past ten years (or even the past five) we can’t wait to see how this technology will progress. DW

1. The foundation for a 16mm P7100 pump is a Bosch P-pump, which can be found on Cummins engines in a variety of applications. A lot of work is needed to turn something like this used-up core pump into a 16mm monster.
1. The foundation for a 16mm P7100 pump is a Bosch P-pump, which can be found on Cummins engines in a variety of applications. A lot of work is needed to turn something like this used-up core pump into a 16mm monster.
2. Before a 16mm pump can be built, the core pump must be torn down to its foundation and machined to accept a number of new parts and pieces from Scheid Diesel.
2. Before a 16mm pump can be built, the core pump must be torn down to its foundation and machined to accept a number of new parts and pieces from Scheid Diesel.
3. The heart of the massive-flowing P7100 is its large plungers and barrels (16mm versus 12mm for a stock P-pump). Not only do larger plungers lead to more flow, they inject fuel quicker, which makes more power.
3. The heart of the massive-flowing P7100 is its large plungers and barrels (16mm versus 12mm for a stock P-pump). Not only do larger plungers lead to more flow, they inject fuel quicker, which makes more power.
4. Scheid has their own governor spring setup that is well past the factory's under-3,000 rpm defueling point. Scheid reports that based on customer needs, fueling up to 7,000 rpm is available.
4. Scheid has their own governor spring setup that is well past the factory’s under-3,000 rpm defueling point. Scheid reports that based on customer needs, fueling up to 7,000 rpm is available.
5. Another important piece of the 16mm build is the pump cam, which was designed by Scheid, and also features some of their proprietary coatings, which improves reliability, smoothness of operation, and reduces friction.
5. Another important piece of the 16mm build is the pump cam, which was designed by Scheid, and also features some of their proprietary coatings, which improves reliability, smoothness of operation, and reduces friction.
6. The delivery valves and holder also have to be custom on the 16mm application, as everything is oversized in the Scheid pump.
6. The delivery valves and holder also have to be custom on the 16mm application, as everything is oversized in the Scheid pump.
7. Even parts you wouldn't think about, like these control sleeves, are parts that have to be built specifically for this application because of the oversized plungers and barrels.
7. Even parts you wouldn’t think about, like these control sleeves, are parts that have to be built specifically for this application because of the oversized plungers and barrels.
8. Fuel control is important on these monster pumps, and can be achieved in a few different ways. In an automotive governor type application (which is less popular) a screw-adjusted fuel plate can be used, which is marked off in tiny increments for precise fuel tuning.
8. Fuel control is important on these monster pumps, and can be achieved in a few different ways. In an automotive governor type application (which is less popular) a screw-adjusted fuel plate can be used, which is marked off in tiny increments for precise fuel tuning.
9. The more popular RSV (or "Ag") governor uses a simple fuel screw for adjustments, just like the old Bosch VE pumps. This makes adding fuel quick and easy, since everything is external.
9. The more popular RSV (or “Ag”) governor uses a simple fuel screw for adjustments, just like the old Bosch VE pumps. This makes adding fuel quick and easy, since everything is external.
10. Fuel flow into the P7100 is also very important, and Scheid recommends dual-feeding its pumps (with one return port) with a lift pump that's in the 400-gph-plus range at more than 60 psi.
10. Fuel flow into the P7100 is also very important, and Scheid recommends dual-feeding its pumps (with one return port) with a lift pump that’s in the 400-gph-plus range at more than 60 psi.
11. Even the drive of the pump is changed on the 16mm application. Because these pumps take so much power to drive, a keyed shaft is incorporated into the build, with timing adjustments coming courtesy of an adjustable timing gear.
11. Even the drive of the pump is changed on the 16mm application. Because these pumps take so much power to drive, a keyed shaft is incorporated into the build, with timing adjustments coming courtesy of an adjustable timing gear.
12. Things we'd never even thought of can be found on the 16mm pump. How about a pump vent to relieve pressure during high-rpm operation?
12. Things we’d never even thought of can be found on the 16mm pump. How about a pump vent to relieve pressure during high-rpm operation?
13. Looking nothing like the original 12mm P7100, the 16mm Scheid Diesel P7100 is capable of fueling into the 1,500-cc range!
13. Looking nothing like the original 12mm P7100, the 16mm Scheid Diesel P7100 is capable of fueling into the 1,500-cc range!
14. If the customer so desires, they can step up from a P7100, and into the P8600 category. The P8600 assembly (left) has the same size plungers, but larger parts offer a greater margin of safety if the end user really wants to max-out their setup.
14. If the customer so desires, they can step up from a P7100, and into the P8600 category. The P8600 assembly (left) has the same size plungers, but larger parts offer a greater margin of safety if the end user really wants to max-out their setup.
15. With a pump like the Scheid 16mm, everything else in the injection system must also be up to the task. A set of Scheid triple-feed injectors (top) can be purchased in either 7mm or 9mm tip configurations and are available up to a shopping 5 x .039-inch size.
15. With a pump like the Scheid 16mm, everything else in the injection system must also be up to the task. A set of Scheid triple-feed injectors (top) can be purchased in either 7mm or 9mm tip configurations and are available up to a shopping 5 x .039-inch size.
16. As this piece is being written, even more advancements are being made in the all-out $100,000 race engines that use this type of injection pump. With more than 3,000 horsepower from less than 400 cubic inches, modern diesel pulling engines are some of the most advanced on the planet.
16. As this piece is being written, even more advancements are being made in the all-out $100,000 race engines that use this type of injection pump. With more than 3,000 horsepower from less than 400 cubic inches, modern diesel pulling engines are some of the most advanced on the planet.

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