Dodge Cummins Blog

Dodge Cummins Performance Work Truck ‘The Crapbox’

Here is our 12 Valve Dodge Cummins performance story.
In March of 2017 we bought this used up truck for the engine and transmission and planned on scrapping the rest.

The truck was very beat up and neglected with an odometer reading over 347,000 miles; it did however run and drive ok despite having the usual problems associated with a 23-year-old work truck.  The trucks’ interior was so bad that no one wanted to get in the truck let alone drive it.

A decision was made to clean up the interior a bit to make sitting in it bearable and we already had many of the parts needed to make it somewhat presentable so nothing would be lost if we parted it out later.

After many jokes were made about what to do with the truck the Crapbox got its name. We needed a shop truck and the Crapbox fit the bill. Going with the ‘’parts on hand’’ theme we used parts that were laying around the shop to keep costs down.

At that time the truck had very little power and a slight miss so we pulled the injectors and tested them and to our surprise they tested good. Rather than reinstalling the 175HP injectors we opted to install a good used set of factory 215HP injectors out of a ’97 12 valve.

While the injectors were out we performed a compression test and found the truck had good compression, which was not all that surprising given that the truck had almost no blow-by.

Next we focused on the injection pump. We had a factory 215HP injection pump freshly built by Gillett Diesel Service, with confidence that the ‘’miss’’ was being caused by the worn pump we installed the fresh pump.

The Dodge Cummins Performance work truck was running great at this point and had more power but not enough to write home about. ‘’Scotty, we need more power!’’

We decided we wanted to see how much clean power we could make on stock injectors with only pump and turbo work.

Two things make more power in an engine, fuel and air. Typically when people want more power in a diesel they concentrate on fuel modifications like big injectors which usually leaves them with a hot smoky mess that is not very useable for towing, daily driving, or very friendly to other drivers. Although they have more power, it is usually only usable in short bursts because of excessive EGTs (exhaust gas temperatures).

The other main contributor of power is air. In most cases people want to increase boost PSI. But, boost pressure is not as important as flow. A bigger volume of cool air will yield lower EGTs, less smoke, and more power. 

To give our Cummins performance truck every advantage we could we installed a larger, freer-flowing, exhaust built from used scrap exhaust pieces.

We installed the new updated S&B true “cold-air intake,” which lowered our EGTs by 50 degrees and looks great.

12 Valve Cummins Performance Air Filter
S&B Cold Air Intake

With the larger exhaust expelling spent gases faster and the S&B intake introducing more cool air, EGTs were under control.  Then it was time to add fuel and RPM.

When it came to adding fuel one of the easiest and most cost-effective upgrades you can do to a P-pump 12 valve is a fuel plate. We chose a Dynomite Diesel fuel plate that adds 25-140 RWHP. We installed the fuel plate in the middle at 50% of its fueling capability.

To add RPM on the cummins performance work truck we installed 4000 RPM governor springs in the P-7100 injection pump which allows the pump to fuel the engine well past 3000 RPM. To reliably rev over 3000 RPM we installed 60LB over valve springs to keep the valves from floating and making contact with the pistons.

          With the added power and RPM we had a new problem.

The clutch that had who knows how many miles on it was not up to the task and needed to be replaced. To hold the newfound power an oversized South Bend clutch and flywheel was installed that is capable of holding 425 HP and 900LBS of torque.

Cummins Performance Dyno time!

For dyno testing our Cummins performance truck, the Crapbox went to Real Performance Speed Shop in Reno, Nevada. This is where they use a Dyno-jet dynamometer for testing the crazy turbo and supercharged brutes built there.

12 Valve Cummins Performance Dyno Pull

With the stock turbo set at 20 PSI and the fuel plate slid only 50% forward the truck made a decent 211.42HP and 555.14FT.LBS. We knew the truck had a lot left in it and it comes down to fuel and air.

For more air we wanted to do a modification that was cost-effective and easy enough to do. To increase airflow on our 12 valve Dodge Cummins performance work truck we turned to the guys at Heath Diesel. After talking with Bill about all the modifications done to the Crapbox. Heath Diesel’s Hurricane wheel and Turbo Master seemed to fit the bill perfectly.

Typically, the Hurricane wheel will add around 30 HP, 5 PSI of boost, and lower EGTs on a fairly stock truck. We opted for a fully balanced center cartridge with a Hurricane wheel.

Heath Diesel Hurricane Center Section
Heath Diesel Hurricane Center Section

To further increase and control boost on our Dodge Cummins performance work truck we paired the Hurricane wheel with Heath Diesel’s Turbo Master.

12 Valve Cummins Performance Turbocharger!
Heath Diesel Model 12 Turbo Master Installed on an HX35W

We have been using the turbo master at Patriot Diesel for a few years now with fantastic results. The turbo master is a spring operated waste-gate controller that is much more precise than the factory vacuum/boost controller. Most vacuum controller’s start opening around 40% of the set PSI. So, if your turbo is set at 20 PSI it will typically start opening around 12 PSI. This causes you to waste boost and causes turbo lag.

The Turbo Master keeps the wastegate closed until it reaches the adjustable set pressure reducing turbo lag and increasing pressure. Which translates to roughly 25-30HP and a much more fun and useable driving experience.

Proof is in the numbers.

After our baseline dyno pulls we installed the Heath Diesel Hurricane Center Section, Turbo Master. We also slid the fuel plate all the way forward. We adjusted the waste-gate and made 29 PSI right off the bat.

The results speak for themselves! We gained 143.27 HP and 280.85 FT.LBS for a total of 354.69 horsepower and 835.99 FT.LBS of torque.

Dyno Numbers

Real world results

Our old 12 Valve Dodge Cummins Performance Work Truck accelerates faster and is much more fun to drive but how about drivability?

While towing the EGT‘s are very controllable and the added power is definitely nice. Towing over 11,000LBS, at highway speeds, the EGT‘s maintained around 800° while cruising. While accelerating it was easy to keep the EGTs under 1300°.

Final thoughts

The truck is very drivable and usable for towing and daily driving; yet it is quick and fun to drive while still averaging over 18 MPG.

Head on over to Off-road Authority to take a look at all of our offroading articles!

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