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Cheap 12v Cummins Upgrades

Budget Performance Options for the 12v Cummins

The performance potential of the 12v Cummins far exceeds that of other mechanically operated, low tech diesels. It is undoubtedly one of the simplest engines to modify and can be can be upgraded to intense performance levels without the need for extensive alterations. 1989 to 1993 model year engines relied on a VE injection pump, while 94 to 98 12 valves featured the potent P1700 "P pump". The following are inexpensive modifications that will unlock more horsepower and torque from your 12v Cummins.

VE Pump Fuel Screw

Applications - 1989 to 1993 model year 12v Cummins

Both the main fuel screw (full load) and low boost fuel screw are adjustable on the VE injection pump for 89 to 93 Cummins engines. The low boost fuel screw, nicknamed the "Smoke Screw", is located on the top of the pump and controls fuel flow when turbocharger boost is low (i.e. limits fuel flow while the turbocharger is spooling). Tightening the screw will result in more fuel, loosening will result in less. The primary benefit of this adjustment is throttle response, though as with any fuel pump adjustment there is a fine line between too much and not enough.

The main fuel screw, or full load fuel screw is located on the side of the pump. It controls maximum fuel flow under full load. Extreme care must be taken when adjusting the main fuel screw, as if it is tightened too much, the engine may have a tendency to run away. As a precaution, remove the intake tubing from the turbocharger and keep a 2x6 handy to choke the engine should it run away on you. Tighten the screw for more fuel, loosen for less. Also keep in mind that engine idle rpm will increase with fueling.

VE Power Pin

Applications - 1989 to 1993 model year 12v Cummins

While playing with the fuel screws on the VE pump may result in free power, upgrading the power pin is a safer way to increase fueling characteristics for 89 - 93 model year 12v Cummins engines. The power pin essentially controls fuel flow - when fuel flows and how much fuel flows. Performance fuel pins, nicknamed "Power Pins", will not only increase peak horsepower and torque, but broaden the power band. Manufacturers advertise increases of up to 40 horsepower and 90 lb-ft; not bad for a modification that costs less $200.

Governor Spring

Applications - All 12v Cummins

3,200 and 4,200 rpm governor springs are available for VE pump Cummins (89-93), and 3,000 and 4,000 rpm governor springs are available for P1700 pump Cummins (94-98.5). The purpose of an aftermarket governor spring is to keep fueling constant and relative to rpm. For a factory VE pump, fuel flow starts to plateau as early as 2,300 rpm, less than ideal if you demand power beyond this. An aftermarket spring not only gives you more revs to play with, but allows for increased fueling in this range. If you have a manual transmission, you'll feel like you've got an extra gear once you have changed the governor spring. The 4,200 and 4,000 rpm gov springs are designed for race use and require stiffer valve springs; valve float may occur in this rpm range should you neglect these warnings.

Delivery Valves (DVs)

Applications - 1994 to 1998 model year 12v Cummins

Delivery valves, usually referred to simply as "DVs", serve as check valves for each individual fuel line coming out of the pump while also controlling injection duration. Upgraded DVs can yield significant increases in performance and throttle response for the 94-98.5 12v Cummins. Gains will vary considerably depending on the application and supporting mods. Aftermarket DVs are often described as creating a "crisper" injection event.

P1700 Fuel Plate

Applications - 1994 to 1998 model year 12v Cummins

A fuel stop plate, typically referred to as a fuel plate, is found inside of the P1700 injection pump on the 94 to 98 12v Cummins. Performance fuel plates increase the maximum flowrate of fuel from the P1700. This is a very versatile, entry level modification that can provide substantial performance gains for everything from tow rigs to full blown race engines. The fuel plate regulates fuel flow. A modified plate simply increases the maximum flow of the injection pump, and as a result provides increases in horsepower and torque.

Fuel plates are typically categorized by size #12 through #5. The higher the number, the less aggressive the fuel plate. Modifications should be performed by a qualified technician to ensure proper installation. Adjustable fuel plates are also available. Contact the manufacturer for recommendations on the correctly sized plate for your application and supporting mods.

A fuel plate that is overly aggressive for your application will lead to EGT (exhaust gas temperature) issues. As with any fuel modification, it is vital to match fueling and airflow characteristics. Stock trucks can see a nice bump in performance, but the potential is increased on engines that already have turbochargers that can feed a higher volume of air. Expect gains from 30 to 150 horsepower and 70 to 300 lb-ft of torque, dependent on your setup.