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With our new BD transmission and torque converter installed, we were ready to crank up the power on our Project 12-Valve. But where to start? The cheapest and easiest way to get big numbers without a lot of dough is by cranking up the fuel, so we decided on a three-pronged approach of adding a fuel plate, performance injectors, and delivery valves. We'll go over each of these in turn and tell you why we picked them and what they will do to give your diesel more power.
Fuel PlateA fuel plate is basically a stop inside the Bosch P7100 injection pump on '94-'98 12-valves that's designed to limit how much fuel your engine can receive at a certain rpm and boost level. There are many different fuel plates to choose from, all with different fuel curves and maximum power levels. We chose a #6 fuel plate, which is rated to give an increase of 70 hp over stock. There are more aggressive designs available, but we were concerned about our exhaust gas temperatures (EGT) with larger injectors and delivery valves, so we chose a more conservative design.Cost: $225
InjectorsNot all injectors are created equal, and factory injectors are often built more for mileage than for adding a bunch of power. Again, we took a conservative approach by having Imler Diesel add some of BD Diesel's 40hp injectors, which feature a modified Bosch nozzle design that has been enlarged with Electrical Discharge Machining (EDM) and has Extrude Honed injector tips. Our hope was the injectors would work well with our mild fuel plate.Cost: $500
Delivery ValvesDelivery valves are located inside the injection pump and are used to regulate how much fuel is sent to the injectors. Our fuel curve had been modified with the fuel plate, and the injectors were now larger, so the last step was to put in a set of high-flow delivery valves to make sure the new injectors were receiving plenty of fuel.Cost: $450
The ResultWith the new fuel modifications in place, our truck came alive on the dyno. In stock form (but with the performance transmission), the truck put out 172 rear-wheel horsepower and 391 lb-ft of torque on the chassis dyno. EGT stabilized at about 950-1,000 degrees F, and boost was approximately 20 psi.
With the new fuel plate, injectors, and delivery valves in place, the truck made an impressive 272 rwhp and 636 lb-ft of torque, but EGT rose to 1,400 degrees while boost remained steady at about 20 psi. On a subsequent dyno run in Overdrive, our EGT hit 1,500 degrees, which was the self-imposed limit for our 300,000 mile truck, so although this setup makes power, it also makes plenty of heat and smoke.
We were very impressed with how well our truck responded to bolt-on parts. We didn't adjust the star wheel in the injection pump, slide the fuel plate, advance the pump timing, or use any other tuning tricks to get more fuel, yet we gained an additional 100 hp and 245 lb-ft of torque. With our EGT at 1,500 in Overdrive, we figured we had enough anyway. With all the fuel, the opacity level was pretty high and the truck would haze throughout the entire rpm range; the stock turbo wasn't cleaning up the smoke at all.
With these types of fuel modifications, one should really keep an eye on the EGT gauge because the truck will be able to peg it if you keep your foot in the throttle long enough. We wanted to do full quarter-mile runs and needed more than just 50-70-mph passing power, so stay tuned for next month when we will install a new turbocharger, an exhaust manifold, and an intake in hopes of cooling things down and adding even more power.Cost: $1,175 for 100 hp and 245 lb-ft of torque
