Dyno-Tested
Now that we've given you all your warnings, you're probably ready to see how it performed. Our last baseline with injectors was 196 hp, so we figured we should now be well over 200 hp. On our first pull with the fuel screw turned in 1 turns, we made 234 hp. On our next pull at 2 turns we netted 250 hp. Finally, our last pull at 3 turns got us 264 hp and 500 lb-ft of torque, or an extra 70 horsepower and 98 lb-ft of torque over our number with the pump on its stock setting. We made one more pull with the screw turned in 4 turns (close to runaway), but it didn't make any more power, despite blowing more black smoke.
So were we happy with how our weekend turned out? You bet we were! We're in swinging distance of 300 hp at the rear wheels and so far have only spent $800 on injectors. Also, our transmission was slipping even worse with each pull we made, so we're expecting even better numbers once a tighter converter and new transmission are installed. We'll also be installing gauges so we can stop tuning blindly, and throw on an eBay-sourced nitrous system to burn up our extra fuel. Stay tuned: It's going to get fun.
Getting the collar off is a pain, as seen by our mangled fuel screw. We used a pair of pliers to yank it the rest of the way off after we broke it apart. | 
With the fuel screw out, slowly work it back up the damaged thread, where the collar was. We found out that we now had 14 turns total, or about eight more than stock. | 
Put the fuel screw back in at one turn over stock and take the piping off the turbo to choke the engine if needed. We used the box that our old injectors were in because it was the right size, laminated, and pretty thick. A 2x4 is also a good bet; just make sure it is clean. |
With the collar off, you can see how many more turns we have left on our pump (arrow). | 
With the pump turned up, you'll have to adjust your idle back down. This is done with the idle screw (arrow). With the fuel screw at three turns, our truck idled at 1,100 rpm in neutral, so a lot of adjustment was needed to get it back to 750 rpm. There is a 10mm nut on the back of the idle screw that is a real pain to get to. Cummins makes a 90-degree tool specifically for this, or you can just try to break it loose with a punch. Either way, it's frustrating. | 
With the truck on the dyno, we were excited to see a 70hp gain at the wheels. We also noticed that the pump fuels longer. At 80 mph with just the injectors, the truck only had 50 hp left at the wheels because of defueling, whereas with the pump turned up 3 turns, we were still making 200 hp. |