Injectors
With any diesel engine you must first supply additional fuel to increase power. To achieve this, we decided to try out a set of Mach 2 (105 hp) injectors from Formula One Diesel. We could have sourced bigger injectors from BD. However, the guys at Formula One Diesel happened to be present at a local drag race event when we were ready to install. We won't bore you on these pages with the installation process, but instead illustrate the principle by which they function. Picture a regular run-of-the-mill garden hose, just like the one you'd find in your backyard. Now imagine this hose is turned on just slightly, enough so that water trickles freely from the open mouth of the hose. Though a bit exaggerated, we'll say this is your fuel system at idle. Next, imagine turning on the hose full blast; we'll say this simulates your truck's fuel injectors at wide-open throttle. Now picture a fire hose hooked up to a fire hydrant out in front of the house, and it's not hard to see where this little analogy is going. A set of bigger injectors simply allows more fuel into the combustion chamber, and they also create more efficient atomization.
Lift Pump
Unfortunately, Chrysler used a weak lift pump on '94-'01 Cummins-equipped trucks. These pumps are located down low, near the back of the engine on the driver side. Over time, these pumps tend to fail. When they do, they typically take the injector pump with them. This can cost thousands of dollars to repair, so anyone who is looking into beefing up a Cummins-powered Ram should at least install a low fuel-pressure indicator light (PN 1081130) or simply replace the fuel pump altogether with a new higher-flowing unit. BD offers a simple bolt-in replacement unit (PN 1050226) that is good to 600 hp. Retailing for under $265, this is extremely cheap insurance against injection-pump failure.
Fueling Box
We expect the Bomber to run competitively in the increasingly popular diesel drag racing circuits. So, we needed a fueling box that could help deliver more than enough fuel to exceed the demands of our new BD twin-turbo intake system. BD recommended the Edge Products Power Edge Comp box, which they stock. This little black box connects to the MAP sensor, injection pump, and a boost source. Once connected, the box is positioned in the cab where the driver can reach the controls. The driver interface on the Comp box is composed of three touch-sensitive buttons. Two of them activate the five different power levels, and one button turns the unit on or off. The box has a display that lights up, indicating which power levels are selected. Essentially the Comp box talks to the injection pump and changes the timing and quantity of fuel delivered to the injectors. Edge claims power gains up to 120 rear-wheel hp with the box on level five. Our dyno test confirms these claims.
More Air
Now that we've taken care of the fueling side of the equation, we'll move on to the other side. Without additional air, fuel alone will only create high EGTs and black smoke. So it is necessary to introduce more oxygen into the combustion chamber. The kit shown above was engineered to deliver just that for 24-valve Cummins-powered Rams with modified transmissions. With this setup, a smaller primary turbo feeds a larger secondary turbo, thereby multiplying air volume and head pressure. Back in Part 2 (Sept. '04) we installed a Scotty Air 2 intake system, which gave the Bomber cool-cowl induction via the HVAC intake cavity located just behind the firewall. This intake worked out great for us. However, due to spatial constraints under the hood, we had to abandon the Scotty Air system as it was not physically compatible with BD's twin turbo kit.
More Air = More Cylinder Pressure
Stock head bolts tend to stretch over time and should at the very least be re-torqued with any increase in cylinder pressure. We recommend replacing head bolts altogether with studs to prevent head-gasket failure. Cummins claims the stock head gasket on a 24-valve will typically remain intact with up to 55 psi of boost. Go much over that and you're running on borrowed time. Unfortunately, we learned this the hard way on our trip back to California, when halfway through Oregon our head gasket let loose, leaving us with a huge oily mess under the hood, an expensive tow bill, and a contaminated cooling system. The guys at Cummins Northwest of Medford, Oregon, replaced the Bomber's head gasket with a new OE unit. The repair cost nearly $2,500 and delayed our return home by nearly a week. Luckily, ARP makes a set of studs that can prevent this (shown at left). No doubt another thing we plan to do very soon. Another option is to remove the head from the vehicle and have a machine shop install reliefs around each cylinder for wire O-rings. With O-rings, we've seen Rams with boost levels as high as 100 psi with no problem.
BRING IN THE TWINS
First, the BD technician removed the Bomber's intake system, stock turbo, exhaust downpipe, and intercooler intake tube. Next, the radiator was drained so that the steel coolant line running beneath the exhaust manifold could be modified. A brass compression fitting was used to allow proper alignment of the coolant line once it was reinstalled.
Then the BD technician removed the exhaust manifold from the head of the engine. The center of the three-piece ATS manifold had to be inverted to provide a mounting surface for the new secondary turbo. While the exhaust manifold was removed, the BD technician also drilled and tapped the manifold for an Exhaust Gas Temp (EGT) port and a turbo drive pressure probe. The holes for the original EGT probes on the opposite side were plugged and the mounting base with its four holes was tapped for studs (shown above).
Next the BD technician removed the freeze plug from the lower rear area of the engine block. This required careful attention so as not to let the plug drop into the crankcase. To remove the plug, he first drilled a small pilot hole in the center of the plug. Then he installed a short sheetmetal screw. This created a way to pry the plug from the block with a pair of pliers. Once the freeze plug was removed from the block, the BD technician inserted an aluminum fitting to provide a return drain connection for each turbo's cooling oil line.