Our Back to Basics project continues as we are in the process of building a 1998 Dodge 2500 Quad Cab, powered by the Cummins 6BT (12-valve) engine. Our goal with this truck is to build significant horsepower and torque, making this truck a lot of fun to drive, while at the same time, tune this truck so that it can be driven as a daily driver with good fuel economy and practicality. Normally with 12-valve engines, because they're not electronically adjustable, you have to make a choice: Either drive a tractor with great reliability and economy, sacrificing excitement. Or drive a hot rod with big power, big smoke, but with limited drivability. Unfortunately, life's full of compromise. Sometimes you just have to settle. However, in this case, we demand more. We want the best of both worlds. With the right tuning, we think we can have it all.
Project Recap
So far, we've replaced the transmission with a full billet, Fat Shaft trans from Ultimate Transmission It's firm, shifts quickly, runs cool, and the Ultimate Transmission assures us that it will hold up to anything we throw at it. After the tranny was done, we took the truck to Big Twin Diesel in Boise, Idaho to rebuild the top end of the engine. They installed a new Hamilton street/strip camshaft and did a complete valve job, including new 165 pound valve springs, also from Hamilton Cams. BT also milled and cut the head for a fire-ring head gasket and ARP head studs. We also installed a Baja bumper with an integrated Warn HD PowerPlant winch and (four) PIAA ATP (All Terrain Pattern) beam lights. Our next project on the mighty 12-valve is a fuel makeover.
Upgrading
Big Twin Diesel began our fuel upgrade by replacing the stock lift pump with a FASS Titanium Series fuel and air separation system. We chose the Titanium pump because it packs all the power of the heavy-duty FASS system into a smaller, more compact unit. It actually uses the same pump as the HD system. Our FASS mounts to the underside of bed on the driver's side. It will supply the P7100 injection pump with 200 gallons of fuel per hour at 45 psi as it separates water, and removes contaminates and air from the fuel. Fuel that's free of air and contaminates means longer life out of our injection pump and injectors and better fuel economy. We chose to use a FASS pressure regulator in addition to the Titanium pump so we could control the fuel pressure to the injection pump. This will allow us to provide exactly 45 psi of fuel at idle and then increase fuel volume as the injection pump consumes more fuel under power. We can do this by running a boost reference line from the charge air manifold on the engine to the FASS regulator. The regulator will allow more fuel volume as it senses the higher boost pressure. Our FASS pump eliminates the need to use the stock fuel filter, mechanical lift pump, and fuel heater that are currently mounted on the engine. By eliminating these, we have removed fuel restriction and the possibility of the common 12-valve fuel leak from the fuel heater.
Pat Liskey at Big Twin told us we'd need around 550 cc's of fuel output from our P7100 injection pump to drive the turbos efficiently. Beyond the injection pump, we'd use 90hp injectors from Dynomite Diesel to atomize the fuel. We removed the injection pump and sent it to Dynomite Diesel to be built for higher fuel output. DDP converted our 180hp pump (that comes with automatic trucks) to a 215hp pump (these came in manual transmission trucks before they built the pump for power). The 215 pump is a much better platform for building a hot pump. At the end of the day, DDP sent us back a big, bad pump that will flow 900 cc's of fuel. We won't be able to utilize all of this fuel with our 90hp injectors, but if we ever want to build this truck for racing, we'll have enough fuel on tap for 1000hp. However, for this build we're going for efficient, drivable power, so the 90hp sticks should provide enough fuel for the truck to build 600hp, but burn lean enough with the compound turbos to drive daily without being a smoky pig.
Boost Equals Fuel
Before Justin Collingham at Big Twin installed the pump he primed the pumps governor circuit with oil to make sure the internal parts receive enough lubrication when we first start the engine.
The pump is installed with eight bolts, the T block, and AFC (Air Fuel Control) boost reference control line.
The AFC could be thought of as the brain of the pump. It controls the fueling rate of the pump based on the amount of boost pressure it receives from the boost reference line that comes from the charge air intake manifold. More boost equals more fuel.
Delivery valves sit on top of the fuel barrels. The delivery valves regulate the amount of fuel that is allowed to flow from the plungers inside the barrels into the injector lines and then through to the injectors. This 900 cc pump from DDP has "full cut" delivery valves that flow a huge amount of fuel.
Now that the pump has been bolted into place, Pat sets the timing on the injection pump. He sets it to an aggressive 22 degrees advance timing. First, he pulls the timing lock pin from the side of the pump. This is a plastic pin that has a slot in it that locks the pump in place for shipment so the timing doesn't get completely out of whack during transit. This pin must be removed before attempting to make adjustments on the pump timing. Pat attaches a dial indicator to the top of the number one plunger barrel, installs the pump gear on the front of the engine and then rotates the engine forward so that the pump plungers move to 22 degrees advance position. After the pump plungers have been set, he carefully removes the pump gear without disturbing the position of the plungers and rotates the engine to TDC without changing the pump position. It's important to note that the engine should always be rotated clockwise when doing this so that gear lash doesn't make the timing sloppy. After the engine is at TDC, Pat reinstalls the pump gear and replaces the timing lock pin in the side of the pump, but with the non-slotted side facing in on the pump, so it can turn freely. When installing the pump gear, Pat torques the gear nut to 175 ft./lbs. in a four stage process. First to 50, then 100, 150 and 175 ft./lbs. because the stock torque spec. of 120 ft/lbs. can allow the gear to spin on the pump spindle on a high horsepower build.
After the pump timing is complete, Justin adds a dual feed line to the injection pump from the FASS pump. One line feeds the P7100 front three plungers, one feeds the rear plungers.
Now that the injection pump is plumbed and ready to go, they install the 90hp DDP injectors.