If you've followed our Duramax Build-Up project, you've seen us take a 2005 Chevy LLY Duramax from complete stock condition and add a little life to it here and there. We've added an MBRP Cool Duals off-road exhaust, Dynomite Diesel Performance 50 horsepower injectors, a Torquemaster intercooler from Black Widow Diesel and AEM Brute Force HD intake, all centered around the Hot + 2 Xcelerator programmer from Pacific Performance Engineering.
Further plans include a Garrett 4094 ball-bearing turbo, Industrial Injection's modified CP3 and Dual Feed fuel line, PPE's 40-Series Turbo Installation Kit, and of course, more fuel from the Hot + 2 Xcelerator (to be featured in the August issue of Diesel Tech).
But before we cross that bridge, we had a couple items to install to tie up some loose ends (that, and we were still waiting on parts for the other stuff). What better time to add a PureFlow Technologies Air Dog fuel system.
Vacuum vs. Pressurized
Stock GM Duramax fuel systems are vacuum systems where the CP3 draws fuel from the supply tank. By installing the Air Dog, we've changed that to a 10 psi pressurized supply system. The real difference, however, is how the fuel is prepared by the Air Dog unit prior to injection. The Air Dog removes air and water vapor from diesel fuel (which has a tendency to hold air-as evidenced by how easily diesel fuel foams in the tank during fill-ups). Clean, air-free diesel fuel is sent through the fuel system to the CP3 and on to the injectors, while the air and excess fuel filtered by the Air Dog unit is returned to the fuel supply tank.
The result is a better spray at injection and a more efficient burn of the fuel. That turns into more power at the pedal and, if you're not so heavy on the pedal, improved fuel economy.
After installing the Air Dog Fuel Preparator on our LLY project truck, we first noticed how quiet the system is compared to other fuel supply systems. In fact, we re-checked our connections on the system because when we turned the key to the run position, we expected to hear more noise.
To further see what was happening inside the fuel system between the tank and CP3 pump, we installed a fitting on the fuel filter housing for a low-pressure digital fuel gauge from Dakota Digital. With the Air Dog installed, we see about 9.8 psi static pressure in the system. Under heavy acceleration, the pressure drops slightly (the biggest drop we've seen was down to just under 7 psi). Where fuel pressure really matters on a Duramax is in the common rail, but it's interesting to see what change the Air Dog had on the other side of the CP3.
As for performance, we did see gains from the Air Dog. We ran the truck on Custom Auto's SuperFlow dynamometer before and after the installation, and saw noticeable gains in horsepower. With stock programming in the truck's PCM, the Air Dog added about 10 horsepower on the dyno. With a mid-range tune uploaded to the truck, we saw a gain of nearly 35 horsepower on the dyno-simply by installing the Air Dog.
Since 10 pounds of pressure in the fuel system outside of a pump that creates 26,000 psi, we know that's not the reason for the power gains. The only explanation is the condition of the fuel with and without the Air Dog preparator in place. Why? According to PureFlow Technologies, air and vapor are compressible, which creates a delay in the injection timing process. Delayed or retarded injector timing causes a loss of power. When the air and vapor is eliminated from the fuel, the injector timing is corrected and power is restored. Basically, the Air Dog Fuel Preparator is eliminating a huge variable behind diesel engineering (contaminated fuel) and correcting the injection process to the way the engineers originally intended it to be.
One more observation we've made after driving the truck for a few thousand miles with the Air Dog installed: The exhaust's black smoke output has decreased substantially. We attribute that to the corrected injector timing, since retarded injector timing can cause excessive emissions.
Pacific Performance Engineering
Black Widow Diesel
Dynomite Diesel Performance
Sun Coast Converters
Titan Fuel Tanks