Increasing injector size and pulse width are typical methods, but that comes with a caution: When you increase the volume of fuel sprayed into the cylinder, the pressure drops in the line between the pump and the injector. That, in turn, reduces atomization, and those bigger diesel molecules burn less efficiently, pushing fuel out the exhaust manifold (and producing the inky smoke commonly seen at diesel drags). Not only is that wasted energy, it also spikes the exhaust-gas temperature, causing a host of other problems.
Twin Cp3 Injection PumpsOne of the first steps in the performance upgrade of a common-rail diesel is to increase the fuel flow from the pump. The Bosch CP3 injection pump is a good unit, but since it has a positive displacement configuration, it can only move a fixed volume, hence the need for some backup. ATS has a relatively simple way to add a secondary CP3 pump. The system also includes a computer to coordinate the increased flow since two pumps are doing the work of one.
Clint Cannon of ATS points out that the immediate result of this install, even on a stock engine, is a crisper tip-in of the throttle response, along with an improvement in fuel economy. He also says he has seen the EGT drop as much as 200 degrees. But he emphasizes that these benefits all depend on precise engine tuning, and the ATS system includes a custom fuel curve in the computer module.
The improved mileage of a dual-pump setup might sound counterintuitive, but realize its purpose is not merely to increase volume, but also to maintain optimum pressure, and thus improve the fuel burn-which is what a performance diesel is ultimately all about.
Indeed, that's exactly what happened on Steve's oil burner. "Aside from the huge power gain, I noticed about an increase in fuel economy," he states. "This twin CP3 pump is a must when larger injectors are installed in order to maintain fuel pressure in the high-pressure rail. This simple modification made one of the biggest improvements to the engine performance, aside from the Multi-Stage twin turbo kit."
Turbo TestingWith the fuel delivery system fully loaded, Steve was ready to install his secret weapon: the MST. Another innovative aspect of Steve's twin-compound configuration is that it uses the factory Holset turbocharger as the high-pressure stage and the new MST Aurora 4000 as the large turbo. This combination of factory and aftermarket components reduces cost in comparison to other conventional twin turbo kits. As already noted above, the twin volute turbine design of the ATS MST Aurora eliminates the slow response of the large turbo, so there's almost no turbo lag.
That all sounds fine and good, but just how much of a power gain did Steve achieve? In relation to horsepower, the output at the rear wheels jumped from 325 to 498. The torque is what really tells the story, though, with a jump from 600 to nearly 900 lb-ft.
Prepping The Rest Of The PackageWhen the vehicle was at ATS, Steve also had head studs installed into the engine to ensure there would be no problems keeping the head gasket intact. With the street MST, he didn't need to have fire rings installed. A set of Bully Dog gauges monitor the engine vitals, two for turbo boost and one for EGT.
But that's not the end of the story. As noted at the outset, on any performance pickup it's important to not only work smarter, but also harder. That's why gathering some intelligence on the drivetrain is so valuable, in this case by using an ATS Billet transmission and Five Star Viskus drive torque converter with a deeper aluminum pan. The torque converter application is controlled using an ATS Co-Pilot transmission control module.