Gale Banks and the rest of the crew at Banks Power have tried one way after another to kill their Duramax L5P diesel test engine, but so far, it just ain't happenin'. People had their doubts when they gunned for 912 horsepower on stock internals, but it pulled that off without issue. Now, they've tweaked the cam and installed an even larger Precision 8085 turbo, among other mods, pushing it past the 1,000-horsepower mark—and it's still going.
Quite a bit has changed on this current-gen Duramax to surpass the four-figure threshold, though it retains its stock pistons, valves and the like. The 6.6-liter required loads of extra fuel and even more air to produce such mountainous power figures, and you won't see it belching smoke, either. Banks has long stood against excessive smoke given his background in forced induction, so his MO is to increase both fuel and air in a way that's actually conducive to making power.
Banks reiterated this stance while discussing his approach to the project with The Drive. See, he's pretty familiar with these power plants as he builds them not only for street use but also for military applications. Banks is contracted with the United States armed forces and as other defense contractors learn the true capabilities of the new Duramax, they want to push the bar higher for even more output.
In Banks' video recapping the most recent power feat, there's a rundown of all the newest upgrades following the admittedly civil dyno run. Since hitting their last goal and achieving 912 hp on the engine dyno, they've added a Banks-spec Comp camshaft, a custom 8085 Precision turbo, a four-port TurboSmart boost controller and a 12-millimeter CP3 Bosch high-pressure fuel pump. The key mod here is that Comp cam, which allows them to alter valve duration and allow more turbocharged air into the combustion chamber.
The hot-rodding pioneer does a stellar job explaining these tweaks and how they result in more usable output. Peak horsepower is made at 3,809 rpm, or nearly 400 rpm higher than their last run, and Banks tells how this affects important parameters like revolutions per second, valve open time and power pulses per minute. The engineering speak gets pretty heavy here—that's what you came for, right?
Quick trivia for those who care: If valve open time is 7.5 milliseconds at 3,800 rpm, that's equivalent to 2.5 percent of the time it takes to blink an eye. Not that you needed to know that, but now you do.
Finally, Banks goes in-depth when discussing air and how much horsepower is truly gained with a high-functioning charge air cooler. He mentions that at these output levels, the cooler is adding just as much horsepower as the upsized turbo. Chew on that for a second.
The most impressive part about these dyno runs is how long Banks operates the engines at-speed. Not only does it prove that these power numbers are more than a fluke, but it shows how the Duramax can sustain at wide-open throttle for minutes at a time. Banks told The Drive that this is essential for testing and stems from his background in endurance racing, which just so happens to apply to military use as well given the harsh conditions they run in for hours on-end.
As for what's next, Banks told us he plans to keep pushing the L5P until it literally blows apart—whether that be at 1,100 hp, 1,200 hp or beyond. Once that happens, he said they can get into modifying more of the engine and seeing what the outright limits are. Whenever that time comes, we'll be here for it as this series is all sorts of addicting for the engine nerd inside us all.
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