Q. I have a Cummins diesel-powered drag race truck. I’m thinking about adding a nitrous oxide system to reduce turbo spool time and improve overall power. Do diesel engines react to nitrous the same way as gas engines?

Turbocharged diesel engines are an excellent platform for nitrous oxide. When correctly tuned, it’s one of the best ways to extract more power while simultaneously reducing exhaust gas temperature (EGT).

Unlike a conventional gasoline engine that draws in an air/fuel charge and uses a spark plug to ignite the mixture, a diesel engine compresses only air in its cylinder, then injects fuel directly into the cylinder just before the piston reaches top dead center. A high compression ratio creates high cylinder temperatures that spontaneously ignite the fuel.

Additionally, diesel engines have no throttle body, so they’re free to take in as much air as the turbo can supply. Also, they operate at a broader air/fuel ratio range than gas engines, commonly functioning between 10:1 and 20:1 lambda.

Making maximum power in a diesel is a matter of providing the engine with as much fuel as can be burned by the available air. EGT is one of the primary limitations when attempting to add more fuel for additional power.

Injecting supplemental oxygen via a dry shot of nitrous allows the engine to burn extra fuel more efficiently during rich conditions, spools the turbo faster, speeds up the staging process, improves consistency and ETs, and lowers EGTs.

Wiring up a nitrous system can be as basic as a momentary driver-controlled button or as cutting-edge
as using a progressive controller, like the Nitrous Express Maximizer 5.

In fact, there are several diesel-specific nitrous systems out there from several popular manufacturers like Nitrous Express, ZEX, and Nitrous Outlet.

engine bay with cummins ram diesel engine in a gmc sierra pickup truck
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Author: Dave Matthews

Dave Matthews was a mechanic for the U.S. Army, a Ford dealership, and served for many years as a fleet mechanic for construction companies. Now a technical content producer at Summit Racing, Dave has spent decades working on everything from military vehicles to high performance race machines.