Diesel Tuning Options

How Diesel Tuners, Programmers, & Modules Work

For modern diesels, tuning alone can unleash significant performance improvements and increased fuel economy. The diesel performance industry has come to experience tuning in many forms, which includes tuners, programmers, and modules. For most, these devices are simply mingled into the term "chip", despite inherent differences in the device's approach. Performance tuning involves modifying various operating parameters, primarily timing and fueling characteristics, to favor maximum power output, often with little or no regard for emissions. For our purposes, we'll refer to a "tuner" as any of the aforementioned devices that aim to increase performance, fuel economy, or offer addition features through reprogramming or modification of an engine's factory calibration.

Popular performance tuner/programmer manufacturers include SCT Flash Performance, Edge Products, Bully Dog, TS Performance, and Superchips.

Diesel Tuners/Chips - Chips or tuners typically connect directly to the engine's PCM/ECM, though some examples connect through the OBDII system. Because of their direct link with the engine control module, these devices often offer "on-the-fly" selection of various performance levels and can be adjusted while driving. Chips/tuners do not reprogram the control module, they alter various parameters in real-time.

Diesel Programmers - A programmer plugs into a vehicle's OBDII (on-board diagnostic system) port and allows the PCM/ECM to be completely reprogrammed. The uploaded "tune" provides the control module with parameters that favor performance and/or fuel economy. Programmers often feature in-cab monitors that display various parameters that may include engine load, coolant temperature, boost, fuel pressure, transmission temperature, and exhaust gas temperature (with the installation of a suitable thermocouple). With programmers, tunes may typically only be uploaded (or changed) with the engine off. Changing performance settings can take several minutes.

Diesel Modules - A module or box is installed under the hood of the vehicle and typically intersects various sensors (fuel pressure and manifold pressure, for example). Doing so allows the module to read an operating parameter but deliver a different parameter to the PCM/ECM, essentially tricking the engine's control system into making adjustments that favor performance. For example, a module may read 5 psi of turbo boost, but tell the engine that it is currently making 10 psi of boost. Subsequently, the engine will deliver more fuel to match the airflow it "thinks" it is getting. Modules may accompany a programmer or tuner.

In all instances, tuners alter and/or modify the factory engine calibration. The actual parameters that are affected will vary by manufacturer and application, but may include a combination of the following:

Injector timing - The time at which an injection event occurs. The timing of injection events is critical in maximizing the efficiency of combustion.

Injector pulse width - The amount of time (in milliseconds) an injector stays open. A greater injector pulse width translates into a greater fuel flowrate per injection event and therefore a higher quantity of fuel injected per event.

Occurrence of injection events - Modern common rail diesels with piezo electric injectors are capable of performing multiple injection events for a single combustion cycle.

Fuel pressure - Fuel pressure is inherently important in maximizing the efficiency of combustion by promoting complete atomization of fuel, as well as increasing the potential fuel flowrate through an injector.

There is an abundance of tuning options for all Power Stroke, Duramax, and Cummins turbodiesel owners. The installation of a pyrometer is highly recommended when performing any performance enhancing tuning devices.

Pros & Cons of Tuning



Best "bang for your buck" performance modification for electronically controlled diesel engines

Increased fueling characteristics can cause excessive EGTs - a pyrometer is highly recommended in the presence of any performance tunes

Relatively simply installation

Higher cylinder pressures may be experienced with some tunes, increasing the risk of premature failure

Possibility of integrated monitor to display important parameters

Voids warranty for any repair stemming from the use of such devices (most dealerships will not warranty any powertrain related problems for owners with tuners installed). Although these devices may not leave any electronic trace, the use of performance tunes may be detected by other means.

Modified transmission shift schedule (for most automatic transmission applications)

Increased fuel economy (with proper tunes)


Canned Tunes vs Custom Tunes

"Canned tunes" are considered tunes developed for a specific year, make, and model engine. Canned tunes are mass produced and do not typically account for the use of additional performance enhancing equipment, such as aftermarket intake systems, turbochargers, and injectors. As a result, canned tunes do not always take advantage of improvements you have made or modifications you plan to install at a later date. Canned tunes are perfect for stock to mildly modified engines, but are less desirable in heavily modified applications.

"Custom tunes" are tunes developed specifically for your application, including any modifications you may have performed or plan on performing. Acquiring a custom tune can be as simple as notifying a product manufacturer of your setup and obtaining custom tunes, or as in-depth as having tunes installed, tested, and tweaked after multiple pulls on a dynamometer. In high performance applications, such as racing, having a truck dyno tuned is obviously preferred. Custom tunes are a must for outrageous twin turbo systems, large injectors, and heavily modified fuel systems.