The Myth of SOTF Truck Tuning
Tuning a diesel engine with switch-on-the-fly (SOTF) tuning is a longstanding trend that has been going on for many years in the industry. With plenty of after-market parts and options to choose from, it has historically been rather easy to change up the power potential of your truck, allowing for more or less torque and horsepower depending on the job at hand.
So what is SOTF tuning? Up until 2011, Duramax powered diesel trucks could have an upgrade installed called a DSP5 (Duramax Switchable Position 5). This upgrade began with an update to the electronic files in the Engine Control Module, using a custom EFI LIVE operating system, and was accompanied by a dial wired into the dash that allowed the driver to choose between five different settings (as pictured on this page). As this dial was turned, the ECM would change tune files in the operating system, changing the fuel pressure maps, throttle maps, etc. to match the setting and give more or less power to the engine.
However, in 2011, the stock ECM in the Duramax vehicles were changed, and are no longer able to be customized in the same way. This means that multiple tuning files are unusable, and any modifications have to work within the stock GM software. So while we can tune up the ECM to give more power, it’s no longer able to switch between different files “on the fly.”
This brings us to the biggest myth of modern SOTF tuning. You may see some people with post-2010 trucks and a DSP5 dial, who have installed workarounds that (they say) allow them to go from the max setting, all the way down to the lowest one, changing their horsepower in between. But those methods work in the opposite way than they used to: now, they limit fuel and power to the engine from the new high-level tuning, as opposed to increasing it from stock with different tune files. The new dials are, more or less, glorified electronic throttle limiters. This is most often done by fooling the fuel temp sensor readings.
This is bad for your vehicle!
When the new tune file is installed to your ECM, your transmission doesn’t change with it. It takes some time for the transmission to “learn” the shifting patterns and get used to the way the ECM works. If the power level is constantly being limited and increased by the dial, but the ECM is stuck with a single tune file to try and interpret that input, the shifting patterns will be erratic, inefficient, and even dangerous and/or damaging to the transmission.
Take towing, for example. You may think it’s safe to set your dial to a low setting and floor the pedal – after all, it’s not that much power, right? But the first 50% of your throttle is the same power as the first 50% in your race tuning, and if you don’t know when that limiter kicks in, your transmission can easily burn out. It’s not unheard of for one single error like this to wreck a transmission completely.
While it may be great for our business to rebuild or sell a new $5,000 - $10,000 transmission on every truck, not everyone can afford that kind of setback. That’s why we don’t do these "sensor fooling" SOTF tunes, and we will always recommend that our customers don’t get them, either. We’re happy to tune your diesel powered trucks up to its highest potential – but that’s where we’ll leave it, so you can get years of service out of it with one less problem to worry about!