The Myth of SOTF Truck Tuning
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!
9/20/2020 07:09:22 pm
I already paid a trusted individual to delete my truck with a SOTF switch, I understand the view point you guys have on the subject matter. With that being the case, on mine the 1 on the dial is no added horsepower or torque. It’s just the truck without the emissions devices. Would you recommend that until a transmission tune is available?
12/29/2020 04:55:28 pm
Thanks for the information about engine tuning. I would like to find a tuning service. I think my truck is going poorly.
2/19/2021 05:30:12 am
The article “The Myth of SOTF Truck Tuning” has me rethinking about tuning my truck. The article mentions post 2010 trucks don’t respond to multiple tunes. Is this the same for 2006 Chevy trucks with a DSP5 and TCM tuning? Would the transmission always be learning because of switching between power levels, or does the TCM tune fix that issue?
6/17/2021 07:55:54 am
Thanks for clarifying how any modification needs to work within the original GM software. I don't want to do anything that can seriously damage my vehicle. So keeping within the original software can hopefully help with that.
7/5/2021 07:28:45 am
I appreciated it when you shared that you are able to change up the power potential of your truck in order to achieve more or less torque and horsepower depending on the job at hand. In this way, it helps to improve the performance of your equipment. I would like to think if a company needs to fix its heavy equipment, it should consider getting it tuned at a reliable place.
8/23/2021 08:43:39 am
I had no clue that I could choose from so many after-market parts for a diesel engine. I am looking into getting my first diesel vehicle. Being able to customize with after-market parts is a huge selling point for me.
8/31/2021 10:12:41 pm
Great write up! Would this be true for 2010 and up Cummins and powerstokes too or is it just relevant to the duramax?
Steven R Weltys
4/10/2022 03:06:05 pm
I have a 2016 duramax tuned with efi live soft tuning & tcm tuned. Your Myth of Soft Truck Tuning artical is very informative and helps me understand my truck better. I transport RV from the factory to the dealers. So I put on a lot of miles on my truck and gives me plenty of time to try different settings. So I have learned to run in the number one slot or the number 2 slot anything higher just really heats up the exhaust temperatures really fast. So pulling hills or passes or vehicles you need to get around in 3-5 slot will burn your motor up and transmission . So soft tuning was a big waist of money and know i now why after reading your article. Your other articles you wrote where very good also. My question for you is my truck has 500,000 miles on it should I leave the tune alone or reprogram it. I life in MT not that far from your shop.
10/7/2022 07:12:15 am
Useful information is provided. I must thank the author. I'll use these information for my clients. Thank you once again.
11/14/2022 10:06:19 pm
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