There are three different kinds of tuners you can use to boost the performance of your truck:

1. ECM flashers: Reprograms ECMs (engine control modules) to alter fueling and timing
2. CAN bus tuners: Hacks into the truck’s CAN (controller area network) to change settings for fuel, timing, traction control, engine management, and more
3. Wiretap only tuners: Does not alter ECM settings, but alters the fuel system itself; i.e. holds the fueling solenoid opening longer than usual to give your truck more fuel

Basically, tuners help your truck create more power by boosting its fuel intake and advancing timing. There are a few other things tuners do to increase your truck’s performance, but fuel and timing are the two main ones. They manipulate your truck's ECM into giving the engine more fuel than usual and advancing the timing as much as possible.

Some people like to install more than one tuner on their trucks to achieve a super optimized tune. If you’re thinking about doing that, we highly advise against it. Here’s why:

1. It Can Mess Up the Air/Fuel Ratio

To put it plainly, having multiple tuners on your truck can make the ECM go haywire.

Your ECM has a few tables to determine your truck’s timing and fuel levels. If multiple tuners have access to those tables, the numbers can become skewed and throw the air/fuel ratio out of whack. Running lean or running rich can lead to a bunch of problems, including excess exhaust temperatures, excess wastegate temperatures, transmission problems, and destroyed engines. It's definitely not a risk worth taking.

2. It Maxes Out Fueling Sooner

Using two or more fueling tuners can result in your truck using more fuel than needed. What a fueling tuner does is raise your truck’s minimum fuel intake. So let’s say one tuner makes your truck use 20% more fuel. A second one may see the raised minimum intake set by the first tuner and think that it's the truck’s OEM level, and then raise that number by another 20%. As a result, your truck will be using 40% more fuel than usual. Why have your truck guzzle that much gas all the time?

Cummins Forum poster me78569 came up with a great analogy to explain this:

“Stacking tuners is like only being able to control your volume on your stereo between 5 and 10. You'd be pissed if your radio never went below 5, why do you want your truck to drive the same way?”

Drastically increasing your truck's fuel intake not only wastes fuel, but also may flood the engine, which brings us to our next point...

3. It May Flood the Engine

Running too rich may flood your engine, resulting in smoke and/or the engine’s inability to start. It’s because an excessively rich air/fuel mixture cannot be ignited. You want to keep your fueling level low enough to prevent flooding the engine.

4. It May Blow Up Your Head Gaskets

When you have multiple tuners controlling the timing, you’re putting your truck at risk of over-advancing the timing and making the cylinder pressure reach dangerously high levels. That can result in blown head gaskets.

5. It’s a Waste of Money

Many people think that stacking tuners will give their trucks more power than ever. That’s actually not true. While it’ll get more power, its power will max out and stagnate after it reaches a certain point. However, you’ll get less and less control of your truck as the throttle will continue to decrease. Why waste money on multiple tuners to achieve the same results you could get with one tuner?

What To Do Instead

It’s much safer to size your injectors correctly to match the one tuner you have controlling your truck’s fueling. If you must stack tuners for some reason, only use tuners that do different things. For example, install one tuner to control the fueling and install another tuner that controls the timing. Make sure they don’t override each other.

If you're looking for a quality tuner, we recommend Edge Products or Superchips. And if you have any questions about the right tuner for your truck, feel free to email us - info@performancetruckproducts.com.