What does a tune do?

So, you want more performance from your car and everyone is telling you to get a tune, but you’re not sure what that means.  Tunes are essentially a reconfiguration of your car’s software with the end result being increased horsepower and torque.  However,  tuning is important for reasons beyond maximizing power.

Big brother?

It’s important to understand that all modern cars are heavily controlled and monitored by computers.  Since the 80’s and I’m sure even earlier than that, certain aspects of the cars were controlled by a computer to some degree.  As time went on, more and more functionality went from mechanical to digital.  A great example of this are the gauges which are no longer mechanically driven or even fed by a sensor directly, but instead, managed by one or more of the cars computers.

The most important computer is the one that monitors and controls the engine.  You’ll hear this referred to as ECU, ECM, PCM and a few others.  The term will be different depending on platform, and who you’re talking to but the important part is that they are all referring to engine management.  I personally use ECU, so sorry if you don’t agree with that.

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What is engine management?

Engine management is exactly that.  The job of the ECU is to take in data, make decisions on what is going on, then tell the engine and related components what they need to be doing in response.  The decisions the ECU makes depends on how it was programmed, or tuned.  The ECU does this using both inputs and outputs.

Inputs are from sensors like oil temperature, engine rpm, throttle position, boost levels, O2 sensors, knock sensors, and so on.  Inputs can also be calculated values based on one or more inputs. Modern cars can monitor hundreds of data points.

Outputs control aspects like fuel injectors, ignition timing, boost control, rev limiters, valve and cam timing, and so forth.

If you took two identical engines, you could give them two different personalities just by changing the software on the ECU.  For example, one could be configured for high power output while the other could be configured for maximum fuel economy.  An engine can be configured to do both, and actually there are many cars on the market today that do achieve a balance of good power while still having the ability to get good fuel economy.

The software is the key to everything and when you hear the term, “tune” or “tuning”, it’s referring to the software and changing the parameters the software uses to control how the engine behaves.

What does a tune change?

What a tune changes depends on the platform, the software’s capabilities and the tuner. Some of the more common parameters are the rev limiter, ignition timing, fueling to adjust or correct air fuel ratio, changing the boost levels, changing the valve timing, changing the fan kick-on temperature, and increasing or removing the speedometer governor.

There are also features that tuners can add in like launch control, boost by gear, select-a-tune, and safety features like richening the air fuel ratio when knock is detected or remove features like torque management.  Again, these all depend on the platform, its capabilities and the tuner so be sure you do your own research for your specific car and setup.

Not just for engines!

Another important computer is the computer that controls the automatic transmission. These are referred to as TCU or TCM.  Again, it depends on platform and who you’re talking to.  When referring to tuning the transmission, it’s the same as tuning the ECU except the goal here is to improve shift points, remove certain features like gear lock out and adaptive learning.  If you’ve ever driven a car with a horrible shifting automatic, it can most likely be solved or significantly improved with a tune.

When is tuning required?

Tuning is important when you’re looking to maximize your power output, but tuning is also necessary and/or required when you are upgrading or changing out parts. Certain parts work differently and have different characteristics than the parts you’re replacing. Because of this, tuning is necessary in order for the ECU to be able to work with these different parts.

A perfect example is installing a turbo kit on a naturally aspirated engine.  The engine wasn’t programmed to understand boost and there are many areas of the engine software that need to be changed to properly understand and support boost.

Two more common upgrades are fuel injectors and atmospheric blow-off valves.  You can’t just install bigger injectors and expect the ECU to know how to use them.  Injectors might look the same but they have varying operational parameters that the ECU needs to know about in order to correctly adjust for fueling.

Installing an atmospheric blow off valve on a car that uses a mass air-flow sensor requires a tune because you’ve now changed the airflow vs what the ECU metered and adjusted fueling for.

As you can see, it’s not always a simple matter of just bolting on new parts.


To sum it up, tuning is basically changing the parameters the software uses to control the engine and/or transmission behavior with the goal usually being to increase performance, make the software understand how to correctly work with different parts or add features the car didn’t originally come with.

I do want to end with a response to the ever so common, “but I installed XYZ part(s) without a tune and the car is fine”.  First, it is entirely possible to install and use parts without a tune.  Secondly, just because your car drives doesn’t mean it’s optimal or even correct.  My point here is that research should always be done before making any modifications.

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About the author: Dustin Davis

I'm a car enthusiast always learning and sharing with other enthusiasts. My goal is to help novice enthusiast learn the fundamentals so they can start modifying their car the correct way. You can learn more by checking out my YouTube Channel   

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