One of the top 5 questions we hear is: Do I need a tune for my new part (that I am about to install)? It might seem like tuning is black magic when in reality it is not. In fact, it’s quite simple once you understand the fundamentals. In this blog, I am going to give you a very brief 101 level look at how your engine computer makes decisions so you can determine if you need a tune for that part you just bought. A tune is just changing the data tables your engine computer uses to make decisions.

In perhaps the simplest form we can break down the process of the engine control unit (ECU) or powertrain control module (PCM) into 3 simple steps. 

Input → Lookup Table → Output

The input is various sensors on your car that measure stuff. The Manifold Absolute Pressure reads boost, the Mass Airflow Sensor measures air going into the engine, the engine coolant temperature sensor measures engine coolant temperature etc. There are dozens of sensors on the car all measuring and then giving their values to the ECU.

The ECU operates as a sort of “lookup table”. Think of the ECU as a place that stores dozens of these lookup tables. Depending on the “input” the ECU does its thing and then sends out a specific “output” or output(s). If my intake air temp (input) is X and my mass airflow grams is Y (input) then use Z to tell something to do something. Z is the output.

The outputs are devices on the car that perform an action. Our fuel injectors and ignition coils for our spark plugs are great examples of things ECU outputs control. The devices perform an action based on the ECU that made its decision from the “inputs”. With me here? Let’s do a real over-generalized example of this flow. 

Let's say your car at wide-open throttle has inputs of 6000 rpm, is making 25 psi of boost, and has intake air temps around 70deg F. That info is now all sent to the ECU and it does some math and lookups. The ECU now sends an output, let’s say to an injector, that tells it to open for a brief period of time(duty cycle) so the engine can get the amount of fuel needed for proper combustion. And there you go, you understand engine control. This same logic applies to transmission control, suspension control, and many other systems and components. 

So now that you have the gist of the ECU let's move on to when do I need a tune for my aftermarket parts? The factory lookup tables, aka the stock tune, on your car are for a “stock” car with some margins for error and wear. Those hundreds of complex formulas are all written and tested on stock cars with stock OEM parts by Honda. We enthusiasts and tuners swap out those stock parts for bigger more free-flowing parts in the pursuit of power. 

Do I need to tune for “xyz” part I just installed? 

In a perfect world, the answer is yes. You would tune for every single power part you install on the car. In this way, that new part can be optimized via a new lookup table to get the most power and performance gain from it. 

Practically, a tune often doesn’t always make sense because the time and money involved with a tune doesn’t always give a great benefit. Most people don’t want to swap in a part and then pay another $200-$300 for a tune and take a bunch of data logs. If you did that every time you added a part then you could spend thousands on tuning and not get much benefit. It all depends on the parts added. It’s all about timing. 

Sometimes when we swap out parts the formulas no longer work correctly so we have to “Tune” for those changes. For example, our Race MAF requires a rescale of the MAF sensor because the housing is now bigger. The stock “lookup table” does not understand that we took a 2” hole and made it 3”. It requires a tune to give the ECU data it can make sense of. 

The stock ECU is very smart and can accommodate some small changes in parts. Generally, add-ons like a cold air intake, turbo inlet pipe, and front-pipe back exhaust don’t require a tune. That’s not to say that there is no benefit from a tune with those parts. It’s just that it’s ok to run these parts without one and the benefit of a tune will be small unless the tune also includes upping the boost. However, big airflow modifiers like a Turbocharger upgrade or emission-related devices like downpipes should get a tune. If we don’t get a tune then we can expect a car that feels slower than stock and may get unwanted check engine lights. 

We usually say that if you are just starting on your parts journey then 3 to 4 basic bolt-on parts are okay with a factory tune. As you grow into the bigger power mods you will most certainly want to start customizing your CivicX ECU and get a tune for your setup. 

You’ll need a tuner to even get a tune. Hondata and Ktuner are the most popular tuners for CivicX. They even include some base maps. This can be a happy middle ground between no tune (because it’s not worth the return) and custom tune (more time and money). 

I hope you guys found this useful and if you want to see more blogs like this drop a comment below.

-Vincent