If you have ever googled anything about chip tuning, ECU tuning, ECU flashing or similar, chances are you’ve seen everything from “wow, the best thing I’ve ever done” to absolute horror stories.
You know what? They are both true!
Just not at the same time, because the first person has had their car tuned properly and the second one took it to the cheapest guy with the cheapest copy of a tuning tool and “awesome, it was done in 20 minutes.”
If you are considering tuning your car, this is the article for you. We will discuss if your particular car should be tuned, what you can gain and lose and if it is possible to have more power and better fuel efficiency at the same time, as many tuners advertise. However, before all that, you need to understand what chip tuning is.
Naturally, the complete art of good tuning greatly surpasses the limitations of a single article, but if you bear with us, you will understand the points even if you’re not familiar with the basic engineering terminology.
So let’s get to it!
What is chip tuning?
Also called ECU tuning, ECU flashing and engine tuning, chip tuning refers to adjusting ECU (engine control unit) software to make it work in a different way — usually to gain more power.
These adjustments are based on the way engines work.
In short, air goes into the engine cylinders and gets mixed with fuel. The mixture ignites and the explosion that it creates makes the wheels of your car turn. The more versed among you will know the amount of intricacies that have not been mentioned in the previous sentence, but this (very) basic knowledge is enough to get the message across.
As you can see, the main aspects of this process are the air (actually, the oxygen in it) and fuel in the engine. Both are needed for an engine to work, and the more of them there are, the more power the engine has. The third aspect is ignition timing, i.e. at what point the air-fuel mixture ignites.
For optimal operation, the amounts of air and fuel inside the engine should be at a certain ratio. This ratio is called stoichiometric and when the engine operates at this ratio, it should mean that all the air and fuel are burned during combustion. For gasoline engines, this ratio is 14.7:1, which means that for every unit of fuel, there are 14.7 units of air.
Chip tuning is performed by adjusting the amounts of air and fuel and optimizing ignition timing. If you manage to increase the amount of air, you need to also increase the amount of fuel in order to have stoichiometric ratio. At higher RPMs, tuners and manufacturers often add a bit more fuel to the mixture to ensure that all the air has burned. This is why some cars, especially diesels, shoot black smoke from the exhaust during hard acceleration. They have more fuel than they can burn efficiently and they throw it out in the form of black smoke. However, this is usually not a sign of good tuning.
So, to recapitulate, tuning is most often performed by increasing the amount of oxygen fed into the engine, adjusting the amount of fuel to match the increase in oxygen and adjusting the timing of their ignition to make the best use of the combustion.
This brings us back to the two guys from the beginning with the two vastly different tuning experiences. Good tuning is performed using good tools that connect to the ECU and can read and write the information in it reliably. They are not cheap. Moreover, the measurements that give the tuners information to work with are performed on dynamometers that are also not cheap or small. A good tuning process also takes time.
What is usually cheap are generic tuning files that increase the amounts of fuel and oxygen by guessing where they should be. This is not a good option, as you will see below.
Is tuning safe?
It can be completely safe. A good tuner needs to have all the necessary equipment and be familiar with the stress levels that various car parts can endure. These are usually tuners who offer optional tuning stages 2 and 3, where they change some hardware parts that cannot deal with the desired power increase. They also need to make sure that your engine is in good condition before tuning. These tuners can perform perfectly safe tuning and their work is very highly regarded. Each engine is different and having reliable, real-time information gathered by using good tools and dynamometers means that a tuner can tailor each tuning to suit that particular car perfectly and stay within the safe boundaries. Of course, the importance of expertise goes without saying.
Some “tuners” buy a (usually cheap) tuning tool that connects to your car and they download the mentioned generic tuning files in bulk from the Internet, install the one that “matches” your car into your ECU and hope for the best. Hopes are rarely enough.
Some tuners are in the middle of the two. They usually have good tools, but they don’t have a dyno. They download the stock file from your ECU and send it to a respectable tuner who uses the information to tune the parameters. He then sends the file back to your tuner, who installs it in your car. This can be satisfying, although it can never be as efficient and safe as tuning based on real-time dyno measurements. Simply put — more information, better tuning.
So, why don’t manufacturers tune cars to the max? Why do they leave room for the tuners?
There are several reasons.
First, fuel quality plays a big role in tuning. The same model is sold in many different markets, so they have to make sure it will work well in all of them. They tune it down to make sure bad fuel is still good enough.
Secondly, they actually do tune. The Mercedes-Benz E-Class W211 had several I4 diesel variants ranging from 136 hp (102 hp in some markets) to 170 hp. That was all the same OM646 engine, just tuned differently.
Lastly, you probably know just how a facelifted model is also a bit more powerful than the pre-facelift. Manufacturers leave some space for improvement so that they can justify the price increase and boost marketing. The mentioned version of the OM646 with 170 hp came in 2006. The same engine in the same car from 2002 to 2006 had 150 hp. And this goes for vast majority of manufacturers and almost all of their models.
What cars should/shouldn’t be tuned?
Almost all cars can be tuned, but the gains for some of them simply do not justify the effort. Of course, we are talking about chip tuning only, without major changes in hardware parts.
In the section where we explained what tuning is, we said that one of the steps in tuning is increasing the amount of oxygen that the engine gets. This is virtually impossible with naturally aspirated cars (cars without turbo or compressor/supercharger), since they get only as much air as can naturally reach the engine. Some increase could be gained with O2 sensor adjustments, but it would be negligible in the vast majority of naturally aspirated cars. If you own one of these, splash out for some hardware parts or forget about tuning.
If you do have a turbo or a supercharger, you can gain some cool power from chip tuning, because these two parts are used to increase the amount of air sent to the cylinders. In most cases, adjusting turbo is a simple and very efficient software tweak, while adjusting supercharger requires a change in its pulley size — a minor hardware change that makes the software adjustments possible.
If we are talking about chip tuning only, turbocharged engines are the best option, supercharged come second and naturally aspirated — just don’t.
How much can you gain with tuning?
This depends on the car and tuning, but in most non-naturally aspirated cars, 10-15% is definitely possible. It also depends on the original tune done by the manufacturer. The mentioned OM646 from Mercedes usually gives about 190 hp after chip tuning. Now, if you start with the version with 170 hp, this is a nice increase of 20 hp. If you start with the version with 136 hp, you get about 54 hp more, which is a very healthy bump for a 10-15 years old I4 diesel.
Can you have more power and better fuel efficiency?
This is something that most tuners boast about, but it is fairly counterintuitive, especially now that you know that an increase in power also means an increase in the amount of fuel.
However, it is often true. Aside from just increasing the top power rating, chip tuning also inevitably improves torque. Both of these together mean that you can shift up earlier and maintain the same speed using less throttle and in a higher gear. This actually decreases fuel consumption, because the car requires less effort for the same results.
However, if your newly gained boost urges you to press the pedal to the metal, your consumption will inevitably increase.
We hope this article has given you a better insight into the possibilities of tuning and its potential safety. There is a lot more to say, but this should be enough to give you some basic info and do away with the idea that tuning is inevitably a bad idea, or that it can be done in a back alley in 20 minutes. Let us know if you have any thoughts or questions in the comments below.