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Tuning Box – How do they work safely? (Petrol Turbo)

How can you plug a tuning box into a modern engine and get more power without a check engine light and without any problems?

In the case of turbo petrol engines, is was not so easy as it is today to simply plug in a device and get more power safely. ECUs of days gone by were simply not advanced enough to deal with something like a tuning box.

Modern ECUs are constantly adapting ignition timing to get the best power and the best fuel economy. This is probably the single biggest factor that allows a tuning box to be used on a modern turbo petrol engine.

In the old days you would set the ignition timing according to load and rpm and that would be it. This made simply increasing the boost less safe and less effective that it is today.

The second big advancement has been wideband exhaust oxygen sensor technology. Whereas in the past sensor technology only allowed the car’s ECU to monitor exhaust gas mixture at cruise. Now the ECU can monitor exhaust gas mixture all of the time, including full throttle which is when a tuning box is doing its thing.

What does a tuning box do?

On a turbo petrol engine it increases boost pressure, the amount by which it adjusts the boost pressure depends on the load on the engine.

Because a modern turbo petrol ECU is constantly monitoring ignition timing, constantly changing ignition timing and constantly monitoring the air fuel ratio both by using a wideband lambda sensor and also by measuring the amount of air entering the engine through the MAF sensor, modern turbo petrol engines can run safely with the increased boost of a tuning box.

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What is the limit of a turbo petrol tuning box?

While you can increase the boost with a tuning box there is a limit and the car’s ECU identifies that limit by monitoring the air fuel ratio but more so by measuring the amount of air going into the engine.

For a given RPM and given boost pressure, the car’s ECU will have a range of acceptable values for the MAF sensor. ie the minimum plausible amount of air entering the engine will be X and the maximum plausible amount of air entering the engine will be Y. As you increase the boost pressure you will also be increasing the amount of air entering the engine.

When the value from the MAF sensor seems implausible to the car’s ECU it will throw a check engine light or may even put the engine into limp mode.

Why is there a range of acceptable values for each RPM and engine load?

Because the volume, well technically speaking the mass of air entering the engine will be different depending on the weather conditions. High pressure, cold temperatures will mean more air is being ingested by the engine per RPM. And likewise high temperatures will mean a lower mass of air entering the engine for a given RPM.

For the engine to be able to operate in different weather conditions there needs to be a range of values by which it can operate.

And this is the factor that the tuning box manufacturers are exploiting. There are exploiting this range. They know an engine will work properly even if the engine measures air entering the engine increasing but at the same time it also see that boost pressure has not changed. This can happen in real life.

Getting back to the point, ie what is the limit of a tuning box. The limit is the acceptable air value that the car manufacturer has put into the engine programs.

Is there a problem with the tuning box approach to getting more boost and engine power?

Yes. Because the tuning box is exploiting the operating range built into the ECU for extreme weather conditions, when the car is actually in extreme weather conditions it can put the sensor readings out of range ie they become implausible for the ECU.

So while you may be able to turn up the settings on your tuning box in the summer, when the cold weather comes in the winter you may find your car throwing a fault code even though nothing has changed on the engine. The solution to this is reduce the settings on your tuning box and this is why it is so important to have an adjustable tuning box so you can maximise engine power during extreme weather conditions.

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This page was last modified Jun 25, 2018 @ 3:24 pm

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2 thoughts on “Tuning Box – How do they work safely? (Petrol Turbo)

  1. Hi,

    Two identical Mercedes 1800cc cgi engines, one tuned to 156bhp and one tuned to 186 bhp, as said the two engines are identical other than one has a state of lower tune. If a tuning box is purchased for the 186bhp engine and gives an increase to 210 bhp, can that same box be put on the 156bhp engine and give the same power.




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