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Are Tuning Boxes Safe? (Turbo Petrol Engine Tuning)

In a word, “depends”. The safety of a tuning box depends on how many sensors the tuning box is intercepting and how much development work the company has done.

This article deals specifically with tuning boxes being used on turbo petrol engines and the two main perceived problems with them.

Are Tuning Boxes Safe? – The Argument Against Tuning Boxes

Some internet forums will have debates between Team Remap and Team Tuning Box.

Air Fuel Ratios

The big argument Team Remap likes to use is the when the tuning box increases the boost pressure it does so by lying to the engine. Because the engine does not know the boost has increased, it also does not know there is more entering the engine meaning the air fuel ratios will be lean.

Lean equals heat and/or detonation which has the potential to kill an engine very quickly.

Lambda Sensor

The argument continues, if the car is fitted with a wideband lambda from the factory this offers some level of safety but the damage has already been done because the lambda sensor is measuring what happened in the past ie the car’s ECU will be making adjustments after the combustion process has been completed which is too late.

Ignition Timing

And finally ignition timing, specifically, if more is entering the engine then ignition timing needs to be retarded and if the tuning box is lying to the ECU about the boost pressure then the ECU will not know the accurate amount of air entering the engine meaning ignition timing will be too advanced causing engine damage

Are Tuning Boxes Safe? – The 3 Issues With These Points

Looking at the lambda aspect first.

Modern lambda sensors react in fractions of a second. Granted, it is not ideal measuring after the combustion process has been done, but the lambda sensor updates the ECU many times a second, so the chances of the air fuel ratio being able to go dangerously wrong in a fraction of a second is unlikely.

Addressing the air fuel ratio argument directly.

The car’s ECU does not use the lambda sensor as the primary way of controlling the amount of fuel it injects into the engine. In most modern car’s, the key signal comes from the MAF (Mass Airflow) sensor.

Even though the tuning box is manipulating the boost signal going to the car’s ECU. The car still knows exactly how much air is entering the engine and can alter the fuelling to suit.

On ignition timing.

Ignition timing is calculated according to the mass of air in the cylinder and the RPM of the engine. Again, the car’s ECU is still reading the MAF signal and the RPM signal so the car’s ECU will still be using the correct ignition timing.

Ignition timing is also monitored by a knock sensor.

One of the biggest advances in modern turbo petrol cars over older generations is the way modern ECU’s adjust ignition timing.

Older generation cars had fairly crude ignition timing strategies. If the car was fitted with a knock sensor from the factory, the signal from this sensor would be treated as a safety device ie if the engine detected knock it would pull timing by a set amount until the knock stopped.

New cars use the knock sensor to constantly change the ignition timing, in effect modern ECUs rely on the knock sensor to constantly tune the engine as the car is driven. No longer is the knock sensor a safety device, it has become integral to the operation of the engine in normal use much like a MAF or a MAP sensor.

The point I am getting to is that tuning boxes may rely on the car’s ECU ability to monitor ignition timing to ensure the engine car run safely even though it is being fed inaccurate sensor data.


There are some exceptions to this rule, ie tuning boxes which alter the MAF sensor signal going to the ECU.

In these cases the tuning box manufacturer will be satisfied that the car’s ECU can adapt the fueling correctly using just the lambda sensor. Tuning boxes which intercept the MAF sensor signal are not common but they do exist, for some BMW models for example.

How a tuning box manufacturer will discover on which engines it can do this safely is not clear to me but here are some hypothetical examples.

Certain tuning box manufacturers may have contacts inside the car manufacturer ie they can speak to the people that wrote the factory coding.

Alternatively a tuning box manufacturer may simply copy another manufacturer eg if company A has a product which manipulates the MAF sensor on X engine, then company B also makes a product that manipulates the MAF sensor without doing any testing of its own and/or without understanding what the car’s ECU is doing.

Are Tuning Boxes Safe? – Safety Measures

One of the most common lines rolled out by tuning box manufacturers is “100% safe” or “factory safe”, or something along these lines.

Why and how can they say that?

Because tuning boxes rely on the safety measures/parameters programmed into the car’s ECU factory software


The MAF signal.

On an engine where the tuning box manipulates the boost pressures sensors, the MAF sensor is used as a fail safe.

Even though the car’s ECU is under-reading the true boost pressure, it does know how much air is entering the engine at the specific RPM. If the volume/mass of air entering the engine exceeds the maximum value in the car’s ECU factory software table, the car’s ECU can trigger a check engine light for the MAF sensor eg “sensor out” of range and if required, put the engine into limp mode.

Injector duration.

An engine where the MAF sensor signal is manipulated along with the MAP sensor signal, the lambda sensor can be the fail safe.

Even though the car’s ECU is under-reading the mass of air entering the engine it can see from the lambda sensor signal that it is having to add more fuel. The car’s ECU can compare how much fuel it is injecting into the engine to achieve the target air fuel ratio against the amount of air it is measuring entering the engine.

If these two numbers become implausible eg the engine thinks “hold on, I’m having to open the injectors 15% more than I think is normal for this mass of air to get the air fuel ratio I need, something must be wrong with a sensor or sensors” It may give a check engine light for the MAF sensor and/or the lambda sensor. If there is a massive divergence between the two signals it may even put the engine into limp mode.

Ignition timing.

On an engine where the MAF sensor signal is manipulated along with the MAP sensor signal, the  knock sensor can be the fail safe.

The car’s ECU is under-reading the air mass entering the engine.

If the difference between injector duration and the MAF sensor signal is not enough to cause a check engine light.

But the car’s ECU is registering slight engine knock and is having to retard ignition timing. If the amount of ignition retard it is having to implement is implausible eg the engine is thinking “why is the engine wanting to knock even when I am pulling ignition timing more than I think is normal? There must be a problem with a sensor or sensors, I’ll give a check engine light”

The ECU might give a check engine light for the MAF sensor, it might give a check engine light for the fuel system eg low pressure, it might give a check engine light for a timing sensor eg crack or cam sensor it may even give a check engine light for the knock sensor itself.

Whatever the case may be, there are many interconnected maps in the car’s ECU. If any of them go out of range the engine has the ability to inform the driver and even put the engine into a safe mode or a limp mode if necessary.

And this is how and why tuning box manufacturers can say their product is safe.

Are they correct to say it is 100% safe?

Yes and no.

If you look at the situation as black and white you can say the tuning box manufacturers are correct. If the engine performs in a way that causes damage, that damage is 100% down to the car manufacturer for allowing the engine to operate in a way that was damaging.

But nothing is black and white. There are grey areas.

To give an example

The car manufacturers will carry out extensive testing of their products in various conditions and temperatures.

They could conclude that X car was driven at maximum power in X heat and had no issues, the engineers could say “we do not see how someone could operate the vehicle in these conditions and have problems”.

But throw a tuning box into the equation, the car could be performing in the same conditions as tested by the car manufacturer but it is making 20% more power. The car manufacturer would never have tested the car in these conditions.

And in these circumstance you could say the claims of the tuning box manufacturer are not correct.

But you could also say that the user of the tuning box also has to use some common sense. If the user of the tuning box is towing a heavy load up a big hill in summer, you could argue that common sense would dictate they should take it a bit easier than they would if the car was not using a tuning box.

Are Tuning Boxes Safe? – Dumb Devices

Ultimately tuning boxes are dumb devices. They are no different other dumb devices like bigger turbos, bigger cams, nitrous, bigger intercoolers etc.

You could say that tuning box manufacturers are making their products out to be something they are not.

You could say tuning box manufacturers portray their products as advanced tuning tools which use X processors, and have “digital” technology etc

But the reality is they are a dumb device because they rely on the programming of something else to work properly, just like other passive/dumb parts like cams and big turbos.

The performance of their product is ultimately constrained/controlled by the car’s ECU original software and it is in the car’s original ECU software where the intelligence is found.

So in short are tuning boxes safe?

Assuming the design of the tuning box is done well, ie the design of the tuning box is suitable for the car it is intended for, 99% of the time they are safe because they rely on the car’s original safety measures.

However the user of the tuning box needs to exercise some common sense and needs to accept that like any other device or part, anything that increases the power of an engine is going to reduce the life of the engine, the difference it makes will depend on the user.



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This page was last modified Jun 4, 2019 @ 7:02 pm

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