Before we get in to working out which is best, a diesel tuning box or a diesel remap, let us look at how diesel tuning works in the most basic sense
More fuel = More power
However there is a limit to how much fuel can be injected into the engine and the limits come from combustion chamber temperatures, more fuel = more heat
And secondly smoke, having a car belching black smoke out the back may not be want you want.
Remap vs tuning box – How they work
Generally speaking a remap and a tuning box will do the same thing, they will both inject more fuel into the engine to make more power, where they differ is in the method.
A remap involves rewriting some of the software in the engine’s ECU. A basic remap will increase the fuel pressure at certain points to make more power.
A diesel tuning box will also increase the fuel pressure and certain points but instead of rewriting the software in the engine’s ECU, it will under-report the signal coming from the fuel pressure sensor which will cause the engine ECU to increase fuel pressure until it gets the signal it expects/wants.
Different types of tuning boxes
There are two types of diesel tuning box
The vast majority deal with changing the fuel pressure but there are a minority which will alter the injector duration.
Which is best?
In my opinion, fuel pressure tuning is the way to go. Yes you will be running the fuel system at higher pressures than normal for some of the time but at no point will the fuel pressure be too high as to be unsafe.
Injection timing on modern diesel engines is extremely precise both with regards to the amount of fuel being injected and also with regards to when the fuel is injected. If the duration of fuel injection is changed, then things are potentially not working at their optimum.
There is also the argument to say if you are injecting more fuel with the same duration things will also not be optimum but in my opinion, injection times and timing are more critical than the amount of fuel being injected.
Remap vs tuning box – Which lies?
Fundamentally a basic remap and a tuning box both lie to the ECU.
The remap lies by saying X fuel pressure = Y amount of fuel when the amount of fuel actually equals Z
The tuning box lies by saying the fuel pressure is X, when it is actually Y
Is there a difference? Not really
Tuning box vs remap – 2 questions
Which is best comes down to two questions.
Is it a stock engine?
Is the stock engine sand bagged badly from the factory?
On a stock engine I would say a tuning box is the way to go over a basic remap. Because the remap is only altering 1 table, the limits to making power will be the same as for a tuning box
If an engine is sand bagged from the factory then an advanced remap may be able to liberate a lot more power than a tuning box and still have factory levels of reliability. An advanced remap being a program which alters multiple maps within the cars factory ECU to stop it from limiting power.
Sand bagged meaning a car with the same engine as another model but for whatever reason the car manufacturer has reduced the power output on the one model to differentiate it from the more expensive car.
Tuning box vs remap – The winner is….
Generally speaking a tuning box is as good as a basic remap with the added benefit that you get something physical which you can sell later and something which you can adjust yourself without paying anyone else.
If you have modified the engine or you want to spend more money for a more in-depth remap ie a remap that changes multiples tables in the factory ECU, a remap is the way to go
It comes down to how much extra horsepower you get from an advanced remap vs the premium you will be paying.
Stock engine, basic remap vs tuning box = For the money, tuning box
Sandbagged engine = Depends how much you want to pay for the extra horsepower of the advanced remap, is the difference too small to justify the price?
Modified engine = Remap