Originally Posted by BigBanana
It's obviously not a simple subject.
Looking at this link, they explicitly state the box does not increase pressure.
There's a lot of processing goes on in a tuning box. Hence the 'high' cost.
There's a lot it can't do, as you say, turbo pressure, torque limiters, top speed limiter....
But, I can understand that intercepting the pressure signal can have an effect on the injection time, if the signal feedback is not [just] changed in amplitude, but time displaced. Yes, it's fooling the ecu.
However, if it were just effectively reducing the signal, would it cost £300+.
Details on how it works seem a bit vague but, lets see what else turns up.....
The statement on Tuningbox website is not very clear. A tuning box cannot extend opening times of the injectors as the tuning box does not connect to the injectors. It connects to the fuel rail pressure sensor, a sensor that purely monitors fuel rail pressure and feeds the rail pressure back to the ECU to monitor. The fuel raise pressure is set by the ECU mapping and monitered by the fuel rail pressure sensor, if the two dont match then the engine will go into limp mode to protect the engine, ie fuel leak, blown injector. The tuning box fools these values and pushes the pump pressure up. The clever part in the tuning box is to keep the actual pressure and required pressure the same.
The link below is a picture of the fuel rail and components on a 335d, item 3 is where the tunit box connects into, fuel rail pressure sensor.