Thread: Chipbox for M5
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      01-16-2013, 12:11 AM   #3
Second Lieutenant
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Drives: MCB F10 M5
Join Date: Oct 2012
Location: Hong Kong

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Originally Posted by Boss330 View Post
This product is basically a very crude way of increasing power. It's been very popular in the diesel tuning arena after the common rail diesel engines came along.

The power box simply alters the signals that some sensors (on a common rail diesel it's the fuel pressure sensor) give to the ECU. Fooling the ECU to believe that it's running a low fuel pressure and increasing fuel pressure to increase power.

Say that the (diesel) fuel pressure is supposed to be 1800bar under normal conditions. The fuel pressure sensor gives a certain value/feedback to the ECU when the pressure is 1800bar. By bypassing the signal via the power box and altering that signal the ECU believes the fuel pressure is just 1500bar and increases the signal to the fuel pump and gets the fuel pressure higher. This then leads to the ECU receiving the correct fuel pressure feedback for 1800bar, but the real fuel pressure is 2100bar...!!!

This is probably also the same method applied to the M5. Most likely both fuel and boost pressure signals are altered to fool the ECU into believing that it's running low boost and fuel pressure...

The power boxes are really nothing more than a added resistance in the circuit to some of the sensors...
Yes, this should be how it works. Since it kinda of 'fools' the ECU, without actually altering the ECU settings, if you unplug it & go for service, in theory, BMW should not able to detect anything & thus no issue with warranty. Is that right ?

The other questions are :
- does it actually produce such performance gain ?
- any drawbacks for using this kind of chipbox ?