Running over the sensors range has multiple effects....


1) NO OVERBOOST PROTECTION.
E.G. Say you run 35 psi on a 3bar that only measures 29 psi then suddenly your
wastgate jams open and you get 40 psi = engine melt no warning.

2) OVER RANGE BOOST WEARS THE SENSOR OUT
A three bar sensor is designed for two bar of boost. If you continuously keep
stressing the sensor by over pressure you are reducing its usefull working life.
3 bar sensors are fragile even when kept in range from my experience.

3) ECU IS PRETTY DUMB
If the ecu is mapped for the boost out of range say at 35 psi and the sensor tops
out at 29 psi, all is ok if you run 35 psi but drop the throttle back a bit then the
boost tails off, if the boost is 32 psi then it is still getting fuel for 35 psi causing a
rich mixture. Some ecu's can overcome this but not many !

On my car, I run a 5 bar bosch sensor which can measure over 45 psi boost.
My normall running boost is 34-36 psi which is fuelled correctly and I have an over
boost fuel cut at 38 psi.
Also, I have closed loop boost control as the sensor measures the boost through
out the whole range.

Hope all this makes sense..