map clamping

[sierra3dr]

Is it just a myth?

installing a Zener Diode between the Signal and Signal Return Line so the engine controller will only see Map voltage to a certain point.
A Zener Diode is a Voltage Regulator.
When voltage reaches the threshold that the diode id designed for it closes allowing the excess current back to ground.
In this case the Zener Diode is 2 Watts/4.3 Volts so the Map Sensor will never see voltage above 4.3 Volts which is equal to approx. 11 lbs of boost.
Using a Zener Diode will prevent overboost shutdown BUT the controller will not add fuel above 11 lbs of boost so if you go over that you will be LEAN.

[capri v8 driver]

Ford map sensor work on frequency, not on voltage.

If you want a map sensor for boost, buy one thats ment for boost applications.

Using a Zener Diode will prevent overboost shutdown BUT the controller will not add fuel above 11 lbs of boost so if you go over that you will be LEAN.

And what happens if the engine goes lean at boost? Most ecu, programmed for N/A applications arent programmed for boost, so it will not compensated for boost anyhow.

[Dave]

I have done it with TT kits to push them closer to the overboost limit but as Paul says it is a bodge make no mistake.

Can be usefull but you are taking a big risk!

[JFB Tech]

TT used MAP clamping on their DOHC turbo kit but only to stop the ECU seeing the boost signal and going into LOS.  The DOHC uses a frequency output and the frequency was limited by a pcb wired into the MAP sensor wiring.  On this setup, the additional fuelling was controlled by a DCU, firing an additional injector.

In general, clamping the MAP sensor signal should only be used to prevent an OEM n/asp ECU seeing boost while additional fuelling/ignition advance would need to be handled by a piggy back device.

The best method, obviously would be do remap the ECU to cope with boost, or if not possible, ditch the n/asp management and fit something suitable for boost.