How does the TCU reads the fuel pressure?

Joaquim

The TCU does not read fuel pressure.  Fuel pressure must always exceed airbox pressure (Rotax calls it manifold pressure to the sensor is on the airbox) The fuel pressure is a delta in relationship to the airbox pressure to prevent the airbox boost pressure from simply forcing all the fuel out of the float bowl.  UMA does make such a gauge that will connect to the fuel pressure regulator and to the airbox to read that pressure delta for fuel pressure.  I don't know what Stemme has, perhaps ask them or try to find online a wire and fuel system schematic.  

The TCU actually reads the engine RPM, the throttle position, the ambient temperature, ambient pressure, The manifold pressure (with sensor on the airbox), manifold (airbox) temperature and finally the servo position for wastegate control. You can find all this in the maintenance manual heavy for the type 914. 

Cheers

Hi Joaquim,

In addition to R.W. confirming the TCU does not read fuel pressure, I offer the following.

The “fuse box” you found is the E-Box as described in the Stemme S10-VT maintenance manual.

The UMA fuel pressure sensor you found is wired to the “Fuel Pressure Module” within the E-Box which in turn is wired to your fuel pressure warning light on the instrument panel. The fuel pressure monitoring system and the “Ignition Retarding Module” share the same (3A) power circuit breaker.

What you found is the original fuel pressure monitoring system installation from the Stemme factory, my suggestion is :- if it is functioning correctly, do not mess with it.

A screen shot of the Stemme wiring diagram (MM page 3-41) showing the fuel pressure monitoring system is attached.

I think if you want to display fuel pressure on your new computer, install the new transducer in a convenient position (with new, dedicated wiring) as we discussed previously and do not alter the existing fuel pressure monitoring installation.

Cheers, Des.