I Want my 4.09 Spit FM's back.........

[WTE_Galway]

Originally Posted by Ernst

As far as i known Mrs Shilling Orifice was a not a definitive solution. The time for engine recovery was just lesser, but the negative g effect still there. Even carburetor was not as good as fuel injection.

All the Tilly Orifice did was restrict the maximum rate of fuel flow to the float chamber and hence reduce the rate of flooding and resultant over rich mixture cut-out in the SU carbs fitted to early Merlins. (The needle valve was also modified.)

It absolutely did NOT eliminate the problem just made it more manageable.

Eliminating the problem completely was impossible without using a totally different type of carb or going to fuel injection ... the neg G issue was "built in" to the float chamber based SU carb design.

The onset of neg G flooding and cut out was much later in a Tilly/Shilling Orifice equipped Merlin than with a standard SU but the problem remained and sustained inverted flight was still impossible.

From 42/43 onwards Bendix and later Rolls Royce pressure carburettors were fitted and these actually DID eliminate the problem altogether.

[JtD]

Originally Posted by WTE_Galway

All the Tilly Orifice did was restrict the maximum rate of fuel flow to the float chamber and hence reduce the rate of flooding and resultant over rich mixture cut-out in the SU carbs fitted to early Merlins.
...
but the problem remained and sustained inverted flight was still impossible.

The Tilly Orifice reduced the fuel flow to the amount of fuel needed at maximum power - 12/16 lb of boost and 3000 rpm. At that power setting, the engine would not cut out in sustained inverted flight due to flooding.