Quote:
Originally Posted by Dougal
Photo is correct, you might need to scroll across to see the altitude compensator, depending on your screen size.
Adding boost pressure to that port is going to reduce fueling on boost.
All the different devices which can be added to the back of an A type pump work by pushing or pulling on one pin.
When that pin is pushed in, it reduces rack travel and reduces max fuel delivery.
When that pin is released, it allows full fuel delivery.
The real aneroid (which my engine has) is set off to the side of the governor housing and it's housing includes a rocker. This rocker is used to release the pin when boost pressure is added to the can.
As you can see the altitude compensator is directly inline with this pin, so adding pressure to the port on the back will push the pin into the housing, restricting rack travel and reducing fuel delivery.
If you want it to deliver full fuel on boost then you need to hook a boost line up to the other side of the can.
But such an endeavour is pointless as when set correctly, your altitude compensator won't be restricting fuelling unless at very high altitude.
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Dougal,
thanks for more explanation, it sounds like you have some key knowledge as to what is actually happening on the inside of the pump. I have not taken these apart, and do not know what reaction there is to the ALTCOMP/ANEROID getting more pressure. but I am trying to wrap my mind around some key facts, and the two devices in my mind work the same. one though is for no turbo, one is for turbo.
Something above seems inconsistent. What I think we are comparing is:
ALTCOMP set up without boost, only ambient pressure. Max fuel is delivered at max pressure which is sea level. so more pressure, pushing, should mean more fuel?
Aneroid - set up with boost pressure. Again, max fuel is delivered at Max pressure, in this case max boost pressure. max pressure, pushing, means more fuel?