Quote:
Originally Posted by E Sully
It has no effect once the engine is running. It's the zero point Bosch used for the base position a in figures 12 and 14 when the engine is off. The air plate is at the narrowest point, and the fuel distributor piston is blocking fuel flow.
If the plate were set above that position, fuel could flow with the engine off due to a higher starting point of the plunger. If set too low then the plate would not be at the narrowest part of the venturi, it might leave a gap allowing for air to bypass the plate when starting, perhaps preventing the plate from lifting during startup.
The screw (4) on the small arm adjusts the fuel distributor piston to get the best fuel air mixture when the engine is running.
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Outstanding explanation with illustrations thank so much. Thanks too for defining the two extremes- too high would allow fuel flow too soon, too low the plate would not lift.
So on to my next question. There is a long ways, relatively speaking, between those two extremes. I’ve been to both ends. Off the top of my head over 1/4 inch between high and low (6mm) and maybe more. About 8-10 turns of the screw. The engine starts and runs the same as far as I can tell over a pretty wide area in the middle of that range.
It’s clear why Porsche would not want the plate too high for safety reasons.
Porsche says the plate can only be .5mm below the venturi edge. Anyone know where this lower limit comes from?
Thanks to all for the interesting discussion so far.