Quote:
Originally Posted by Schulisco
The sensor plate height defines the way the lever can make and related to this it defines the amount of fuel being injected. Will say - the lower the sensor plate is adjusted the more way it will make based on the same amount of sucked air. In other words the mixture gets richer on lower rpms over the rpm band. The opposite is the higher position of the sensor plate will lean the mixture because the lever has less way to travel. According to this the basic setup is directly connected. If the basic(my personal wording "injection begin") setup is not correct, this affects the mixture in the same way but finer resolution: The CO screw is nothing else than a fine tuning mechanism for the sensor plate height. The goal is to find the right point that the injection begins precisely exact then when the lever is lifted by the sucked air of the starting engine (on engine startup) or to keep the mixture especially on idle as lean as possible and as rich as required. The rest is easy: The CIS and the setup of every component is "hard coded" to match the engine's requiremnents. Will say you cannot exchange freely a fuel distributor from e.g. a Mercedes 6cyl engine with 911SC one.
You can imagine the way the sensor plate lever travels as a "sliding window". If the window is either too low or too high, the mixture is partly correct only, but never over the full rpm band! This explains why some engines will start good, but having poor performance and really bad fuel economy. Others start really bad, but run better, have bad low rpm behaviour etc.
Thomas
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You are talking about the CO 3mm mixture screw moving the FD plunger. I have a good understanding of how this effects everything. It affects plunger height in the FD at all times.
I am asking about the AFSP zero position at rest prior to start. This is altered by the 7mm nut and screw underneath the FD inside the air box. Porsche says the edge has to be level with the venturi or up to .5mm below.
After the start the plate floats in the air well above the screw so Im not sure how the “zero position”, as its called in the Bosch book, effects a running engine. My thinking is that the sensor plate height (and really, we are talking about the position of the plunger resting on the arm) effects the initial start for a second or two and then has no effect.
Having said that, the AFSP height at rest IS important. But only to put the plunger in the right place for start. After that the plate moves with the air column.
This screw changes the resting height of the plate. I have moved it all over the place and have never noticed any change in the AFM or how it runs after start except at the very extremes.