Mixture

[Isimmo]

Originally Posted by Audi Derek

Its been in bits at least twice now and all is well, just can't seem to get the CO right.



..

We set up the Hydrocarbons first, then when hot, worked the CO back... Then, ultimately the CO went too low, so we 'upped' the fuelling again, and it was incredible, as we upped the fuel so the HC's 'didn't' increase.

[Phil Payne]

Originally Posted by Audi Derek

Which way do I turn the mixture screw to increase the fuel, is it clockwise or anticiockwise.

Clockwise to increase (richen) and anti-clockwise to decrease (lean).

But it ain't quite that simple. The dish in which the paddle moves is actually a set of truncated cone sections that approximate a curved surface. As the paddle rises through these cones, more and more air passes per unit angular displacement.

The mechanism (a kind of pantograph) that uses paddle displacement to lift the metering head's plunger also moves non-linearly.

Cocking all this up in a third dimension is the volumetric efficiency of the engine, which varies dramatically with rpm, etc.

You can get an engine in almost any state (air leaks, etc.) to idle - but the key point is that all components should be set up at the same point on the graph. Audi is very insistent, for instance, that the breathers should be detached and plugged whenever an engine is set up - if it doesn't run properly when they're reattached, fix the problem and don't fudge the setup.

[andydunn2]

Originally Posted by Phil Payne

Clockwise to increase (richen) and anti-clockwise to decrease (lean).

But it ain't quite that simple. The dish in which the paddle moves is actually a set of truncated cone sections that approximate a curved surface. As the paddle rises through these cones, more and more air passes per unit angular displacement.

The mechanism (a kind of pantograph) that uses paddle displacement to lift the metering head's plunger also moves non-linearly.

Cocking all this up in a third dimension is the volumetric efficiency of the engine, which varies dramatically with rpm, etc.

You can get an engine in almost any state (air leaks, etc.) to idle - but the key point is that all components should be set up at the same point on the graph. Audi is very insistent, for instance, that the breathers should be detached and plugged whenever an engine is set up - if it doesn't run properly when they're reattached, fix the problem and don't fudge the setup.

Wow.... I am just glad the answer was so simple...