Glowgeek

I'm convinced that how well the temp/pressure compensation works, richening vs. leaning, depends entirely on where the carb needles are set. I mentioned this earlier but didn't get my point across well because of my poor technical communications skills. I'll try again.

In the following example I'm using the phrase "over richen" as meaning the point on the fuel curve where a notable drop in rpm can be detected while moving a curve point upwards (richening) from the stoichiometric center value.

If say the needles are set to where an increase in the curve value of only 10% is required to over richen the mixture, the fixed compensation values for temp/pressure will have X affect on mixture strength. Fine, now, if say the needles are set (leaned) to where an increase in the curve value of 20% is required to over richen the mixture, the fixed compensation values for temp/pressure will have X/2 or 1/2 the affect on mixture strength. Of course this also applies to leaning.

I have found that in attempts to flatten the overall curve using leaner low speed needle adjustments that it is possible to end up having to increase a given curve point value as much as 80% (-100/+100 scale) from the stoichiometric center value to detect an over rich condition. When a needle is pinching off fuel to this degree the solenoid has to be modulated open much longer to supply a given increase in fuel. With the same needle setting it may only take only a 10% (-100/+100 scale) decrease in curve value from the stoichiometric center value to detect an overly lean condition. I'm not sure what to call this condition, "skewing the center line"? "Unbalanced adjustment"? Not sure, but in my thinking that HAS to negatively affect temp/pressure correction.

Intuitively I am now setting the needles to where the % of increase and % of decrease on the curve required to over richen or over lean from the stoichiometric center value are closer to equal. This is not possible to achieve at every point on the curve due to our compensating/overriding the mechanical fuel metering curve ground into our glow carb barrels, however it can be averaged, kind of, across the rpm range. Perhaps adjusted this way, more balanced, the temp/pressure compensation will have the best chance to work properly?