As a habitual high-flyer, I've used my mixture control more than the majority of Coupers (which still isn't all that much).
First I got it cleaned and re-wired for a control cable. Sometimes you have to lap the moving plate to get a good fit -- sorry I can't tell you how. I FIRMLY think that you should install a SENSITIVE EGT where the 25 degree marks are far apart. On some gauges, there may be 25 degree lines, but they're so close together they are useless. At any altitude, 2,000' and up, I can lean the engine by the accurate gauge. True, with any engine/carb, you don't gain much at low altitude. Unless you are on a very long cross country that stretches you fuel load, I wouldn't bother down low. In my Coupe, I don't get enough roughness at cruising RPMs to be accurate in my mixture settings from just sound and feel. However, using the gauge, I can lean the engine to peak EGT and push it accurately back to the rich side the prescribed number of degrees. Warning: the changes take a few seconds to stabilize. Make a change, see the effect on the gauge, make an adjustment, see the effect on the gauge, till you get it where you want it. I have no trouble setting my mixture to 50 degrees on the rich side of peak temperature for cruising or to 100 degrees on the rich side of peak temperature for max power. I've talked to dozens of Coupers who don't understand the concept of going high -- they've never, ever had their Coupes above 5,000'. Why not? It's nice up there too! See the article on "There's gold in them there hills" in the back of Stick and Rudder for a thorough discussion of the range effects of high cruising. Up high there are no thermal bumps -- perfectly smooth air, different view, natural air-conditioning in summer, sometimes _wonderful_ tail winds, longer range out of your tanks on long trips, 10-16 MILES of gliding range if there's loss of power -- lots of reasons to go high. But going high only pays you back in improved range if you accurately use your mixture control. -- Ed Burkhead East Peoria, Ill. N3802H, 415-D
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