Friends, I had the joy of flying my Coupe today and did experiment with the mixture control a little.
Here is what I experienced. I can feel a leaning effect from 3000ft on. It does not take much then on the push-pull control to feel the effect. The engine then will just run a little slower, it does not stumble or starting to miss. That happens when I pull more. I do not have a egt, so I can only go by the rpm, but for my purposes, that is enough of indication. So pushing it back to gain the rpms brings the knob to an almost closed position. Almost seems alright to me at 3000ft. At 5000ft, I can pull farther and find it easier to find the point for the correct mixture. If I pull too much, the engine will start to miss. Pushing back the knob, the engine smoothes out and I settle by having the mixture control pulled out approx. half an inch. While I was playing around with the control, it came to my mind that it might not be emphasized enough that the mixture control on Stromberg works ONLY when you have throttled back a bit, like 3/4 th of the full range. The Stromberg will not show signs of leaning at full throttle or at idle. It is important to remember that. At full throttle, the leaning effect is maybe there but I can not feel any roughness, regardless how far I pull the control. At idle there is no effect either, since the throttle is closed and no low pressure can be used for creating the leaner mixture - the low pressure port of the leaning mechanism lies below the throttle flap. Ok this is hard to understand without seeing at least a diagram. To say it simple, Strombergs can only be leaned at a partial throttle setting and one should put that into consideration. In any case, leaning is a good thing , it can be done down to 3000ft at least in my setup and less gas burned leads to a healthier engine and a fatter wallet. Hartmut ----- Original Message ----- From: Ed Burkhead To: 'Linda Abrams' ; 'David Winters' ; [email protected] Sent: Saturday, February 23, 2008 6:55 PM Subject: RE: [ercoupe-tech] Re: LEANING THE MIXTURE..the secret Linda and Dave, Dave is on to something there. I noted the same phenomenon a while back and wrote a similar comment into the ercoupe.org FAQ. The Stromberg carb reacts slowly but with good accuracy. I found that I could do 10° control of the temperature with an accurate EGT gauge. I could easily control whether I was at peak, 50° rich of peak or 100° rich of peak or whatever. But I had to move my standard push-pull very slowly and carefully but I could do it. I thought about installing a vernier mixture control but never got around to doing so. The standard push-pull is adequate but *I* think it's important to have a high accuracy EGT gauge with 10° marks or a digital readout. Ed
