Light Aircraft Association

Just a thought...at low throttle you have a large vacuum between the valves and the throttle plate that may be sucking air through a leaking gasket or rubber joint. Don't those BINGs have a rubber neck to hold them onto the inlet manifold? Could it be leaking air in at low throttle?

Are you using a wideband Lambda or a narrowband?

I used a Weber-Alpha narrowband for a while but later invested in an INNOVATE system using a wideband and a digital display. You can see exactly what the Lambda is and even see the change in Lambda as the carb float valve opens and the float chamber fills up. Very accurate.

On the Bing, is there a seal on the throttle butterfly hinge? On HIF44 carbs (Mini Metro etc) they have a rubber seal in there.

If you slacken off all of the valve rockers (valves then closed) you could blow down the Bing intakes and listen for leaks?

Useful articles:
http://www.krnet.org/misc/mixture_meter.pdf

http://home.hiwaay.net/~langford/corvair/o2meter/

http://www.ellison-fluid-systems.com/ar ... ystems.htm

Could you have blocked the breather for the float chamber?

Good point. If the carbs are enclosed in the high pressure area of the cowling then they'd possibly have enough ambient pressure to overcome the fuel flow by making something like 3psi, enough to force the float chamber needle valve back up to the valve seat? Just a thought. My carb is aft facing and out of the pressure 'zone'. Have you a photo of your installation?

I'm clutching at straws a bit, I know, but between all of us I'm sure we'll get there eventually!

Cripes!!! I might have got something right?

Just feed the carb float vents to the area in the air box that has the high pressure this will help compensate the mixture . This is a similar way a Rotax 914 keeps the mix when the boost comes up.
Kev