CraigLandrum
Jedi Hopeful
Offline
I recently bought a Gunson Colortune to try and be a bit more scientific about setting the mixture on the twin H6 SUs in our TR3A. The concept is quite attractive-by observing the color of combustion thru a special glass topped spark plug, you can exactly set your mixture to achieve the most efficient combustion, thereby maximizing both power and fuel economy. The target color is a neon blue-the more yellow you see, the richer you are running and the more fuel you are wasting. Installing the plug is easy and-in a shaded area-the combustion color is easy to see.
My main problem is the closer I got to blue, the weaker the engine ran and-using the old school method of raising the piston 1/8 inch and listening to engine revs(increase=too rich, decrease=too lean, no change=just right) the leaner it got. I finally ignored the color and went old school. The engine is running fine, although the yellow combustion color(and the black deposits on my plugs) tell me the mix is too rich.
I was never able to get to pure blue, even with lean needles installed and the mixture nut screwed all the way up. My son informed me that when he rebuilt the carbs he may have used HS6 rebuild kits instead of H6-don't know if that matters.
I'm worried since the plug deposits and the Colortune say I'm running too rich, but old school apparently tells me I'm dead on. FYI, timing is set at 6 deg btdc, floats verified to be set at 7/16, and there is no fuel overflow.
Can anyone here vouch for the accuracy of the Colortune/blue combustion method with respect to SU carbs? Any suggestions on why I seem to be running too rich but the old school tests would tell me I'm right on?
My main problem is the closer I got to blue, the weaker the engine ran and-using the old school method of raising the piston 1/8 inch and listening to engine revs(increase=too rich, decrease=too lean, no change=just right) the leaner it got. I finally ignored the color and went old school. The engine is running fine, although the yellow combustion color(and the black deposits on my plugs) tell me the mix is too rich.
I was never able to get to pure blue, even with lean needles installed and the mixture nut screwed all the way up. My son informed me that when he rebuilt the carbs he may have used HS6 rebuild kits instead of H6-don't know if that matters.
I'm worried since the plug deposits and the Colortune say I'm running too rich, but old school apparently tells me I'm dead on. FYI, timing is set at 6 deg btdc, floats verified to be set at 7/16, and there is no fuel overflow.
Can anyone here vouch for the accuracy of the Colortune/blue combustion method with respect to SU carbs? Any suggestions on why I seem to be running too rich but the old school tests would tell me I'm right on?