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Fuel/Air Ratio, Fuel Flow and Vacuum Gauges


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Has anyone tried them before?


I know the vacuum gauges are pretty simple, they just use manifold vacuum to give you an idea how hard your engine is working. I've never installed one, but I've driven cars that had them from the factory, both NA and turbo.


The fuel/air ratio gauges use an oxygen sensor ( wide band IIRC ) to show you how much oxygen is in the exhaust stream. I wonder how fast the accuracy & response time is vs the cost? If these work well enough, they would be great for tuning carbs. Anyone used the old Gunson colortune glass see through spark plug?


Fuel flow gauges use a tiny wheel to measure the fuel flowing thru it. You would need some type of computer tied in with the vehicle speed to measure the miles per gallon traveled. 

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I've had pretty good luck with AEM wide band air/fuel gauges. They make it much easier to dial in carburetors. Make sure you use the weld on bung they give you for mounting the o2 sensor. How much the tip of the o2 sensor is in the exhaust stream will effect the readings. 

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Some O2 gauges and sensors only register stoichiometric with red lean and green rich LEDS. The better ones are wide band and display the actual rich or lean numbers. Better ones again have a heater to bring them on line almost instantly.  Mine's in after all four pipes merge into a single pipe so it reads the average of all four carburetors.


Gunson colortune glass see through spark plug? Great for setting idle mixture but how you going to see what's happening at full throttle out on the highway???


Vacuum gauge. I find that you automatically tailor your driving to get best mileage if you have the constant reminder of a vacuum gauge.


Fuel flow gauge. Can't see how this is any use whatever. New cars have EFI and know how much fuel is being injected at any time. Easy enough to compute and display flow over distance traveled for a mileage estimate and knowing the tank capacity and the average MPG, a remainder distance can be displayed. I just look at the fuel gauge to know if I need to fill up. 



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