I heard both ,the carburetor runs richer or leaner with no air cleaner. Edelbrock says no air filter will mess up the metering and the engine runs richer. Some expert tuners say it leans the mixture. Is it dependent on carburetor design?
No air filter generally increases air flow thru the carb. That should draw more fuel to match the additional air and stay in tune. But the air flow is not diffused and broken by the filter so it could run thru the Venturi choppy and not draw fuel causing lean conditions. The filter could be acting as a restriction and act like a choke when it's put back on causing rich conditions. So I say it depends on carb design, filter type and condition.
Not a carb expert, but I did stay at a Holiday Inn Express last night, so....I do know that air cleaner design will affect airflow over/past air bleeds, bowl vents, etc. No air filter creates air shear and flow disturbance as air tries to enter the venturis without direction. Holley has attempted to address this with the HP style carb bodies that help smooth air flow, but again air cleaner design will be a factor by restricting and redirecting air flow. I've looked at a few air cleaner bases and the differences are subtle but make sense from a flow perspective. If it's an Edelbrock carb you are interested in, I know even less, but I can't help but think the same basics apply. Just my .02....
Most carburetors have the float bowl vented in the area above the venturi. This is to ensure that the fuel metered thru the venturis is controlled by airflow. If their is a restriction in airflow from the air cleaner the pressure drop is also applied to the float bowl, neutralizing the effect. If a bowl is externally vented and you have a restriction this will increase fuel flow or richen the mixture. Another function of the Air Cleaner, intended or not, is to straighten the airflow. This effect is unpredictable.
From what I have seen on a 600 Edelbrock with mechanical secondarys and a 450 Holley with mechanical secondarys using a wideband O2 sensor; if you take the aircleaner off it gets leaner and when you put it back on it gets richer. Weather or not this is from airflow restrictions or aiflow patters I dont know.
Depends - (figuring the filter is new !) What's the air cleaner media ? What's the diameter of the filter ? What's the height of the filter ? What's the shape of the filter base ? What height is the filter bottom vs. the carb. entrance ? How is air directed to the carburetor/air filter ? How much air is comming at the carburetor ? Air just from the fan ? Hot air from the radiator ? Cooler air from outside the underhood area ? Many questions to answer, many more "combinations" of answers to concider...! Mike
Interesting answers. If the engine is properly tuned with a filter and you remove it the engine will see more pounds of air (cubic feet) and will run lean. I think when edelbrock says it'll mess the metering up and run rich they are speaking of dirt plugging the airbleeds and that'll richen it up...but with flowing air they are selfcleaning so i wouldn't worry much about that heppening unless it sits for a long time. I wouldn't run without an aircleaner unless you are racing.
It's done plenty ! Not that it's a good practice or conducive to engine longevity but its done quite a bit. Also some times it's a MOFO to tune with the air cleaner on. Get it tuned perfect and reinstall the air cleaner and your tune is off. It's nice to know which side of perfect to aim for or be off to so that the re installation provides a perfect tune. Oh yea, Period.
I've tried different sizes and shapes and I always end up adjusting my carb accordingly. But, I'd NEVER run without. I tried a K&N for about 10 miles and there was so much **** in my carb, when I popped the cover, I tossed it in the trash. WORSE filter for a street car EVER. That's what running without an air cleaner is like... ****. I've had my best luck with a 14" air cleaner, but it looks like **** on a hoodless hot rod.
I once did some testing on my OT roundy round car (Mini Sprint) on a dyno: with pre filter and filter, with just filter and no filter at all. Basically no noticable change at all on the ch***is dyno. BUT this is with a high quality racing filter and airbox. I would imagine with a poorer quality filter, airflow would absolutely be affected.
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