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Posted 01 August 2003 - 11:10 AM
CFM. Cubic feet per minute... maximum volume of air allowable to speed through the carb in a minute. my carb from the caluclators I've used is 113CFM (EA81 hitachi carb).
If I put a 500CFM (overestimating of course, it's just an example, I don't plan on adapting a huge holley to my car!) carb on my car, is the rating for the CFM the MAX it can try to mix gas with?
the N/A of the engine sucking in air, is that the only force that sucks/puts the air/fuel mixture into the cylinders? So if I put a huge carb on my car, it assumes at full throttle it's sucking in 500CFM of air, and so it puts the correct mixture of gas for the 500CFM into the engine, despite the fact that it's not *actually* pulling 500CFM worth of air in a minute? *thereby havnig a whole crapload of gas in the ratio gas/air* and flooding the engine? That would be a massive flood.
that would suck, if I'm right. or not suck enough, actually.
thanks for any help, just trying to learn.
Posted 01 August 2003 - 12:44 PM
I think where your thought process has gone arwy is that you realized the air is getting *sucked* into the cylinder by the engine, but didn't realize that the gas gets in by the same method - the carb does not "decide" how much gas to put into the fuel, it only decides the ratio of gas to air. the ratio (for our simple discussion here) will always be the same, say 1/10 (1 part gas for 10 parts fuel), so if your sucking 500 CFM, then 50 CFM of that is gas, and 450 is air. if you drop to 200 CFM, then 20 CFM is gas, and 180 CFM is air. get the idea? In conclusion: The carb determines the ratio, and the engine determines the volume.
BTW, in a not-so-simple discussion, you would have to bring in the fact that as the throttle opens, that ratio may change, in mathematical terms, the ratio of fuel to air is not linear with throttle position.
Posted 01 August 2003 - 02:19 PM
I was contemplating what would happen if I got a dual weber setup. Just for kicks, a thought I had.
Posted 01 August 2003 - 02:20 PM
Posted 01 August 2003 - 02:36 PM
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