Carb Jets

[Street Ryderz]

Can someone educate me on why atmospheric pressure has anything to do with airflow to carburetors? I would assume a larger intake and air rushing in at 35 mph instead of 1 mph or whatever it is usually will cause more air to flow into the carburetor.

I explained it above when you first posted,this is a 2 stroke not a 4 stroke and the intake is not a constant as it is with a multi cylinder 4stroke with constant vacuum.A 2 stroke rely's on atmospheric pressure going through the carb in pulse's.A bigger carb/venturi requires the engine to create a larger vac before it will in more air/fuel,as Chris said you can't push more into it that's just not how it work's!

 

[Street Ryderz]

Actually the 14.7 is the ideal AFR (air fuel ratio) which is 14.7:1. If you want more air/fuel to go through your engine, it has to be ported. A bigger carb and bigger exhaust or like GreasyChris says TURBO!

No actually I WAS referring to atmospheric pressure of 14.696 to be exact! The stoichiometric ratio of 14.7 is corrected by jetting to match the air flow.

 

[BIG BOBBY]

I explained it above when you first posted,this is a 2 stroke not a 4 stroke and the intake is not a constant as it is with a multi cylinder 4stroke with constant vacuum.A 2 stroke rely's on atmospheric pressure going through the carb in pulse's.A bigger carb/venturi requires the engine to create a larger vac before it will in more air/fuel,as Chris said you can't push more into it that's just not how it work's!

the "spitback" effect demonstrates perfectly (IMO) how the vacuum/intake demand ends,..and momentarily goes the OTHER way,...rendering any sort of air-ramming practically useless?? all you can do is make it as easy as possible for that tiny motor to inhale. (one example: low restriction air filters.)

 

[YetiWoodz]

So wider intakes, reed valves, and billet velocity stacks are useless then?

 

[YetiWoodz]

Actually, I know the reed valve works, but what about the other ones and how do they compare to the reed valve?

 

[GreasyChris]

No, they all work when used properly but that all depends on your port mapping and the tuning of your pipe. You just cant bolt on a wider intake and expect miracles.