Carb flow rate?
- Thread starter Morgan
- Start date
How about this calculator:
http://www.efunda.com/formulae/fluids/calc_orifice_flowmeter.cfm#calc
Inputs
Pipe (inlet) diameter upstream of orifice, Di:
Orifice diameter (less than the inlet diameter), Do:
Pressure difference across the orifice, Dp:
Fluid density, r:
Flow Coefficient, Cf:
Answers
Velocity at the inlet, Vi: 2.02 m/s
Volumetric Flowrate, Q: 4.13 ft^3/min
Mass Flowrate: 0.00251 kg/s
Close? I do not know.
http://www.efunda.com/formulae/fluids/calc_orifice_flowmeter.cfm#calc
Inputs
Pipe (inlet) diameter upstream of orifice, Di:
Orifice diameter (less than the inlet diameter), Do:
Pressure difference across the orifice, Dp:
Fluid density, r:
Flow Coefficient, Cf:
Answers
Velocity at the inlet, Vi: 2.02 m/s
Volumetric Flowrate, Q: 4.13 ft^3/min
Mass Flowrate: 0.00251 kg/s
Close? I do not know.
It should be in the 70-70 range but that's a guess. Either way it will not be the limiting factor for most street apps, unless you plan on using it on a very large engine. What's the app and what cfm reading are you getting on the intakes at peak cam lift?
The thing is, that intake flow is a pulse, not steady state and the intake port acts somewhat like a plenum and the flow at the carb is smoothed slightly versus the valve, so the flow rates are not the same. Port diameter and flow velocity are a better way to match carbs to intakes.
The thing is, that intake flow is a pulse, not steady state and the intake port acts somewhat like a plenum and the flow at the carb is smoothed slightly versus the valve, so the flow rates are not the same. Port diameter and flow velocity are a better way to match carbs to intakes.
crazypj
Split personality, I fake being smart
cafematty said:
I could of told you a a while ago but I've forgotten.
Doesn't really matter, 30mm carb will support about 28~35bhp per cylinder with pulse flow, around 25~28 on a manifold (if you were using a single 30mm on a twin cylinder)
I posted it up probably beginning of year?
With 4,000 posts it may be difficult to find though
It's a common problem, people always want to fit biggest carb that goes in there.
On a CB350 full race motor, a 32mm is usable, but, even then 30mm would probably be better for 98% of people
(saying that, I'm going to fit some 32's on my 378cc motor, mainly because I have them but they may end up on the Yamaha XS800)
Thanks for the info.
I'm toying with the idea of putting them on a CM450 in place of the usual lean running 30mm CV's (which Honda stepped down to from 32mm on their 400's to keep the EPA happy). It certainly sounds like they would have enough extra capacity for the few extra ponies I might be able to squeeze out.
The whole project is only at the toying with the possibilities/dream stage at the moment because I already spent too much money on toys this year.
I'm toying with the idea of putting them on a CM450 in place of the usual lean running 30mm CV's (which Honda stepped down to from 32mm on their 400's to keep the EPA happy). It certainly sounds like they would have enough extra capacity for the few extra ponies I might be able to squeeze out.
The whole project is only at the toying with the possibilities/dream stage at the moment because I already spent too much money on toys this year.
