volumetric efficiency? *warning math may lurk inside*

[Black wing]

i am in the planning phase of building the vmax mod for my first gen and am trying to get to designing the exhaust system, but i cant really begin until i can figure out the real flow i am going to be dealing with. any one here know the numbers for the stock venture 1300 motor and the vmax? or able to teach me how to properly calculate it so i can get some accurate numbers for the expected outcome of the mods.

[Flyinfool]

Volumetric efficiency is not usually calculated unless you have some really fancy software. It is normally measured. It is easy to calculate the theoretical flow at 100% efficiency. Displacement in cubic feet X RPM ÷ 2. You will only ever hit 100% flow if you have some kind of forced induction like a turbo or super charger. Yes it is possible to get better than 100% flow naturally aspirated with some highly tuned systems but we don't have those.

 

A realistic Volumetric efficiency for a V-Max is probably close to 90% and closer to 80% on a Venture, these are purely guesses on my part.

[MikeWa]

VE is the actual air flow of an engine verses the theoretical maximum. Cylinder head design, valve guides intake manifolds etc. all work to reduce efficiency by some percentage.

The easiest formula for a 4 stroke engine. CU inches X desired RPM / 3456 equals the VE at 100% for the given RPM. This number should be adjusted for the flow efficiency of a given engine ie: times 80 90 or 100 %. Most HP street vehicles are around 80% Very high performance can be around 90% All out top fuel dragsters approach 100%. It can be further adjusted for air temp, relative humidity and barometric pressure but that is probably not necessary in your case. To exceed 100% generally requires a turbo or blower. The 3456 converts cu inches to cu feet and adjusts for every other stroke in a four stroke.

 

Mike

[Dragonslayer]

I love this site for the wealth of knowledge and wisdom contain within.

 

Just think... this morning I had never heard the term volumetric efficiency and now I know what it means.... and understand the concept.... I think I might have even spelled it right.