School me on Volumetric Efficiency oppo

"traderQAMobileTestAutomationMobileBoostOn" (el-peasant) 08/08/2016 at 09:03 • Filed to: None

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I’ve always heard “More air = More torque = More power” but what about things like valves, cams, heads, intake, exhaust, etc?

That’s where VE comes in, the ratio of actual airflow to potential airflow, at any given RPM. Yes, More air = More torque so the VE chart looks just like the torque chart. Of course changing the intake, exhaust, and valvetrain will change the shape of that VE chart.

Berang > traderQAMobileTestAutomationMobileBoostOn 08/08/2016 at 09:15

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Poor volumetric efficiency is why 2-strokes sound so cool at idle.

CobraJoe > traderQAMobileTestAutomationMobileBoostOn 08/08/2016 at 10:14

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Volumetric efficiency is just a measure of how much air is going into each cylinder compared to how much it could theoretically hold.

The higher the VE, the more air going into the cylinders. So, yes, more air in = more torque and power.

Everything else, the cam, valves, head design, intake runner design, exhaust manifold design, any boost... They all affect the VE, sometimes in different ways. Sometimes they all work together to boost the VE at low RPM, resulting in more low end torque and less high end power. Sometimes they’re idealized for high RPM power and low end torque suffers as a result. Sometimes they use some neat tricks like VTEC and intake runner controls to get the best of both worlds.

Now, how all those parts individually affect VE... That’s an entire semester’s worth of theory.

Snuze: Needs another Swede > traderQAMobileTestAutomationMobileBoostOn 08/08/2016 at 10:28

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I think you have a pretty good handle on it.