Calculate the volumetric efficiency of your engine with this calculator.
What information does the VE calculator need?
- Engine capacity in CC (cubic centimeters)
- Engine power in bhp
- RPM of peak power
What is volumetric efficiency?
In simple terms, volumetric efficiency is how filled the cylinder is, (immediately before the compression stroke starts), compared to the actual capacity of the cylinder.
In other words, how easy is it for the air to enter the engine. The better the VE the more power the engine has.
Generic VE Examples
A normally aspirated engine which is designed for torque will have a low VE at high RPM because cylinder filling at low RPM is the priority
A turbo engine can have a VE of over 100% because air is being forced into the engine under pressure by the turbo ie the amount of air in the engine is more than the actual capacity of the cylinder because the air is pressurized above atmospheric pressure (by the turbo)
Actual VE Examples & Power Potential
If we can move the peak VE to a higher RPM we can increase the power of the engine while theoretically not increasing stress on the engine.
Below is a list of three cars, we look at the RPM of the peak VE and see how much tuning potential these engines have (without increasing engine stress)
Honda S2000, 2004 – Normally Aspirated (Non Turbo)
Nissan Micra 1.2, 2009 – Normally Aspirated (Non Turbo)
Ford Focus ST, 2014 – Turbo
Honda S2000, 2004: 237bhp at 8,300 rpm = 99% VE
Nissan Micra 1.2, 2009: 79bhp at 4000rpm = 110% VE
Ford Focus ST, 2014: 286bhp @ 5500 rpm = 180% VE
With the Honda, not a lot we can do because the peak VE is already close to redline.
The engine, even though it is normally aspirated, is making over 100% VE at 4000rpm.
If we move the power band of the engine to higher RPM with a camshaft or turbo upgrade for example, how much power would the engine make at 6000rpm with 110% VE?
Bolting the numbers into the VE calculator we get
115bhp, an increase of 36bhp or 45%. How can we increase the VE at 6000rpm?
Ford Focus ST
Redline on this engine is only 6500rpm
What power would the car make if we move peak VE from 5500rpm to 6500rpm?
338bhp, an increase of 52bhp (18%).
How can we move the VE up?
The car has a turbo from the factory so increasing the boost at 6500rpm would be the easiest solution.