# Calculating engine pressure from measureable quantities

How can I calculate the engine pressure in units of Bars by using torque, the cylinder volume, motor efficiency, and the gear reduction ratio?

My values are as follows:

Torque = 1063 Nm
Hydraulic Motor Cylinder Volume = 2.56 ℓ [litres]
Gear Reduction = 1
Overall Efficiency = 0.76 [76%]


Q: Do I need any more values to calculate the engine pressure caused by the torque generated? If not how can I calculate the pressure in units of Bars?

• Depends on what pressure you have in mind? this information can be useful (RPM is missing) to calculate mean effective pressure $MEP$ if this given volume is the displacement volume, however, can you explain what kind of efficiency that is given because that's quite huge number for thermal efficiency. If you want to calculate maximum pressure inside the cylinder that require more complex analysis and more information of course.
– Algo
Jul 14 '15 at 18:09
• @algo thanks Algo, in the meantime I was doing research and I came across; this where pressure = torque / 1.588. The next thing is to find a use of the volume gear reduction and efficiency. The efficiency is the overall system efficiency Jul 14 '15 at 22:10
• This table is for nut runner torque conversions, how is this related to piston cylinder pressure?
– Algo
Jul 15 '15 at 7:05
• May I ask where did you get your values? and what is the type of your engine?
– Algo
Jul 15 '15 at 8:29
• @Algo these values were taken from an excel spread sheet. P=T/1.588 was the only equation that I could find converting torque to pressure. I don't know how correct this is, 1063/1.588 = 669.39 bar. 669.39 / 2.56 = 261.5 bar (per litre volume). 261.5 bar / 1 (gear reduction) = 261.5 bar. At 76% eff, the system needs to be producing 261.5 * (1/(76%)) = 344.056 bar per litre of motor cylinder volume. Jul 16 '15 at 22:37