Typical Values of Maximum Cylinder Pressures in IC Engines

Although the BMEP can be obtained from the engine torque, the peak pressures occurring during combustion are much higher and are more difficult to obtain by calculation. As a starting point for calculations it is reasonable to use typical peak values, based on 'indicator diagrams' that can be found in some texts (e.g: ref. 1 and 2). The values below assume that the engine is operating at 'wide open throttle' (WOT).

Four stroke diesel engine: 5 - 7 MPa.

Two stroke petrol engine: 1.5 MPa.

Four stroke petrol engine: 2 - 5 MPa.

Reference:
1. 'The Motor Vehicle', K Newton, W Steeds, T K Garrett, Butterworth Group, 9th ed. 1972.
2. 'Engines, an Introduction', by J L Lumley, Cambridge University Press, 1999, ISBN: 0-521-64489-5.

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David J Grieve, Revised 17th January 2008. Original 30th January 2003.