Piston & Connecting Rod !?

Turbo-charging the M10 engine

Having some basic insight into the standard BMW M10 engine components and most importantly there limits, might have some influence one tuning ambitions . More power means the expanses increase exponential.

That being said the BMW M10 engine is one of the most over-engineered engines I come across in resent years. 1,5 bar boost seems to be no problem yielding approxametly 400 Hp. But 2,2 bar was pushing it and soon an oil consumption of 1 liter every 50 Kilometers putting most two stroke engine to shame was definitely an omen of engine damage ie excessive wear .

So here an analysis of the stresses an M10 endures and why and what kind of performance components an engine might benefit from:

Calculating the compression pressure P2 at top dead center gives a rough estimate of the pressure the piston and rod have to endure.

The following parameters are required to complete the equation describing pressure for adiabatic compression.

1. compresion ratio Egeo = 8.1:1

2. Stroke volume Vs = 500 cc = V1

3. Manifold air pressure MAP = 320 KPa = 2.2 bar of boost = P1

4. combustion volume Vc = needs to be measured or calculated = V2

according to the ideal gas law and the adiabatic process which is suitable to calculate the compression pressure at top dead center:

Modeling the piston and connecting-rod into CAD software together with the aid of Finite Element Analysis gives some basic understanding of the maximum output one could expect from these old but robust engines.

Below the results of 100 bar pressure at top dead center. The deformation plotted is extremely exaggerated in order to better show how every part is effected by

the loads put on them.