Originally Posted by
Millord
Why do you think the engines are designed with a pinch? I think if there would be a constant temerature during operation, it would be easy to calculate the thermal expansion of piston and sleeve and produce the piston and sleeve with tight tolerances and no break in would be required at all.
My personal expectation is, that a well done classical break in will result in better performance than the break in dutch method.
The engines are designed with a pinch because the max. piston acceleration by 45.000 rpm is far to high for piston rings.
The calculation is indeed pretty simple and linear, bellow a .12 piston in FEM analyses. A temperature difference of 50 degree celcius for a 120 degree radial angle of the exhaust direction. You can see a resultant displacement due to thermal expansion. The difference in around 0.002 mm between the exhaust and intake direction of the piston.
Think producing a piston with a ovality of 0.002mm would be expensive. The differential thermal expansion is just not as big as we all would expect.
My expectation is that the temperature difference is a lot smaller then the 50 degrees celcius, so the expention is also a lot smaller.
The final ovality is done by driving the car the first 15 minutes.
But experience really shows more then all this discussion (saying that on a forum..lol). I would advice you al to make a small machine, it`s very easy to do and makes life easy for break-in an engine.
Remember, I`m just like you all a guy who likes to race, i like to design all kinds of machines and hop-ups for my own cars. Don`t care if i sell a lot of products or break-in engines...it`s not my job, have a normal engineering job for 1:1 models.
But i do like to defend my design on a forum...
