Eric's cam challenge

Newbomb Turk said

I don’t know another way to say it. Did you think about it?

Let’s just look at the exhaust valve.

I’m just pulling a number out of my *** but let’s say there is 500 psi in the chamber 1 degree before the valve opens. Now move the valve .006 off the seat.

What happens to the pressure?

Stop and think about it. When the valve cracks the seat the pressure changes.

So it matters exactly when the valve opens and closes.

These engines run off of pressure differential. So when the valve leaves the seat shut happens.

And the engine knows it.

Slow lobes are easier to control at higher rpm but they kill torque at low rpm.

You need to forget what you think you know and think in terms of pressure differential.

Then it will make sense.

Or don’t bother.

Click to expand...

I'm a retired engineering tech (not specializing in engines) so I think I understand although I'm not sure what your level of understanding of physics is when you talk about the engine knowing things and running off of pressure differential. Delta P is just a means to an end. As we know camshaft theory is complex although doesn't need to be for most people. There are as with everything drawbacks from maximizing aspects of design such as duration, life, area under the curve, etc. A lot more experienced people than you or I came up with the 0.050" number but it is only one measure for helping builders. Rate of lift might be another good number to look at or perhaps a curve. The problem is a squarish lobe would give the best looking curve. Looking at something and knowing what to do with it are 2 different things.