Unkl Ian wrote:Can anyone suggest a website that covers the basics of cam design ?
I know it's a full time job trying to come up with the "perfect" design,
I'm just looking for some general guidelines,based on displacement and rpm.
UDHarold wrote:There are some cam companies that claim that Intake Closing is the most important event in a cam cycle.
I claim it is the 3rd most important event, beating only where the Exhaust closes.
UDHarold wrote:I consider the intake opening and the exhaust opening points to be so close in equal importance, I do not know which is MORE important. Here are some thoughts:
The most important single degree in your camshaft may be the degree before the intake valve opens. At that point, the exhaust valve is open and closing, there is a volume of exhaust gases left in the cylinder, being pushed out the exhaust port by the piston. These exhaust gases have a positive pressure, known as back pressure. They cause reversion when the intake valve opens. The volume and pressure of the exhaust gases will determine how the cylinder fills on the intake stroke.
Proof? Most engine builders have tried 2 cams with the same intake and exhaust grinds, but different LSAs. Put both cams in the same engine, on the same intake center line, and dyno. Result? Two different power curves.
You say, but they were different LSAs! I said put them in on the SAME intake center line--Same intake cam grind, same opening and closing points, 2 different cylinder filling rates, 2 different power curves. The exhaust opening and closing points were different, though. The exhaust reversion/back pressure governed how the intake would fill the cylinder.
The intake opening point is important though. Different opening points of the same intake profile produce different power curves, also.
So I put equal value on both. The intake closing point is next, but different cam durations/profiles with the same intake closing point produce different results.
UDHarold wrote:One of those articles either has words in in that I cannot even guess the meaning of, or else they are terrible, repeated, typos.
UDHarold wrote:None of the various cam designs programs really tell you how to design a cam, they just provide the tools to design cams with.
Knowledge and experience use those tools to design the cams. UDHarold