Overlap Triangle
Those numbers only put peak torque at 5k rpm? 272/288 @050 on 410 inches seems like it would make peak TQ higher than that. At least in my head.
I ran the numbers again to make sure I didn’t end up with a green weenie but that’s the math.
So far, this math hasn’t lied to me. The math I’m using starts with finding intake duration. It’s based on peak torque rpm, stroke, compression ratio and bore size. And it’s weighted more to stroke and peak torque rpm.
Then it takes the intake duration and rpm for peak power and rod to stroke ratio to determine LSA.
Then it takes the LSA and uses whatever effective compression ratio you choose to determine ICL.
The last calculation is exhaust duration. It uses intake duration and a combination of piston speed and crank pin speed to calculate it.
One of the limits I’ve found is what I consider low rpm, low compression stuff. Say 9:1 and peak torque at 3200 and peak power at 5200.
It will almost always end up with a low 100’s or as low as a 98 degree LSA. If you then get the ICL, it will likely be 6-8 degrees advanced.
On the exhaust lobe, I can’t make the numbers make sense with exhaust manifolds. I get some pretty wild numbers that you would probably never would think of.
I suppose if you were doing a FAST build or something the numbers might make sense, but PRH or someone who is actually building or running a class like that can say if they have cams with very very tight LSA’s in their stuff.
Of course, that’s getting to the point that valve notches would be so deep that you just can’t fit all that lift around TDC and have a piston worth a crap.
My kid is coming home from college for Christmas and I’m going to have him look at the math and see if we can change the math a bit to be able to do stuff like that.
And I need to point out this math makes the assumption you are optimizing the engine for the rpm that’s been calculated. And really everything else.