| stock plenum create a tunnel ram effect through the midrange RPM of our engines. I dont have the spreadsheet imaged on my website but I did the maths on it a couple years back to determine this. From a qualitative position it doesn't take much to see that those long runners are restrictive to flow in the higher RPMs where the intake stroke is occurring >50 times per second. Shorter runners with lengths tuned for improved tunnel ram effect at higher RPMs will shift the torque curve upwards in the RPM band and result in better VE up high. I have the spreadsheet open, here's the calc: 19.75" from valve to plenum wall
RPM 4500
RPS: 75
DPS: 27000
CriticalT: 0.016592593
D1/2: 19.41333333" (this is close to our runner length)
D1: 9.706666667 For that sweet spot to be around 6500RPM, here's the calcs for that: RPM: 6500
RPS: 108.33
DPS: 39000
CriticalT 0.011487179
D1/2 13.44
D1: 6.72 13.44" would be the target. These were simple calculations I used and are by no means complete. These simple maths were constrained to a fixed temperature and pressure of the air, which obviously play roles in the speed of sound (one more than another, of course. :)
Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the
tailor.
Albert Einstein
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