mk e wrote:
Madhatter wrote:
interesting, I was trying to recall if it was 11" or 11.5" fired up and check'd and I also get better peak for 11". Though for Nicks new 4L and ITB's the sweet spot is 13.5", nets peak 610hp @ 10.5k rpm.
The exact length depends on the taper and diameter. The more taper the longer it needs to be to "tune" to the same RPM as a straight stack. Also the more taper the more volume and lower energy the wave pulse.....but that generates higher flow losses so there is also a sweet spot on taper.
Now try this exercise. If you are at 10.5k you header primaries are....19-20? Put on headers that are about like mine, 32"(you might want 33") long, 1.65" starting, 1.875 ending, collector is 5" long, 2.8inlet, 2.25 exit. That will tune the header to the 2nd harmonic and the collector to the 6th. Then go 17" or 17.5" on the intake length, staring area 3.4sqin so it's tuned for about 6000rpm and see what happens. I'm guessing around 575hp at 8500-9000 rpm with more torque making a better driver and probably faster without the high rpm wear rates and risks.
The exhaust is 22" w/ 8.5" collector & 3" exit. Intake area is 4.34" yeah BIG ITB's
right now that results in 585Hp @ 9k
The suggested setup chokes the peak and limits it to 10k, picks up 9k to 588. The rest of the curve is close, bumps around a bit but the top end is cut off. Most notable though is that with the shorter headers 4.5k is 286tq vs 255tq with 33" primaries. i.e. the 22" primaries have no dip between 4 & 5k instead it's between 2.5~3.5k giving the 33" a lead of 8 lb/ft.