Spotting exhaust restriction

[Razathorn]

My car is a supercharged k20a2 rsx type-s (jrsc @ 7psi). I did some power tests of 30, 40, and 50 degrees cam, then 40, 45, and 50 on another day to narrow down power. The thing I noticed was that regardless of which cam angles worked best from 4k - 8k, after around 7800 rpm, 30, 40, and 50 all seemed to make about the same power. Assuming that these cams are not just individually tuned wrong, would this be a sign of exhaust restriction?

I have a JRRH (2.25" od) to 2.5 carsound high flow cat to 2.75" mandrel bent piping to 3" resonator and muffler (straight through). I'm hoping that the cat isn't the problem, and if it is, that I may be able to go to a large one to fix it. If it is restriction, I'm betting on the JRRH since I know they start to clog up as you raise the boost from what others have discovered.

[Hondata]

Sometimes with a supercharger it is best to run the cam more advanced as it makes the same power at less boost. It could be the cat - the only way to tell is to make a test pipe or to measure the exhaust back pressure.

[Razathorn]

Sometimes with a supercharger it is best to run the cam more advanced as it makes the same power at less boost. It could be the cat - the only way to tell is to make a test pipe or to measure the exhaust back pressure.

I'm somewhat waiting on a better header to be available -- not spending money on a custom deal or a comptech that I can make into a true 2.5 od. Just not much in the range of good open headers for us S/C folk.

[Hondata]

Put a 1/8 bung in the exhaust, attach a cheap boost gauge using a couple of feet of copper tube then rubber hose, and see what the back pressure is. Should not be more than a couple of PSI.