I was slighty (OK - maybe more than slighty) bored yesterday, so I decided to swap my stock ITR exhaust manifold and cat. onto the Si. Before I installed it, I used the Dremel to open the primaries where they didn't match up with the manifold gasket, and I also removed some of the anti-reversion piece at the collector. Finally, I smoothed the welds at the opening to the cat. and the B-pipe. After struggling with a few stubborn bolts, everything went in nicely.

My friend and I both noticed a bit more power, probably due to the ITR manifold's slightly larger collector and the better-flowing cat. Truthfully, I wasn't expecting much, but it seems like this would be a worth-while mod. for the amount of money these manifolds and cats can be purchased for.

BTW- This may already have been covered, but upon comparing the two manifolds, it seems that only the lower half is different. I believe this was the case with the GS-R manifold vs. ITR as well, though I'm not entirely sure.

 

yes only the lower half is different.
And on a b16a the header will also hang lower.
The collector exit is the same diameter

 

When I measured the two with a set of calipers, the exit was approximately 2 mm smaller on the B16 manifold.

EDIT: This measurement was taken at the inside of the "anti-reversion" tubing rather than the outer piece that the donut gasket surrounds.


[Modified by Spec.R 00-0123, 3:59 PM 5/15/2002]