The fact that the 94-99 GS-R exhaust manifold is shorter than the ITR/00+ GS-R has been well established in numerous posts. However, no one has ever really touched upon why it is shorter. I have an idea that there is some actual intelligent technical discussion to be derived from these seeming useless "GS-R/ITR manifold" posts. Some theories I came up with include the following:

Was this an attempt by Honda to somehow increase some aspect of performance, similar to the dual-stage intake manifold found on the GS-R? If this was the case, why did Honda feel that the LS and the Type R (arguably at two ends of the B-series performance spectrum) required a longer manifold?

Could Honda have determined late in production that the longer design provided better performance, similar to the long-tube header designs we currently see (but then why did it take 5 years to realize this)?

Was it possibily intended to speed catalyst heating (if so, why wasn't the shorter design used on other B-series engines)?

Thoughts/theories?




[Modified by Padawan, 6:11 PM 4/1/2003]

 

Good question. I won't be able to shed much light on the length of the secondaries.

I have flipped through the ITR Tech Manual which describes differences between the ITR and GSR. They made the collector merge a little smoother vs. the GSR. Other than that, no other details mention the length of the secondaries.

 

Well putting in longer secondaries wouldn't help catalyst light off, in fact in might actually hurt it... I would guess that the change had to do with either:
1. Matching the Exhaust manifold to the changed cam lobe duration on the newer cars (ITR specific), probably by speeding up the exhaust pulse through a longer secondary, and thus helping high rpm power.
2. Some kindof change related to tightening emissions on the newer cars.

It doesn't really matter though, cause all USDM Integra headers are basically garbage anyway...


[Modified by Philly_NBP_R, 11:21 PM 4/1/2003]