Quote:
Originally Posted by wstar
The major difference is that the stock tubes are not equal length, and the Stillen headers are. I'm really not an expert on these things, but my basic understanding of this issue is that equal-length headers ensure that the exhaust pulses flow into the single pipe (after the headers) in a steadily-timed train that tend to "suck" each other along, whereas with unequal length headers, you get "collisions" of exhaust pulses followed by empty-time where nothing is actively happening.
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This is some what true but you are forgetting one thing. You forgot to mention why Nissan developed those headers that way. It was developed that way to give you that tq that people have been missing with these headers. Stillen headers look good and have a very good collector. I believe they should of kept the OEM design 100% along with that improved collector. It's all about tuning for velocity, flow, and of course exhaust pulse. Remember the exhaust itself is not a continuous flow because exhaust valves open and close.
In case of the Y-Pipe issue. It will probably have gains with an aftermarket part but you would have to do a couple of tests. If the y-pipe frees up too much backpressure than you will lose velocity and then you will lose tq and but gain hp. Its very difficult to tune for a happy median.
It would be nice to see the following.
1. baseline dyno, stock headers, y-pipe,
2. baseline dyno, aftermarket headers, y-pipe