Porsche-ah

I'm currently running Cargraphic 100cell "cross" pipes

Having the upgrade itch...

Is there any gain/benefit if I went with the fabspeed or similar type "X-pipe"?

thanks in advance!

GBX

JZ98-993

Bill Verburg

All exhaust setups are a compromise of many design variables
what it needs to do is allow the movement of the largest mass of exhaust gas in the shortest amount of time w/ the least amount of restriction while at the same time(in a street car) keeping the noise level down to an acceptable level.

A 911 6 cyl motor has a very favorable even firing pattern, every 240° of crank rotation a slug of exhaust gas enters a given bank, these slugs are merged in the collector, if the merge is properly done the lower pressure region between slugs can help accelerate the flow of the next slug in the procession, if the transition isn't carefully and properly managed it can slow and disrupt the parade, having more room between the pulses makes the management easier to process. The pipes can't be too big or too small, shorter is better than longer, heat retention is a +, the transitions and bends need to be as smooth and few as possible, merges need to be carefully crafted to induce less turbulence.

An x pipe merges the 2 sides, as w/ the merge at the collectors this can be a good or a bad thing depending on how carefully it is done, The separation between pulses is half that in the collectors so the merge is more difficult to construct, pressures and speeds are lower which further muddies the water. The fact that merges are a huge plus on odd fire engines like US V8s further confuses peoples evaluation of an X. In odd fire engines like say a Chevrolet V8 the pules are irregularly spaced, 270-180-90-180 on a a given side, the 180 is fine the 270 is great but the 90 overloads the collector and downstream flow unless it is oversized for that one regime, hence a cross over is placed close to the header to relieve the over pressure. 911s don't need that.

The primary benefit of the x is in noise suppression, the acoustic signals have double the choice for paths and so get attenuated more efficiently