so why did they even bother to use an X pipe after the cat? why didn't they just do a true dual exhaust, since they have dual everything exept the X pipe. does it have to do with exhaust gas travel difference between each side of th engine? or other engineering concern?

 

1.) Better sound. Consider the first generation Dodge Viper which doesn't sound good from the drivers seat. The new Viper has to have a cross over (probably an H pipe) to get the exhaust to sound better. I'd guess a true dual exhaust Z could have a similar problem though not to the same degree as a side exhaust (like the Viper).

2.) Exhaust pulses from one cylinder can be used to "suck" exhaust from another cylinder. One typically worries about this when tuning headers, but it can also be useful in exhausts.

All that said, I'm not so sure that a true dual is any better than a single outlet.

--
Jeff

 

Jeff has it right, better sound and performance. The pulses blend better and you get the added "vacumn" effect.

 

so in that sense, the Greddy true dual exhaust is gonna make less power than stillen?