Can anyone tell me what the best size exhaust is that i should get...
I have a 98 A4 1.8T Quattro and im getting the exhaust done but im waying up whether i should get a 3 inch pipe all the way through or 2.5 inch. Im sure the exhaust shop will tell me whats best but im curious to see what some of you think.
Is anyone better then the other? which one would sound better?
and all that kinda stuff.... if anyone can fill me in it would be much appreciated.

cheers

 

Sound is a relative thing; it will depend on more than just the size. Resonator type, design, and size will affect sound more directly.
As far as diameter: 2.5 inches will get you good torque from the backpressure, while the 3 inch will give a bit more hp at the top end. Either way you compromise one performance statistic for the other's gain. In fact the differences will be minimal - you may not notice them if you tested them back-to-back.
Depending on the overall routing of the pipes, you may be restricted to 2.5 inches.
Lastly, it won't matter about using 3 inch pipes if the DP's joint is at 2.5 inches going into a 3 inch and then it has to reduce again to 2.5 at the tails.

 

cheers for your input..
I forgot to mention it will be fully a mandrell bent system too.
but yeh i guess i'll see what happens when i go to get it done

 

A mandrell bent system is the only way to go!

Good luck and post your comments as it gets sorted out.