Question On Midpipes

[fungoolie]

Had a good look at my exhaust the other day and noted that the exit from the first cats is 70mm OD narrowing down to 54 mm at the bellows/flex joints and into the resonator and then emerging from the resonator back at 70mm OD. My question is this, if you have no intention of changing the rear system what is the point of going to, (say), a 76mm primaries midpipe exiting at 90mm when the following pipe is just 70mm? Ive seen some pipes advertised at 76mm at both ends which is closer but still not a match for the stock system. If I bought a 90mm exit midpipe would it pay for me to taper the outlet down to 70mm internally or grind the rear flange out so I don't have a 10 mm step/edge in my system to cause turbulence etc? Are all these 76mm/90mm midpipes really designed for a big bore aftermarket system and would I be better off just making the midpipe 70mm all the way through if I plan on leaving all else stock?

Also other than weight saving. What are the advantages/disadvantages of titanium over stainless? Im concerned about things like durability, heat radiation etc. And why doesn't anyone ceramic coat the titanium pipes for durability/heat insulation purposes? Weight being the primary reason I imagine? I'm not that fussed about 3 kgs but I would be if my pipe falls apart after 50,000 kms....

Edited November 30, 2010 by fungoolie