New exhaust design.

[KDog]

Ok it time to put a new exhaust on the car, old one has some problems courtesy of some rocks on my driveway.

It has the stock crown royal saloon headers.
It has to have a single outlet.
It already has a 3" mandrel bent part to go over the diff. I would like to keep this part.
The cats are 2.5". Then it goes through 2.5" to a crappy Y if you could call it a Y. Then its 3" all the way out including a 3" inch straight through muffler and 3" resonator.

Its currently too loud and does not perform well, it was put on becuase the original plan was to turbo the engine. This is no longer plausible as I can't be bothered and don't have the time.

I would guess the new system should be;

2" out of headers into the 2.5" cats. I assume you can flare 2" out to 2.5" and back again???

2" pipes into a proper "Y" with 2.5" outlet.
2.5" pipe to 2.5" muffler, or should I use a 3" muffler. I assume that 2.5" can be flared to 3"???

2.5" pipe to the 3" mandrel pipe over rear axles. If I use a 3" muffler should I bother to go down to 2.5" pipe inbetween the rear of muffler and start of mandrel pipe?

Should I bother reducing to 2.5" pipe from the rear of mandrel section to the 3" resonator???

Or should I replace the cats/resonator/muffler with 2.5" ones???

 

[madmont]

Mine is going all right these days Looks a bit strange but it works allright
http://www.lextreme.com/forums/showthread.php?t=2179&page=2&pp=20

 

[JBrady]

Ok it time to put a new exhaust on the car, old one has some problems courtesy of some rocks on my driveway.

It has the stock crown royal saloon headers.
It has to have a single outlet.
It already has a 3" mandrel bent part to go over the diff. I would like to keep this part.
The cats are 2.5". Then it goes through 2.5" to a crappy Y if you could call it a Y. Then its 3" all the way out including a 3" inch straight through muffler and 3" resonator.

Its currently too loud and does not perform well, it was put on becuase the original plan was to turbo the engine. This is no longer plausible as I can't be bothered and don't have the time.

I would guess the new system should be;

2" out of headers into the 2.5" cats. I assume you can flare 2" out to 2.5" and back again???

2" pipes into a proper "Y" with 2.5" outlet.
2.5" pipe to 2.5" muffler, or should I use a 3" muffler. I assume that 2.5" can be flared to 3"???

2.5" pipe to the 3" mandrel pipe over rear axles. If I use a 3" muffler should I bother to go down to 2.5" pipe inbetween the rear of muffler and start of mandrel pipe?

Should I bother reducing to 2.5" pipe from the rear of mandrel section to the 3" resonator???

Or should I replace the cats/resonator/muffler with 2.5" ones???

Your plan should work fine. The 2.5" cats are fine. You may or may not give up any torque with the 3" rear pipe, muffler and resonator. I would try it as you already have it on the car. Of course a 2.5" muffler and resonator would be quieter.

Have you taken any measurements? 0-60? Dyno? Before and after data is always great to have.