does 3" test pipe need 3" downpipe?

[dunndilly]

Do i need a 3in down pipe for a 3in test pipe?
I already ordered 3in cat-back.

 

[90GSX]

3" DP, 3" TP, & 3" Cat-back would be the best setup. A smaller TP would cause a bottle neck would create lots of unnecessary pressure.

 

[nine5raptor]

you can leave the dp smaller if funds are low, but you don't want to have a larger dp than tp. the closer the piping is to the engine, the smaller it can be because the hot exhaust gases are better able to keep up their velocity. that's why you start at the back of the car and work your way in.

 

[dunndilly]

No
I am starting with a apex N1 cat back, then i want to know if I can install a test pipe before I get the downpipe

 

[nine5raptor]

yes. I run a 2.5" tp with the stock dp. no probs. just don't go the other way and make sure you put the cat-back on first

 

[dunndilly]

yes, but i'm asking about a 3 inch test pipe for a stock down pipe.

 

[Phoenix_RsX]

Originally posted by 90GSX
3" DP, 3" TP, & 3" Cat-back would be the best setup. A smaller TP would cause a bottle neck would create lots of unnecessary pressure.

word. perfect setup.

 

[jim97gst]

Here is an answer to YOUR question......

I'm sure you can get a 3" testpipe with Apex flanges on both ends. Then you can use that 3" to 2.5" reducer that comes with the N1 to reduce between the testpipe and stock downpipe. The flange is the same on both ends of the stock cat. If you can't find that testpipe, get a 3" pipe from wherever, order a couple of Apex flanges from Road Race Engineering ($12 a piece I think), and weld or get them welded on to the pipe. You'll be golden. Then you can just chuck that reducer if you get a 3" downpipe. Good luck!