Downpipes

[JesseG]

What is the power difference if you only get primary downpipes as opposed to getting primary and secondary? Do you need both? What if you only get primary downpipes will you still see gains in hp?

 

[rpoffen]

What is the power difference if you only get primary downpipes as opposed to getting primary and secondary? Do you need both? What if you only get primary downpipes will you still see gains in hp?

Are you talking about catless primaries? These are very short, if you go catless, then you are obviously removing some restriction. The secondaries have a lot of pinch points in them, you might get better results just doing those, easier to install too from what I have heard.
Another issue I have heard is that doing both, at least, might tend to make the turbo seals leak due to less backpressure and you will burn oil.

 

[Avon]

I have run both full catless and only primaries catless. Can't say any of it increased performance any. Both add significant exhaust noise.

Will say changing primaries is a real pain and not for the faint at heart. Even with just primaries catless I occasionally smell burning oil so that is a thing too.

You also get over boost unless you have ECU tune or jb4 with EWG.

If I had to do it again I would have never bothered doing it if that tells you anything.

 

[General_Vodka]

The overboost thing can be tuned out and fixed. However you don't really gain that much. Just do resonated secondaries and get a jb4 or something. That will give you more gains than primary plus secondary.

 

[Stiletto]

Secondary (catless) only pipes won't net you much. I have dyno logged both factory tune (first graph) and JB4 map 2 (second graph) comparisons.