Is it restrictive if the exhaust system starts out smaller and then gets bigger?

say right now if my header collector is a 2.0" into a 2.0" cat and then to a bigger catback (say like 2.38" or so, or ITR size) then is that still efficient? or does the piping difference cause a problem in terms of flow?

 

depends on how much exhaust is trying to flow at that point. The more gas thats flowing the more restrictive it is on a small pipe but it is opposite with bigger pipe such as if too little gas is flowing thru a big pipe it slows and increases back pressure. The smaller pipe pretty much acts like a venture speedign up the gases and keeping them hot and when it hits the larger piping it has a good amount of velocity and can almost cause a vacume. This is why piping size is so important to exhaust gas output

 

It is better to start small to big, rather than big to small - simply put.

 

ya thats pretty much it

 

so...a 2.0" collector to a 2.5" or stock cat to a bigger catback would work well?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xprohx &raquo;</TD></TR><TR><TD CLASS="quote">It is better to start small to big, rather than big to small - simply put.</TD></TR></TABLE>

Not necessarily, im gonna run a 3" downpipe to a 2.5" catback exhaust on my GTI and its been proven to get better results then 2.5" turbo back.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mkiv98 &raquo;</TD></TR><TR><TD CLASS="quote">so...a 2.0" collector to a 2.5" or stock cat to a bigger catback would work well?</TD></TR></TABLE>

that'll be fine i think i'm going to do the same.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by teknoracing &raquo;</TD></TR><TR><TD CLASS="quote">

Not necessarily, im gonna run a 3" downpipe to a 2.5" catback exhaust on my GTI and its been proven to get better results then 2.5" turbo back. </TD></TR></TABLE>

never heard of that....

 

Well theres dyno sheets on some of the VW forums and i dont want to hijack this thread but i am giving my opinion based on dynosheets and butt dynos. So to each his own.

I have noticed gains with catback systems and stock manifold, but the addition of an aftermarket header will increase power output

 

well if i had a turbo id just get an electric cutout.