[cyam]

OK so can someone explain to me exactly what a downpipe is and why it improves performance?

Also what exactly does "catted downpipe" mean. I mean I got a pretty good idea but the terms are thrown around so much, I like to know exactly.

Any help appreciated.

[s58_oreO]

There are no dumb questions, unless something has already been posted; the only way to learn something is to ask.

https://www.cobbtuning.com/different...pes-explained/

Good read, a little bit different then our platforms but most of the general information regarding what an actual downpipe is and catted vs catless is pretty much the same. Someone correct me if im wrong.

[Trex]

OreoO - Good link. Thanks.

[chenry]

Not dumb at all - this forum is all about discovering something new and leaving something for others to benefit from (I learned a thing or two today)

Good info already shared! With our cars the cat (catalytic converter) and downpipe are a single unit. Aftermarket alternatives consist of a downpipe that may be slightly larger in diameter and incorporate a less restrictive cat or no cat at all - in either case you will achieve a less restrictive exhaust flow which in turn will result in a quicker turbo spool and more HP (to what extent is subjective - dynos vary)

A non catted DP will result in a check engine light (CEL) which can only be squashed by a flash tune (piggybacks no) and a catted DP by some companies will not throw a CEL

I really enjoyed my catted DP - while the performance gain was minimal the sound alone was intoxicating

Hope this helps - here's a quick pic I put together - that may help anyone reading this post. It's a pic of an aftermarket catted DP

[mike@x-ph.com]

Originally Posted by cyam

OK so can someone explain to me exactly what a downpipe is and why it improves performance?

Also what exactly does "catted downpipe" mean. I mean I got a pretty good idea but the terms are thrown around so much, I like to know exactly.

Any help appreciated.

The downpipe is the part connecting your turbo to your exhaust.

The stock downpipe comes with highly restrictive cats; these cats are used for emission control purposes.

Aftermarket downpipes have either higher flow cats or no cat at all (catless); this reduces the backpressure on your turbo, allowing it to spool faster and maintain boost better.

A simplistic example is that if you target the same boost, your turbo has to work harder with the stock downpipe versus an aftermarket one.

[cyam]

OK understand what a Downpipe is, I've never referred to it as that before, but guessed that was it.

In looking at the stock downpipe, it is huge, biggest I've seen on any turbo I've owned. So I'd guess its quite efficient as it is.

My understanding is the design of the downpipe really has an effect on turbo lag, and this car really has very very little lag and I am comparing to other turbo's I've owned, including a 996 Turbo Porsche back when that was new.

This b58 is a really well designed engine. Do mods like a downpipe really make such an increase in power or eliminate any remaining lag that it is worth the expense - or is it only worth considering if you are doing other big mods like significant increase in boost?

[xnick101]

Originally Posted by cyam

OK understand what a Downpipe is, I've never referred to it as that before, but guessed that was it.

In looking at the stock downpipe, it is huge, biggest I've seen on any turbo I've owned. So I'd guess its quite efficient as it is.

My understanding is the design of the downpipe really has an effect on turbo lag, and this car really has very very little lag and I am comparing to other turbo's I've owned, including a 996 Turbo Porsche back when that was new.

This b58 is a really well designed engine. Do mods like a downpipe really make such an increase in power or eliminate any remaining lag that it is worth the expense - or is it only worth considering if you are doing other big mods like significant increase in boost?

A downpipe by itself will give you some performance but not a lot. For reference, my quarter-mile time went from 12.30 stock to 12.19 just from adding the downpipe. And then adding my ecutek tune took it down to 11.42 in the quarter. The tune is where the significant power is added. Also the "boost lag" you are talking about is just the throttle mapping, the turbo is tiny, there is no lag. It makes peak torque way down low. A tune and downpipe are a must have for any B58 car. It makes the car MUCH faster.

[mike@x-ph.com]

Originally Posted by cyam

In looking at the stock downpipe, it is huge, biggest I've seen on any turbo I've owned. So I'd guess its quite efficient as it is.

My understanding is the design of the downpipe really has an effect on turbo lag, and this car really has very very little lag and I am comparing to other turbo's I've owned, including a 996 Turbo Porsche back when that was new.

This b58 is a really well designed engine. Do mods like a downpipe really make such an increase in power or eliminate any remaining lag that it is worth the expense - or is it only worth considering if you are doing other big mods like significant increase in boost?

The stock downpipe is huge because it has a huge and highly restrictive catalytic converter in it. It's not efficient.

When replacing the downpipe you get a noticeable jump in power and reduce the backpressure on your turbo so it can make more power easily.