Does adding a massive exhaust to a car decrease performance?

[Stissy]

I've heard a lot about this... i'm just wondering if its true,

and if so, why?

[JamesRm]

Big backbox = No

Bigger centre section than its needed = Yes

I assume the manifold is the same as the centre section.

[de4n0]

A big back box shouldnt reduce power but putting a system on it with a centre section pipe thats too big will make it louder but the back presure will be shit and slow the car down, would feel better at high speeds but lower your 0-60 time. not worth it if you ask me. and if you de-cat it aswell it makes it soo much worse.

[Sparco_Tom]

depends on bore size, bends, length.

[JamesRm]

Originally Posted by de4n0

A big back box shouldnt reduce power but putting a system on it with a centre section pipe thats too big will make it louder but the back presure will be shit and slow the car down, would feel better at high speeds but lower your 0-60 time. not worth it if you ask me. and if you de-cat it aswell it makes it soo much worse.

No it doesnt

[Sparco_Tom]

yes it can, if the bore is too big after the cat and you then add a decat it will make it worse

[Slugshead]

Originally Posted by Saxo_vtr

No it doesnt

+1 biatch

[JamesRm]

Originally Posted by Sparco_Tom

yes it can, if the bore is too big after the cat and you then add a decat it will make it worse

But why would you have part of the exhaust too big?

[Sparco_Tom]

what im saying is. IF you were running cat - centre section with a too bigger bore

adding a decat would futher damage pulse tuning and reduce even more pressure causing a bigger drop in performance

[JamesRm]

Originally Posted by Sparco_Tom

what im saying is. IF you were running cat - centre section with a too bigger bore

adding a decat would futher damage pulse tuning and reduce even more pressure causing a bigger drop in performance

I know that, but i dont see why anyone would be running a centre section where the bore is too big?

[Krys_23]

I'd imagine the likes of powerflow and jap cheap systems would have a bigger diameter centre section than the more sought after models. So i'd agree with if it was decatted and oversized centre pipe it'd be shite.

[Sparco_Tom]

point of this thead my friend.
explaining what can happen and does happen when fitting a big exhaust and decat. Sort of things people get from powerflow etc

[Stissy]

Originally Posted by Sparco_Tom

point of this thead my friend.
explaining what can happen and does happen when fitting a big exhaust and decat. Sort of things people get from powerflow etc

[Sparco_Tom]

Now if you have a turbo engine you want a big bore centre and back box to let the gases out without restriction so the turbo can spool up quicker and easier creating more power/less lag

[KrisB]

Agreed, or a supercharger, or if its a diesel.

[Sparco_Tom]

ayye hope that answers your question now mate

[Krys_23]

Not aimed at this thread but i'm nearly suicidal from reading this sort of stuff. And i know there's nothing else to talk about to do with saxo performance/ Engine components, But it's seriously sad how i'm remembering basically everything to do with a saxo.

[Sparco_Tom]

Its down to the new breed of saxp-ers

[gouldy87]

its all to do with pulse tuning, back pressure, nominal bore, turbulence in the pipe work etc

there is a real lot of thought that goes into designing an exhaust system. like subaru imprezas, they hav a flat 4 engine with a specially designed manifold that has differnt lengths for each cylinder that gives it that really nice pur when moving through the rev range.

the question you have asked is rather expansive, you could be slightly more specific.

if you put a 6 inch back box on a naturally aspirated saxo standard exhaust, you will lose a very minute amount of power, but you would not notice although you might get the placebo efffect of hearing a loud roar as you move through the rev range and thinking to your self "wow this is fucking well fast now!"

when actually its not.

[gouldy87]

Originally Posted by Sparco_Tom

Now if you have a turbo engine you want a big bore centre and back box to let the gases out without restriction so the turbo can spool up quicker and easier creating more power/less lag

i agree, now i have no cat on my car and my down pipe has been replaced with 2.25 inch from 2 inch my turbo spools up alot faster