Exhaust options for stock standard sti's

[scoobygt]

I see most people go for a full 3" straight through but my question is why? are there any real gains over a 2.5" or a 2.75" for example?

[Marky]

Same cost for smaller

why go smaller

Slightly more on topic - can be genuine hp gains going to 3" over 2.5"

Someone will pipe up with "But 2.5" will make 400hp" - yes this is true, but the same setup with 3" might make 410hp

Same story different angle - you can force 300hp down a 2" tube but it\'s doing it hard - let it breathe = more horseypowers Or use less boosty boosty OR less timing etc etc

When it\'s a turbo motor bigger is better - 0 back pressure post turbo is ideal - n/a motors there\'s some dark sciencey magic I\'ve never bothered to understand with scavenging gas & wanting pressure in some cases... for some reason

Enhances the vtecs or something I don\'t know

[scoobygt]

but the question was is there any advantage over bigger vs smaller involving the said sizes

[Marky]

Sorry - I elaborated

[Kiwi_Fozze]

Advantages over bigger, more potential bang for the same cost as smaller. And why not?

Think that\'s what marky was trying to say

[scoobygt]

so basically go full 3" then your all set for any future mods!

[Marky]

I\'m not good at stuff like words

And yes exactly

[scoobygt]

what about the likes of a twin turbo vs single turbo.. heard they don\'t like too much flow e.g. 3"

[Kiwi_Fozze]

Them words seem to make good elaboration simple

Yep, 3 inch gives you plenty of tunability room, its a good midway between volume and performance.

Turbo cars, hell just run a 6 inch bellmouth tapered to a 5 inch pipe straight through for wicked spool, hell no exhaust from back of turbo for teh lulz, but you\'ll get nailed by mr plod for stupid loud.

Don\'t go messing with bigger pre turbo up pipes unless you have mods to suit, you can end up going backwards performance wise

[Kiwi_Fozze]

Twin turbo can overspool the primary turbo if the boost control isnt adjusted to suit the faster flow

[scoobygt]

fair enough! good info so far

[pedro]

The bigger the hole...The bigger the noise...In most cases...In my experience...

[Trent]

I literally ran 3 inch pipe with a 3inch siamese downpipe on my coupe got 18kw straight away plus awesome noise haha

[Guest]

I was looking at a US wrx dyno sheet last night back to back with 2.5" vs 3" TB. Gains in torque/power down low with 2.5" better after 5kish with 3". Fucked if Im digging the sheet up again but it was mid 250wkwasp territory.

[lachlan]

assuming for that power it was tuned ecu . did they tune in in between pipes ? just for interest sake

mantaining speed in the exhaust is also important . bigger pipe = greater speed loss

[Guest]

I cant say - dont know. Its on here somewhere maybe qwerty or someone? Idk I troll through google on a regular basis.