optimal exhaust size

[Benjamin]

i'm making a home made downpipe and exhaust on my 1.9 with the vnt25.
i dont wanna become a loud honda sound when i drive normal (problebly also not possible), but it need to be a good perfomance choice for +200hp.

What is better, 2,25 or 2,5" for the exhaust? Os this size the diameter from the inner or the outside diameter (with or without matrial)?
the exhaust side on the turbo is 45mm, how big should i make the downpipe?

is it better to take a bigger downpipe than the exhaust, or is it the best to take the same size for the whole line?

(i know this discussion is done several times, i also readed the faq, but i ask again becouse i will have a bigger power gain)

Greetz, Benjamin

[g-spec]

I will be running a 2.5 outer diameter all the way from the turbo back....no mufflers and from the sound clips I have heard on here its not loud at all!!! I dont think you would need more than 2.5 inch....besides its a lot easier to fit rather than a 3inch.....if you want a different size downpipe i would make the exhaust bigger than the downpipe!!!

[Cheesetoast]

i am running 2.5" from the downpipe back, no cat, no muffler, nothing, straight pipe.  Not loud at all, the turbo is your muffler.

[Benjamin]

i am running 2.5" from the downpipe back, no cat, no muffler, nothing, straight pipe.  Not loud at all, the turbo is your muffler.

is it louder on idle? is 2.5" the inner or outer diameter?

Sounds to me i go will for a 2.5" outer diameter exhaust, what size is the best choice for the dowpipe on this install?

Greetz, Benjamin

[Cheesetoast]

when i removed the cat and muffler, i noticed no increase in noise, the engine is louder than the exhaust.

[Mark(The Miser)UK]

when i removed the cat and muffler, i noticed no increase in noise, the engine is louder than the exhaust.

[/size]

How does this affect the MOT?
Thanks

[Cheesetoast]

What's a MOT? you mean emissions or legallity? It's legal here anyway, emissions passed aircare no problem.

when i removed the cat and muffler, i noticed no increase in noise, the engine is louder than the exhaust.

[/size]

How does this affect the MOT?
Thanks

[Mark(The Miser)UK]

What's a MOT? you mean emissions or legallity? It's legal here anyway, emissions passed aircare no problem.

Woops!
Confused you with 'Regcheesman' in UK but you answered  correctly...
MOT 'Ministry of Transport' annual roadworthyness test... :oops:

[veeman]

i noticed no increase in noise, the engine is louder than the exhaust.

Yep... same here.  I've got a 2.5" downpipe and exhaust and I can hear the turbo and exhaust note, but the engine is louder than that.  Rattly for sure.  I've always been told that turbo engines don't need any restriction at all for "back pressure" after the turbo.

[Diesel Fumes]

Got a custom made 2.5" system made up today.  Sounds great and has a lot more power  :shock:

To go 3" is of more benefit especially if you plan to up the boost.  But it requires more custom fabricating and will cost a significant deal more money.

[Diesel Fumes]

Does anyone know the size of the stock downpipe?  I want to upgrade this part, but is it really necessary if im not running much power right now?  Also, is a 2.5" exhaust going to make a big difference if you still have the stock downpipe?  Perhaps the feeling of power is just all in my head?

[zagarus]

straight piped with 2.5inch on a TD is quieter then a gasser with 2 resonators, a cat, and a muffler lol.

you're good to go.

[935racer]

2.5-3"

[Diesel Fumes]

straight piped with 2.5inch on a TD is quieter then a gasser with 2 resonators, a cat, and a muffler lol.

you're good to go.

Its pretty loud under full throttle though  :lol:

Sounds like a semi truck and the whistle exhaust sound.  Ooo, I love it.  I won't regret it  :shock:

[zagarus]

^ i concur 101%!


as my friends following call it, "The whoooshy zoot noise!"