Ashp1989

iTrader: (1)

Hi all. Iv currently got a 3" (I think) turbo back exhaust on my v5 type r. Unsure of the make. But iv spoken to a few people and they say it would run better with a 2.5" exhaust because it's only around 320bhp and the 3" is not needed? It's been mapped with the 3"'on but I don't mind getting the mapped tweeked if it will be better with the 2.5".

imprezaworks

iTrader: (9)

Unsure wether it runs better, but from what ive been told swapping to a 2.5 will be fine without a map. 3" helps spool better iirc? may be wrong mind.

adz556

iTrader: (5)

I can't see it running better on a 2.5..... The general consensus on exhausts is bigger the better on a turbo (after the turbo of course) but open to being proved wrong

imprezaworks

iTrader: (9)

I think it would be marginal

Reshard1977

iTrader: (17)

I had the opposite. I had fitted a 3" straight through exhaust, with a TD04 hybrid exhaust. Lots of people told me i would be better off with 2.5" for spool and torque. I swapped to a 2.5" and found that actually it felt restricted and less responsive than with a 3".

So i swapped back to a 3"!!! And took a bit of a loss on the 2.5" system i bought!

Oh well, you live and you learn!

Ashp1989

iTrader: (1)

That's what iv heard with people saying it helps spool and torque. But it's good to hear someone that's actually done it. Cheers

daijones

Too wide an up pipe would be a problem, because it would reduce the velocity of the exhaust gases hitting the turbo wheel. On the way out after the turbo though you're not concerned with the velocity of the gases, more with the volume, so a wider exhaust pushing out say 50% more gas at 25% less velocity would be better, because you want to get the exhaust gases out of the way as quickly as poss. You're more likely to get a spool restriction with a narrow exhaust because it can't shift the same volume of gas, so the turbo wheel will have to work harder to push away the exhaust gases and have less energy to expend on spinning over the inlet compressor wheel

Ashp1989

iTrader: (1)

cheers

wrx fifer

iTrader: (34)

I run a full 3" turbo back on my new age sti, running at around 410bhp mapped by Andy Forrest, after the mapping when I asked what I could do for better spool and to bring the torque up, he suggested removing the 3" system and replacing with a good 2.5" system, not just any old crap though but a decent make and flowing system.

who am I to question him? I still have the 3" system in place though through lack of funds but just another point

Grant

imprezaworks

iTrader: (9)

If he said that then either or if you ask me.