Exhaust Size

[ONO2HI]

Hey guys
I know this topic was thrashed on the old site, but what is the ultimate exhaust set up for a 4JB1 intercooled engine?
At this stage i am looking at going to go 3" dump pipe in to 2.5" with a single Coby, any pros or cons?
I also have the 3.1 oil filter housing to swap if the 3" pipe is in the way

Thanks

[mulover]

You can do a 3" dump pipe past the oil filter on a 2.8, but its more a rectangle than a pipe!!
That is a pretty good set-up, I've never used Coby mufflers, never seen one, just got a $100 straight through round one and it works fine. I think a 3" system all the way through is a bit of over kill, would probably only do a 2.5" one if i ever did one again, but the 3" does sound good.
If you do a 2.5", I would be using either a mandril bent system or weld elbows as i think a crush bent system would be too restrictive.

[geeves]

Even press bent 2.5 is a big improvement over stock (I still have original dump pipe as well)

[ONO2HI]

I went and saw the exhuast guy, he couldnt understand the the logic of having a 3" dump pipe? so im looking at 2.5 madrel the whole way through at this stage

[Demonic]

No muffler?, I am getting a 2.5in from turbo straight through with no muffler...., well... maybe 1 if i can find one small enough.

[dasnoboarder]

Legal limit for exhuast volume in NZ is 90dBa, I'd be interested to know what a MU with 2.5" from turbo and no muffler measures (and sounds like).

[geeves]

90dba is louder than most lawn mowers (mine quotes 84 on the sticker) Do you realy want to be hearing that all day every day?

[MrBIGHORN]

Ultra tuff mufflers in Mt Maunganui will make any size muffler you wont.
Have a free flow muffler on my bighorn and it sounds good

[mulover]

3" and no muffler sounds like a quiet bulldozer, which i think sounds good, but the missus doesn't!!!
3" with straight through muffler sounds mean, and the missus can put up with it!!!

[justinw]

4JG2 with 2.5" and no muffler sounds like a Fergie tractor. I know I've done it. Went back and had a freeflow put in. A lot quieter (read too quiet). My mate had a Wizard with a 2.5"and a rear mounted Coby. Was louder than mine but sounded cool.

[dasnoboarder]

Do resonators ever get used on diesel exhausts?

[bedford4x4]

Do resonators ever get used on diesel exhausts?

They do on mine - my truck has a free-flow muffler with a resonator behind it so it doesn't drone at highway speeds. It's probably not necessary but someone put it on and I can't be bothered taking it off. It's not as if it's restrictive.