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Building My Exhaust

Astro Bear

By Astro Bear,
in Engines & Forced Induction

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Astro Bear Veteran

Astro Bear

Posted
Posted

Hey all.

So I've got a completely stock r33 s2, and want to build it up as a bit of a sleeper. Really stock looking on the outside, but with a bit of a punch under the bonnet. Nothing too crazy, maybe would like to push up to 200kw over time.

The aim of the game is to have the car 100% legal, or as legal as is humanly possible. I got a Just Jap return pipe intercooler put on which uses the standard intercooler pipes and did not require the cutting of the body etc. First mod= legal. A dyno run after the installation revealed that the car has 145kw at the wheels.

The other day I chuck a high flow k&n panel filter in the standard air box. Noticibly smoother accelleration etc. Second mod= Legal.

Now it comes time for the exhaust. The car needs to be under the legal db limit.

I bought a second hand 3 inch dump pipe from the forums, ready to bolt on.

I also bought a second hand 3 inch cat back exhaust, minus the end muffler. The system is designed to bolt up to the cat and can accomodate an aftermarket muffler, and has a flange, so that the standard muffler can be bolted on as well (for when the EPA bites you in teh ass presumably. The idea is to not get to this point however). Both of these parts appear to be mild steel, not stainless.

So now, to recap, I need a 3 inch high flow cat and an end muffler to complete the system. (If anyone is selling any of these items btw, let me know)

My question is. What sort of muffler should I have put on that will flow well, yet ensure that the system falls within the legal db limit? Please also keep in mind that I would like the muffler to look as stock as possible- I guess that rules out cannons etc.

Does anyone have any suggestions? Also, does anyone have any idea how much of an increase in power this should net me? Any tips etc, let me hear them as I am relatively new to the scene and am keen to learn.

Cheers.

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JMW Mentor

JMW

Posted
Posted

Going 3" straight through you will be pushing it for legal db's!

Your best shot would be to talk to a good exhaust shop (some have a db meter handy), but i would recomend fitting a resinator of some sort

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

^^ you couldn't be more wrong. Easy to get a 3" legal. I have a 3.5" - 92dB, ended up with under 90.

And resonators do not work, so another piece of bad advice in afraid.

You need two decent sized mufflers. Simple as that.

A panel filter isn't illegal. You're using the stock airbox, that's all that matters.

Vanilla_Rice Enthusiast

Vanilla_Rice

Posted
Posted

So you cant use a pod filter in Australia? thats gotta suck

Australia's laws are so tight ass compared to New Zealand, I have to hand it to our 3rd world approach to things, lets me gets away with a straight through exhaust and ground clearance that turns me into a grader on any gravel road.

bnr034 Apprentice

bnr034

Posted
Posted
So you cant use a pod filter in Australia? thats gotta suck

Australia's laws are so tight ass compared to New Zealand, I have to hand it to our 3rd world approach to things, lets me gets away with a straight through exhaust and ground clearance that turns me into a grader on any gravel road.

Our exhaust law still states that it has to be under 95db :blush:

89CAL Grand Master

89CAL

Posted
Posted

oh i see

damn aye

in regards to the exhaust but i have a 3 inch turbo back with high flow cat and rear resonator + cannon and atm mines losing boost pressure up higher in the revs so im only pulling 170 on the dyno instead of about 200 which my tuner reakons i should be seeing

so yeh I'll have to see if its the exhaust doing this but i suspect its the problem

MBS206 Grand Master

MBS206

Posted
Posted
boost is on the intake side, you cannot loose boost from an exhaust, as boost does not exist on the exhaust side

I think the poster about losing boost wasn't referring to losing it out the exhaust, more so eluding to the fact the exhaust might be a large restriction causing a drop in flow, causing a loss of boost.

As to a legal exhaust:

You will want a 3" exhaust, with a 3" high flow cat, a 5" bodied mid muffler, with some decent length, and then you will want as large of a rear muffler as you can fit.

I would also say to put the twin tips on the exhaust, and have them painted black.

I run a 5" mid, and a 7" end muffler (Cannon style) except they're not stainless, and not all shiney, and the whole exhaust, when looking at it from the back any more then 2 metres away, and it looks invisible, matched with a nice and quiet exhaust note, no issues there with the plod.

My mufflers are also 650 and 550mm long respectively. You want LENGTH AND DIAMETER for a good muffler. And yes, mine are both straight through and are custom built.

r32-25t Grand Master

r32-25t

Posted
Posted

i had a 3inch exhuast on my 33 s2 with a hot dog as the centre muffler (needed the ground clearance)

and a full size muffler out the back and the db meter hit 89.5 on back off (wich is ur loudest figure)

and was given a certificate to state that the exhuast was legal in every way

frozenwaffles Mentor

frozenwaffles

Posted
Posted

just one thing to know....your front mount is not 'legal' in the true sense of the term...its only legal if you pass a free emisions test at the RTA in botany or penrith...

SORRY but my comments are for NSW...

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Orig poster = Vic

Vic = the laws being discussed/applied here.

Can people from other states please refrain from posting about legalities if they do not know Victorian law?

All it does is confuse the issue for people reading at present, and then later on if they search and find this thread.

MBS206 Grand Master

MBS206

Posted
Posted

R31, It'd be handy if we actually knew the person was from vic.

Nothing in the post states location, and the only way we can assume he's in Vic, is being a Vic club member, and hey, they could have moved or anything since becoming a member.

Maybe get the board admin to show everyones state at least...

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