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Is It Possible To Have A 3" Exhaust And Still Make Power?

Mid_Nite_R33
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TiTAN Grand Master

TiTAN

Posted
Posted

R31 nismoid is making around 300kw and has a legal exhaust, my car is 92db and makes over 300kw.

ask an exhaust place to make you up an exhaust with the biggest straight through mufflers they can fit.

Mid_Nite_R33 Mentor

Mid_Nite_R33

Posted
  • Author
Posted
R31 nismoid is making around 300kw and has a legal exhaust, my car is 92db and makes over 300kw.

ask an exhaust place to make you up an exhaust with the biggest straight through mufflers they can fit.

Awesome, I heard magnaflow muffler are the quietest, any others?

cheers

NYTSKY Grand Master

NYTSKY

Posted
Posted

The Kakimoto Regu and Trust PE2 are the quieter exhausts out of the Jap ones, im sure there are others.

Or like has been mentioned get an exhaust shop to make you one. My friends 700hp 25/30 sounds stock. 4inch dump with 3 1/2 exhaust with big mufflers.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Yes it's possible...

I'm just over legal, ~91dB with a 3.5" exhaust (it'll be good for 350rwkw). 3" can be made legal, plenty of people have done that on the forum.

My mufflers are fully custom (hand made) etc. So it wasn't cheap, but then to keep the fuzz outta your hair these are the measures we have get to today :woot:

There are some off shelf Jap ones that are under, I'm not sure what their names are though.

Basically just get a custom 3" made and have 2x the biggest possible mufflers installed + 4" cat. Should sort you out.

Mid_Nite_R33 Mentor

Mid_Nite_R33

Posted
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Posted

to put things into perspective, im making 250rwkw now and might be increasing to about 280 soon,

I have a 3" turbo back exhaust atm, I was thinking of leavin the first section of the exhaust as is and maybe having a 3.5" catback made up implementing the largest 2 mufflers, that way the extra 0.5" diaemeter will make up for the restriction of the mufflers......

Anyone know any exhaust shops in inner melbourne that could look after me?

cheers

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

280rwkw = 3" is fine.

Straight through mufflers really should not post much restriction at all mate, so i'm not sure what you mean about the extra half inch alleviating restriction...

Mid_Nite_R33 Mentor

Mid_Nite_R33

Posted
  • Author
Posted
280rwkw = 3" is fine.

Straight through mufflers really should not post much restriction at all mate, so i'm not sure what you mean about the extra half inch alleviating restriction...

I thought that the mufflers may restrict so gotta increase diaemeter...

Who should i head to for this in melb inner suburbs ??

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Well they do restrict, but you ain't talking massive amounts mate.

280rwkw you need -

1x 3" piping, mandrel bent. A little bends through the system as possible

2x 3" straight through mufflers, largest possible you can get under the car

1x 4-4.5" Hi-Flow cat

Just get it done in mild steel and it'll be nice and cheap. Turbos make enough heat to keep rust @ bay.

As for where to get it done - NFI mate, i don't use anyone inner city.

discopotato03 Grand Master

discopotato03

Posted
Posted

Personally I think the greatest gains are from being larger in the first 1/3 to 1/2 of the exhaust system .

The gasses are pretty hot out of the turbo on full load so giving them some volume to expand into seems to work .

The gasses cool and contract (increase in density) quite quickly and you can afford to go a bit smaller in tube size toward the rear half of the exhaust system . Usually the cat and mufflers are back there anyway so 3.25 or 3" mufflers should be reasonably easy to fit .

Cheers A .

Mid_Nite_R33 Mentor

Mid_Nite_R33

Posted
  • Author
Posted
Well they do restrict, but you ain't talking massive amounts mate.

280rwkw you need -

1x 3" piping, mandrel bent. A little bends through the system as possible

2x 3" straight through mufflers, largest possible you can get under the car

1x 4-4.5" Hi-Flow cat

Just get it done in mild steel and it'll be nice and cheap. Turbos make enough heat to keep rust @ bay.

As for where to get it done - NFI mate, i don't use anyone inner city.

Ok, why the 4.5" cat? cant i just retain my 3" high flow cat?

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

CAT's are restrictive. Just have a look @ em :woot:

Such tight honeycomb blocks are the enemy of good flow... so hence get a larger CAT and help the process along.

Car is still legal and emissions will be good so there is no real downside.

I would hedge a bet that if you had a 3" hi-flow cat on there and then dropped it for the next dyno run - you'd see a power increase :D

Hell even with my 4.5" CAT i can feel a difference in or out... It's not a massive difference but it's noticeable.

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