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What's The Legal Limit On Muffler Size?

fcruz3r

By fcruz3r,
in Four Door Family & Wagoneers

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AlexCim Grand Master

AlexCim

Posted
Posted
On a twin 2 inch system

R = 1 inch X pi (3.14) then square it = 9.88 cubic inches

times 2 pipes = 19.77 cubic inches

On a single 3 inch

R = 1.5 inches X pi = 4.7 squared = 22.22 cubic inches

So a single 3 inch pipe has more volumn then a twin 2 inch.

I rest my case...

Why are you talking about cubic inches?

Cubic = Volume

Volume is dependent on length, as V = Surface area x Length. So, if my 10 inch exhaust is 1 inch long, does that mean that my 1 inch exhaust that is 10 inches long has the same flow rate? No, because flow is more highly based on surface area rather than length (Unless you really want to get technical with gas velocity etc)

Hence, my use of surface area of a circle (exhaust size) as a comparo.

Also, fcruz3r, you will be more than happy with the Apexi muffler, STAGEN has one on his car.....AND I WANNA STEAL IT! :laugh:

mr manfringinsen Contributor

mr manfringinsen

Posted
Posted

Why are you talking about cubic inches?

Cubic = Volume

Volume is dependent on length, as V = Surface area x Length. So, if my 10 inch exhaust is 1 inch long, does that mean that my 1 inch exhaust that is 10 inches long has the same flow rate? No, because flow is more highly based on surface area rather than length (Unless you really want to get technical with gas velocity etc)

You could choose between 1x4" pipe or 16x1" pipes out the back as flow is inversly proportional. But this doesn't take into account the boundry layer separation that would create drag at the surface of each pipe which means the surface area has to be minimised. This means the 4" would outflow the 16x1". But just imagine the chicks you'd pull with 16x1" pipes. It'd be fully sick mate..

I don't think mr plod would be worried about that when he see's the pimpmobile, He'd be worried about db and clearance. Then again if he sees a 4" pipe out the back of a stocker, and a discreet pair of 2" out the back of a 600kW firebreather he's probably gonna pick on the 4" because he looks like jailbait.

One day I'll figure out how to separate the quote from the text. but today is not that day.

fcruz3r Experienced

fcruz3r

Posted
  • Author
Posted
Why are you talking about cubic inches?

Cubic = Volume

Volume is dependent on length, as V = Surface area x Length. So, if my 10 inch exhaust is 1 inch long, does that mean that my 1 inch exhaust that is 10 inches long has the same flow rate? No, because flow is more highly based on surface area rather than length (Unless you really want to get technical with gas velocity etc)

Hence, my use of surface area of a circle (exhaust size) as a comparo.

Also, fcruz3r, you will be more than happy with the Apexi muffler, STAGEN has one on his car.....AND I WANNA STEAL IT! :whistling:

Thanks alexcim ...the apexi unit comes with a 4 inch inlet so I'd have to step up the current piping ...although there is a hks super dragger unit on ebay which looks oh so tempting :devil:

http://cgi.ebay.com.au/HKS-SuperDrager-Sta...1QQcmdZViewItem

too bad shipping will cost too much :woot:

fcruz3r Experienced

fcruz3r

Posted
  • Author
Posted
You dont want a super dragger eh, went cruising with a mate in his old r33 with one and after 30mins I had to stop and get out, the drone was giving me a headache!

Got the whole end section replaced on saturday...must say that the guy at ian diffens osborne park did a fantastic job ...used 2 mandrel bends, a flange plate and a section of pipe...very pleased indeed.

the muffler does drone quite a fair bit at lower rpms (1.5-2k) but the beauty is at high revs...especially when it pulls past 3k rpm ...the exhaust sound almost completly fades away and all u can hear is the turbo chirping ...and got it mounted high so the body of the muffler is tucked away...very stealthy.

will be looking at a split dump..or a screamer for the next part of my project.

KR.15.YS Collaborator

KR.15.YS

Posted
Posted (edited)

Don't even talk to me bout exhausts I got defected for mine the other week.

While yes I will agree it was loud (altough my kids never complain) the police officer was a dick!!

My exhaust is 3" from the cat bak with a cannon.

Won't even bother to quote the db reading before I got it fixed but it was loud..

Afterwards with the silencer in place and a shit load of steel wool in the guts it still only just passed. (and by saying this the guy felt sorry for and just let it pass)

But now I have the car engineered the Police cannot pick on me anymore.

Now I wish I had just left the car standard would have saved a shit load of money and all the hassles..

Edited by Mum's Taxi
chrissso Proficient

chrissso

Posted
Posted (edited)

huh?

area or a circle is pie x radius squared

radius of a 2 inch pipe is 1 inch

1x1x3.14= 3.14sq inces x2 pipes is 6.28 sqinchs

radius of 3"=1.5

1.5x1.5x3.14= 7.065 sqinches.

2 2"inches has more cross-sectional area than 1 3" pipe...

you all should go back to school... :thumbsup::)

or am I missing the point....

EDIT - looks like I can't add up either. Changed to correct value...

Edited by chrissso
fcruz3r Experienced

fcruz3r

Posted
  • Author
Posted
Don't even talk to me bout exhausts I got defected for mine the other week.

While yes I will agree it was loud (altough my kids never complain) the police officer was a dick!!

My exhaust is 3" from the cat bak with a cannon.

Won't even bother to quote the db reading before I got it fixed but it was loud..

Afterwards with the silencer in place and a shit load of steel wool in the guts it still only just passed. (and by saying this the guy felt sorry for and just let it pass)

But now I have the car engineered the Police cannot pick on me anymore.

Now I wish I had just left the car standard would have saved a shit load of money and all the hassles..

oh sheet...i just got a speed ticket today + 1 demerit....last thing i want is to get my car defected :sleep:

might have my speedo checked....i swear i was doing 70...was picked up doin 78

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