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2.5" twin or 3" exhaust? 

 

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Posted: Sat Jul 22, 2006 12:16 pm 
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Look at the cross sectional area

for example; two 2.5" squares have the same area (slightly larger) as a single 3.5" square.
two 3.5" squares have the same area (nearly) as a single 5" square.

hmmm... four 2.5" squares would have the same area as a single 5" square....

I used squares, not cubes, as an example because i cant remember the equation used to work out the area of a circle.

 

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Posted: Sat Jul 22, 2006 1:22 pm 
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im just throwin ideas at ya

but I liken exhaust flow rates to water in a pipe and more water flows thru a larger diameter pipe.

area of 2.5" = 19.63 sq (4.43)
area of 5.0" = 78.53sq (8.86)
area of 3.5" = 38.48 sq (6.20)
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Posted: Sun Jul 23, 2006 12:43 pm 
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Get the twin 2.5 " exhaust as it is better all round for legalities and performance. Get a set that flows too much and you lose the scavenging properties which eat into the slight performance gains. Its also a pain in the a** to after spending money on a exhaust to have to get it looked at again cos a certain Mr Plod thinks its too loud. By law (last time i checked) states that adr complient vehicles exhaust to be no louder than 90 DB at 1 meter at a 45 degree angle from the rear of the vehicle. Just ask all the corolla, excel owners who thought they'd put a milo tin on the back to make it sound "tough" ( cough cough ).

 

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Posted: Sun Jul 23, 2006 1:17 pm 
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This would be an even better thread with some sound clips of your exhaust setup. Feel free to upload!


mickoxhxr8 wrote:
but I liken exhaust flow rates to water in a pipe and more water flows thru a larger diameter pipe.

Isn't it also about air speed as well as decent airflow?

 

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Posted: Mon Jul 24, 2006 2:21 am 
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i like your idea of the sound clips Vic, so if anyone has one let us hear :)

well i think i've gone off the idea of hotdogs, i might just wait til i can afford a full system (which shouldnt be too long) but what to get?

mild steel vs stainless
herrod vs difilipo

any opinions or feedback from owners with either exhausts?

 

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Posted: Mon Jul 24, 2006 9:22 pm 
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[quote="Vic"]Isn't it also about air speed as well as decent airflow?

Agreed, the quicker its out the better :lol:

--------------------------------------------------------------------------------

[quote="schnoods"]Get the twin 2.5 " exhaust as it is better all round for legalities and performance. Get a set that flows too much and you lose the scavenging properties which eat into the slight performance gains. Its also a pain in the a** to after spending money on a exhaust to have to get it looked at again cos a certain Mr Plod thinks its too loud. By law (last time i checked) states that adr complient vehicles exhaust to be no louder than 90 DB at 1 meter at a 45 degree angle from the rear of the vehicle. Just ask all the corolla, excel owners who thought they'd put a milo tin on the back to make it sound "tough" ( cough cough ). "

Agreed 2.5" for most,

With the performance, I disagree with any power loss with big pipes, I had only noticable gains throughout the rev range and whilst I agree that 3" may be slightl overkill and cross pipes etc make a difference in performance results I dont believe you would notice it much at all once you alrerady had the big pipes, though in saying that I will consider them when my new pipes are made.
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Posted: Tue Jul 25, 2006 11:42 am 
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look at the manta range i run one on my xr8 and it souonds very nice twin 2.5" cat back didnt want it to loud as mr plod starts lookn a set of hi flo cats will make the beast sound and perform better as well

 

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boss 260 with BPT motorsport tune helix tower power spacer C.A.I kit 25% under drive kit cat back twin 2.5" exhaust 250-260kw at the rears

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Posted: Tue Jul 25, 2006 6:00 pm 
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i think twin 2.5" is the way im gonna go... looks better too :)

is it worth getting stainless?

 

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Posted: Tue Jul 25, 2006 8:09 pm 
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I went stainless on my XF 6 and its a waste of money. With an 8 theres even more of a waste of money going stainless especially if you run twins the whole way.
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Posted: Tue Jul 25, 2006 8:18 pm 
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why's that? i've always been told "get stainless, better sound, last longer" and that crap

 

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Posted: Tue Jul 25, 2006 9:15 pm 
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Last longer but that's about it. Have no idea where they pull sound from unless they are audiophiles.
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Posted: Tue Jul 25, 2006 10:23 pm 
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anyone else got any comments about stainless?

 

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Posted: Wed Jul 26, 2006 4:55 pm 
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waste of money ask the same question when i had mine done bloke said if you want it to last longer then spend the money theres no difference in performance or sound otherwise

 

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Holy Crap what was that, that my son was BLACK LIGHTNING!!!!!!
boss 260 with BPT motorsport tune helix tower power spacer C.A.I kit 25% under drive kit cat back twin 2.5" exhaust 250-260kw at the rears

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Posted: Wed Jul 26, 2006 5:57 pm 
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punktured wrote:
anyone else got any comments about stainless?


don't get stainless.........i don't think its worth it. spend the rest of the money u save on the blower ;)....dw i won't tell es about it :P

 

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Posted: Wed Jul 26, 2006 6:30 pm 
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hahahaha ye the blowers a long way off there phong :)

just a thought, is it legal to put side exhaust like the v8 supercars?

 

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