coby exhaust

jumper · Post by **jumper** » Mon Jul 16, 2007 6:31 pm

The fj40 has dual exhausts with 1 coby 14in resonator on each side i want to tone down the exhaust note. Would adding 1 10in coby on each side be ok or should i do somthing else.
I was quoted $155 for a generic muffler, coby 10in would be $58 each

Goose · Post by **Goose** » Mon Jul 16, 2007 6:39 pm

Awwww, c'mon now jumper!!

louder is better!!! :twisted:

Just cut it off 3" from the manifold flange :lol:

anyway, did you get your stalling problem sorted?

Steve_t647 · Post by **Steve_t647** » Mon Jul 16, 2007 9:55 pm

you could put in a couple of resonators to change the note or 2 mufflers alternatively you can just wear earmuffs or turn up the sterio.

jumper · Post by **jumper** » Tue Jul 17, 2007 11:43 am

Going with a couple of glass packed 250mm mufflers. If i start the 40 in the garage i have to where ear muffs to think :roll:

Stalling is on the list today :!:

Cloggy_NZ · Post by **Cloggy_NZ** » Tue Jul 17, 2007 11:53 am

I used to get HQ Holden Statesman V8 mufflers (don't know if they are still available). The standard oval muffler does a much better job of quieting down the sound as opposed to a Coby type. Gets rid of the high notes leaving just a nice low burble.

jumper · Post by **jumper** » Tue Jul 17, 2007 12:26 pm

57mm pipe x 250mm long at $120 each. i want to run this length as i an make it fit with the cobys without to much work or i have to loose the cobys and go with 350,400 or 500mm plus the extra cost.
Do cobys affect the noise level alot?

IcedJohnno · Post by **IcedJohnno** » Tue Jul 17, 2007 3:40 pm

jumper wrote:Do cobys affect the noise level alot?

Yes they do.
Because the coby style are round, they only work around one specific frequency. Adding more mufflers of a similar dia will not really alter the pitch & therefore the volume of sound will be similar.

The oval style of muffler works over a range of frequencies due to the differing distances from the centre of the pipe to the outer cover.
A multi pass muffler will reduce the putch range further still, due to noise cancellations where the pipes pass each other. This is via the same wave lengths frequencies but in opposite directions.

Go dfor a multi-pass oval muffler for max noise reduction There are triple pass ones that suit the bigger V8's ie falcon & Chev etc, that flow well made by Magoos. These units have radii where the direction changes.

xorph · Post by **xorph** » Tue Jul 17, 2007 6:34 pm

On the advice of an exhaust shop I fitted a single 2.5 inch 'extra long' coby to my p76 v8. The guy claimed they 'seem twice as quiet' as conventional ones. think its about 20inches long. Unlike other cobys they have a prechamber plenum at the start.
seems to really work, engine sounds smooth and throaty right through the range and isnt as loud as I was expected.
My friend and I fitted a short coby to his Prelude and it was substantially louder!
A possible explaination is that ducting the two exhausts into one muffler on a v8 provides a noise cancellation effect

jumper · Post by **jumper** » Tue Jul 17, 2007 7:01 pm

the cobys i have on it are 14in x 2 1/4in so if i add a 250mm oval glass pack muffler it should be good :twisted:

thanks for the help

Sadam_Husain · Post by **Sadam_Husain** » Tue Jul 17, 2007 8:01 pm

Jumper....

Can you please let us all hear that V8 exhaust one last time before you shut it all down :shock:

skid · Post by **skid** » Tue Jul 17, 2007 8:12 pm

go single bro.

i had twins out each side and got pissed at the noise being louder in one ear, even with a crossover pipe.

now have the sweetest sounding chev with block hugger headers into a 3" single through one HSV muffler and then exiting at the back on the passengers side. It sounds a million times better.

i only wish I could show you before you rush into your twin system.

sig · Post by **sig** » Tue Jul 17, 2007 8:25 pm

i can vouch for skids ,it sounds awesome.

wopass · Post by **wopass** » Tue Jul 17, 2007 10:46 pm

mine has a 3" oval muf on each side (30 buks each new)and is relatively sedate (quiet) sounding,not intrusive at all when driving and has a nice deep rumble to it. some say it needs a balance pipe but.... its working and sounds nice from the drivers seat so who cares about everyone else :wink:

jumper · Post by **jumper** » Tue Jul 17, 2007 10:53 pm

where did you get them? what model muffler?

I will get a recording of the exhaust before i change it.

skid · Post by **skid** » Tue Jul 17, 2007 10:56 pm

wopass wrote:mine has a 3" oval muf on each side (30 buks each new)and is relatively sedate (quiet) sounding,not intrusive at all when driving and has a nice deep rumble to it. some say it needs a balance pipe but.... its working and sounds nice from the drivers seat so who cares about everyone else

do you find that you mainly hear the drivers side. I did and it never sounded right, even with the balance tube. But thats only my opinion.

wopass · Post by **wopass** » Tue Jul 17, 2007 10:57 pm

chase autos (muffler and exhaust parts shop) in hamilton,just his standard 3"muffler the 30 buks was to me tho, think they are like 50 retail ? ask your local PIT STOP, i think he suplies them all.

jumper · Post by **jumper** » Tue Jul 17, 2007 11:14 pm

Is it Chase Auto Components? there is one down here in the hutt. How long are the mufflers?
Mine can't go out the back as that is where the lpg tank sits

Can't say i notice the difference between each side. How protected is your exhaust from getting crushed?

wopass · Post by **wopass** » Wed Jul 18, 2007 11:05 pm

muffler body is 360mm long,offset pipe in and out 3".

protection....they are 600mm off the ground :wink:

skid · Post by **skid** » Wed Jul 18, 2007 11:12 pm

wopass wrote:muffler body is 360mm long,offset pipe in and out 3".

protection....they are 600mm off the ground

used to have a 19" coby on each side just like you got there Wop. they got crushed till they couldn't breathe any more. My 3" single is above the chassis rails now, so no more exhaust bashing. 2c

wopass · Post by **wopass** » Thu Jul 19, 2007 10:48 am

skid wrote:used to have a 19" coby on each side just like you got there Wop. they got crushed till they couldn't breathe any more. My 3" single is above the chassis rails now, so no more exhaust bashing. 2c

yea but yours would have been MUCH closer to the ground tho. mine only barly hang lower than the chassis rails and have a lot of clearance from ground, it would have to be a fkn big log or rock to get my zaust ! :wink: