Exhaust. quiet vs power.

[HachirokuGTV]

Im due to get an exhaust soon and it has to be pretty quiet, just a low hum. Extractors are 2.25inch and im wondering what will keep the noise level low but give some reasonable power (or am I dreaming).
I was thinking of one of those Powerpro eevc mufflers with the butterfly valve but I dont know if they are any good and they only do a twin muffler style anyway.

Your opinions would be greatly appreciated.

[Stealer Of Souls]

Here's my unsubstantiated suggestion...

You should be able to go for a 2.25 straight through system. Fit a high flow cat (if your rich) or at least a muffler where the cat would normally go, a resonator, and for the rear muffler drop to a 2 inch.
If you're concerned about flow, make the mid muffler and reso 2.5 inch.

An article on Autospeed suggested that the rear muffler makes the least impact on flow/restriction, but can have an effective impact on volume. Another article (or perhaps it was the same one...) noted that the first muffler/cat makes the most impact on flow/restriction. Being in Oz they are required to have a cat, so in the article they got a 2nd hand cat from a V8 commodore that was practically brand new.

[HachirokuGTV]

Who sells high flow cat converters around here?

[barryogen]

I agree with the above comments.

and pretty much any muffler shop sells cats... and they'll all ream you for the priviledge.

[Bling]

why put a cat in? just to help the environment out? (serious question)

i'd just go muffler or resonator where factory cat usually sits and a muffler at the rear. when I say muffler I don't mean straight thru trademe bargain bling

2.25" seems a good size as recommended

[barryogen]

why put a cat in? just to help the environment out? (serious question)

ummm, yeah*, and also to take a lot of the drone out of it.

I thought I'd de-cat my exhaust on my 2zz-ge RunX when changing to 2.5", and all I ended up with was a horrible tinny noise that droned whenever it was on vacuum, and some horrible harmonic resonances between 2500 and 4000 RPM, ie, whenever I was cruising.

I ended up putting two 19" resonators, a mid-mounted oval muffler, then the end muffler, and it still drone a bit more than stock. A friend(well, acquaintance) who did the same(2.5") put a high flow cat on it, a single 19" resonator, and the end muffler, and his sounds and goes much better, and quieter.

*No doubt with the introduction of the emissions testing at entrance to the country, it'll become a warrant item in the next few years.

[Stealer Of Souls]

why put a cat in? just to help the environment out? (serious question)

Personally. I think that helping the environment is a good enough reason to do it. I have no other real reason for suggesting a cat. Of course after paying for a high flow cat you will probably need some butt tampons...
For the more cost concious go with a muffler. Not a reso. Reso's are nice and all, but a good muffler should be much better and reducing the actual noise level. A reso is good if your exhaust has a particular note which drones, or a barky sound to it.

[HachirokuGTV]

I definately want to go cat. I have been looking on the Aussie Ebay site at their prices. Metalcat seems to be the best brand and has cert papers but are about $350 AUD or Magnaflow which is about $135 AUD.
How much do you pay here for a high flow cat?

[Mr Revhead]

a cat off a larger engined car would be a good start
just have to make sure its mounted in a place that its temp range is correct.

with all the new laws coming i forget.... but dont the new ones state the car must comply with original equipment. ie if it was made with a cat, it needs a cat? cant recall if that one is in or still coming
but make no mistake, if its not law yet, it WILL be sooner rather than later

[ChaosAD]

How about a pair of hsv mid mufflers? one in the middle, one at the back? They are straight through but center in, offset out. They look very well made. The internal bends are smooth compared to the cheap ones which are just butted together.

I got some for $30 each on trademe which seems to be the going price.
Heres some but theyre a bit overpriced. http://www.trademe.co.nz/Trade-Me-Motors/Car-parts-accessories/Holden/Engines-drive-trains/auction-135003447.htm

[Stealer Of Souls]

ChaosAD is right. That's a good option. I couldn't find any when I was looking... I must be blinder than I look...

I saw an advert in Performance Car some time ago. Pitstop perhaps? Hi flow cats from around the $350 mark.

[matt dunn]

we have been playing around with mufflers on dads GT40,
as there is limited room.

Had some custom one on it, but they made too much heat and it lost over 50hp with the mufflers on compared to none.

so made up some longer length with two supposedly less restrictive
type mufflers in line and trippled the total exhaust length,

result, was slightly more noise and a whole lot less power again,

so going to another different type of muffler altogether again.

[Mr Revhead]

you need to make a recording of it with no mufflers

[matt dunn]

you need to make a recording of it with no mufflers

at 7000rpm, lol