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Posted: Sun Dec 28, 2008 1:31 am 
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metasaiah wrote:
Personally I don't think there's any real need for anything bigger than 2.5" unless you want a big turbo setup. 2.5 is still a very big pipe and will cater for most applications without compromise. It's also way cheaper to keep a 2.5 quiet if that's what you're concerned about. But I look at it like this:
You want a blower later on. It might happen.
You want a cam and head work. It probably will happen.
You want a huge pipe that will never need upgrading. When you get a few quotes, you then decide you can live with an "average" exhaust upgrade. It's a certainty.

No offence intended mate. We have all been there (or are still there) :)


you hit the nail on the head. pretty much summed it up in one.

the thing i may not have elaborated on was that if the boosted setup goes ahead, i wont be going big power, just a st1-st2 setup. Maybe look at 250rwkw???

But yeah i spose im not alone in the above thought.

 

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Posted: Sun Dec 28, 2008 6:08 pm 
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A 3" wont cost much more than a 2.5", as you can get the rear section from redback in 3" off the shelf (listed for V8s) - then all you need is a basically straight bit of 3" from the cat to the diff with a muffler on it.

 

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Posted: Sun Dec 28, 2008 6:54 pm 
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If you go forced induction, having to fork over a couple of hundred more dollars for a new exhaust will only be a minor expense.

If your cars auto I definately wouldn't even consider the 3" with NA.


alfy wrote:
GeZza200 wrote:
mmm im thinking about getting a 3" now lol, it would be bloody loud though wouldn't it.


friend of mine went from a 2.5'' Lukey to a 3'' Manta on his VS Commodore, and f**k me its probably 5 times louder. i can hear it from almost 4 blocks away.


That can be more to do with the choice in mufflers (i.e. brands, models, styles) than the actual pipe size.
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Posted: Sun Dec 28, 2008 10:17 pm 
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thanks fellas.

the car is auto and that was my next issue. the last thing i want is issues of poor back pressure for an oversized exhaust.

i think the conclusion is get the 2.5" system now with the cam, head and edit and run that for as long as possible, then when its time to boost, upgrade the exhaust then and just fork out for it.

OR

Be patient, hold off with fitting cam, head and edit and buy s/c or turbo kit and fit it all at once, doing it one time only.

Question is, do I have the will power to wait for more power so I can do it all at once? hmm tough decision

 

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Posted: Mon Dec 29, 2008 4:01 pm 
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shav wrote:
thanks fellas.

the car is auto and that was my next issue. the last thing i want is issues of poor back pressure for an oversized exhaust.

i think the conclusion is get the 2.5" system now with the cam, head and edit and run that for as long as possible, then when its time to boost, upgrade the exhaust then and just fork out for it.

OR

Be patient, hold off with fitting cam, head and edit and buy s/c or turbo kit and fit it all at once, doing it one time only.

Question is, do I have the will power to wait for more power so I can do it all at once? hmm tough decision


backpressure is a myth.

 

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Cramping in the hand from having it on your Wang for an excessive period of time is a definate con.
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Posted: Mon Dec 29, 2008 4:04 pm 
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care to elaborate skidder?

 

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Posted: Mon Dec 29, 2008 4:30 pm 
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I'm only gonna give the short version as there's several long versions I've written on here.

With an exhaust system you want minimal pressure. Hot air weighs less, cold air is more dense and weighs more (however the weight difference is greater than the difference of volume).

If you have a smaller diameter exhaust, velocity will be higher, meaning hotter air (which weighs less) is forced through cats/mufflers/resi's etc. The opposite will occur as the exhaust gets larger. Obviously having too small an exhaust will restrict the engine in higher revs and too small an exhaust will lead to lower velocity and heavier air being pushed through restrictive areas.

A cat back exhaust (when needed) should be designed to be able to flow accordingly to where torque is desired.

 

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EVL098 wrote:
Cramping in the hand from having it on your Wang for an excessive period of time is a definate con.
Seriously do people google "f**k up modifications for Fords owned by Jews" and get linked straight to this site nowadays?

AU,factory fitted tickford kit/IRS, t5,Sports ryder/KYB: gone.

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Posted: Mon Dec 29, 2008 4:32 pm 
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Sorry forgot to state the obvious, hotter + lighter air being pushed through cats/mufflers/resi's being easier also means its less of a restriction on the engine.

And in relation to your question, either 2.5in or 3in will provide negligable difference performance wise N/A, I doub't you will tell the difference driving.

 

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EVL098 wrote:
Cramping in the hand from having it on your Wang for an excessive period of time is a definate con.
Seriously do people google "f**k up modifications for Fords owned by Jews" and get linked straight to this site nowadays?

AU,factory fitted tickford kit/IRS, t5,Sports ryder/KYB: gone.

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Posted: Mon Dec 29, 2008 5:24 pm 
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Thanks skidder, that makes sense to some degree for me. Its still a learning curve for me, but Im getting there.

Effectively speaking, Id like the power to be low - mid range as that is where the car's rev range is most often. Between idle and 4000rpm. But that doesnt mean I dont take it up to redline on occasions.

I think it just comes down to wanting N/A or forced induction, and choosing the appropriate parts from there.

 

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Posted: Mon Dec 29, 2008 10:05 pm 
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pretty much, as was said if you go forced induction a new exhaust shouldn't eat into the budget as unless you are very good at doing stuff yourself it will be around 5% of the cost.

 

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EVL098 wrote:
Cramping in the hand from having it on your Wang for an excessive period of time is a definate con.
Seriously do people google "f**k up modifications for Fords owned by Jews" and get linked straight to this site nowadays?

AU,factory fitted tickford kit/IRS, t5,Sports ryder/KYB: gone.

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Posted: Mon Dec 29, 2008 11:31 pm 
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cheers.

thinking of sticking to N/A for now.

 

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 Post subject: Re: exhaust size
Posted: Sat Oct 09, 2010 6:10 pm 
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stupid question guys but i've got a na BA with cat back exhaust wanting better sound, is the turbo or XR8 exhaust larger than 2 1/4 inch?
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 Post subject: Re: exhaust size
Posted: Sat Oct 09, 2010 7:08 pm 
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violentg wrote:
stupid question guys but i've got a na BA with cat back exhaust wanting better sound, is the turbo or XR8 exhaust larger than 2 1/4 inch?


I believe xr6t exhaust has same volumetric efficiency as a 3" system. But don't quote me on this.

 

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 Post subject: Re: exhaust size
Posted: Sat Oct 09, 2010 10:17 pm 
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there is a simple fix to the question of 2.5 or 3

Fit a 3inch cat back system with a good 3 inch cat. Only you mount the cat at the main system flange instead of the extractor flange. you then use a short 20-25cm long bit of 2.5inch pipe from the extractors back to the cat. problem solved.

You get good air speed through the 2.5inch pipe and the extractors will function as if there is a complete 2.5inch system fitted only they won't be a strangled at higher RPM.
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 Post subject: Re: exhaust size
Posted: Tue Oct 12, 2010 2:35 pm 
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tickford_6 wrote:
there is a simple fix to the question of 2.5 or 3

Fit a 3inch cat back system with a good 3 inch cat. Only you mount the cat at the main system flange instead of the extractor flange. you then use a short 20-25cm long bit of 2.5inch pipe from the extractors back to the cat. problem solved.

You get good air speed through the 2.5inch pipe and the extractors will function as if there is a complete 2.5inch system fitted only they won't be a strangled at higher RPM.


Interesting option there tickford. Have you seen this done before or is this just a suggestion?

Are you also saying to make the short piece of pipe adaptable with extra flanges to accept the extractors and cat?

 

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