Exhaust Questions..........

[justin]

First...what is the difference between a test pipe and just cutting the cat off and we
lding in a piece of pipe? Second... should I run 2 1\2 pipe or bigger, I know I need back pressure.I would like to run 2 1\2 pipe from the down pipe all the way back to my muffler. Third... would it be louder and if so how loud without the cat? I've got the state inspections taken care of for the rest of my life .......... 83'944 standard shift.

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Drive it like you stole it........Justin

[justin]

Oh yea ............Thanks in advance

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Drive it like you stole it........Justin

[EGSMachine]

a typical street application doesnt run more than 2.25". you don't want back pressure, you want "exhaust velocity". Back pressure is a result of resistance to exhaust gas velocity. this is where acoustics comes in to play in the design of your exhaust system, and why too large of a pipe will not be as beneficial as one sized properly. a general rule of thumb is a 2.25 for 1.6 to 2.5l, and 2.5" up to 4l. this is just a rule of thumb, "not the rule".

very loud without the cat.

i would love to chat more. pick up a book about exhaust system and intake design to learn alot more.
e

[justin]

bump.........

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Drive it like you stole it........Justin

[Gordon Rankin]

Exactly how do you have things taken care of? I certainly would like to know how I could get away with taking my cat off...Share please...

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Gordon
1981 924 N/A

[justin]

I know a guy that owns a oil change place...

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Drive it like you stole it........Justin

[951carter]

but what if you outlive him? ;-)

[jhobbs]

Justin,

As far as I know, a test pipe is nothing more than a straight pipe. Of course it has flanges welded to the ends so that it's easy to bolt in/out. Might be handy just in case your lifetime pass doesn't last a lifetime (***** happens).

Another option that costs $0 is to gut your cat. Pull it off, than take a straightened coat hanger (or similar) and poke and scrape at the inside of the cat until all of the "stuff" is out of it. It may take a while, and it can get messy, but the price is right Removes the restiction while maintaining a legal appearance.

Jon

[This message has been edited by jhobbs (edited 06-27-2001).]

[This message has been edited by jhobbs (edited 06-27-2001).]

[1.2gees]

A broomstick works much better than a coathanger. Actually, I don't think you can gut a healthy cat with a coathanger alone.

The screen will usually give you problems if you gut it yourself, and even if the thing appears perfectly clean, you'll still have small parts work their way to inside the muffler, and make noise. A lot of people complain about the extra noise on 944s without a cat, but it's mostly loose crap resonating in the muffler (a straight through one would solve that problem).

Anyway, there's also extra resonance, but the price is indeed right, and it does look legal.
Ahmet

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It's all the driver...
My page over1g@hotmail.com
Porsche owners Gallery.../My 944

[justin]

Thanks everyone............I think I'm goin to try to get 2 1\4 inch pipe all the way back and see what it sounds like.

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Drive it like you stole it........Justin