Afew basic questions?

**MrPlow** · 18-03-2004 11:02 PM

I want to replace my stock exhaust piping to 2.25", when they do this do they replace from the headers all the way to the muffler? Whats an estimate price to get the piping changed to 2.25"?

Should i replace the cat with a hi flow item when i get this done?

Also how much is it to install headers?

Anyone recommend some places in sydney to get all this done?

**Weq** · 18-03-2004 11:05 PM

Liverpool exhaust were great to me. catback 2.25" mild steal is around $300, headers price all depend on brand. if u go headers, get a hi-flow cat and flex piping.. looking at around the $1000 mark

**MrPlow** · 18-03-2004 11:08 PM

thanks but i ment, if i had my own headers already, how much to install in my car?

**hondar** · 19-03-2004 05:46 AM

hi there,

whats the collector size of your header? whats the size of your cat converter flange?

as a rule of guide, you must have at least equal size or greater along the exhaust system. otherwise there is a "bottleneck" and defeat the purpose of having an exhaust system. EG, if you header collector, cat con, cat back is 2inch>2inch>2inch, is okay. 2inch, 2.25inch, 2.5inch is fine as well. Howver if it is 2inch>1.75inch>2.25inch, you will see that the cat-con flange is too small and there is a bottleneck and restrict the flow. it is no good.

I am suggesting your GOAL should determine the exhaust size and not the other way round.

We are after exhaust velocity and not volume like turbo car. The car gain maximum peak torque when reaches about 240feet/seconds of exhaust velocity. Your exhaust system size will determine where you want to land at the rpm range, your peak torque.

Also, if you know that locally made exhaust is different from jap counterpart even though they are both mandrel bent exhaust system.

The japs one come in one or two piece cat-back system which are bolted together (usually). Over here, even though they are mandrel bent, they are welded together a few pieces of piping as to do a mandrel bent over a long pipe is too expensive. It is worthwhile to look at their welding quality before plunging your hard earned money into buying one.

I have some shoddy work in sydney and these people have no knowledge whatsoever about building a good exhaust system.

one guy even offer a cat-convertor that is 2.5inch in size when my cat back diameter size is only 2.25 inch.

when i told him that it will restrict the flow, he just shrugged away and say,
"mate, thats too complicated.... u should speak to mr XYZ about those things..."

yeah rite, and exhaust shop and doesnt know about this rules. i probably wont go to the shop that dont know why they do it.

That bring another pointer if you want to shop for exhaust, ask them questions and from there you can know whether these guys know what they are doing.

I hope i have been helpful.

hondar