Outer Limits 4x4 Board

Hi to the forum
I am fitting a 5 litre VT commodore motor to my GQ.
I have the HSV extractors and my question is what size exhaust system have people that have performed this conversion run and how many cats.
I have spoken to three different exhaust shops and so far been told two and a half inch, three inch and three and a half inch with varying options on weather to run one or two cats.
The motor is a stock 179kw 5 liter.
And help and experience appreciated.


Regards
Nigel

i have a 5.7 and it uses a single 3" pipe with 1 cat 1 muffler, sounds very nice not super loud but everyone knows its a v8

i'd go with a single 2.5inch system with one good cat.

any more on a stock engine is a waste of money

I can tell you that if anyone tells you to get high flow cats they don't know what they are talking about. I know a ten second street car that runs standard cats. I can put a link up to his car if you like. A 2.5 inch system with 1 cat and a resonator will be all you need. It will still sound tuff and you will get that sweet 304i sound.

1TUFFGQ wrote:I can tell you that if anyone tells you to get high flow cats they don't know what they are talking about. I know a ten second street car that runs standard cats. I can put a link up to his car if you like. A 2.5 inch system with 1 cat and a resonator will be all you need. It will still sound tuff and you will get that sweet 304i sound.

that would depend on what car it is. some cars have very restrictive cat converters on them. while others have more flow then they will ever need.

Generaly, if you are starting a system from scratch, an average priced cat that has the right sized inlet and outlet is all you need.