If there is no back pressure then the exhaust gases will leave the engine slowly, as there is no pressure. If there is pressure then they will be made to move out quicker.

Like if you put your finger over the end of a hose pipe, it sprays much faster!

Ok that was exactly what i wanted to hear cause my friend recently has made a custom exhaust with a straight through pipes on his Astra and he wasnt satisfied with the result.He told me that he felt that the car lost power.Why is that?No back pressure?Explain no back pressure..thanks alot.:)

it all depends on how free flowing the GSI std exhaust is to begin with.

i cant exactly see it being very restrictive. so ur really only gonna get noise by removing boxes

personally id keep all boxes and just remove the cat, as this will be the most restritive bit on the exhaust

Well the top option includes silencers as you can see, so will be quieter.

The bottom one will be much louder and seeings as its striaght through you might get more power.

There will be no back pressure though so you may lose torque.

Ok,wich is better for performance:
1.Lexmaul inlet manifold and this:

Front exhaust,replaces Kat.

Center exhaust

And a back box

or

2.Lexmaul inlet manifold and this:
Front pipe:

Centre pipe:

And a back box
Make:Supersprint

Your help is very appriciated.thanks guys.


:wave: