3inch or 2.5 straight through exhaust

[Pottsy1990]

Is there or would there be a difference between the 3 and 2.5 inch exhausts if only doing cat back ?

 

[calcal]

Same shit mate!! Your better off doing your dump pipe aswel though

 

[dan-0]

Same shit mate!! Your better off doing your dump pipe aswel though

Agreed. You could put a 5" cat back exhaust on and you will get no imprement with the stock dump and cat in place.

The difference between 2.5 and 3 exhaust has been
Everyone who has a 3" will say "get a 3" but a 2.5 will do the same job and cost alot less.

 

[tweak'e]

Is there or would there be a difference between the 3 and 2.5 inch exhausts if only doing cat back ?

depends a lot on what engine you have.
2.5" is generally fine, 3" harder to fit.

the biggest restriction is often the rear muffler. fitting the dump pipe doesn't make as much of a difference as changing the muffler does (on a zd30 3litre)

 

[Pix]

Just go a 2.75in system... I have one on a zd30 and it's great!

 

[Pottsy1990]

Thanks guys! I have the ZD30 and a small budget so value for money i spose is the most important

 

[cyc10n]

I'm looking at putting an exhaust on my ZD30 once my intercooler is installed and I was torn between a 2.5 inch and a 3 inch system.

 

[tweak'e]

Thanks guys! I have the ZD30 and a small budget so value for money i spose is the most important

2.5" and a single hotdog muffler/resonator. getting rid of the main muffler will make a big difference. you will see why when you look at pipe at the front of the muffler.

 

[petez]

I have a 2 3/4 beaudesert, dont bother just putting a cat back, you wont get the full potential out of the system, it'll just be noisy no power...like those rice burners that asians drive.

 

[tweak'e]

have any of you guys actually tried cat back ?

i originally just changed rear muffler and got a big improvement.
fitting the dump pipe later and fittign the rest of the exhaust only improved the lower rpm. boost came on quicker but no increase in top end like the muffler change did.

 

[chule]

Yep. I originally had a 3" straight through pipe fitted from the cat back. Definately gave the motor more top end power. The dump pipe livens up the low end response. Both work together well.

 

[Rumpig]

I did 2.5 from the cat back.
Made a noticable difference down low. Still undecided on whether do do the dump pipe.

 

[Lance S]

I split the difference and went for the 2.75" with cat and it made a hell of difference in power, torque and getting rid of the turbo lag which is very commom

 

[Pane]

G'day

What fuel ecconomy changes were noticed, better or worse?

The local exhaust bloke here reckons a 3 inch will give better fuel ecconomy.
That's on a 2.5 engine

Cheers

 

[tweak'e]

i do not think 3" will be any more or less economical than a 2.5". same goes for mandrel bent or not. once its big enough there minimal gains going any bigger.

 

[LLadnar]

Try Beaudesert, they do a 2 3/4" exhaust.