Hi guys
I am thinking about changing rear exhaust box with free flow muffler.
The biggest interest for me is to gain a bit louder exhaust.
So I went to „exhaust shop“ and found one universal free-flow muffler that looks nice and seems to be OK.
It is one in two system (one inlet pipe and 2 outlet pipes), with oval body, „suitable for 1.6 engine“.
The muffler tips would look cool once mounted at the car.

But, there is one „but“… I'm a bit undecided. The reason for this is „fear“ of degrading power output, mpg or torque. I've found some opposed articles through web, discussing about backpressure and how hard it is to get proper muffler…


So, if you can help me a bit with this…
Is it worthed to change original muffler with this kind of muffler.
Is it going to be too much loud ??
Bad or good experiences ??
Please share it with me.
Thank you very much.

Problems would occur with back pressure if you made the diameter of the exhaust wider than standard - 2" is standard spec iirc, if you made it wider then you'd slow down the rate the exhuast gets pushed out by the engine which will reduce performance. Vice versa with a smaller diameter - not enough space for the exhaust to be expelled so back pressure will increase causing the engine to reduce performance.

If you go for a vehicle specific exhaust then it should be made to the cars original spec. Have a look at these:

http://www.gazzellaracing.com/home.php?cat=3238

So, placing narrower pipe would cause higher back-pressure at higher rpm's, and therefore a loss of power in that range? So, there is still a choice which muffler to buy...

Yep that pretty much sums it up Don't need to make it wider really unless you decided to go forced induction...

i wont ever put another non standard exhaust on a car.
our 1.6 exhaust went, so i had a custom stainless steel put on, initally i was happy until the cat broke, after getting that repaired, and 3 flex joints later im chewing over getting it put back to standard.
my reasons are, it feels gutless, even though it is the underpowered 1.6 plant it just feels under powered at higher speed - overtaking on a motorway is a joke, but im a bit bias to the 1.9jtd plant now.
the noise of the exhaust wears very thin over time, first of all its nice having the rumble and burbling but when you put your foot down, but the car is slow it make you look like a bit of a fool.
thats just my take on ownership of custom exhausts, i maybe getting old thus my feelings towards it.

Thanks 4 reply.
That's the reason i don't want it to be very loud.
Just a bit louder then original and also with less restriction (for engine to rev more freely).

But, you think that "unproper" muffler can break (damage) cat?

na not an end part, i had a full system fitted to the wifes car and they didnt allow enough movement on the exhaust to allow the engine to swing, thus it broke at the weakest point which was the cat.
the end buffer should have no effect at the front of the engine if you use the original hangers.

So, if i understood you right you have replaced the middle box (resonator) and rear box (muffler) with non standard..?
If so, that's probably the reason it was too loud. The stock resonator on stilo 1.6 cuts off a lot of exhaust noise (that's what I was told).

And finally I've chosen one... at local shop ordered inox - oval type muffler (by popular producer) with two outlets, length as I preffered is 50cm (to keep it quiet enough), inlet diameter 50mm (as on original muffler)
I have made tips by myself, also in inox, with diameter 45mm


The "fitting" is scheduled for next monday. Can't wait...

And, ...done! It looks cool. Sound was very silent at start, but now it makes decent bass.
Here are some pics:

Well, after a couple of months, here's a short update:
There were no problems at all, I can feel car is responding better, and even the MPG is slightly better. No errors of any kind.
The sound is non-intrusive. ((Even without back box the sound is not especially loud.))

The man at the exhaust service told me that I should check sound with free-flow centre-box.
What do you think about removing centre box and installing free-flow one? Anybody had experiences with it?

ivand said:

Well, after a couple of months, here's a short update:
There were no problems at all, I can feel car is responding better, and even the MPG is slightly better. No errors of any kind.
The sound is non-intrusive. ((Even without back box the sound is not especially loud.))

The man at the exhaust service told me that I should check sound with free-flow centre-box.
What do you think about removing centre box and installing free-flow one? Anybody had experiences with it?

Click to expand...

That's good to know. I am looking at exhausts for my 1.6, my main concern about a free-flow box is whether it will effect the MOT, I don't want to be failing every year because of the emissions.

Toby