Can anyone tell me what sort of noise change with a sports cat fitted under acceleration will be:confused:

Yesterday I fitted a new Milltek sports cat. Nice bit of kit:thumbup: The problem is that now I get a vibration through the floor pan & pedals when accelerating & get a knocking if the engine labours slightly. also inside the car the noise is quite louder around the front of the cat area & the mpg has fallen, but no loss of power. The noise is like a loud firm rasp when accelerating & it over-powers the woosh from the CAI. From what people have wrote on this forum, the noise is "slightly" louder than the standard cat, so abit worried. I don't know anyone locally who has had a cat fitted to ask if there is a noise level increase & what it now sounds like. The cat was fitted with the gasket supplied & all the nuts on the turbo to downpipe were tightened then checked after getting things up to temp.

I have been told by JBS the knocking & vibration possibly will be when the engine rocks under load, the downpipe catches the the heatsheild on the sub frame... so a powerflex dogbone bush is getting fitted next sat, but I'm parranoid about the noise increase!! Should this be expected with the larger bore & free-flowing cat:confused:

sounds like a hole or gap there???

sounds like a hole or gap there???

having failed to correctly tighten a couple of bolts when I fitted a new flexi a rasp when accelerating make me think there's like a hole/gap there somewhere, particularly as my brother's got a larger bore downpipe, turbo-back exhaust and sports cat on his octavia and there's no rasp

was the knocking sound there before the new cat fitted?

having failed to correctly tighten a couple of bolts when I fitted a new flexi a rasp when accelerating make me think there's like a hole/gap there somewhere, particularly as my brother's got a larger bore downpipe, turbo-back exhaust and sports cat on his octavia and there's no rasp

was the knocking sound there before the new cat fitted?

No, the knocking wasn't there before the cat was fitted!! Have you got a OE Skoda gasket fitted?

my Milltek system sometimes does it when im in very low revs under loads but not when accelerating

No, the knocking wasn't there before the cat was fitted!! Have you got a OE Skoda gasket fitted?

nope, but i don't have a skoda whether or not the brother does, i've no idea and i doubt he does either. sorry. but the knocking and the rasap does make it sound like there's something not done up/fitted quite right :confused:

Hi Oggy,

Picking up on this thread. I had a sport Cat fitted today. The minute I drove away the knocking and clunky noise started. I took it straight back, and after it was put up on the ramps very quickly noticed that the centre resonator was hiting the brace that it fitted to the underside of the car. After slaking off all the nuts and re aligning exhaust the noise was fixed. All is well now. I do get a slight rasp only when accelerating. I also notice the turbo whistle slightly louder(very slight). I have a Forge DV and an hear this lightly more too, just put this down to better flow. Noise level is not much different in the car at normal diving. Pick up however is much improved, so i can see fuel consumption going down.

Cheers

Bowders1

Which is pretty much my first thought too; before I wondered about anything serious, I'd double-check the exhaust alignment.

Hi Oggy,

Picking up on this thread. I had a sport Cat fitted today. The minute I drove away the knocking and clunky noise started. I took it straight back, and after it was put up on the ramps very quickly noticed that the centre resonator was hiting the brace that it fitted to the underside of the car. After slaking off all the nuts and re aligning exhaust the noise was fixed. All is well now. I do get a slight rasp only when accelerating. I also notice the turbo whistle slightly louder(very slight). I have a Forge DV and an hear this lightly more too, just put this down to better flow. Noise level is not much different in the car at normal diving. Pick up however is much improved, so i can see fuel consumption going down.

Cheers

Bowders1

Last weekend I had a Powerflex dogbone mount fitted & that has cured the knocking on the sub frame & that dogbone mount has transformed the car as well. Now the engine doesn't rock as much under load, the power transferd to the wheels feels more direct & quicker. Well impressed:thumbup: !! For the price, certainly a mod worth doing!!

When I had the car on the ramp we found a slight leak on the cat/middle section joint & that has toned the noise quite alot now sealed, but I have a problem with the back box with a loose plate or baffle which possibly might not be helping the noise. The car is booked in to have the back box replaced this weekend.

I've heard that you have to get the milltek fitted just right to stop it knocking. Ive not had any probs at all with my blueflame.

Makes me wounder why after all this time milltek haven't quite got the fitting right:confused:

I've heard that you have to get the milltek fitted just right to stop it knocking. Ive not had any probs at all with my blueflame.

Makes me wounder why after all this time milltek haven't quite got the fitting right:confused:

I dunno. I couldn't see how I could have fitted it any differently.

Here's how close my 2.5" downpipe gets to the crossmember (not a miltek/blueflame one as it happens)

I snipped the heatshield either side as you can see so I could fold it down to add clearance. Before I fitted the poly dogbone bush it was bashing the top of the steering rack/heatshield heavily as drive was taken up and the engine tilted, now it's fine

My milltek doesn't fit as well as I'd hoped I'm dissapointed to say, although with a lot of adjusting I've got it as well as it can be and learnt to live with it, as it's pretty much ok when hot, but when cold it buzzes aginst the heatshield round the back end of the resonator - this pic shows how it's offset to one side and sits very close to the shield, that's the best I could get it..

fitting a non-resonated centre pipe would solve the problem I guess at the expense of a bit more noise. However I have to say, as it is now with a 2.5" downpipe and 200CEL sports CAT it's really not much different to standard noise-wise.