After market exhaust issues

[Rezmund]

I started a thread before on MTorque regarding the full Milltek system on my CSL. After having it adjusted due to it knocking against the heat protector (whilst expanding and contracting) I'm still having issues with noise and vibration.

When I start her up in the morning the exhaust makes a very loud vibrating sound for a good few minutes and at high revs there is a whistling type sound coming from the middle section/cats area.

I also get a lot of popping when the engine is left to decelerate or I take my foot off the gas.

Just wondering if these kinds of noises or vibrations are common place in aftermarket systmes on our cars or if I need it replacing again?

Cheers

[Mark CSL]

I have the stander system on my csl now but it sounds to me you might have a small hole for it to make whistling type sound coming from the middle section/cats area.

also the poping sound on over run is normal when you change the exhaust.

any 1 else have any sugestions he might try

[Rezmund]

Have you ever have any bad vibrations or knocking sound on start up though with aftermarket systems? It's really annoying and ruining my enjoyment of the car!

I dunno if there is a hole as there doesn't seem to be a lack of power/shuv at high engine speeds but will get it all checked over at the place I had it fitted.

[sailorbaz]

I recently had an aftermarket exhaust fitted and agree with the high level of noise when its cold. It gets quieter as it heats up though, thank god as it mega loud when cold.

No knocking or rattling issues to report though.

I agree with someone on Mtorque, maybe loose o-ring, maybe the one that slides up and down the pipe between the middle pipe and the back box...

[Rezmund]

Cheers Baz, have you changed the CATS as well? Do you get droning at around 2500rpm?

[sailorbaz]

I haven't changed the cats no, they're still standard.

But yes, I get major droning about 2600rpm. Can be quite tiring after a while and its typical as 70mph in 6th is bang on those revs.

A mate of mine also gets droning at same revs with a Borla back box, its just a characteristic of the car with more flowing exhausts.

Meant to say also, I get popping when lifting off and letting the car idle down...but I love that bit of it.

[Rezmund]

Yes, I find I have to cruise at an indicated 80mph which on GPS is 73mph to avoid said noise. I run 275/245 tyres hence the 10% difference in real to indicated speed.

[sailorbaz]

I run the same tyres, and find 80 as indicated is a good speed for reducing booming noise.

[mole]

I also get the resonating from cold, and the popping when letting off (all goes when warmed up) - running standard system. Is this not normal?

[Rezmund]

Not sure if that's normal on standard system as I never ran mine in winter. I assume therefore it's a characteristic of the weather and M engines.