Exhaust sound mod

[bob4333]

Do you have to put your secondary cats back on come MOT time....?

 

[Jasper ham]

No, it's a permanent mod. I did the same on my SLK55 which did sound amazing. The secondary cats keep down the emissions for countries with very tight regs, it will and has passed an MOT with them removed. The lambda sensors are only on the first cats on the downpipes so they also don't through up any errors once removed. The car is not noisy, but rumbles nicer and no drone. Would highly recommend.

 

[benv6]

:evil:

Any effects on the MPG though ?

 

[Maniac]

On my 35is one thing I find very noticeable is that before I did the mod it would start up from cold with the flap open and be really rorty and then after 2/3 seconds as the flap closed it would quieten down and sound quite tame, also being a fairly steady driver, though not quite pipe and slippers yet !! I love to hear the extra growl you get pulling a high gear at low revs. One last thing I completely disagree with Maniac on the drone at motorway speeds because even as standard the flap would be fully open at speed, but I do appreciate the 35i/35is have different exhausts which may make a difference.

This is incorrect, the flap will close at moderate motorway speeds to reduce drone. It is intended to open and close at different criteria such as revs speed engine temp and so on hence why it is ECU controlled.

 

[HillWalker]

Maniac, first of all let me say that I personally don't get any drone at motorway speeds with the exhaust mod, but I do acknowledge your greater wisdom on all things Z4. So are we saying that if the flap is controlled by the ECU it affects the performance parameters more than just the little bit of extra noise on start up ? could it affect the torque figures due to reduced back pressure ? I certainly noticed a slight drop in fuel consumption figures after the mod, but put that down to me just giving it a few more beans to hear that sweet 6cyl sing.

As of this afternoon I've reconnected mine after 2years of running with it disconnected, as anyone else any thoughts on how it might affect driving characteristics other than the extra noise.

 

[Anonymous]

On almost all modern engines with free flowing well designed exhaust systems, the impact of changing the exhaust note will be negligible given where in the system the valve lies..its purely an emotion jerker.. :!: :thumbsdown:

 

[Jasper ham]

:evil:

Any effects on the MPG though ?

No MPG still the same ...... poor with a lead foot lol