Afternmarket Exhaust questions


As a keen motorcyclist for most of my adult life, I often fitted an aftermarket exhaust to my bikes, not for any performance reasons , but because they looked and sounded better.

Although I haven’t had the Mazda long I am considering getting a Cobra/Cobalt or IL Motorsport back box fitted, maybe in the Spring of next year, my questions are:

Can a double outlet backbox alone be fitted to the existing pipework? ( MK3 1.8 2006 )

Does this affect fuel efficiency

Is it a modification that  I have to tell my insurance Co about.

And will it affect my MOT as the Cobalt ad on E bay says not TUV approved

Any info would be helpful






Mk3 has double outlet standard

TUV approval is German, so not a problem here

yes you should tell your insurance

If you are worried about fuel efficiency…you bought the wrong car :slight_smile:

Thanks for your reply, just didnt want fuel economy to be even worse although I totally accept it for what it is at the moment, still a great car and worth it.

Can a new backbox alone be fitted, without messing with the rest of the original system ?



You can fit just a new back box, just need new bolts/nuts as the original box has captive bolts, you may need to cut them free if badly rusted.

I got around 37 mpg (2 litre sport) on a tour around Scotland earlier this year, I have the Cobalt back box fitted.

I told the insurance company I fitted a shiny new SS back box, not original equipement and it was recorded, they wasn’t too fussed (Admiral)

Just for your info regarding what I have done over a few years. 2.0 Sport Tech Nav 2013.

I fitted a “Go Perform” rear box first and it was “Okay” for a couple of years. It looks nice, not the best fabrication/welding. But also may be a bit too loud for you… (all about opinions).

But we change them for a bit more noise and looks which is the whole point really.

(Probably a good track day exhaust with other mods).


I then had the Skuzzle Fast Road Package fitted this year and was well pleased with the results. 

More BHP, more torque and a remap which does actually improve the fuel economy. The car drives like a dream now, better throttle response etc etc

Yes I agree with the post you have bought the wrong car if fuel economy is a concern!

Again, Admiral and very helpful.

First problem though was the Go Perform box was just far too loud and horrible to be honest. Roof up or down it drove me mad and hurt my ears in particular at motorway speeds.

Various obvious reasons why really.

That went straight away on eBay.

After a fair amount of research swapped it for the COBALT box (on special offer as we speak for for £210 from Moss yes I missed out!!).

Now that is a really nice rear box.

Comes with bolts, gasket etc. Would advise putting some exhaust paste in the join when fitting though.

Personally I have now got the car how I want it and it makes me smile every time I drive it. 

My wife is happy too, so job done. 

Yes an ex motor cyclist too. 

Enjoy your car.