I've got a 1.8 mk1 mx5, so its 2 1/2 inch exhaust pipe. I'm not sure what diameter silencer pipe to put onto it.

Currently its got a 5 inch bike exhaust on it (its a mess)

Just need it to pass IVA sound reqs really. any recommendations?

I'm guessing around 6 inch dia (with 2 inch tube), around 24inches long, should see you through IVA....That said, there are a number of other factors that come into play...i.e. induction noise, location of exhaust in relation to engine, engine top rpm, etc.

you do get quiet bike silencers and I used them both on my buggy and the JBA Falcon, I actually bought them to be very loud but they were anything but and far quieter than the car ones I had on. They were also super light (carbon shell) and far less stress on the exhaust system.

I now have a 146bhp MX5 1.8 and the standard exhaust is 2". Only the last 200mm tail pipe is 2.5".
If you have a 2.5" then its an after market one.
I have fitted a 2.5 sports silencer on mine but even with that it's only 93dBa. (see pic)

However, there are two major differences between a seven type car and the original MX5.

One is that the cat acts as a sound restriction and lowers the reading, and two, seven systems are short and the longer
the system the quieter it will be.


A 2" system will easily handle anything below 200 bhp.

Paul G


New back box

Thanks for the advice everyone. After a bit more of a look the exhaust manifold looks like a bit of a mess, somewhere between 2.25 and 2.5 inch diameter. Looks like its going to be a bit of a jiggle to get something sorted.

Its all going to get changed when it gets turbo'd anyway!