mx5cartalk.com

Hi All,

I've got a straight 2.5" exhaust with a 200 cell CAT and a single resonator under the boot.

The issue is it drones quite a lot and tbh, I miss hearing my engine.

Would adding a resonator help? Where should I install it? After CAT? How would it impact turbo performance?

Any advice would be appreciated.

Cheers,

Fitntge largest body straight through perforated core muffler that you can possibly fit in a different length to the current one

No performance change or tune required.

Dann, just so that I learn the science behind it. Is it because a resonator is basically a straight thru muffler, so fitting a longer muffler is a neater way of doing the same as adding a resonator?

When you say resonator I assume you mean a hotdog.


A straight through perforated core muffler is just a hotdog with much much more sound deadening material.

You want a different length to cancel resonance at different frequencies to your current muffler rather than the same length and still ending up with an rpm band which the mufflers do not cancel.

Makes sense.

I am talking about a hotdog yes, with no onion.

Longer the better makes sense now for a material effect. I've read i should be able to go for roughly a 4" diameter hot dog bun.

Hopefully will get this done today or tomorrow.

I've embarked on a soundproofing journey with mass loading on panels with a foam layer which make me realise the drone is actually insanely loud

My worry around performance was turbo spool- just a nominal impact?

I think the basics are that hotdogs/resonators/straight through exhausts don't add much, if any restriction to flow if they are sized correctly.

If you were putting in a more standard style of muffler, where the exhaust passes around multiple baffles, or passes through the muffler mutliple times, then it might be more a problem.

Cool - so back from the exhaust shop and i can't pretty confidently say it has made zero difference.

Still got 3 different drones; idle, 2,800rpm and 3,500 rpm.

I haven't inspected the installation, but pretty safe to say the 'resonator' failed to perform it's purpose.

Next options? muffler?

^ Paul, what is the diameter of your exhaust and what material. Ss or mild?
Also think you said straight thru muffler. How long?

Here's what I got- sorry about terrible pics

I have a reasonable muffler on the back beneath the boot (what I wrote in the first post was wrong)

Rear of resonator



Cat into the 'new' resonator



Side on

The idea is to fit the biggest resonator you can. Usually double that length.

I don't think you could go longer as you'd hit the rear subframe.. I'll have to take a closer look.

I literally had to leave the car with them stating "fix the drone" before heading to my white collar job. Suspect all that was heard was "fit a resonator". The guy told me he had some long hotdogs yesterday. :/

Looking at the first pic, it does look like you could get at least 50% more length.. Unless it's fouling somewhere. I'll have to take a closer look.

I hate this situation... I know that reasonably I'd have to pay the same again for a new install.. Where I'm concerned it won't do anything. Paid $140, which I thought was fairly reasonable

Basically, your exhaust is of poor design.

I mean not just the components but their position and the shape and placement of the pipes also.