Hi Guys,

I've recently upgraded to a 3 inch cat back single exit exhaust and am currently chasing to remove a very loud drone between 2400 and 3500 rpm.
It's especially bad when you stop accelerating, making around town driving anoying.

Current exhaust setup is:
Littlebo custom 4-2-1 headers
High flow 2.5inch cat
Reducer to 3 inch
2 foot straight through hot dog resonator
Then 3 inch all the way to 2.5 inch baffled muffler.

The resonator and muffler are both redback exhaust branded.

I have tried to the fix this drone by adding a Helmholtz resonator that is just before the muffler and angled towards the other exit.
The length is roughly 370mm.

It's helped to remove a lot of the deep bass notes, but it's still far from perfect. I had a friend on my car recently and they said it sounds like a truck, especially when you are on deaccleration.

Any suggestions on what to do?

I am planning on modifying the Helmholtz resonator to make it slightly longer at 430mm to see if this helps, using the below forumla.
((343)÷(3000×4×(1÷60)))÷4.
The 3000 is my Rpm


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