Drone reduction ideas please

68conv4sp · Dec 7, 2009

My 96 Cobra vert has twin Flow 40s with an h pipe. It sounds great except for 1900-2000 RPM (severe drone). I have read a few ideas to help:

1. Put Dynamat on the body above the mufflers. I'm not sure how safe this is...
2. Strap something solid and fireproof to the outside of the muffler body to change the resonance frequency.
3. Add short glasspacks before the mufflers.

I want to experiment before spending $ to make major changes, so,thanks for your ideas/experience.

scupking · Dec 7, 2009

When I went from a catted H to a VRS catted X my drone went away.

nmcgrawj · Dec 8, 2009

T into the tail pipes with a closed ended pipe thats half the length of the tail pipes. Search on corral for a very long and detailed thread. Seems pretty easy and a lot of people have had success.

bhuff30 · Dec 8, 2009

Or, you could try getting rid of the cause of the drone... the blowmaster.

A magnaflow or one of the many dynomax mufflers would sound good without the resonation.

nmcgrawj · Dec 8, 2009

bhuff30 said:
Or, you could try getting rid of the cause of the drone... the blowmaster.

A magnaflow or one of the many dynomax mufflers would sound good without the resonation.

100%

The only muffler you can even begin to make that claim on are corsa mufflers....and thats because they build in the cancellation inside of the muffler. (which is what those tubes do).

timeless2 · Dec 8, 2009

I have to agree with the others. Best way to get rid of the drone from Flowmasters, quite frankly, is to get rid of them.

streethorse · Dec 8, 2009

When I had flowmasters on my 99 I tried an experiment to dampen the
brutal drone. I filled the trunk and floorboards with blankets and pillows...
Didnt make a tiny bit of difference, so I dought even dynamat would help.

bhuff30 · Dec 8, 2009

Chambered style mufflers are bad about causing resonation. They reflect the sound waves and at certain frequencies, a resonation is caused internal to the exhaust system. If the resonation is bad at 2000 rpm, then I would expect if you hold 4000 rpm, it will resonate badly too. You won't be able to cover up the noise with sound deadner... you can only change the resonance points. For example, add a sound chamber or cat and you will change the harmonics of the system. It will still resonate at some rpm, but hopefully an rpm which you aren't typically at in normal driving.

In fact, other styles of muffler will drone MUCH less noticibly. The dynomax super turbo and other 'turbo' style mufflers should drone very little if at all. The design doesn't reflect sound waves back. Streight through mufflers can be very loud, but don't drone as much as a flowmaster or other chambers style muffler would.

Tim2002GT · Dec 8, 2009

Unfortunately, while it does sound good, your combo is one of the worst as far as the dreaded drone!

I would also recommend you switch mufflers.

twogts4us · Dec 8, 2009

bhuff30 said:
Chambered style mufflers are bad about causing resonation.

Go with a straight-thru design such as Magnaflow MagnaPack or Borla Stinger (S Style)...or hell, get a set of glasspacks.

Shiroelex · Dec 8, 2009

nmcgrawj said:
T into the tail pipes with a closed ended pipe thats half the length of the tail pipes. Search on corral for a very long and detailed thread. Seems pretty easy and a lot of people have had success.

This has worked quite well in the past from my experiences.

SaleenGT2001 · Dec 8, 2009

the "dronemasters" are the cause of the problem. ditch them and get some better mufflers

32ValveRom · Dec 8, 2009

nmcgrawj said:
100%

The only muffler you can even begin to make that claim on are corsa mufflers....and thats because they build in the cancellation inside of the muffler. (which is what those tubes do).

I have Magnaflows and just found out what drone was just the other day.

GettinThere · Dec 8, 2009

I agree, the best solution is to replace the mufflers.

I don't know how to explain this, but changing to 4.10 gears (from stock 3.27) seemed to reduce the drone for me. It's probably related to:

bhuff30 said:
It will still resonate at some rpm, but hopefully an rpm which you aren't typically at in normal driving.

While the drone is still loud and annoying, to me it's not nearly as bad as it used to be. If I had the bux, I'd change to SLP Loudmouth catback.

SaleenGT2001 · Dec 8, 2009

magnaflow makes a great muffler. i'll be running them on the ranger when it's finished

007 · Dec 8, 2009

Magnaflows are great! Had em for a long long time. No drone. They get a lot louder with age. I would NEVER want the Packs.

tag4car · Dec 9, 2009

i wrapped my bassani X with header wrap on my Gt, toned it done

COBRA90GT · Dec 9, 2009

007 said:
...Iwould NEVER want the Packs...

Love my 'packs on the '94...heh

For the OP:

Yes, swap out the Flowmasters for a "straight through" style muffler instead. The amount of drone should be significantly less...

1fun281 · Dec 9, 2009

Am i the only one on here who loves the sound of there flowmasters, and doesnt really get bothered by the drone?

streethorse · Dec 9, 2009

I loved the sound of them, but I cruise lots of highway miles, and thats
when they just lock into the drone mode.

Drone reduction ideas please

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