3” Exhaust Drone Gone

[944m3]

Last year I installed Lindsey’s 3” exhaust with sport CAT and Magnaflow muffler. Right away I noticed the dreaded 3” exhaust drone but was living with it. But finally decided to try to eliminate it. I first had a shop weld all the pipes together and use a V clamp in the middle. The exhaust comes with the belt clamps which just work themselves loose after a while. I then added all the stock exhaust hangers with new rubber.

Sadly the vibration and drone got worse. The muffler would now vibrate and shake at around 2k RPM and when I shifted gears. I was not enjoying the car at all.

I remember reading a post of someone adding flex pipe to the downpipe. I didn’t want to pay for that fab work, so I decided to install a flex pipe between CAT and middle stock hanger ( so after the CAT). We also installed a small flex pipe on the wastegate dumb pipe. Took the shop less than an hour.

WOW what a difference. I actually didn’t realize how much the car vibrated in general. My shifter is almost zero vibration now. My steering wheel has about zero vibration. The whole car feels refined and smooth. Don’t get me wrong, it’s still an 80s sports car but it just feels better. I was thinking my next step was to install a resonator for the audio drone, but turns out the flex pipes seem to have resolved that too. Car sounds great.

Highly recommended if you’re using a 3” or bigger exhaust. Flex pipes should be included by default from Lindsey in my opinion.

[duqx]

Thanks for posting this

I had been dealing with the same issue for quite some time on my car with a 3" turbo back exhuast and a sport cat

I got the car with the exhaust already installed, so I really didn't have a good reference point around how much noise/vibration there should be stock. My last stock 944 was almost 20 year ago, so I figured I just didn't remember it

I was able to get rid of most of the 2k rpm drone by re-installing the heat shields with some some deadening around the edges and installing plastic washers on the hangers and tightening them up

There is still noise / vibrations, but it is MUCH better. Next steps will be looking into a solution like you found

[Tom]

Last year I installed Lindsey’s 3” exhaust with sport CAT and Magnaflow muffler. Right away I noticed the dreaded 3” exhaust drone but was living with it. But finally decided to try to eliminate it. I first had a shop weld all the pipes together and use a V clamp in the middle. The exhaust comes with the belt clamps which just work themselves loose after a while. I then added all the stock exhaust hangers with new rubber.

Sadly the vibration and drone got worse. The muffler would now vibrate and shake at around 2k RPM and when I shifted gears. I was not enjoying the car at all.

I remember reading a post of someone adding flex pipe to the downpipe. I didn’t want to pay for that fab work, so I decided to install a flex pipe between CAT and middle stock hanger ( so after the CAT). We also installed a small flex pipe on the wastegate dumb pipe. Took the shop less than an hour.

WOW what a difference. I actually didn’t realize how much the car vibrated in general. My shifter is almost zero vibration now. My steering wheel has about zero vibration. The whole car feels refined and smooth. Don’t get me wrong, it’s still an 80s sports car but it just feels better. I was thinking my next step was to install a resonator for the audio drone, but turns out the flex pipes seem to have resolved that too. Car sounds great.

Highly recommended if you’re using a 3” or bigger exhaust. Flex pipes should be included by default from Lindsey in my opinion.

Any pictures of this? By 'drone' do you mean exhaust vibration/buzz, as opposed to harmonic drone from the muffler/exhaust? I do get a vibration/buzz and have it on my list to figure out. I was thinking it was the lack of wastegate bracket on mine, but now very curious...

[duqx]

Are you able to post a few pics of the changes?

EDIT - whoops! didn't refresh and see that pics were already asked for

[944m3]

I’ll add pictures tonight. But yes I mean all of the above. Harmonic drone, general vibration at all RPM range, and buzzing at specific RPMs. Basically, for some reason, the bigger exhaust pipes are perfect to become a tuning fork that amplifies the inherent vibrations of an our 4 bangers. So there is a science behind it. You can even buy an app that identifies the frequency in your car. You can then add a dedicated resonator for that frequency. Search for exhaust drone and flex pipe on YouTube, tons of info.

In my case all I needed was the flex pipes. A night and day difference, at least in my particular case.

I drove the car to confirm it wasn’t wishful thinking. Car feels great. As I said before, I’m not saying all vibrations are gone. But they are diminished substantially. But more important to me is no more buzzing and general drone sounds. I will also add I have new OEM hydraulic motor mounts. Those also help a lot.

I can’t recommend the flex pipes enough.

[ROB III]

@944m3
That's a great explanation of what you tried before and what addressed a common issue.
Thank you for passing that on!

[944m3]

Actually correction, the flex pipe was placed before the CAT as you can see in the picture. Not the prettiest welds but they do the job fine.

I’m not using the wastegate bracelet/brace either.

[Tom]

I think my rattle is different. Only happens when cold, and sounds like metal vibrating against metal. But I like the idea of the flex couplers in general. Summit has them in every size imaginable too for the DIY types..

flex-ex.jpg (102.25 KiB) Viewed 255 times

[944m3]

Where is it coming from, front or back?

If it’s in the front, it might be the downpipe of the exhaust section hitting the crossover pipe. That is a very tight gap with the 3” exhaust. In my case, it seems the flex pipe helped with that too. I was hearing a lot on fast right sweepers.

Drove the car this morning and I’m kicking myself I didn’t do this sooner.

[Tom]

Where is it coming from, front or back?

If it’s in the front, it might be the downpipe of the exhaust section hitting the crossover pipe. That is a very tight gap with the 3” exhaust. In my case, it seems the flex pipe helped with that too. I was hearing a lot on fast right sweepers.

Drove the car this morning and I’m kicking myself I didn’t do this sooner.

I have the world's worst directional hearing (yet I'm cruelly obsessed with interior rattles) so hard for me to pinpoint by sound, but I 'think' it's coming from the wastegate area, which is also a tight squeeze due to the Tial 46mm. I need to get under there and just investigate. It's been on my "I gotta fix that" list for years. I like the idea of a flex extension for the downpipe -- to isolate vibrations and make it easier to swap in converters and test pipes...