Anyone else run into really bad exhaust drone?

[Turbo]

My turbo FA20 (with an EL header) has some seriously bad exhaust drone. 2-3,000RPM around town I'm regularly seeing 80+ DB inside the car. Windows up, it's even worse. After the 1.5 hour drive to the track (with ear plugs in) I'm starting to get a headache. At some frequencies, it feels like the whole car is vibrating!

Anyone else have to deal with this? I figured an element of this was the straight front pipe on the car, but really aren't sure.


The exhaust on the car started as a Spec-D tuning catback. The mid-pipe was spliced into a custom front pipe that necks down from 3"->2.5" right after a flex joint that mates up to the 3" over-pipe. It's all stainless, front-to-back.


2 things I noticed under the car: One is that there are only 4 rubber exhaust hangars mounting the exhaust, and they're all on the back section and stretched pretty tight. Is this perhaps a factor? They may actually be urethane - I don't know for sure until I get back under there and poke around. The other thing I noticed was that the only other mount on the exhaust is bolted right onto a metal bracket hanging down from the back of the transmission. While it looks to be an OE bracket, I can't believe the car would have a "hard" connection there stock. Is this part of the problem?


I did notice the drone increased when I had the rear seat down, which got me looking in the trunk to see if the spare was there, etc, thinking that area could be acting like an echo chamber and causing the problem. No such luck. Spare was there and bolted down tight. In fact, I had some fiberglass insulation lying around so I put a batt under the spare and wrapped another around the outside of it, filling up the rest of the area under the rear floor and -if anything- it made the problem even worse.


I would appreciate any suggestions you have, as it's annoying as FK the way it is, and I have to do something.


I thought I'd ask here first since the FI guys are the ones with more extreme fabbed exhausts.

[MCTeeJ]

Not trying to offend, but both the straight front pipe and the spec D are the problem. Recipe for drone right there.

[sid94]

I have an Hks legamax on at the moment and car pretty much sounds like stock until you get on it. Wishing I never got rid of my N1 lol


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[agill]

Full blown full kit and exhaust, also have no cats, just a muffler. Makes basically no noise until 4/5k and no drone. But I definitely feel like going from 3 to 2.5 to 3 is going to cause issues. Don’t quote me on that but it doesn’t seem like a very free flowing exhaust, especially for a turbo

[sid94]

Originally Posted by agill

Full blown full kit and exhaust, also have no cats, just a muffler. Makes basically no noise until 4/5k and no drone. But I definitely feel like going from 3 to 2.5 to 3 is going to cause issues. Don’t quote me on that but it doesn’t seem like a very free flowing exhaust, especially for a turbo

Ive been wanting to get the full blown exhaust which one do you have the single or the dual?


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[agill]

Originally Posted by sid94

Ive been wanting to get the full blown exhaust which one do you have the single or the dual?


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Dual, it’s really quiet honestly. Perfect for a daily/sleeper, and it doesn’t sound like I have any power. A ton of stock engines with exhaust done (invidia n1 is the one I see the most, borla, greddy, think I’ve driven past a magnaflow at some point too) sound much much louder. But I’m pretty sure it’s because of the shape of the exit. I’m planning on cutting it and welding on some 4in circle exits and then it’d sound perfect I think, maybe a little raspy. I’d recommend the full blown exhaust in a heart beat


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[sid94]

Originally Posted by agill

Dual, it’s really quiet honestly. Perfect for a daily/sleeper, and it doesn’t sound like I have any power. A ton of stock engines with exhaust done (invidia n1 is the one I see the most, borla, greddy, think I’ve driven past a magnaflow at some point too) sound much much louder. But I’m pretty sure it’s because of the shape of the exit. I’m planning on cutting it and welding on some 4in circle exits and then it’d sound perfect I think, maybe a little raspy. I’d recommend the full blown exhaust in a heart beat


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I saw this video but this is the single and it reminded me of my 240 so I kind of want to get the single one I just would prefer the dual one better


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[CSG Mike]

Drone will depend on your exhaust setup.

The CSG Touring86 will kill all drone, and won't choke your turbo unless you're well north of 400whp.

[Turbo]

I appreciate the feedback.

What about replacing the Spec D with an MXP Comp RS? Anyone here running that exhaust catless with a turbo?


How would it compare to the CSG Touring86 that MXP also makes?

[sid94]

Originally Posted by CSG Mike

Drone will depend on your exhaust setup.

The CSG Touring86 will kill all drone, and won't choke your turbo unless you're well north of 400whp.

This was on my list of want as well but what is far north? I should be like 500ish when I’m done


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[CSG Mike]

Originally Posted by sid94

This was on my list of want as well but what is far north? I should be like 500ish when I’m done


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At that point, you have to determine, if you want no drone, or spoolup time, cuz you need to decide on an exhaust diameter.

a 4" will give you best spool and worst drone.

At 400whp (500 crank), the Touring86 is not choking the engine at all, but will reduce spoolup compared to an open dump.

What about using a Touring86, with a cutout for when you want that extra spoolup speed?

[Ultramaroon]

Before you change anything, just to prove it to yourself, stuff your trunk full of pillows, blankets, whatever. I mean STUFF it.

Then go for a drive. The source of the excitation is the exhaust but the source of the drone (aka resonance, flutter) is that drum head of a spare tire well.

[Turbo]

Originally Posted by Ultramaroon

Before you change anything, just to prove it to yourself, stuff your trunk full of pillows, blankets, whatever. I mean STUFF it.

Then go for a drive. The source of the excitation is the exhaust but the source of the drone (aka resonance, flutter) is that drum head of a spare tire well.

I did stuff a pile of fiberglass insulation in the trunk under the removable floor. I was very surprised it did not seem to change things much - but I will try your suggestion to help understand the situation better.


Do you think covering the tire well in dynamat will help with this? And a little or a lot? I will be changing to a higher quality cat-back, but curious if this would/could improve things further.

[guybo]

If you want to try something that is less expansive than getting a whole new exhaust, talk to a local exhaust shop and see if they can fab a custom helmholtz chamber for you. Look around online you can find a lot of info about size