Hey guys,

The whole time I've had my FD, it's had this weird sound from the exhaust. If I were to describe it, it's like deflating a balloon really fast. That low and dirty rasp. Not at all what you want to hear in your right ear all day when you daily one of these bad boys like me.

It is mostly noticeable at slight loads, and I can't really hear it as much at full boost. Around 5 PSI is when it's loudest, I would say. I've driven a few FDs and none of them sound like this at all. Has anyone had this problem?

Things I've tried:
-ignition and fuel (thought it might be breakup, but I'm not so sure about that now) I have went through 3 sets of plug wires, new leading coil, igniter, and 4 sets of plugs in the last few months, as well as checking the FPR and its solenoid. My wideband reads pretty much bang on stock AFRs, maybe a little rich if anything. I am on the stock S6 JDM ecu. I do get misfiring on cold starts for some reason.
-swapped catbacks; I put a much louder one on because I thought my Kakimoto may have been plugged or blown, but it didn't fix the problem
-swapped stock cat out for midpipe
-all intake gaskets except throttle body to UIM, which was replaced by the previous owner and definitely isn't leaking
-all hoses and check valves are fine, as are solenoids
-throttle actuator (maybe one of the butterfly valves inside is loose though?)

Other things it could be:
-exhaust gasket; mine aren't in great shape, and I'm going to put new gaskets on, but could it cause this annoying sound? It's worth noting that the noise is close to my right ear, whereas the FDs I've driven in have projected their exhaust notes further back
-precontrol valve flopping around
-noisy or floppy wastegate
-bad trailing coils
-my engine, since the rear rotor is about 1 bar lower in compression than the front


Has anyone experienced this issue? It's driving me crazy. It's like driving a boxer or V8. I want my rotary buzz.

 

If it makes a high-pitch screaming sound in tunnels you probably have an exhaust leak close to the turbo.

 

I've got the same problems. Cold start missing, sputtering. The fart sound is worst when letting off at higher rpm and engine braking. I know I have new gaskets for turbo and down pipe. I'm gonna replace engine to manifold gaskets next when I feel like it/ have money. May need to have the surfaces taken down by a machinist

 

Are you sure it isn't the air pump making sound? The air pump makes all sorts of terrible noises.

If you still have it, unplug the power connector to the air pump and drive around.

Dale

 

I don't get much in the way of screaming besides the turbos themselves, but I'll take a look.

Air pump is deleted and all lines are blocked off with plates.

Damn, it sucks doesn't it? What else have you tried? I know my engine was replaced in Japan before I got the car, so I wonder if the turbo manifold to engine gaskset could be buggered from the last owner installing it.

 

Yeah I don't think the air pump would be it.. I've heard the moo some before, this is more like somebody making a fart noise with their mouth loosely lol I'll unplug it next time I take it out just to see

 

Turbos with mufflers aren't usually that loud unless you've got a dump pipe.

 

Did you ever get that smoke test?

 

Did one myself Dave

I have confirmed I have a sizeable exhaust leak and will be replacing the gaskets. However, this sound was here before I touched the exhaust at all. Was it always leaking? Stay tuned to find out. On a related note, to people with loudish exhausts, do you hear the exhaust note right in your ear, or does it sound farther back?

​​​​​The airpump moo is a very different sound. This is much more annoying.

 

A very loud exhaust will basically sound like it's coming from everywhere.

It's basically the sound of exhaust pulses.

A stock exhaust is mostly the sound of the rotational assembly and turbo noise, hence the vacuum cleaner sound.

 

I had a very quiet Kakimoto on before (with resonator) and it still made this noise that sounds close to my ear. It could just be such an annoying noise than I pinpoint it though, and it's not actually close to me. Plus, I've driven other FDs with fairly loud exhausts and they don't make this sound.

 

You're going to need to take a video.

 

My Kakimoto could not handle the street port and parallelled turbos even with a dynaflow resonator. At 65 mph my skull started to develop an annoying harmonic vibration in tune with the drone of the muffler. I switched to a Tanabe Medallion before my brain turned to mush. Now I hear the motor, not the muffler.


My friend has the Kakimoto now and it is just fine with an unmolested sequential set-up.

 

Is your car a right side drive car? If so, that would explain your "right ear" issue. Fix the leak!!!

 

I fixed the exhaust leak. It got better for sure, but I swear I can still hear the noise, only now it's far back. Maybe it's my choice in catbacks so I'm going to try swapping for one that I know doesn't sound like that.
I'll see if I can borrow a go pro and mount.
You may be right. I like your setup, it's nice and wide. Both cans I've had on my car have been narrow and long, which I believe translates to a deeper and potentially weird sounding note on a rotary. Tradesies for an hour?


​​​​​

 

All we really need is the sound, so you can use your phone to record the audio (or a video).

 

Where was the leak at?

 

We could tape up my 25 year old OEM and see how that sounds.

 

Here, I dug up some older clips too.

This is with my Kakimoto with stock cat: You can hear the note change when I hit boost, which is probably just the wastegate, but it still sounds off to me.

This is with the Kakimoto but I had a midpipe in there: You can hear the flapping noise in second gear, it's the lowest pitch noise in the video.

This is with an unknown catback that is basically straight piped; I just had my friend take this video for me: You can't really hear it so well in this one.

This is from inside while I was driving. Excuse the wind noise. After 15 seconds in the video, you can really hear the sound:
Downpipe to midpipe. What have you tried to fix your sound?

We may have to.

 

First off, when the transition occurs the turbo control valve opens and the exhaust will get louder. You sometimes can't hear the change in sound with quieter cat-backs but with something more free-flowing you definitely can.

You said you have the air pump removed, have all the parts of that system been removed? The air control valve, piping, etc? I know that if some of those openings in the LIM aren't blocked off you can get some odd noises but I think that may be all the time, not just under boost.

Could also be a gasket or something on the intake side of the turbos, if the gasket is torn or something the inrushing air could make a noise. Or a gasket or O-ring on the Y-pipe.

Also possible it could be something deep with the turbos, like the waste gate flapper is loose or something.

Dale

 

If you don't use a proper block-off plate when you remove the air control valve, it will cause a very noisy but probably not harmful exhaust leak.

Ask me how I know this....

I'm not 100% sure what sound he's talking about out in those videos, other than the car being kind of loud and possibly having an exhaust leak.

 

Are we overlooking the obvious here?
The fault, dear Brutus, lies not in our cars, but in ourselves...

 

The first video has the air pump and acv intact. The second has the air pump relay pulled and the lines left open for the acv. The other two have blockoff plates covering the acv and both related holes. I did leave the check valve in the acv hole but since its not doing anything, I don't think it's the problem.. Though I must say it was burnt to hell when I pulled the acv.

I recently had my downpipe out to install a wideband. To do this, I had to remove the y pipe and related pieces. The gaskets looked fine and I made sure all the bolts were snug. The only thing I didn't actually pull apart was the two halves of the y pipe. I assume there is a fat o ring in between them, and didn't want to mess with it.

I'm going to check my waste gate and precontrol valves next. The precontrol actuator rod was incredibly rusty, and it's the only spot of rust on the whole car. My turbos seem to work okay, but I do lose some boost at the top on the secondary. Drops to about 7psi at redline but I'm at sea level.

The first two videos I find the car is very quiet. Definitely the quietest FD in my group... But I could always hear that flapping noise. Maybe I didn't get rid of that exhaust leak in full. I'm going to plug my catback and feel around again.

I wish you could drive it. It didn't pick up perfectly in videos. I can hear it because I know what to look for.

I wish it were that simple

 

https://youtu.be/VjCJgDNQ3I0

This is what mine does. Pretty sure it's manifold to engine but have yet to get it smoke tested

 

Is that the stock exhaust? It just sounds like your cat or muffler has disintegrated internally to me.