Downpipe Rattle?

[B5addiction]

Shortly after having catless 3" AR design dp's installed I started feeling a knocking vibration.
I went back and put the car on the lift to inspect and everything was tight and normal?
The car will not vibrate under load, only when I let off. If I push the clutch in it kills all vibrations.

I can feel the vibration while:
Slowly turning right
Faintly at idle, depends on pitch of the road. If I rev the car, it vibrates when the rpm's fall.
Downshifting, any speed

It does not feel/sound like a heat sheild. I can feel the knocking under my feet. It sounds like it is under the center dash area.
Any feedback would be great, I can't stand driving the car like this.
Thanks

[papoaudis4]

this was happeneing when i first bought my car and it just had piggie pipes. i wish i could help you more but when i installed the dp's and catback i havent heard it since so maybe itll go away??

[Blake2423]

I have the same problem but i have the ssac downpipes with welded on flex pipes except it feel lik it is coming from under my seat more than anywhere else when I lifted the car my exhaust was close to hitting the drive shaft stabilizer but wasn't. I get it at the same exact times as you are though. Curious as to what is causing this, its a little annoying!

[kbS42001]

I'm trying to diagnose this exact problem now as well. It sounds terrible and only occurs after the car is warm. I know there is a certain amount of expansion in the exhaust after it warms up. i have been under the car 4+ times trying to clearance all of the heat shielding with no avail. Let us know if you figure it out. it drives me crazy

[B5addiction]

I was thinking of heat wrapping part of the exhaust to cut down on the knocking, only letting it move at the flex.
Doesn't help much since I cannot see where it is hitting, there is no marks or anything.

[ECS Tuning-Audi]

Have you had the car on the lift while its running and some one reving it? Sometimes thats about the only way to really pin point exactly where its coming from.

Good luck!

Jason

[koolkoreanked]

make sure your downpipes are tight... Mine started making the same noise cause there a little loose. Does it when I turn and before the car is warmed up.

[Timtheguru]

Sounds like it's backfiring, even without CATs unburned fuel can backfire on hot exhaust pipes. Just a thought.

[Trile]

Sounds like it's backfiring, even without CATs unburned fuel can backfire on hot exhaust pipes. Just a thought.

what?
It'll almost always backfire when cats are deleted.
Mine does...

[Timtheguru]

[/B]

what?
It'll almost always backfire when cats are deleted.
Mine does...

What?

[Trile]

you said 'EVEN WITHOUT CATS it will backfire' like it's a rare thing.
Chances are it'll backfire more without the cats then with them

[Timtheguru]

Cats would cause you to missfire more, don't know your logic, but we are both saying the same thing. The noises the OP are hearing are probably backfires, too rich probably.

[Corrado]

I had a similar noise with my stock downpipes. It only rattled when the engine was cold, after 5-10 minutes, it got much better and *almost* went away. Also, when taking off from a stop light..as is 1-5 mph, it was the worst as you slipped the clutch. However, when the clutch pedal was fully pressed to the floor, it went away (taking the load off the engine)

It turned out to be the old rusty heatshields. The mounting points were rusty and there was just enough wobble/space to create a horrible rattling noise at certain times.

I ended up getting piggies so removed the heat shields during the piggie install and the horrible noise went away.

[B5addiction]

I do not think it has to do with heat expansion, I can actually feel the downpipe hitting something.
I have checked it few times and everything is tight. 100%
My question is what I can do to fill the space and minimize the movement of the pipes, sort of cushion the knocking sound.

Unfortunately I am at school, not one garage here in town will accept my car since it is low, I would rev it on jack-stands but that
kind of freaks me out. Again thanks for all the help

[S4<M3]

mine does the same exact thing but only AFTER the downpipes were installed and its strange because it only rattles when in the rain then dissipates after about 5 minuets

[sherbet]

LMAO...just had a set of 034 3" dp's installed with cats and no heatshields. It makes a vibrating when the engine is decelerating around 2300 RPMs. I kind of thought maybe it was just sound resonating and making some vibrating...

[jibberjive]

Wow, there's a lot of us. Got the same issue, though I'm pretty sure mine is driveshaft heateshield related. Symptoms are very similar, knocking on the floorboard under my feet, maybe towards the rear a little bit more, especially when I'm letting off of the throttle and coast from higher RPM's. I'm going to straight up pull the driveshaft heatshield out and see if it goes away. The center driveshaft bearing is located pretty much under the driver as well, so that's always a suspect.

[sherbet]

Wow, there's a lot of us. Got the same issue, though I'm pretty sure mine is driveshaft heateshield related. Symptoms are very similar, knocking on the floorboard under my feet, maybe towards the rear a little bit more, especially when I'm letting off of the throttle and coast from higher RPM's. I'm going to straight up pull the driveshaft heatshield out and see if it goes away. The center driveshaft bearing is located pretty much under the driver as well, so that's always a suspect.

That actually sounds like it could be whats happening with me. Especially since those 3" pipes + cats are not exactly small under there

[shorterthanrich]

LMAO...just had a set of 034 3" dp's installed with cats and no heatshields. It makes a vibrating when the engine is decelerating around 2300 RPMs. I kind of thought maybe it was just sound resonating and making some vibrating...

THIS. I have exactly this problem (VAST DPs) and its driving my insane. Mine vibrates during deceleration at around 1,600 RPMs, but it usually doesn't start until the engine is warmed up...

I think its the DPs hitting my DTS bar, but I'm not totally sure. Hopefully I'll resolve it with the build...

[Trile]

I don't have vibrations, but I feel a 'farting' sound when decelerating (goes away when I press the clutch).
Coming from somewhere around the olive clamps I think. Checked twice at the exhaust shop and they found no leaks.

[shorterthanrich]

I don't have vibrations, but I feel a 'farting' sound when decelerating (goes away when I press the clutch).
Coming from somewhere around the olive clamps I think. Checked twice at the exhaust shop and they found no leaks.

Yeah, that's what mine sounds like. Pressing the clutch also eliminates it for me. it almost makes me think its chatter...but I don't think it is.

[sherbet]

Yeah, that's what mine sounds like. Pressing the clutch also eliminates it for me. it almost makes me think its chatter...but I don't think it is.

yes, exactly. Only when warm, decelerating ~2000 rpms. Pressing the clutch in eliminates it as well, but thats also just taking the engine back to idle.

[Dr. Jekyll]

I had the same problem. Smash the heat shields up into the body, they are probably touching the DP's somewhere. Careful on the passanger side though, there is a drain plug for the A/C behind the heat shield. I cut the rubber flap off of the drain plug and then pushed the heat shield all the way up. If you don't cut the flap off the heat shield will keep the plug closed and you'll have water in the footwell.

If that doesn't work the DP's might be rubbing the trans mount brackets. Remove the heat shield off those and hopefully you'll have enough clearance. If not you'll have to put a small dent in the DP's or grind down the brackets.

[BlingOnMyWrist]

Does it sound like this??

[Blake2423]

Mine sounds more like the rumble of a semi truck when its engine breaking

[sherbet]

^^blingonmywrist, no, car does not sound like that. Its more of a deep rumble that you cant so much hear rather than feel. ill try to get a video tonight...

[skizzik41]

I have the same problem but i have the ssac downpipes with welded on flex pipes except it feel lik it is coming from under my seat more than anywhere else when I lifted the car my exhaust was close to hitting the drive shaft stabilizer but wasn't. I get it at the same exact times as you are though. Curious as to what is causing this, its a little annoying!

I had that problem with the SSAC It was the exhaust hitting a bolt that held the shield for the drive shaft in place. There a a few of them under there. It was a bolt that was further to the drivers side. I just cut the bolt down and haven't had any noise or felt it vibrating since

[Yesmar]

I can feel the vibration while:

Faintly at idle, depends on pitch of the road. If I rev the car, it vibrates when the rpm's fall.
Downshifting, any speed

when i read the first post the first thing that popped into my head that would make that sort of noise under those conditions was flywheel/maybe clutch. idk everyone else seems to have the same problem. im prob. way off base, but a suggestion nontheless.

[Blake2423]

I had that problem with the SSAC It was the exhaust hitting a bolt that held the shield for the drive shaft in place. There a a few of them under there. It was a bolt that was further to the drivers side. I just cut the bolt down and haven't had any noise or felt it vibrating since

Ill look into this the next time I have a chance, Thanks

[Alan_11gl]

Hello

Someone could tell me how they solved the problem?

I have the same problem!

Thanks!

[Kruat]

I have the same problem. Stock dps with a milltek 3" exhaust. But I also have a DTS bar, and that is what my dp is hitting. Once I upgrade my dps I'll figure out why it rattles. And it doesnt do it much, just ever so slightly on downshifts and mid rpm throttle.

[Alex44]

I have the same problem. Stock dps with a milltek 3" exhaust. But I also have a DTS bar, and that is what my dp is hitting. Once I upgrade my dps I'll figure out why it rattles. And it doesnt do it much, just ever so slightly on downshifts and mid rpm throttle.

my 3" supersprint exhaust hits and vibrates on downshifts/engine braking once its really warmed up, its hitting at the differential mount. When the weather is nicer im going to adjust it to sit back a bit further, should give the clearance i need. Now if i can only get the giant 3" downpipes to fit nicely in the tunnel where the driveshaft connects to the trans. i might go ahead and see if i can remove the flexible aluminum heat shield material in that area which is what the pipes rub against.