Some of us with the RMW Street ("Shorty") header are experiencing what I would describe as a "resonant exhaust vibration" at some specific RPMs. As far as I can tell, this is NOT widespread, it is NOT a defect in the RMW Header design (as far as we know) and everyone who has reported it says "I still LOVE my RMW Header!"...

I'm not talking about a heat shield rattle/buzz. And I'm not talking about what most folks refer to as "drone". I'm talking about what sounds like someone using a hammer drill or jackhammer on your chassis - LOUD - at one or two specific RPM points. It's a VERY LOUD metal-on-metal vibration sound...

I'm starting this thread to try to collect all cases of this, to see if we can find specific combinations that make it more or less likely. So far, I've only heard this reported with:

One-ball exhaust (BlimeyCabrio, rberga1)
Stock exhaust (Intense, Ifa, Some Guy)
Invidia exhaust (Intense, SlowGSX98, OctaneGuy)
Milltek (custard, blue al)
Magnaflow (duvinclunk)
Alta? (jeffc2) (confirming this is the same issue)
littlehandegan - custom exhaust, 2 hushpowers, no resonator

rberga1 installed a new Alta 2.5" and vibration is gone
custard installed JCW exhaust and vibration is gone
davisflyer also has JCW exhaust with no vibration
BlimeyCabrio's is FIXED - was a broken joint between the exhaust flange and catback. Still resonates, but no more jackhammering rattle.
Intense installed RMW custom exhaust and vibration is gone

OctaneGuy and SlowGSX98 both had bad Invidia resonators

If you have this same issue, please post so we can figure this out...
And if you had the issue and resolved it, please provide details!

Thanks!

 

A header (any header) changes the acoustics or resonance of the exhaust gases via tubing diameter, length and shape changes. The same can be said for an exhaust system.

Typically, resolved by a resonator.

 

Yep - makes sense. I understand why you'd get different exhaust behavior before and after - thanks for the clear & concise explanation.

We're just trying to find patterns here, since we're in the trial & error stage of resolution...

 

Mines doing it with 2 hushpower rear section/ no res.

 

The pattern here is Jan .

His stuff is just creating too much HP/TQ .

At the rate he is going, the side mirrors will begin to vibrate .

So in a nutshell, its all Jan's fault.

 

Yep. And he's shredding front wheels, too.

All we need is a flux capacitor... and some stainless steel body panels...

 

I'm thinking about maybe having a resonator welded into the one-ball up front.... to see if that improves things... otherwise an Alta exhaust...

 

Has no one put there car on a lift to see what it is first? I havent had time but i will asap.

 

Mine happens around the 3000-3200 mark. It also happens while going steady at 65 mph. I am going to pull the arogel blanket off tonight and try to separate the heat shields and see if that takes care of it.

 

My assumption is when the car is under load/vibrating and when the exhaust has heated up/expanded the resonator comes in contact with the center brace that holds the exhaust up in the center of the tunnel.

For those with an Alta

 

Not on mine...

To recap:
1) Mine has been on stands and I've spent an hour probing every heat shield and every metal part near the exhaust.
2) I've confirmed that the sound is resonant vibration *of the exhaust pipe itself* - it's not rattling *against* anything. Confirmed with both a probe, and with holding my ear 1" from the exhaust at the loudest point.
3) I don't have a resonator.
4) Mine does it hot and cold.

 

Did you do the screw driver test

 

Yep - that's what I meant by "probe"...

 

Hoping to have my shorty header on with a Magnaflow this week. I'll let ya know...

 

Old Skool

 

I can confirm the same with a RMW shorty header and Magnaflow exhaust. Vibration starts around 2200 rpm and stops somewhere just shy of 3000. I LOVE my set-up and the noise is easy to deal with when you make so much more power!

 

spdfreak... I think you have a different noise... I don't think the harmonic range would be a continuous band 800RPM.... and, if I had the noise I'm talking about for 800 RPM at that point in the power band, the header would be off my car already.... I'm sure you have a pretty good noise! Just not the same noise....

 

Same here. Mine does it at 2200 and then at 3300 rpm. BlimeyCabrio it is on a stock and not a one-ball exhaust. I removed the back heat shield but no progress.

 

What is the screw driver test??

 

Agreed.

 

I get what you are talking about, around 1800rpm with the stock 05 exhaust. It sounds like a very nasty vibration basically.

 

Anyone has this vibration with JCW exhaust?

 

I may have been mistaken re: RPM for noise. The "noise" only appears at something like 2700 give or take. Sorry for not being more accurate but I only drive my car once every couple weeks and tried to guess the RPM in my previous post. I took it out last night to find out something a little more exact. I like others have been underneth the car looking to find the source of the noise with no luck. Again I gladly deal the noise for the performace these parts provide, besides, I don't often drive below 3000 rpm anyway

 

For those of you thinking that a resonator will help, I've tried and it did not.
I had a 22 inch magnaflow resonator welded into my Invida replacing the stock one. It didn't make any difference.

It is a harmonic resonant vibration. I haven't been able to get my car on a lift yet but I want to determine if the flex joint has a preload in it. Jan feels like it might be the cause if it does. From being under the car on a creeper its to hard to tell if it has one or not. I don't think it does tho, I'll keep you posted if I find anything

 

My theory is the location of the flex joint being a greater distance from the centroid of the engine assembly has increased the amplitude if the vibration that was always in the car. Not much to do about it. I am considering the damper from VIP and perhaps urethane mounts to try and decrease the amount the engine moves. Also considering stiffer hangers on the exhaust, especially the forward one.