ARCTICWHITE98Z28

iTrader: (1)

I have a 98 Z28 with stock exhaust, which is way too quiet for me. So I had a cutout installed on the I pipe last week just before it bends to go over the axle. It is under the passenger seat and is facing straight out to the passenger side. This looked to be a good spot, BUT I get a really, loud vibration right around 1900 RPM. It is almost like a loud deep, metal humming noise. So I went back to my local muffler shop today and put her up on the hoist. We were unable to find anywhere that any of the exhaust is hitting which may cause the stupid noise. So I capped the cutout and drove it around. The noise went away. So it appears the noise must be the actual exhaust fumes/pressure bouncing off the underside of the car or the rear axle that is causing this noise. I then decided to get some undercoating with sound dampener from AZ. I sprayed on a lot of that stuff everywhere I thought the exhaust may be causing a vibration. This seemed to help a little. Any ideas on how to fix this issue? Thanks.

RollinSScamaro

iTrader: (25)

have you checked any heat shields? maybe thats where it vibrating from? if not is it something inside your car thats loose? like in the spare tire area? i used to have an annoying problem like that.. and it just went away somehow haha.. i could never find it though.. good luck!

ARCTICWHITE98Z28

iTrader: (1)

I did remove the heat shield that was close to it. That did not help. I will check out the spare tire area. Hmmm guess I will try to avoid 1900 - 2000 RPMs by going WOT all of the time

01formula6

iTrader: (7)

Thats just what happens with a open cutout. Mine rattled the interior pretty bad as well. Bad rasp in that rpm range.

SilverLS1

iTrader: (2)

I about fell out of my chair laughing when I read this thread! No offense tho, seriously! Cutouts turn what we consider "rasp" into what sounds like somebody beating the underside of your car with a sledge hammer! But yeah, thats normal! Put a catback on the mother, cap it up, and leave it capped til you need the extra ponies!

ARCTICWHITE98Z28

iTrader: (1)

My car does have more rasp now, but the vibrational noise is different. It is more of a very loud humming noise when giving the car gas at 1900-2000 RPM. The rasp occurs when I left off the throttle. I don't believe it is a normal noise. I mean is everybody with a cutout getting this loud humming vibration???

Speed Density

iTrader: (38)

Yep mine rattles like a bitch, but i love it. Thats muscle. try running open headers youll ******* hate it.

ebear

I love the roughness, and shaking of an american car

SUX2BU

iTrader: (14)

I LOVE my open headered daily driver.

SUX2BU

iTrader: (14)

The cut out or Borla RASP is what you are experiencing. it happens during accelerating at around1900 rpms. yes it sounds like ***.

Speed Density

iTrader: (38)

SCORE, if you dont like it loud, go from 8 to 4 cylinders, its such a nice feeling when your *** goes numb from WOT.

yell03

Mine sounds amazing at all Acceleration points and even all deceleration points in the rpm range. I leave it open ALL the time.

The only thing I don't like is once in a while I get a backfire type sound (not as loud) when I let off the gas after accelerating kind of hard at low rpms, but for an $85 exhaust that sounds amazing I'll live with it.

Howard