Excessive drone and Vibration

[TheGrimReaper]

Hey there. Recently completed my exhaust system but think I may have givin the car a bit more then she can handle. So far I have headers to 2 and a half inch pipe. Welded into a 100cpi high flow cat followed by a 2 half inch straight pipe out back. The sound out of it is remarkable but I have only one problem. Taking off the sound is heavenly but one the revs reach 2000-2500 and above I hear an almighty drone and the car floor vibrates. Driving on the freeway at constant speed there is no drone or vibration yet as soon as I go to overtake and put my foot down and the revs climb the vibration and noise sounds like my exhaust has a milo tin on the back of the tailpipe. Does anyone have any idea how to clear this problem so I can have the nice sound all up the revs. Is something loose are things hitting or am I missing some clips or holders somewhere. I will try to take a photo of the exhaust system and upload it so you can see.

 

[vongy10]

So it's all straight pipe without a resonator/muffler? If so then there's your problem.

 

[EYY]

The engine/exhaust will be moving under acceleration and touching the body somewhere. Make sure the exhaust has good clearance everywhere, and that all of the mounts are in good condition.

 

[Interloper94]

Agreed with all of the above, having absolutely no muffler/resonator is gonna have its downfalls;makes me wonder why you bothered with cats at all, if a cop pulls you over, you're gonna get a reaming either way.

 

[TheGrimReaper]

I'll have to have a look tomorrow if anything is rubbing. And why is driving without a muffler or resonator illegal. I believe if they sell straight pipes then they must be legal as expecally since the exhaust place said that everything on my car is legal. I do believe once this problem is found the car will sound amazing.

 

[sleepa]

Basically noise levels. Not having a rear resonator or muffler makes the car louder, and can therefore be illegal if the noise increase is over the decibel limit for your vehicle.
Also cats make a difference to sound levels, stock cats are a lot quieter and a bit deeper.

I recently had some extractors installed with some (temporary) *cats* and straight pipe in place of my rear resonator and it was super droney at 1500rpm to 2000rpm, like holy **** this sounds like a constant fog horn in my head, hated it.
Changed back to factory cats ASAP and it quietened it down heaps, still sounds good but next to no drone. This is in a wagon too where drone tends to be worse due to the large expanse of flat floor just above where the resonator is.

I also see you have a V6. That could be a part of your problem, and autos don't really help the situation.

Your other thread from a few days ago?
http://forums.justcommodores.com.au/vy-holden-commodore-2002-2004/253956-legal-not.html

Straight pipe?
If so then there is your problem.

 

[Dirbatua]

I'll have to have a look tomorrow if anything is rubbing. And why is driving without a muffler or resonator illegal. I believe if they sell straight pipes then they must be legal as expecally since the exhaust place said that everything on my car is legal. I do believe once this problem is found the car will sound amazing.

exhaust shop will tell you whatever they thing you want to hear.

Straight pipes are never legal and never will be, doesnt matter if they sell em, its on the person who installs them on a road registered vehicle.

Your car must have same amount of mufflers it came out of the factory with, so on a VY it requires either 1 or 2 mufflers and all must have a rear resi..

and since you said a single cat i assume you got a v6, that must sound like a wet fart with no mufflers and a 100 cell cat.

Also 100 cell cats are not legal, only 200 cell and up are legal.

So when the cops pull you over for the fart machine and see a straight system expect an EPA check and possible a 10 grand EPA fine for an illegal cat on top of the major defect.

 

[TheGrimReaper]

I just checked and I'm not sure how to post photos on a thread as I've never done it but I do have a muffler I think. I did get the exhaust from Redback and the codes on mine match a Redback muffler. If someone could tell me how to add photos to this tread I'll send photos of the setup so you can all have a look.

 

[Interloper94]

Cant win them all, having a better flowing exhaust is gonna be louder and have a louder drone

 

[TheGrimReaper]

Yeah very true. Might leave it as it is then if I'm giving a warning I'll chuck on a resi. Until that day I'll probably leave it