Anyone have a 3" DP to stock CBE? Need help tracking down exhaust noise.

[Max Capacity]

I would think that if you have a leak at the up pipe, you would clearly hear that.

Have you removed the mufflers and taken the car for a ride ?

 

IMO that's easier then messing with the up pipe gasket.

[paintpollz]

I would think that if you have a leak at the up pipe, you would clearly hear that.

Have you removed the mufflers and taken the car for a ride ?

 

IMO that's easier then messing with the up pipe gasket.

 

Byron, it sounds like its coming from the turbo area. It very well could be an up pipe gasket, or the header gaskets.

 

I have not tried to remove the mufflers

[bmx045]

here's your answer: buy a can of seafoam, pour a little into a drinking cup, start car, let it idle, while running disconnect brake boost line from the master cyl, put hose into cup to allow the engine to suck in the seafoam liquid, wait for white smoke to appear from the tail pipes, don't submerge the booster line so much into the cup as to stall the engine, keep it running, sucking a little at a time, once you see smoke coming from the back of the car, inspect engine bay for smoke and where it appears...instant exhaust leak finder. Use as much seafoam as you want, the whole can if need be.

[paintpollz]

here's your answer: buy a can of seafoam, pour a little into a drinking cup, start car, let it idle, while running disconnect brake boost line from the master cyl, put hose into cup to allow the engine to suck in the seafoam liquid, wait for white smoke to appear from the tail pipes, don't submerge the booster line so much into the cup as to stall the engine, keep it running, sucking a little at a time, once you see smoke coming from the back of the car, inspect engine bay for smoke and where it appears...instant exhaust leak finder. Use as much seafoam as you want, the whole can if need be.

 

After seafoaming, there are no leaks in the system. This is simply how the car sounds with a divorced 3" downpipe, and stock exhaust on everything else. I'm thinking about putting this DP up for trade for a bellmouth catted DP to see if that will solve the problem.

 

This Perrin is a real nice pipe, It just doesn't sound right on my car.

[kiltedyak50]

I had a bit of a drone at a specific rpm, with a Cobb 3in to stock catback. You could always get a resonator to splice in if it's driving you nuts.

 

I think they're pretty cheap and might be an easier fix.

http://www.sfxperformance.com/parts/VIB1792.htm

[paintpollz]

I had a bit of a drone at a specific rpm, with a Cobb 3in to stock catback. You could always get a resonator to splice in if it's driving you nuts.

 

I think they're pretty cheap and might be an easier fix.

http://www.sfxperformance.com/parts/VIB1792.htm

 

 

splice in where? on the DP?

 

It sounds like its coming right at the turbo DP connection. I'm trying justify the divorced section and the airflow causing the drone under load.

[Max Capacity]

I'm sure he's talking about adding it to mid pipe.

 

If you find a muffler shop, Carr's in Rockville on Rt83 is great, they could cut the mid pipe and flange in a resinator and may be replace the mid pipe flange to DP.

 

The owner went to school with my oldest sister. He's a good guy who's into cars and doing custom work. He has a dual engine old Dodge Dora if I remember the cars name. It was a FWD pick-up body from the mid 1980's.

[paintpollz]

I'm sure he's talking about adding it to mid pipe.

 

If you find a muffler shop, Carr's in Rockville on Rt83 is great, they could cut the mid pipe and flange in a resinator and may be replace the mid pipe flange to DP.

 

The owner went to school with my oldest sister. He's a good guy who's into cars and doing custom work. He has a dual engine old Dodge Dora if I remember the cars name. It was a FWD pick-up body from the mid 1980's.

 

the reason why i asked is because there already is a resonator in the stock mp.

[paintpollz]

OK, so I've been tracking the pattern of exhaust noise. It doesn't happen when the car is cold. So for instance, I left my GFs house this morning, was driving for about 3 minutes before I got on the highway. The temp needle was about a third of the way up the temp gauge, and I still wasn't getting any drone noise while under load at 75ish mph. There probably a 3 percent incline for about a mile long on the highway when I first merge on, so its the perfect place to test the noise from the DP.

 

When the car was warm with the needle right at normal temp, it was easy to replicate the noise while moving along on the highway.

 

Thoughts, maybe as to why it would be like this? Anybody notice a difference in exhaust noise after wrapping/coating?

[GTTuner]

Are you using the spring bolts at the DP to stock CBE connection? What about the bracket that attaches the DP to the trans mount?

[paintpollz]

Are you using the spring bolts at the DP to stock CBE connection? What about the bracket that attaches the DP to the trans mount?

 

No spring bolts, and I don't think I used the tranny bracket either.

 

Very interested to see where you are going with this.............

[paintpollz]

I think we have the solution....I'll keep everyone poasted.

[BarManBean]

What's the solution? You definitely want to be using the tranny bracket for support, especially if you are getting intermittent noise.

 

Those spring bolts suck for aftermarket applications tho, IME.

[paintpollz]

Hi Kevin.

 

I have dealt with a few of my customers droning issues. You need to have that DP to tranny bracket there for support. The spring bolts allow the DP to CBE connection "articulate" if you will. I think the combination of the DP bracket missing and a super rigid connection at the connection is setting up a harmonic resonance. You mentioned it's worse after the car gets warmed up. This would make sense because the pipes do react differently to harmonics when the pipes are hot. I would make sure you have sufficent clearance from the DP and firewall area, disconnect the DP/CBE flange, reconnect the hanger bracket at the trans then bolt up the flange. Remember that a true drone is actually 2 or more vibration frequency's intersecting and causing the noise. You can get away with no spring bolts but you need to not tighten the stainless bolts super tight so the doughnut gasket can allow movement. I typically doubble nut the bolts to stop them from loosening. I hope this helps you, feel free to hit me up anytime you have questions. I don't know everything but I am an auto tech by trade, with an engineering background. Good luck, keep me posted!

 

 

the whole scientific explanation was clearly way to far over my head to attempt to diagnose the problem myself. makes me feel fortunate we have guys like paul around to put it on a silver platter.

[paintpollz]

barman would you wrap the pipe while you were down there doing work? I kinda want to wrap mine, but I'm not sure if its worth it.

[laff79]

just do it. I wrapped mine in the rain on 2 jackstands in the front

[paintpollz]

ur talking to a guy that had a hard time buying a $28 fumoto valve. im a cheap F#$%

[BarManBean]

I wrapped mine while it was off the car. Not impossible to wrap on the car tho, like laff says, jsut a bit more of a PITA. But so is taking the DP off completely so....

[paintpollz]

I wrapped mine while it was off the car. Not impossible to wrap on the car tho, like laff says, jsut a bit more of a PITA. But so is taking the DP off completely so....

 

true. I cant remember, is it possible to wrap the UP while you are in there too?

 

How many feet would you need? Do you just wrap away and put a few hose clamps on every foot or so?

[BarManBean]

is it possible to wrap the UP while you are in there too?

 

eff that. impossible / not worth the trouble.

 

How many feet would you need? Do you just wrap away and put a few hose clamps on every foot or so?

 

Pretty much, it's not rocket science really--just wrap it up and make sure it's secure and not going to fall off. 25 ft of 2" wide wrap should do the front section of a downpipe, no problem. I don't remember exactly how much I used.

[Max Capacity]

I have pictures of mine on the engine before I dropped it in. in the got some new stuff thread.

 

Here,

http://i185.photobucket.com/albums/x40/92Si/DSCN4777.jpg

[paintpollz]

I re-attached the DP tranny mount, and loosened up the DP to stock CBE connection. It leaked pretty bad when I first started it back up, so I had to crank it back down to pretty much the level it was at before.

 

Noticed that the DP was closer to the firewall than I expected, probably a 3mm gap at most. I will be testing it on my drive to my GFs tomorrow

[BarManBean]

If you still have issues, you could take the midpipe to a shop and get a legitimate flange welded on to match up to the downpipe. If you are running 2.5" piping, I can probably get you a downpipe flange with some pipe left on it if you decide to go that route. If you did that, you could connect the pipes up with a normal two-bolt gasket and really wrench it down. If you still have the problem after that it's DEFINITELY not that connection. Might be a bit overkill, but I cant imagine that it would cost much to get a shop to weld it up for you.

[paintpollz]

If you still have issues, you could take the midpipe to a shop and get a legitimate flange welded on to match up to the downpipe. If you are running 2.5" piping, I can probably get you a downpipe flange with some pipe left on it if you decide to go that route. If you did that, you could connect the pipes up with a normal two-bolt gasket and really wrench it down. If you still have the problem after that it's DEFINITELY not that connection. Might be a bit overkill, but I cant imagine that it would cost much to get a shop to weld it up for you.

 

Its wrenched down real good for sure. That can't be where the problem is. It's not leaking at any spot, I think it's just a louder pipe.

[paintpollz]

found it. it was the FMIC. I removed the FMIC and now the highway drone is gone.

 

I took it off because I was sick of tracking down leaks. And the bonus was finding this out.

 

Sweet