Exhaust frustrations; comments?

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pstrang

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May 4, 2006
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I've got a 4" turbo back MBRP exhaust, cat delete, and high flow muffler. I've always had the 1800-2000 rpm turbo droan; the TSB didn't help. It gets the floorboard humming pretty good, annoying. I checked if the exhaust was binded somewhere, no luck. Tried realigned things, no luck. I eventually dampened it a little with a 25 lb. bag of shotgun reloading shot I clamped to my cat delete pipe. So it's still there and annoying, but i've been dealing with it.

Recently I tried a muffler delete, the 1800-2000 rpm droan picked up in amplitude, AND I added another much louder vibration right at 1500 rpms. This is a short one only around 1500 rpms, but it's really strong.

I tried a 2nd 25 lb. bag on the muffler delete pipe, and also tried it on the end of the exhaust right by the tip. I tried removing the bag on the cat delete too. Nothing seems to dampen the 1500 rpm one. :bang

Can anyone suggest a mitigation technique? I've done all I can think of, maybe I'm missing the obvious? Everything looks well clear of other components. I've done bound exhaust techniques. I've clamped weights in various places. I'm out of options.

I don't want to put the MBRP muffler back on. :(
 
Only thing I can think of is welding it all up. I have no droan, at least I don't notice any, but I also don't have much exhaust. :rockwoot: Just a two piece 4" downpipe with a 5" tip pointed down. maybe copy my set up? lol It will sound better. good luck man.
 
Have you tried Reinstalling the exhaust after taking it back off? I know its a PITA but it might work...I have turbo back duals and no droan to date and we are pretty hard on the truck on and off road..Good luck
 
Doesn't it look kinda goofy with bags of shot hanging from your exhaust?? My buddy has a 4" silverline on his with a cat delete and a muffler and the only thing annoying about his is the whistle....he loves it though :doh:
 
Are you absolutely sure there is a 1/4 to 1/2 inch of space near the fire wall, trans dipstick tube, up-pipe to the turbo, firewall, and transmission crossmember?
 
Well, I've played with the spacing and alignment a dozen times. Even wore out the clamp on the turbo, had to get another one. But I'm sure I have at least 1/2"; it's only a 3.5" downpipe.

It's not hitting the firewall, because I've done that before. That sounds like the turbo is chewing on metal spaghetti. It's probably close though because my problem is a droan that is amplified through the cab/floorboard...oh, and my foot on the go pedal. Only at certain rpms...other times it's nice and smooth. 1500 and 1800-2000 rpms.

There isn't much adjustability though. The down pipe needs to mate up with the cat delete pipe on the first exhaust hangar. I've adjusted so they align well without bolting together. That seems to be the least annoying, but still a problem I could do without.

Thanks for the comments everyone!
 
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B.A.Ram said:
Doesn't it look kinda goofy with bags of shot hanging from your exhaust?? My buddy has a 4" silverline on his with a cat delete and a muffler and the only thing annoying about his is the whistle....he loves it though :doh:
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I have them sitting on top of the exhaust. So they aren't visible..normally. Yea, many times I wish I would have tried silverline, but they were quite a bit more expensive.
 
Liftedpsd said:
Have you tried Reinstalling the exhaust after taking it back off?
Click to expand...

Many times. *bdh* I must be missing something obvious. :(

Actually, when I put the cat back on, the droan is much reduced. That's were the idea of weight came from. The cat weighs more than the cat delete pipe. The bags of shot help but don't squash it completely.

It's got to be the downpipe dancing around with higher flows and reduced back pressures.
 
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Did you trim the hanger on the cat delete by about an inch? When the motor torques over the entire exhaust will lift.
 
PSDPlayer said:
Did you trim the hanger on the cat delete by about an inch? When the motor torques over the entire exhaust will lift.
Click to expand...

No, I haven't heard of that. More details please, thx. :thankyou2:

Do you mean cut the length of the hangar welded to the cat delete pipe? I noticed it is pretty long. But it is not coming in contact with the frame after it fits into the rubber mount on the frame.
 
It is extremely long. EVERY one of them has needed to be trimmed off by about an inch.
 
PSDPlayer said:
It is extremely long. EVERY one of them has needed to be trimmed off by about an inch.
Click to expand...

Okay, so I'll trim the length of the hanging rod from the cat delete pipe and re-align with the exhaust running closer to the frame. Right?

How would this help/prevent the exhaust from moaning? lifting? Well, I guess it doesn't matter. At this point, I'll try *anything*.

Thanks.
 
Can you fit a finger between the 2 bolts on the trans crossmember and the downpipe extension piece?
 
PSDPlayer said:
Can you fit a finger between the 2 bolts on the trans crossmember and the downpipe extension piece?
Click to expand...

O yea, two fingers even. I have lots of room around the crossmember. The closest is between the downpipe and the joint in the firewall; I can fit just one finger there, so a little < 1/2".

Overall, it seems I have plenty of clearance; I've played around with alignment enough that I thought I had the sweet spot. Guess not.

Please tell me if your rod off the cat delete pipe fits into the exhaust hanger level (parallel to the ground)? Or is it at an angle? If I cut the rod down by 1", I wonder if I'll be able to shift the exhaust over far enough to get it securely in the rubber hangar.

The clamps for the rest of the exhaust downstream and the rubber hangars seem to line up nicely. If the system is shifted over 1", they'll be tweaked.

Hummm....comments? Anyone have pictures of their install lying around?
 
Update:

I didn't hear back from anyone, so I did some playing around. I cut 1" off the cat delete pipe hangar rod. I was hoping to align closer to the frame rail, but really cant because of that jog in the pipe between the cat and the muff. BTW, what angle is your jog? Horz? Slanted?

I removed all the pieces, started at the turbo. I aligned the downpipe for maximum all around clearance. I have close to 1/2" between the down pipe and the firewall. There is that rounded corner in the firewall where the downpipe fits. I adjusted for maximum clearance. BTW, the passenger side uppipe from the manifold has at least 1/2" of clearance too.

Anyway, I also put the MBRP high flow muffler back on. And the 1500 rpms vibration is squashed. Great. But too bad I couldn't squash it otherwise. With the muffler back on, the 1500 is still there, but it hasn't been a problem.

However, the 1800-2000 rpm vribration/droan is still there. About 77 MPH, it's completely gone and the truck is smooth as glass. But less than that and I have the vibrational floorboard. It sure would be nice to squash it, any other ideas?

Thanks for the comments.
 
Check the clamp from the downpipe. Mine hit the insulation and required a rotation to clear it. Just a few millimeters too close caused a vibration.
 
Thanks Betaracer, but I've even tried it without the clamp. No luck or even a change in the nature of the vibration/droan.

Sure is frustrating...it's smooth as glass above and below the rpm droan range. Any other ideas how to squash it?
 
If my exhaust was giving me that much greif I would uninstall the cat and everything back and call it good. Or..do that then put on piece by piece to see what could be the culprit of the droan. But im a 21yr old kid that loves the piercing whistle. good luck.
 
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