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GS Downpipe burble?

1K views 9 replies 6 participants last post by  lms 
#1 ·
After installing the GS downpipe and making sure it is not rubbing on anything below, the odd time I get a strange burble kinda sound from the front. It sounds almost like a muffler dragging on the ground. Sounds like it's coming from the passenger front side.

The pattern is very hard to figure out. It dose it at random times. Usually the car is in gear but zero throttle (engine break). So I could drive 20 min and then for some reason when I engine break it starts to burble.

Tire rubbing is ruled out. Everything is tight and in place. If a shake the exhaust from the back it is not hitting anything. So I have no idea....

Is this the norm for the downpipe or something else? I'm stumped. What else can I check?
 
#2 ·
Never had something like that. Which version do you have, V1 or V2. If V1 I'd make sure that the first section where the downpipe and flexpipe meet at is sealed up good. I know my clamp is stretched pretty far to hold those two sections together. As for the v2 with the v-band I don't know.
 
#4 ·
I just put in the V2 about 3 weeks ago.

I had what I would call a "rattle/burrble" when engine braking and it got down between 2300-1800 rpm. It wouldnt do it everytime. But enough to make me wonder. I looked under it and everything seems to be fine. Its also seems to have fixed its self as I was trying to do it on my drive home today and it wouldnt.

I am noticing that where the intermediate pipe meats the rest is a little noisy due to my cut job being a hair short.....
 
#5 ·
Is it a burble as in back pressure when you let off, or is it more of a rattle at times. You say it sounds like it's dragging on the ground which to me would sound like a scrape/rattle. Does the GS DP have a u tab welded on it so you can add a support piece to it? I had a rattle kind of sound at certain rpms's which was the cat hitting the 6 point brace, so I tack welded a u-tab and added a support which eliminated it.
 
#6 ·
It sounds like a coffee maker, spit/rattle or a something draging on the road.

It seems to mostly do it when engine braking and at the same time I do sharp left turn. It also dose it in a staright line the odd times. Everything is tight at the flange. The rest of the exhaust can move around a bit after the flex section, but there seems to be pleanty of clearance.

It's just happens the oddest time. I can do a slalom, sawing left , right, fast and it's fine.

I might go for a drive tonight, there is a street with 4 roundabouts so that will help with the left turn idea.

Thanks Saab for turning an owner into a paranoid DIY'er.
 
#8 ·
Mine burbles really loud when I engine brake. I even get backfires. Then again, I have a hole in my downpipe (JT 3" DP, flex pipe rubbed against oilpan and formed a hole).


With the larger exhaust, the backpressure creates a cool burble. You may just be hearing it through the pipe.


I know every know and then I'll get a loud "POP", like unburnt gas igniting in my exhaust.
 
#9 ·
The heat shield is good. Plenty of clearance.

Last night it was consistently doing it when I was in a hard left turn and engine braking.
Maybe the g-forces are enough to really move the exhaust to the side and hit the heat shield (guessing). Maybe it’s that V-band clamp as that is the largest diameter section and closest to the shield. If I have my hand on the e-brake, I can feel little ticking when the burble happens.
Maybe I should try and brace the pipe a bit so it can't move that much around and go for a test drive. What should I try?

Thanks for the comments guys.

I get the occationa pop in the muffler too coming down from high rpm's. Good times.....
 
#10 ·
Take something like a small piece of wood or whatever and jam into a space where you know the cat and dp will not move or hit anything. Take it for ride and see what happens. Just be carefull as you don't want a piece of wood catching fire. So if it goes away, take wood out bring down to exhaust shop and have them tack weld a support on dp. They can then support it by atatching it to the engine block. On my viggen there is a spot for it.
 
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