Help..... Screaching turbo!
06 October 2009, 02:28 PM
#1
Scooby Regular
Thread Starter
Join Date: Mar 2009
Posts: 248
Likes: 0
Received 0 Likes
on
0 Posts
Help..... Screaching turbo!
Hi guys,
I just bought an MY 05 sti with only 19500 miles about 3 weeks ago.
Car is completely standard, and in really good nick, and drove beautifully.
Last weekend i fitted a buddyclub de-cat downpipe.
Having got it on, and sealed up to the original back box I went for a quick spin. (knowing it will need a re-map soon)
Driving in 3rd gear or higher with revs at or below 3000, if you nail the throttle, as the car comes on boost there's a screaching sound coming from the engine bay that dissappears come about 4000rpm when the car comes fully on boost.
It sounds like metal on metal, i'm guessing a thrust bearing in the turbo.
Has anyone else got an idea what this might be, or encountered it before?
Insight is much appreciated, thanks.
I just bought an MY 05 sti with only 19500 miles about 3 weeks ago.
Car is completely standard, and in really good nick, and drove beautifully.
Last weekend i fitted a buddyclub de-cat downpipe.
Having got it on, and sealed up to the original back box I went for a quick spin. (knowing it will need a re-map soon)
Driving in 3rd gear or higher with revs at or below 3000, if you nail the throttle, as the car comes on boost there's a screaching sound coming from the engine bay that dissappears come about 4000rpm when the car comes fully on boost.
It sounds like metal on metal, i'm guessing a thrust bearing in the turbo.
Has anyone else got an idea what this might be, or encountered it before?
Insight is much appreciated, thanks.
06 October 2009, 02:42 PM
#2
Scooby Regular
Join Date: Jan 2006
Posts: 3,695
Likes: 0
Received 0 Likes
on
0 Posts
It's almost impossible to diagnose this sort of thing over the internet, as nothing beats sitting in the car and actually hearing the noise.
If there was nothing wrong with the turbo before you changed the exhaust, it's difficult to think of a method by which merely fitting the decat will have fecked it. The best case scenario is that this is simply the downpipe resonating or ringing. Might also be a fault in it, or one of the joints. Best and quickest way to sort this out would be to drive over to your nearest Subaru specialist and have them take a listen.
Is the pipe heatwrapped, by the way, and did you refit both the sensors?
If there was nothing wrong with the turbo before you changed the exhaust, it's difficult to think of a method by which merely fitting the decat will have fecked it. The best case scenario is that this is simply the downpipe resonating or ringing. Might also be a fault in it, or one of the joints. Best and quickest way to sort this out would be to drive over to your nearest Subaru specialist and have them take a listen.
Is the pipe heatwrapped, by the way, and did you refit both the sensors?
06 October 2009, 02:53 PM
#3
Scooby Regular
Thread Starter
Join Date: Mar 2009
Posts: 248
Likes: 0
Received 0 Likes
on
0 Posts
There was only 1 sensor on the ori down pipe, and yes, its been re-located an re-fitted. No heat wrap on the new down pipe though.
A mechanic in a local tuning shop came for a spin an reconned the noise was definately from the turbo, but they aren't a scoob specialist although do have scoobys in for turbo upgrades etc.
I was thinkin maybe with the reduced back pressure of the de-cat, as the turbo is starting to produce boost the compressor wheel isn't balanced properly, and loads up the thrust bearing, and once the pressure on each side of the compressor wheel balances, the load comes off the thrust bearing making the noise dissappear.
If you bring the car up to 4k rpm without flooring it, then stick the boot in the turbo behaves perfectly normally.
A mechanic in a local tuning shop came for a spin an reconned the noise was definately from the turbo, but they aren't a scoob specialist although do have scoobys in for turbo upgrades etc.
I was thinkin maybe with the reduced back pressure of the de-cat, as the turbo is starting to produce boost the compressor wheel isn't balanced properly, and loads up the thrust bearing, and once the pressure on each side of the compressor wheel balances, the load comes off the thrust bearing making the noise dissappear.
If you bring the car up to 4k rpm without flooring it, then stick the boot in the turbo behaves perfectly normally.
Last edited by ScoobyNoobie; 06 October 2009 at 02:54 PM.
06 October 2009, 05:45 PM
#4
Scooby Regular
Join Date: Jan 2006
Posts: 3,695
Likes: 0
Received 0 Likes
on
0 Posts
That theory's a bit way out there. The compressor wheel doesn't load up "on one side" as it is spooling, it generates pressure all the way round its circumference - that's why the cover looks the the way it does with the tapered scroll.
In addition, the rotating assembly is dynamically balanced both pre- and post- installation in the cartridge. If it was "out of balance" to any noticeable degree, it would quickly shake itself to pieces - and would have done so long before you bought the car.
Unless someone's got a better idea, you really need to get this looked at by someone who knows what they've got in front of them. I suspect it's just a harmonic "feature" of the downpipe, but could be something more perturbing.
You could try heatwrapping the DP, as if it is simple noise, the wrap will probably either eliminate or at least fundamentally alter it. Before that though, I'd have it looked at.
In addition, the rotating assembly is dynamically balanced both pre- and post- installation in the cartridge. If it was "out of balance" to any noticeable degree, it would quickly shake itself to pieces - and would have done so long before you bought the car.
Unless someone's got a better idea, you really need to get this looked at by someone who knows what they've got in front of them. I suspect it's just a harmonic "feature" of the downpipe, but could be something more perturbing.
You could try heatwrapping the DP, as if it is simple noise, the wrap will probably either eliminate or at least fundamentally alter it. Before that though, I'd have it looked at.
06 October 2009, 06:17 PM
#5
Scooby Regular
Thread Starter
Join Date: Mar 2009
Posts: 248
Likes: 0
Received 0 Likes
on
0 Posts
I didnt mean quite what your thinking.
What i was actually thinking was loading up either the inlet or exhaust side, rather than 1 side of either rotor.
Less back pressure would cause the rotor to slide (im guessing towards the exhaust side) more than it did with the ori exhaust with cat in it was on until it starts to produce boost going into the inlet side, hence balancing the load on the bearing, and the squeeling stopping.
Either way, i think having someone who knows there stuff to have a look is a good idea.
Was hoping someone would know what it is though.
What i was actually thinking was loading up either the inlet or exhaust side, rather than 1 side of either rotor.
Less back pressure would cause the rotor to slide (im guessing towards the exhaust side) more than it did with the ori exhaust with cat in it was on until it starts to produce boost going into the inlet side, hence balancing the load on the bearing, and the squeeling stopping.
Either way, i think having someone who knows there stuff to have a look is a good idea.
Was hoping someone would know what it is though.
Last edited by ScoobyNoobie; 06 October 2009 at 06:19 PM.
06 October 2009, 07:15 PM
#6
Scooby Regular
Join Date: Jan 2006
Posts: 3,695
Likes: 0
Received 0 Likes
on
0 Posts
Right, I see what you're saying about the "sides" being longitudinal rather than lateral, but your theory still doesn't fly.
The thrust bearing, and the lubrication through it, is there specifically to hold the rotating parts of the turbo in position and stop exactly the sort of back-forth float you're talking about.
"Screeching", screaming or squealing noises are caused by high frequency vibration. If the rotating assembly in your turbo is bouncing back and forth enough to cause noise, then the thrust bearing is suffering a lubrication failure and metal to metal contact is occurring. If that's happening, your turbo is fecked, and it'll be fecked permanently, not go through a "noisy phase" which clears itself.
The fact that it doesn't perform in a way that points to it obviously being knackered suggests that it isn't. Everything you've said so far points to the turbo being okay. Either way, need to get it investigated properly.
The thrust bearing, and the lubrication through it, is there specifically to hold the rotating parts of the turbo in position and stop exactly the sort of back-forth float you're talking about.
"Screeching", screaming or squealing noises are caused by high frequency vibration. If the rotating assembly in your turbo is bouncing back and forth enough to cause noise, then the thrust bearing is suffering a lubrication failure and metal to metal contact is occurring. If that's happening, your turbo is fecked, and it'll be fecked permanently, not go through a "noisy phase" which clears itself.
The fact that it doesn't perform in a way that points to it obviously being knackered suggests that it isn't. Everything you've said so far points to the turbo being okay. Either way, need to get it investigated properly.
07 October 2009, 08:45 AM
#7
Scooby Regular
Thread Starter
Join Date: Mar 2009
Posts: 248
Likes: 0
Received 0 Likes
on
0 Posts
Right, I see what you're saying about the "sides" being longitudinal rather than lateral, but your theory still doesn't fly.
The thrust bearing, and the lubrication through it, is there specifically to hold the rotating parts of the turbo in position and stop exactly the sort of back-forth float you're talking about.
"Screeching", screaming or squealing noises are caused by high frequency vibration. If the rotating assembly in your turbo is bouncing back and forth enough to cause noise, then the thrust bearing is suffering a lubrication failure and metal to metal contact is occurring. If that's happening, your turbo is fecked, and it'll be fecked permanently, not go through a "noisy phase" which clears itself.
The fact that it doesn't perform in a way that points to it obviously being knackered suggests that it isn't. Everything you've said so far points to the turbo being okay. Either way, need to get it investigated properly.
The thrust bearing, and the lubrication through it, is there specifically to hold the rotating parts of the turbo in position and stop exactly the sort of back-forth float you're talking about.
"Screeching", screaming or squealing noises are caused by high frequency vibration. If the rotating assembly in your turbo is bouncing back and forth enough to cause noise, then the thrust bearing is suffering a lubrication failure and metal to metal contact is occurring. If that's happening, your turbo is fecked, and it'll be fecked permanently, not go through a "noisy phase" which clears itself.
The fact that it doesn't perform in a way that points to it obviously being knackered suggests that it isn't. Everything you've said so far points to the turbo being okay. Either way, need to get it investigated properly.
There's a good scooby garage on my way home from work on friday where they also build an prepare scoob rally cars, so hopefully he'll know a thing or two.
Thanks
Trending Topics
07 October 2009, 01:22 PM
#8
Scooby Regular
Join Date: May 2009
Posts: 107
Likes: 0
Received 0 Likes
on
0 Posts
Sorry i aint read all the thread, but i had a really weird screaching noise on mine just after i had the up-pipe changed and it was the gasket, they had used the old ones .. just a suggestion.
07 October 2009, 01:52 PM
#10
Scooby Regular
Thread Starter
Join Date: Mar 2009
Posts: 248
Likes: 0
Received 0 Likes
on
0 Posts
07 October 2009, 01:59 PM
#11
Scooby Regular
iTrader: (3)
Join Date: Aug 2000
Location: 1600cc's of twin scroll fun :)
Posts: 25,565
Likes: 0
Received 2 Likes
on
2 Posts
Decatting causes boost spikes (rather big ones) and the ecu cannot cope, this causes pre detonation (det) which in turn kills your engine (your big end bearing normally takes the brunt of it) and its about 2.5-3k for a rebuild.
You need the car mapping to stop it doing this, about 600-650 quid, and dont drive it silly, it wont last
(long documented stuff about this on new age STI's on here 
)
Tony
You need the car mapping to stop it doing this, about 600-650 quid, and dont drive it silly, it wont last
(long documented stuff about this on new age STI's on here )Tony
07 October 2009, 02:02 PM
#12
Scooby Regular
Thread Starter
Join Date: Mar 2009
Posts: 248
Likes: 0
Received 0 Likes
on
0 Posts
Well this noise is definately not engine internals.
It's either a really high pressure of air going past a sharp edge, or a metal on metal screech, no knocking.
Unfortunately i know the sound of a failed big end all too well
I did a search for a thread like that but didn't find one.
If you had a link to it, i'd appreciate it.
Cheers
It's either a really high pressure of air going past a sharp edge, or a metal on metal screech, no knocking.
Unfortunately i know the sound of a failed big end all too well
I did a search for a thread like that but didn't find one.
If you had a link to it, i'd appreciate it.
Cheers
07 October 2009, 02:26 PM
#13
Scooby Regular
iTrader: (3)
Join Date: Aug 2000
Location: 1600cc's of twin scroll fun :)
Posts: 25,565
Likes: 0
Received 2 Likes
on
2 Posts
Nah what im saying is decatting a new age STI without remapping will cause you serious engine problems, but that said, its already been suggested that it could be a gasket, though metal on metal is never a good sound, but would have expected it to be there all the time and not just about 1k rpm's worth.
Suggest a remap before your bill gets any bigger also
Tony
Suggest a remap before your bill gets any bigger also
Tony
07 October 2009, 02:33 PM
#14
Scooby Regular
Thread Starter
Join Date: Mar 2009
Posts: 248
Likes: 0
Received 0 Likes
on
0 Posts
Ye.
I think for the time being, i'm going to put the standard pipe back on and see if the noise dissappears.
Unfortunately i dis-located my shoulder on sunday biking, so that could make it a bit difficult!
The gasket thing makes sense now actually, because when i stop at lights etc, sometimes there's a bit of a smell of exhaust in the car, how did that only twig now
With any luck its as simple as a gasket!
I think for the time being, i'm going to put the standard pipe back on and see if the noise dissappears.
Unfortunately i dis-located my shoulder on sunday biking, so that could make it a bit difficult!
The gasket thing makes sense now actually, because when i stop at lights etc, sometimes there's a bit of a smell of exhaust in the car, how did that only twig now
With any luck its as simple as a gasket!
07 October 2009, 02:36 PM
#15
Scooby Regular
iTrader: (1)
Join Date: Jan 2004
Location: Lancaster/Manchester or stuck in a traffic jam somewhere in between
Posts: 2,232
Likes: 0
Received 0 Likes
on
0 Posts
I know when I decatted my Type R a few years ago, I hadnt put the heatshield back on properly and the noise that made due to the vibration/resonating was really noticeable at certain times, like a high pitched 'zinging' noise. So I took it off, modified it and that sorted it.
Thread
Thread Starter
Forum
Replies
Last Post