Annoying exhaust sound
09-12-17, 01:56 AM
#27
To the OP:
I had a very similar, if not the same problem years ago. It turned out to be that a couple of the long turbo assembly bolts had backed out and allowed the plate covering the pre-spool control valve to become somewhat loose. Now it didn't look loose, so I failed to pick it up on a cursory inspection--but it was loose enough that the cover plate would flap around and buzz like a reed with the exhaust pulses--especially when the pre-spool valve started to open. Eventually, the gasket blew out and I traced it down; by that point it sounded horrendous and the setup would only make about 5 or so pounds max secondary boost (due to the leak).
Replaced the cover gasket and torqued everything down per FSM and problem solved. There are 4 bolts that hold the cover on, 2 large that run through the turbo to the exhaust manifold and 2 smaller bolts that are only associated with the cover. *Be sure you've got the correct factory iconel long bolts running through the turbo. DO NOT SUBSTITUTE!* Nothing else will hold up to the heat--they will just stretch and fail.
You can access/check/repair this from under the car no problem; however, iirc, you may need to remove the TCA (big actuator) and some heat shields to access the affected area.
Hope this helps. Good luck.
I had a very similar, if not the same problem years ago. It turned out to be that a couple of the long turbo assembly bolts had backed out and allowed the plate covering the pre-spool control valve to become somewhat loose. Now it didn't look loose, so I failed to pick it up on a cursory inspection--but it was loose enough that the cover plate would flap around and buzz like a reed with the exhaust pulses--especially when the pre-spool valve started to open. Eventually, the gasket blew out and I traced it down; by that point it sounded horrendous and the setup would only make about 5 or so pounds max secondary boost (due to the leak).
Replaced the cover gasket and torqued everything down per FSM and problem solved. There are 4 bolts that hold the cover on, 2 large that run through the turbo to the exhaust manifold and 2 smaller bolts that are only associated with the cover. *Be sure you've got the correct factory iconel long bolts running through the turbo. DO NOT SUBSTITUTE!* Nothing else will hold up to the heat--they will just stretch and fail.
You can access/check/repair this from under the car no problem; however, iirc, you may need to remove the TCA (big actuator) and some heat shields to access the affected area.
Hope this helps. Good luck.
09-12-17, 08:35 AM
#28
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Hmm. And what have you checked so far?
This may be a good place to check, since I know the last owner had the turbos off. They don't look loose but you never know. Sounds exactly like my issue. What do you mean by cover?
I have a very weird and faint sound from my engine bay at idle. I hadn't associated it with this problem until now. It sounds like gentle beeping, but since nothing could really cause that, it could very well be the precontrol valve squeaking away with exhaust pulses.
Redbul's car makes a similar flapping noise, but only when REALLY stepping on the gas. He's non-sequential but has his precontrol valve still inside. As to whether it's that, or simply the wastegate, I'm not sure. However, my issue shows up even when the wastegate should be closed.
I tried using a GoPro, but it didn't pick up the sound I'm talking about at all. My new exhaust is too loud, it seems.
To the OP:
I had a very similar, if not the same problem years ago. It turned out to be that a couple of the long turbo assembly bolts had backed out and allowed the plate covering the pre-spool control valve to become somewhat loose. Now it didn't look loose, so I failed to pick it up on a cursory inspection--but it was loose enough that the cover plate would flap around and buzz like a reed with the exhaust pulses--especially when the pre-spool valve started to open. Eventually, the gasket blew out and I traced it down; by that point it sounded horrendous and the setup would only make about 5 or so pounds max secondary boost (due to the leak).
Replaced the cover gasket and torqued everything down per FSM and problem solved. There are 4 bolts that hold the cover on, 2 large that run through the turbo to the exhaust manifold and 2 smaller bolts that are only associated with the cover. *Be sure you've got the correct factory iconel long bolts running through the turbo. DO NOT SUBSTITUTE!* Nothing else will hold up to the heat--they will just stretch and fail.
You can access/check/repair this from under the car no problem; however, iirc, you may need to remove the TCA (big actuator) and some heat shields to access the affected area.
Hope this helps. Good luck.
I had a very similar, if not the same problem years ago. It turned out to be that a couple of the long turbo assembly bolts had backed out and allowed the plate covering the pre-spool control valve to become somewhat loose. Now it didn't look loose, so I failed to pick it up on a cursory inspection--but it was loose enough that the cover plate would flap around and buzz like a reed with the exhaust pulses--especially when the pre-spool valve started to open. Eventually, the gasket blew out and I traced it down; by that point it sounded horrendous and the setup would only make about 5 or so pounds max secondary boost (due to the leak).
Replaced the cover gasket and torqued everything down per FSM and problem solved. There are 4 bolts that hold the cover on, 2 large that run through the turbo to the exhaust manifold and 2 smaller bolts that are only associated with the cover. *Be sure you've got the correct factory iconel long bolts running through the turbo. DO NOT SUBSTITUTE!* Nothing else will hold up to the heat--they will just stretch and fail.
You can access/check/repair this from under the car no problem; however, iirc, you may need to remove the TCA (big actuator) and some heat shields to access the affected area.
Hope this helps. Good luck.
I have a very weird and faint sound from my engine bay at idle. I hadn't associated it with this problem until now. It sounds like gentle beeping, but since nothing could really cause that, it could very well be the precontrol valve squeaking away with exhaust pulses.
Redbul's car makes a similar flapping noise, but only when REALLY stepping on the gas. He's non-sequential but has his precontrol valve still inside. As to whether it's that, or simply the wastegate, I'm not sure. However, my issue shows up even when the wastegate should be closed.
I tried using a GoPro, but it didn't pick up the sound I'm talking about at all. My new exhaust is too loud, it seems.
09-12-17, 10:02 AM
#29
I haven't checked anything since I assembled it. I tore it down to just the manifold sent the turbos to BNR and went back in with new oem gaskets on the turbo and downpipe. I've done quite a few turbo and exhaust manifolds before at work, although never on an FD. I was planning to just have a smoke test done eventually but that cover plate sounds like a good start
Last edited by #slevin; 09-12-17 at 01:24 PM.
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09-13-17, 11:56 PM
#31
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I haven't checked anything since I assembled it. I tore it down to just the manifold sent the turbos to BNR and went back in with new oem gaskets on the turbo and downpipe. I've done quite a few turbo and exhaust manifolds before at work, although never on an FD. I was planning to just have a smoke test done eventually but that cover plate sounds like a good start
I also took a look at some turbos that were out of another car, and I bet my precontrol arm could use some bending or adjusting. If it's out even a little bit, it doesn't close tightly, and makes a very similar noise to what I'm hearing. I'm going to check that next, and I hope I can find the time to do it soon. I'll update the thread with what I find. Not looking forward to getting back in there when I just had my downpipe off a couple weeks ago, but such is FD life.
09-14-17, 08:45 AM
#32
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Loose waste gate or pre control arms could definitely be the problem, it will have a metallic rattle at certain times. That's something you should be able to fix on the car without pulling the downpipe or anything.
The rule of thumb here is after you remove the E-clip that holds the rod to the flapper arm the rod should need to be pulled onto that peg to attach it. With the rod off it should only cover half of the peg, pulling it on should have a slight amount of preload.
The pre control (I think) has a threaded adjustment, SOMETIMES you can actually get it to thread in and out but many times it's so rusted and seized from age it ain't gonna happen. Worst case you can either bend the rod or put 2 washers between the actuator itself and the compressor housing to shim it outwards a little bit.
Dale
The rule of thumb here is after you remove the E-clip that holds the rod to the flapper arm the rod should need to be pulled onto that peg to attach it. With the rod off it should only cover half of the peg, pulling it on should have a slight amount of preload.
The pre control (I think) has a threaded adjustment, SOMETIMES you can actually get it to thread in and out but many times it's so rusted and seized from age it ain't gonna happen. Worst case you can either bend the rod or put 2 washers between the actuator itself and the compressor housing to shim it outwards a little bit.
Dale
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Leaky Axles
09-14-17, 03:29 PM
#34
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Loose waste gate or pre control arms could definitely be the problem, it will have a metallic rattle at certain times. That's something you should be able to fix on the car without pulling the downpipe or anything.
The rule of thumb here is after you remove the E-clip that holds the rod to the flapper arm the rod should need to be pulled onto that peg to attach it. With the rod off it should only cover half of the peg, pulling it on should have a slight amount of preload.
The pre control (I think) has a threaded adjustment, SOMETIMES you can actually get it to thread in and out but many times it's so rusted and seized from age it ain't gonna happen. Worst case you can either bend the rod or put 2 washers between the actuator itself and the compressor housing to shim it outwards a little bit.
Dale
The rule of thumb here is after you remove the E-clip that holds the rod to the flapper arm the rod should need to be pulled onto that peg to attach it. With the rod off it should only cover half of the peg, pulling it on should have a slight amount of preload.
The pre control (I think) has a threaded adjustment, SOMETIMES you can actually get it to thread in and out but many times it's so rusted and seized from age it ain't gonna happen. Worst case you can either bend the rod or put 2 washers between the actuator itself and the compressor housing to shim it outwards a little bit.
Dale
Adding exhaust restriction helped, so I'm not going to rule out the possibility of sticky solenoids. I'm going to add a Grainger valve to the pressure tank to be sure. Of course, the restrictor could have just muted the noise, but I think this is worth checking--especially since I'm staying sequential.
As redbul has said, I hope that the noise isn't from the hinges.
09-14-17, 06:05 PM
#35
Eats, Sleeps, Dreams Rotary
I don't know if I can do it on the car. There's hardly enough room, even from the bottom. My car is RHD so the steering column is big time in the way of the turbos.
Adding exhaust restriction helped, so I'm not going to rule out the possibility of sticky solenoids. I'm going to add a Grainger valve to the pressure tank to be sure. Of course, the restrictor could have just muted the noise, but I think this is worth checking--especially since I'm staying sequential.
As redbul has said, I hope that the noise isn't from the hinges.
Adding exhaust restriction helped, so I'm not going to rule out the possibility of sticky solenoids. I'm going to add a Grainger valve to the pressure tank to be sure. Of course, the restrictor could have just muted the noise, but I think this is worth checking--especially since I'm staying sequential.
As redbul has said, I hope that the noise isn't from the hinges.
09-14-17, 06:14 PM
#36
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Appreciate the continued help, by the way.
