Really need help determining the cause of this sound!
04-22-2003, 02:23 PM
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Really need help determining the cause of this sound!
<a href="http://www.personal.psu.edu/users/c/w/cwt106/ist210_cwt106/smoke.avi" target="_blank">http://www.personal.psu.edu/users/c/w/cwt106/ist210_cwt106/smoke.avi</a>
I am posting this in a new forum because I really want to figure my problem before I drive 3 hours to Hershey this Saturday. Listen for the noise when I shift at hi rpms.
Another thing I have noticed since I bought the car was the light underneath the hood seems to flicker at hi rpms occassionally, or at least this is what I think it is. The light is from the exact spot the light under the hood is at. It seems just as if it flickers at hi rpms due to a short or the hood unlatching slightly. Now I am starting to think though it may have to do with all of this.
When I shift at hi rpms it occassionaly makes the noise you hear in the video. It sounds like something isn't closing all the way or that a lot is getting dumped from the turbo. Other 944 turbo owners have been in it and don't think it is a problem, but I am concerned.
Take a look at all my modifications (keeping in mind I have an upright wastegate as opposed to the normally upside down wastegate). It has been running this way since it has been checked out, and I do not feel any loss in power or differences in the car.
I am posting this in a new forum because I really want to figure my problem before I drive 3 hours to Hershey this Saturday. Listen for the noise when I shift at hi rpms.
Another thing I have noticed since I bought the car was the light underneath the hood seems to flicker at hi rpms occassionally, or at least this is what I think it is. The light is from the exact spot the light under the hood is at. It seems just as if it flickers at hi rpms due to a short or the hood unlatching slightly. Now I am starting to think though it may have to do with all of this.
When I shift at hi rpms it occassionaly makes the noise you hear in the video. It sounds like something isn't closing all the way or that a lot is getting dumped from the turbo. Other 944 turbo owners have been in it and don't think it is a problem, but I am concerned.
Take a look at all my modifications (keeping in mind I have an upright wastegate as opposed to the normally upside down wastegate). It has been running this way since it has been checked out, and I do not feel any loss in power or differences in the car.
04-22-2003, 03:36 PM
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I'm not sure starting a new thread is going to help. It's almost impossible to diagnose something via video, so you are going to have to help.
It sounds like it happens BEFORE you shift, not as or after you shift. Is that correct?
I also don't see how the light flickering can have anything to do with something coming out the exhaust, although stranger (not much) things have happened.
It doesn't look black, so you can pretty much rule out fuel, unless the video is deceiving.
You need to pull the plugs, take some pics, and post them.
Take a look at the tops of the pistons as well. Note if one of them is shiny and clean.
The position of the wastegate should not matter. If you are able to build boost "quickly" and it holds at 14psi, then it's fine.
It sounds like detonation or a slight misfire and it looks like coolant out the exhaust.
-Matt
It sounds like it happens BEFORE you shift, not as or after you shift. Is that correct?
I also don't see how the light flickering can have anything to do with something coming out the exhaust, although stranger (not much) things have happened.
It doesn't look black, so you can pretty much rule out fuel, unless the video is deceiving.
You need to pull the plugs, take some pics, and post them.
Take a look at the tops of the pistons as well. Note if one of them is shiny and clean.
The position of the wastegate should not matter. If you are able to build boost "quickly" and it holds at 14psi, then it's fine.
It sounds like detonation or a slight misfire and it looks like coolant out the exhaust.
-Matt
04-22-2003, 03:42 PM
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<a href="http://www.personal.psu.edu/users/c/w/cwt106/ist210_cwt106/Smoke.avi" target="_blank">http://www.personal.psu.edu/users/c/w/cwt106/ist210_cwt106/Smoke.avi</a>
04-22-2003, 03:44 PM
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The noise occurs immediately when I shift. It is the sound you hear not as the smoke is coming out, but as I come around the bend and shift u can hear a different noise.
04-22-2003, 03:46 PM
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Pull the little hose off your turbo bypass valve (sometimes referred to as blow off valve or BOV) and see if it holds vacuum (suck on it or use a vac tester). A turbo will do a stuttering sound in between shifts if this valve is breached. If it doesnt hold vac. replace it quickly w/ the updated 993 valve or aftermarket valve of your choice.
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04-22-2003, 03:53 PM
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Matt - you have it EXACTLY RIGHT!! It makes a stuttering sound in between shifts.
Keep in mind there are only 45,000 miles on the turbo in my car. Would it really detonate this early? It has only run at a maximum of 14 psi.
Keep in mind there are only 45,000 miles on the turbo in my car. Would it really detonate this early? It has only run at a maximum of 14 psi.
04-22-2003, 04:13 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by badass951:
<strong>The noise occurs immediately when I shift. It is the sound you hear not as the smoke is coming out, but as I come around the bend and shift u can hear a different noise.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Then its probably the bypass valve. Is it stock?
I think you have multiple problems.
1) Coolant leaking (too many possibilities to list, but probably from an over-pressurized system, see 2)
2) detonation and possible blown head gasket
3) blown bypass valve
-Matt
<strong>The noise occurs immediately when I shift. It is the sound you hear not as the smoke is coming out, but as I come around the bend and shift u can hear a different noise.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Then its probably the bypass valve. Is it stock?
I think you have multiple problems.
1) Coolant leaking (too many possibilities to list, but probably from an over-pressurized system, see 2)
2) detonation and possible blown head gasket
3) blown bypass valve
-Matt
04-22-2003, 04:14 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by badass951:
<strong>Matt - you have it EXACTLY RIGHT!! It makes a stuttering sound in between shifts.
Keep in mind there are only 45,000 miles on the turbo in my car. Would it really detonate this early? It has only run at a maximum of 14 psi.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Miles doesn't matter... turbo doesn't matter... It has too do with temps and a/f ratio.
-Matt
<strong>Matt - you have it EXACTLY RIGHT!! It makes a stuttering sound in between shifts.
Keep in mind there are only 45,000 miles on the turbo in my car. Would it really detonate this early? It has only run at a maximum of 14 psi.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Miles doesn't matter... turbo doesn't matter... It has too do with temps and a/f ratio.
-Matt
04-22-2003, 04:33 PM
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Temps and A/F have been fine since this cars existence. I just spoke with the original owner and after seeing the video he is positive I should just check the manual boost lines and ensure they are getting the proper pressure and not leaking. The 993 valve has already been installed on the car and the head gasket has been replaced all since new and it is only 45,000 miles old.
Also, the smoke is from unburnt fuel while running rich at hi revs I believe.
Also, the smoke is from unburnt fuel while running rich at hi revs I believe.
04-22-2003, 06:29 PM
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After going out to look over everything on the car again, the previous owner and I are most positive it is going to be the bypass valve causing the fluttering-metallic sound. Looks like I will either replace this this week or have someone help me down in Hershey.
If anyone has any other ideas please let me know.
If anyone has any other ideas please let me know.
04-22-2003, 06:51 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by badass951:
<strong>
Also, the smoke is from unburnt fuel while running rich at hi revs I believe.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">All it takes it one bad tank of gas...
Regardless, fuel/rich is black. That stuff coming out of your exhaust doesn't look black from my view.
-Matt
<strong>
Also, the smoke is from unburnt fuel while running rich at hi revs I believe.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">All it takes it one bad tank of gas...
Regardless, fuel/rich is black. That stuff coming out of your exhaust doesn't look black from my view.
-Matt
04-22-2003, 06:56 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by badass951:
<strong>Temps and A/F have been fine since this cars existence. I just spoke with the original owner and after seeing the video he is positive I should just check the manual boost lines and ensure they are getting the proper pressure and not leaking. The 993 valve has already been installed on the car and the head gasket has been replaced all since new and it is only 45,000 miles old.
Also, the smoke is from unburnt fuel while running rich at hi revs I believe.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">So, are you saying the head gasket has already been replaced? If thats the case, then the fuel/temps haven't always been correct, unless they just did it for fun. Which is possible... not likely, but possible.
-Matt
<strong>Temps and A/F have been fine since this cars existence. I just spoke with the original owner and after seeing the video he is positive I should just check the manual boost lines and ensure they are getting the proper pressure and not leaking. The 993 valve has already been installed on the car and the head gasket has been replaced all since new and it is only 45,000 miles old.
Also, the smoke is from unburnt fuel while running rich at hi revs I believe.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">So, are you saying the head gasket has already been replaced? If thats the case, then the fuel/temps haven't always been correct, unless they just did it for fun. Which is possible... not likely, but possible.
-Matt
04-22-2003, 07:17 PM
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Matt, you make a valid point here. If he headgasket was replaced there probably was a problem in the past. For some reason that slipped my mind.
The bypass valve must be the problem though. I have spoken with a 944 specialist and the previous owner today, and both think the fluttering sound during shifts is the bypass valve. I will remove it tomorrow and see if air is drawing through it. If so, looks like I need a new one.
The bypass valve must be the problem though. I have spoken with a 944 specialist and the previous owner today, and both think the fluttering sound during shifts is the bypass valve. I will remove it tomorrow and see if air is drawing through it. If so, looks like I need a new one.