screaching turbo...

[14.5 drift]

Whaassup guys. This is my first of many posts to come, and I hope I am not too much trouble with all my questions. First off i just bought a 96 gsx auto. This car is awesome and I love it (had it for a hole day now) As the thread is titled some times, only during hard driving, my turbo will make a loud screaching sound that does not sound good. It seems like it happens when the rpm's are up and I am hardly on the throttle or better yet down shifting. It happens some times and I dont really know what I was doing at the time but some time with the rpm's high I believe. What could this be? And one more, what does a bov do? I have a ton more questions to lay on you guys, please be patient with me. My first turbo car and i dont wanna F it up. Nice to meet every one and thanks for your feed back

 

[Lordpaxin]

Hi,
Welcome to the community.

First off, how are you sure its comming from the turbo. Is there any drivibility differences when its making the said noise, as compared to driving when tis not doing it. such as, does it feel more responsive normal, and sluggish during the noise? at higher boost levels or does it occur regardless of boost level, and does any specific gear create this noise, or change the pitch or occurancy.

The BOV vents the pressure generated by the turbocharger when the throttle plate is closed.

Imagine, 10psi of air flowing into the engine and SLAP you let off the throttle, that pressurized air has to go someplace, having it slam back into the turbo is not good, so when the intake pressure drops back to a vacuum that negative presssure opens the blow off valve, and the excess pressurized air bypasses the turbo, and enters the intake tract before it. so this air already being read by the MAF sensor can enter the system again.

 

[14.5 drift]

Why would you want to put all that hot air into the intake? Why not release it into the air under the hood or some thing?

Back to the top, yes when the noise happens it takes a lil longer for the throttle to respond. What happened was i was in second gear and charged it up to 60 then let off the throttle. I was still in second doing an engine brake. I wonder if this has any affect on a turbo. The screaching noise seemed to fluctuate according to the engine speed.

 

[nine5raptor]

Originally posted by 14.5 drift
Why would you want to put all that hot air into the intake? Why not release it into the air under the hood or some thing?

When the air decompresses it cools back off quite a bit.

For your 'average driver', hearing the car go "PSSSHHHHH!" loudly would be a bad thing. Most factory turbo cars reroute the bypassed air back into the intake to keep things quiet.

Back to the top, yes when the noise happens it takes a lil longer for the throttle to respond. What happened was i was in second gear and charged it up to 60 then let off the throttle. I was still in second doing an engine brake. I wonder if this has any affect on a turbo. The screaching noise seemed to fluctuate according to the engine speed.

My t-25 used to do that some. I never bothered with figuring it out. It seems like it is overspeeding (think of a boat prop that is going too fast and just churns the water instead of moving the boat).

 

[ConquesTSi]

i know if a turbo is "going out" it can make a "screaching" type noise (usually a very bad thing)...i'm not sure if this is what is happening, but it's worth looking into.

 

[14.5 drift]

No biggie. My first mods will be big 16 and large front mount. I am aware the car needs supporting mods to turn up the boost, but if I leave it at 10 psi with every thing stock will the car be fine? I think the injectors might need to be upgraded but as for the rest of the car will it be able to support this??

 

[Whitetal]

Originally posted by 14.5 drift
Why would you want to put all that hot air into the intake? Why not release it into the air under the hood or some thing?

The air is measured by the mas/maf, releasing the air to the atmosphere screws up the calculations and you get a bad air/fuel ratio. Causes bogging and you loose performance.