heard strange noise...wastegate / turbo related??

[traxshin]

hey,

about 3 weeks ago i did the 6637 intake. since then i began hearing what i think is the wastegate relieving pressure whenever the truck shifts or if i let off the pedal. actually, as you know, this sounds pretty cool and i like it.

this morning, when i left for work i had to pass a truck a couple miles down the road. this pass needed no more than 3/4 pedal. when the truck shifted back into o/d, i heard the wastegate functioning but i also heard a really weird sound with it. hard to explain. almost like a screech sound...or the sound of two parts briefly rubbing together. this ONLY occurs when the wastegate is relieving pressure which ofcourse is just a brief moment.

now whenever the truck shifts (at rpm's high enough to have the wastegate function) i hear that sound.

the turbo itself sounds fine. no drivability problems. only the sound i described seems wrong.

again...its like a screech sound only when the wastegate is functioning. kinda reminds me of some kind of plastic on plastic sound. i haven't had a chance to pop the hood yet...i just got to work.

any thoughts??

thanks in advance

[traxshin]

so i was just searching the net while waiting on an answer and found on one of the other sites that this sound of the backpressure relieving itself upon shifting (hiss sound) may not actually be a good thing. it was said to be "surge" which apparently can be corrected by an ATS housing. i never heard the hiss until i put on the 6637 and ofcourse thought it was cool.

now im really confused. i only know some of the basics when it comes to these motors but nothing technical.

now im getting really confused...anyways, back to the original question posted above.

thanks

by the way...no chip / no gauges yet...stock except for mods listed below

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Last edited by traxshin : 01-07-2009 at 04:53 AM.

[traxshin]

[traxshin]

anyone??? im beggin now j/k. again, i dont have gauges but the strange noise probably only occurs upon shifting when probably atleast 10 or more pounds of boost is built up. remember, stock motor.

[RRonning1984]

I have heard it is bad to but I am not sure why. I will give ya bump

[Jake]

What you are hearing is not the wastegate. You will never hear the wastegate. The wastegate is on the exhaust side of the turbo and routes exhaust gasses around, bypassing the turbine wheel to prevent over spooling. What you are hearing is because of the RPM drop, the engine itself is not taking as much air, so there is excess air in the intake system, and the noise is just the excess air backing up through the compressor wheel. The noise when it shifts and when you let off the throttle isn't really harmful. Surge, however, can cause serious turbo damage, from bending the compressor fins backwards to snapping the shaft. You will hear surge when you have the engine under load, and you will hear kind of a rapid "ch ch ch ch ch". It sounds like the noise you are already hearing, only does it constantly and rapidly.

[traxshin]

Originally Posted by cob32187

What you are hearing is not the wastegate. You will never hear the wastegate. The wastegate is on the exhaust side of the turbo and routes exhaust gasses around, bypassing the turbine wheel to prevent over spooling. What you are hearing is because of the RPM drop, the engine itself is not taking as much air, so there is excess air in the intake system, and the noise is just the excess air backing up through the compressor wheel. The noise when it shifts and when you let off the throttle isn't really harmful. Surge, however, can cause serious turbo damage, from bending the compressor fins backwards to snapping the shaft. You will hear surge when you have the engine under load, and you will hear kind of a rapid "ch ch ch ch ch". It sounds like the noise you are already hearing, only does it constantly and rapidly.

ok, thank you sir. so from what i gather...this new found noise under moderate boost upon shifting may not be a big deal.

this surge you speak of i have never noticed as it has never made a strange / abnormal noise under any load.

i guess that makes me feel better right now but i wish i knew exactly what the heck this is.

thank you much

[NCHornet]

Cob has done a great job of explaining it. The noise has probably always been there and you are simply noticing it more with the open air intake. Trust me you will know surge when it happens. If you don't tow you probably will never encounter it. Surge almost sounds like a helicopter prop and it will get your attention quick. Get those gauges in and you will be doing fine. Now can you go back to sleep, lol!!!

NCH

[traxshin]

Originally Posted by NCHornet

Cob has done a great job of explaining it. The noise has probably always been there and you are simply noticing it more with the open air intake. Trust me you will know surge when it happens. If you don't tow you probably will never encounter it. Surge almost sounds like a helicopter prop and it will get your attention quick. Get those gauges in and you will be doing fine. Now can you go back to sleep, lol!!!

NCH

ok thanks...thats definitely more reassuring. i was fine with the hiss noise it was just at moderate boost levels there was a strange sound developing briefly during the hiss sound (only while the tranny shifted - non tranny related). as long as that strange sound may be normal that occurs w/the hiss is what you are talking about im fine with that and will carry on.

yeah...sleep - whats that? 3 1/2 hours last night and now im at work. this sucks. looks like ill be sleeping when i get off today.

thanks.

[Jake]

Your welcome man, if you ever got any more questions my PM box is always open.