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turbo blows excess pressure, but no BOV??

buddy said:
Mine is kind of like Chris'

I didnt notice the turbo whistle until I put on the cone filter, but now its pretty loud. and with performance E-PROM it got louder and quicker. When I take my foot off of it after accelerating I can hear a little woosh, but just think its the blades slowing with that pressure difference pre and post turbo.
Click to expand...

Same noise mine has made ever since the addition of the cone filter. No housing rub, no bad bearings, no intake leaks.

One of us needs to make a recording of the sound and post it up.

It sounds really bitchin'
 
matuva:..

yes.. that loud swoosh sports cars make..

same scenario.. soon as i chop the throttle from anything above 3/4


Chrisk1500:

very similiar, but very noticeable.. just like a turbo sports car

more like.. (floor it)..... sssSSSSSSSSSS (chop throttle) SWOOSH!!!

and repeat whenever i cycle the throttle. the blow off/swoosh is louder than the boosting whine


ive checked for leaks, and oil seapage as you guys mentioned, nothing,, just the hint from the CDR, which is apparent its coming from there, the inlet ducting is all tight, i do however have a naked K&N, but the swoosh was never this loud.. the silencer is there, and connected properly, and i JUST checked the shaft play, just now, so i can reply, and none, the turbo spins nicely, no rubbing,

and ratman, im going to do that, i have to find a passenger willing enough to hang out of the window and record it while i drive.. it only does it under power

it's just throwing me off, the swoosh wasnt this apparent before i switched to synth oil.. as i mentioned the engine spins ALOT easier now.. and maintains highway speeds uphills with very minimal loss of MPH, nothing like before..

unless i have an intake leak thats not readily apparent..

i knew this much swoosh wasnt normal... lol... just didnt sound right

ok, have to take the intake off anyway while installing the boost gauge, so maybe ill reseal it, im assuming theres a gasket under there right? should i ask for the "upper intake gasket"? "plenum gasket"?
 
Ok, I've corrected my previous post ^ to read 'stock GM 6.5TD', like at 7-8 psi, which post is intended to encourage complete diagnosis and preventive maintenance - sheesh!................
 
Yes the 'blow off' sound is much louder than the boost whistle....your truck is normal....

I just didn't change font size like you did....LOL

Same sound....
 
gmctd said:
Ok, I've corrected my previous post ^ to read 'stock GM 6.5TD', like at 7-8 psi, which post is intended to encourage complete diagnosis and preventive maintenance - sheesh!................
Click to expand...

No worries here!! :D

I knew what ya meant the first time.:thumbsup:
 
Turbine Doc said:
Don't forget WG is always closed on GM-X turbo unless PCM wants less boost, what PCM is doing to regulate boost is dumping exhaust gas by opening the WG so less exh gas is driving the turbo ergo less boost produced; as stated earlier, no throttle plate going shut so no need for a BOV,
Click to expand...

Is the wastegate operation detailed in another thread somewhere? What is moving to deflect exhaust away from turbo when it is "open", becuase I would think it would "close" the gate to deflect the exhaust away from the pipes. I really dont know, just wondering....Thanks
 
buddy said:
Is the wastegate operation detailed in another thread somewhere? What is moving to deflect exhaust away from turbo when it is "open", becuase I would think it would "close" the gate to deflect the exhaust away from the pipes. I really dont know, just wondering....Thanks
Click to expand...

Real basic, waste gate normally closed,Vacuum solenoid is allowing full vacuum to the waste gate actuator holding the exhaust bypass flap in the housing closed. As the PCM decides that boost is exceeding the required normal or expected normal it de-energizes the solenoid on a pulse modulated signal, the vacuum waste gate actuator then looses vacuum and the exhaust flap in the turbine housing opens and lets exhaust energy bleed past the turbine wheel thus effectively by passing the turbo and limiting the boost. There are other factors such as defueling because of over boost and IAT (intake air temp) over normal or coolant temp out of range. They both affect the amount of fuel delivered in the DB-4 set up.
 
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so at idle is 16psi full vacuum and the wastegate is closed allowing all exhaust at idle to go past the turbine, and when we start moving about 35mph it opens it up to not let any boost?

When I read it is always closed I thought that meant when the truck is off its closed until the PCM does something like apply vacuum at idle.
 
correct buddy,

wg is always closed, and opens with reduction of vac to WG actuator via PCM/WG solenoid control, when PCM see "high boost" or boost too far of the boost schedule for a given rpm.power need, vac is vented, less drive gas to the turbo and less boost produced.

This is why bad wg solenoid, or bad vac pump causes black smoke and low power, PCM sees low boost and adds fuel to correct it, even with a floored APP

In a high boost situation the PCM opens wg 1st to lower boost if it remains high, then it defuels,

which is why a reflash or boost fooler is required so PCM either gets a new boost/fuel/timing curve to work with, or you lie to PCM with a fooler so it doesn't know you are making high boost and does not try to open the wg for lowered boost.
 
My 95 Western Star with the 500 Cat will bark real good if I back off right quick during a shift with the boost at 30+ PSI.

Sounds like a horse coughing real loud.

Most folks dont know what causes it.

MGW
 
Any problem with those shattering the fan or breaking the turbine shaft?
 
FWIW i just installed a TM and I have stock 'puter... I set it 1/4 less than the 2" they recommend for 15psi WOT.

I'm heavy, at 10k lbs at times, and climbing large hills on highways I peak 9 boost max, no codes, no defueling.

EGT's dropped on same stretches of highway from 900's to 6-700's pre turbo.

I have no exhaust done yet, (long story), and guages were my first mod.

Boost is strong and steady and the engine loves it.

Just so you know, that boost goes right into the cylinders, so when you let off the pedal, that boost in the intake gets immediately used up in the engine (thats what its for), and does no harm, only good. No reason for a dump valve or anything.

Diesels are giant air-pumps. More air you can push in there (without blowing head gaskets) the better. Most say 15psi is safe.

I havn't let mine hit 10. Once exhaust is done and perhaps a reflash I will adjust it higher, just to give it a fair chance comparison to ATT :).

My hardest dilemma will be to do ATT before or after reflash.

This is summer-time stuff.... And I'll need 6 new skins before that, and pay off the onslaught of winter bills in this junk economy.
 
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