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turbo blows excess pressure, but no BOV??

G

ghost183

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i switched to synth yesterday, and today ran the truck.. engine spins easier and i now own a rev happy turbo..

i've heard it before, but not this apparent..

under quick on /off throttle applications, in the power band (1600-2200), im sure you guys hear the boost pressure blowing out from the turbo/intake?

my question is.... how? we dont have a blow off valve? how/where is it blowing out from? or in to?

or do we have one and im just blind?!?!?!

i looked and cant find one and im dying to know how is the pressure being bled under full boost to slamming the throttle shut conditions!?!

ok, its agiven, 8-10 pounds isnt something to brag about, but its still excess pressure thats going somewhere?!?!

kinda reminds me of those little jap cars riding the turbo, stop light to stop light, vroom/swoosh.... vroom/swoosh....
 
There is no throttle shut function, air will just keep pushing in, on a diesel, no air throttle, just fuel throttled.

our diesel runs "lean" if you think like gasser, the more air it can get the better.

My GM service manual says the PCM uses the boost sensor to determine how much fuel it can add, but no one on this forum will believe that, so maybe it was a copy and paste from a gasser boost sensor.
 
no it doesn't blow it back into the exhaust. the wastegate simply stops the turbo from building more pressure by diverting the exhaust away from the fan on the exhaust side. Any "excess air" is used by the engine fast enough that it is not a problem. If you have a boost guauge you will see this excess air as a spike or peak that doesn't last very long.
 
ak diesel driver said:
no it doesn't blow it back into the exhaust. the wastegate simply stops the turbo from building more pressure by diverting the exhaust away from the fan on the exhaust side. Any "excess air" is used by the engine fast enough that it is not a problem. If you have a boost guauge you will see this excess air as a spike or peak that doesn't last very long.
Click to expand...

oh, so that spike in pressure is actually bled into the engine.. ok.. sounds more feasable i guess.. must be safe for the engine considering it was designed that way right?.. but let me ask you something, when cruising, and i kill the throttle, i notice the engine kinda keeps spinning for a sec or 2, no power, just spinning along, that must be the excess pressure in the intake tract right? my soosh actually lasts about 1-2 secs

ok, so since the wastegate is controlled by the ECM, im assuming a boost fooler and heaths TM would create more excess pressure correct? would that be safe?

it kinda worries me all that pressure and no where to go except into the engine, unless ofcoarse the engine running lean isnt anything to worry about??

can a BOV be installed on the intake with no ill effects?
 
ghost183 said:
oh, so that spike in pressure is actually bled into the engine.. ok.. sounds more feasable i guess.. must be safe for the engine considering it was designed that way right?.. but let me ask you something, when cruising, and i kill the throttle, i notice the engine kinda keeps spinning for a sec or 2, no power, just spinning along, that must be the excess pressure in the intake tract right? my soosh actually lasts about 1-2 secs


no that's just the inertia of the engine.


ok, so since the wastegate is controlled by the ECM, im assuming a boost fooler and heaths TM would create more excess pressure correct? would that be safe?


within reason yes


it kinda worries me all that pressure and no where to go except into the engine, unless ofcoarse the engine running lean isnt anything to worry about??


no its not


can a BOV be installed on the intake with no ill effects?
Click to expand...

i suppose it could but it isn't necessary
 
The air pressure wont hurt anything. The "leaner" the better.

You can adjust the turbomaster to do less PSI or more PSI than the ECM will with the vacuum wastgate acuator. The turbomaster will just adjust based on the amount of backpressure built up in the exhaust based on the amount of fuel you are dumping into the engine.

The boost fooler is to allow the ECM not to defuel the engine based on the boost sensor on the intake. The Turbomaster might be able to make damaging pressure of over 15psi, but it has nothing to do with after you take your foot off the gas.
 
ghost183 said:
i switched to synth yesterday, and today ran the truck.. engine spins easier and i now own a rev happy turbo..

i've heard it before, but not this apparent..

under quick on /off throttle applications, in the power band (1600-2200), im sure you guys hear the boost pressure blowing out from the turbo/intake? my question is.... how? we dont have a blow off valve? how/where is it blowing out from? or in to?

or do we have one and im just blind?!?!?!

i looked and cant find one and im dying to know how is the pressure being bled under full boost to slamming the throttle shut conditions!?!

ok, its agiven, 8-10 pounds isnt something to brag about, but its still excess pressure thats going somewhere?!?!

kinda reminds me of those little jap cars riding the turbo, stop light to stop light, vroom/swoosh.... vroom/swoosh....
Click to expand...


do you mean the same sound that we can hear on turbo sport cars, e.g WRX Subaru?
I had this noise with my previous GM-5 turbo, especially at the moment I release the accelerator after flooring it...
Never know how she made that.
This has disappeared with my A-team turbo...
 
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,
 
If you are hearing a wooshing sound (other than the normal turbo whistle) you may have a leak between the intake air plenum and the manifold or possibly the turbo and air plenum at the connector hose.

A diesel runs full on air all the time (As much as it can take in) there is no "Lean" condition as with a gasser where the fuel is mixed with air and then ignited with a spark plug.

The measured amount of diesel fuel is shot into the combustion chamber (precup with a 6.5) and the fuel ignites on contact with the super hot compressed air and burns.

The amount of fuel dictates the amount of power and RPM the engine will produce.

I am not certain why you would see so much of a difference in operation by simply changing your oil over to synthetic.
This is not a normal occurence. Synth is not all that different and any differences you might see would take very specialized instruments to measure.

Hate to toss cold water on a happy campfire but I am thinking this new found whizzz has been born of wishful expectations.

I have switched 6.5's back and forth from dyno to synth and never saw any effects whatsoever.

The synth may have some benefits as far as overall longevity of the engine when used in a comprehensive maintenance package with recommended service intervals.

As far as performance, the gains will be miniscule.

Best

MGW
 
I agree with Missy,

I think you have a leak on the intake side somewhere. I never hear any noise even remotely similar to Blow Off, except for that one time when the hose connector between my turbo and upper intake manifold was loose. Tightened her up, and voila, no more "blow off valve" sound.
 
i think he is hearin' the turbo BARK.....it happens when it stalls of a split second goin' up or down in rpm...the burb does it when it hits OD...
 
ghitch75 said:
i think he is hearin' the turbo BARK.....it happens when it stalls of a split second goin' up or down in rpm...the burb does it when it hits OD...
Click to expand...

Yep, I agree. Some people also refer to it as "blowback".

On my manual trans, it is particularly noticeable if I take too long in between gears.

As the turbo spools down after making boost, the compressor wheel reaches a point where it can no longer maintain manifold pressure (dead-heading, or stalling), so the accumulated pressure that is in the manifold (that is essentially acting as an air receiver) blows back and escapes back through the inlet of the compressor wheel. It is actually a very cool sound when it happens.

The GM-X turbos seem to have this characteristic more-so than others.
 
I agree - sounds like that is the noise (bark) he is referring to. Typically you won't really hear the bark 'cause GM designed a silencer into the mix. Probably thinking that sound would cause people to stop dead in their tracks and turn right around and go back to the dealership and say "fix that".

The "silencer" is that black, plastic tube that comes off the air intake (after the filter) and runs towards and along the front of the engine. Take the tube off, plug the hole and you'll really hear the bark (especially if you have and open element filter)! Plus, you'll hear the turbo whine a bit more.

As Robin said, I don't understand how synth would change the turbo response by anything even close to being measurable. That's a odd one....
 
Either a leak in the Boosted intake system, including compressor housing loose on the cartridge flange, or the syn loosened up excessively worn turbo bushings\shaft and the compressor blades are contacting the housing, which can also happen if the housing is loose on the flange - check that housing\flange joint-seam for heavy oil leakage, due to normal CDR function - then remove the inlet duct from the compressor, work the shaft in\out, up\down, side-to-side, noting any excess shaft movement, also noting any fan-to-housing contact, no matter how slight - first contact can make a whoosh-similar noise - then check the Boost coupling hose for loose clamps\rips\tears - then check the IAT and MAP sensor o-rings for live rubber - then check the 6 intake plenum bolts for loose - plenum gasket could also be blown - Boost-guage fitting could be loose in intake plenum or loose tubing nut, tubing could be cracked, or tubing fitting at guage inside cabin could be loose - stock GM 6.5TD's don't make quote\unquote "blow-off" whooshes at 7-8psi Boost unless neglected or shade-tree engineered

Word up, dudes...................
 
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Mine makes the same sound...

It goes like this...

Pssssssss.......woooooooooosh......pssssss

The 'psssss' is the normal turbo whistle and the 'woooooosh' is the sound it makes when the truck shifts....
 
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.
 
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