Blow Off Valve

[Diesel Freak]

Has anyone figured this one out, or do I have to build my own?

 

[Mark_Kendrick]

What are you wanting to do with it?



There are blow off valves available from gasser turbo houses. I'm thinking of using an external wastegate for a blow off.

 

[Todd T]

 

[Diesel Freak]

Originally posted by Mark_Kendrick

What are you wanting to do with it?



what do you think I am going to do with it









There are blow off valves available from gasser turbo houses. I'm thinking of using an external wastegate for a blow off.

I know they are available... using a wastgate as a BOV is just overkill, and way too expensive. I already have the control system... just doing a little fishing.

 

[GDouglas]

Do we really need a blow-off or bypass valve on a diesel? The main reason that they are on a gasser is that when you are under boost and then let up off the throttle by closing the throttle butterfly, then the boost that is still coming from the turbo has nowhere to go. It just bounces off the mostly closed throttle plate and goes back through the turbo backwards giving that distinct noise back through the air filter. When all this boost air goes backwards through the turbo, it puts one hell of a thrust load on the turbo shaft that the bearings have to stand up to. Since we don't have a throttle plate to regulate air on a diesel, then the boost on decel just keeps going through the engine to cool off the exhaust gas.

 

[Diesel Freak]

GDouglas, have you ever barked a turbo?

 

[Blair]

It would have to be a really large valve. Be nice if it opened when you pushed the clutch in.

 

[Mark_Kendrick]

Gdouglas. .



try backing out of the throttle at 30psi and 1900rpm. . "WHHHOOOOOMMMPP!!!!" is what you hear. that is a bark.



"Barking" is actually flow reversal through the turbine. It drastically slows the turbine and causes lots of lag before boost gets back up.



L8r,

mark

 

[Agades]

Originally posted by Mark_Kendrick

Gdouglas. .



try backing out of the throttle at 30psi and 1900rpm. . "WHHHOOOOOMMMPP!!!!" is what you hear. that is a bark.



"Barking" is actually flow reversal through the turbine. It drastically slows the turbine and causes lots of lag before boost gets back up.



L8r,

mark

can u say "wreckn bearings"?

 

[Mark_Kendrick]

It's a big reason for some of the hx40 problems.



The B1 handles barking very well. Large bearing journals and shaft. All around heavy duty stuff. It's almost eerie the way it spools up so well.

 

[Diesel Freak]

woo hoo it is Christmas time, just got my new turbo..... OMG the inducer is huge, I think I will be needoing that BOV really bad! This thing is going to spool like there is no tomorrow!

 

[Mark_Kendrick]

DF,

What'd ya get???

 

[Diesel Freak]

A turbo.

 

[Mark_Kendrick]

no sh!#!!!!!!



what turbo?? brand? rough model#?



l8r,

Mark

 

[GDouglas]

I see what you guys are refering to now. The term blow off valve immediately had me thinking for a relief on the compressor side. One of you guys mentioned flow reversal on the turbine side is what causes the "bark". Is the "bark" the sound of the turbine side cavitating? Sorry for getting on anyones nerves, but on gassers we never really have to think about the turbine side much except for an efficient wastegate setup.



I will follow this thread for any more responses. You guys have awakened my curiousity since I have never had to deal with the "bark" noise, at least not yet.



Thanks for your patience and any further info on the subject. I am never too old to learn!

 

[HillCountrykid]

Banshee?

 

[Mark_Kendrick]

It is for relief on the compressor side. The comressor is a turbine also.



The bark is the flow reversal or cavitation of the compressor wheel on the turbo.



there is only a problem with this at high boost (at least 20 psi). when the foot comes off the pedal the drive pressure on the turbine is almost instantaneously removed leaving the compressor with little energy to maintain flow. the compressor stalls and the flow reverses through the compressor all but stopping the turbine shaft.



REALLY HARD ON BEARINGS AND SHAFTS!!!!



later,

Mark

 

[Diesel Freak]

Yes it is the Banshee.



Currently I have the wastgate cut back to 25 psi untill it breaks in. I did some spool up tests..... brought the engine down to 1300 RPM in 6th, let boost fall to zero, and feathered into the fuel... 20 psi of boost occured by 1500 RPM. This turbo is weird sounding..... there is little "turbo whine" below 20 psi..... it sounds like a hungry big block sucking through a 750 double pumper. Just a loud "sucking/whooshing sound" after 23 PSI the turbo whine becomes apparent. There is no silencer ring in this turbo.



Boost at 2000 rpm in 6th cruising at 75 MPH is 12 PSI.



I think this may be a good turbo for the <350 HP engines... . we will see after it breaks in.

 

[Mark_Kendrick]

That doesn't sound like a yamaha quad. . what is it the 'Banshee'?

 

[Diesel Freak]

GDouglas, a turbo 'bark' is the same on a Diesel as on a gas engine..... once us crazy BOMBers go past about the 350HP mark, we need a huge ammount of air. If one were to side step the throttle at over 30 PSI of boost the lack of drive pressure with excess boost pressure and a spinning down turbo can cause the compressor to surge... and at worst case stall and reverse direction... a BOV will allow the venting of the air when the throttle lifts to a pre-set point (or the clutch is initially depressed) and boost pressure is over a pre-set pressure.