For those of you who don't know, &quot;barking the turbo&quot; is the sound you hear when you suddenly come off of full throttle and since the turbo is no longer being driven by the fuel expansion on the exhaust side, cannot maintain the pressure on the intake side. The pressurized intake charge rushing back out of the intake causes a weird noise from the air filter housing. The noise varies, depending on the amount of fuel being fed into the engine. It probably also blows your air filter clean. Note: This does not normally make a noise on trucks without high performance fueling boxes. <br><br>I wonder if, and how much damage this can do to the turbo, or anything else in the intake system. I have just been reading about the Turbo Guard, at BD, and wonder if anyone has had a turbo failure attributable to barking the turbo.<br><br>This is what I was reading:<br>BD Turbo Guard<br><br>Thanks,<br>Chris

 

Looking around one day on the internet I found info on this very subject. I believe it was on the diesel ram .org site and also the Holset site. What I read was that turbo barking is not bad. There is no damage to the turbo and the impeller doesnt turn the other direction like some think. I even called some turbo shop site links to find out first hand. Not one shop even heard of such a thing??? NOT ONE. I would think if the guys that build turbos dont bother with turbo barking then I wasnt going to worry about it either. Now I see BD has a Turbo Guard. ??? Well I dont know. If there is such a problem why dont they make or install a pop off valve? If I can find the info I was refering to I will show you.

 

The bark is caused when the pressure on the intake side exceeds the pressure from the turbo. In other words you've built high pressure in the system and you let off, the boost will try to go back through the turbine compressor. It's not that the turbine is spinning backwards but that it is slowing down very rapidly as the air reverses direction through it. Think of the shaft turning 100,000 rpms and coming to a stop in under a second. The rotational torque on the small shaft would be pretty substantial. The shaft is very small and the high torque from this slow down or attempt to back spin can cause the shaft to break (wring off). The shaft breaking is usually causes by boost pressures much higher than stock. They will occur at 30+ pounds. Again, it's not that the shaft is spinning backwards but that it is acting as though it's going to because of the rapid slowing effect of the backward air flow through the compressor blades. The boost will bleed off before the blades actually spin backwards except in the case of extremely high boost.

 

In the gasser world, the sound you're referring to is not usually called turbo bark, I refer to it as wastegate flutter. The only time I think it will have any ill effects is when compressor slam occurs. I've never experienced it personally, but I've been told that it's very noticeable. In turbo gassers, depending on the car, they say it is something that you can feel in the car. Something along the lines of it feeling like the car has been hit by something.

I think, ideally, a blow off valve is good for both autos and manual tranny vehicles because it does prevent the air from rushing back and trying to slow the turbo down, thus making it easier to spool back up after getting off the throttle to shift of slow down. I've no experience with the BD blow off valve, so I can't make any claims there. Most of the BOVs I've dealt with have been on turbo gassers that run 30psi for short stints.

 

Sorry guys, a turbo bark is more commonly known as a turbo surge (off throttle turbo surge). It can destroy a turbo, take a look at all the HX40s that where destroyed becasue of this.<br><br>If you look at all turbo gassers they all have blow off valves or bypass valves to elimanate this surge.

 

[quote author=Christian Roth link=board=7;threadid=16360;start=0#154117 date=1056734668]
Sorry guys, a turbo bark is more commonly known as a turbo surge (off throttle turbo surge). It can destroy a turbo, take a look at all the HX40s that where destroyed becasue of this.

If you look at all turbo gassers they all have blow off valves or bypass valves to elimanate this surge.
[/quote]

Not all turbo gassers have a BOV. Lots of them don't even come from the factory with one, so it can't be that big of an issue at factory boost settings. I know that they're real popular in the gasser turbo/manual tranny world.

 

Read these pages on turbo information. They both talk a little about noises you here with high boost and closing the throttle fast. HERE<br>and<br>HERE

 

[quote author=LinearX link=board=7;threadid=16360;start=0#154166 date=1056742363]<br>[quote author=Christian Roth link=board=7;threadid=16360;start=0#154117 date=1056734668]<br>Sorry guys, a turbo bark is more commonly known as a turbo surge (off throttle turbo surge). It can destroy a turbo, take a look at all the HX40s that where destroyed becasue of this.<br><br>If you look at all turbo gassers they all have blow off valves or bypass valves to elimanate this surge. <br>[/quote]<br><br>Not all turbo gassers have a BOV. Lots of them don't even come from the factory with one, so it can't be that big of an issue at factory boost settings. I know that they're real popular in the gasser turbo/manual tranny world.<br>[/quote]<br><br>Really, last I checked most of the newer turbocharged cars either have a blow off valve or a bypass valve. I would be intrested in knowing which ones don't. If you understand the theory of operation a gasser would have the off throttle surge almost everytime.

 

While watching Audi, Nissan and Toyota IMSA racing, I used to hear the Audi's really &quot;bark&quot; when coming off the throttle. Is that the same noise? I thought that noise was the waste gate or BOV popping off. Educate me ???

 

Its tractive loss you hear and yes it is damaging. Not a compressor wheel direction change, etc.<br><br>Don~

 

Could this be what I am experiencing.?
HERE is the link to the thread that I posted on &quot;fluttering&quot;

However, mine seems to resonate out of the exhaust.

 

[quote author=Monty(OkieBroncRider) link=board=7;threadid=16360;start=0#154406 date=1056812912]<br>Could this be what I am experiencing.?<br> HERE is the link to the thread that I posted on &quot;fluttering&quot;<br><br>However, mine seems to resonate out of the exhaust.<br>[/quote]<br><br>I doubt that your issue is related to this. The &quot;bark&quot; is caused by the high pressure air pushing back through the turbo and the air filter. This can only happen if you have a lot of boost built up. From your description in that thread, it sounds liek you are in pretty high gears already and don't have much throttle in it, hence little boost, when it happens.<br>I guess you don't have an E-brake? What you describe sounds kind of like an E-brake.<br><br>Chris<br>

 

yeah, the amount of boost has no affect on the sound. In fact, its more prone to happen at low boost conditions. I dont have an E-brake. <br><br>I didnt think this was a problem of turbo barking. I have heard mine do it before after hitting 38psi and backing out real quick. Just didnt know if this was another version of it or not.

 

My turbo barking-<br><br>Happens mostly at medium throttle when the TC locks up.<br>Of course will also do it at WOT when let off quickly.<br><br>Also referred to as &quot;cavitation&quot;, it can't be any good. Cavitation in water pumps will eventually erode the impeller.<br>Whether or not that might happen in our turbos, the stress on the shaft and other components will eventually cause failure.<br><br>I have purchased the Emjay controller to help stretch out my shifts and gain better control of when TC lock up occurs.<br><br>Also on the verge of fabricating twins. Heck, the little HX35W/40 hybrid won't have near the tendency to bark if it's being force-fed by another larger turbo! ;D

 

[quote author=VinDiesel link=board=7;threadid=16360;start=0#154555 date=1056856355]<br>Heck, the little HX35W/40 hybrid won't have near the tendency to bark if it's being force-fed by another larger turbo! ;D<br>[/quote]<br><br><br>