Turbo Bark?

[Hunter4x4]

Hi Guys!



Quick question about 'turbo bark'. I just heard something for the first time tonight on my truck on the way home after just refueling.



After a moderate acceleration and sudden let up on the throttle I heard some thing like a 'heavy sigh' or a fading 'wooosh'. Loud enough to hear, and now repeatable.



I went to the forum search tool and looked up turbo bark and I'm still just a little confused.

1. ) I'm getting a 'woooosh' not a chirp or bark.

2. ) Is a 'wooosh' the same as a bark?

3. ) Is this a problem? Something bad? Is a 'wooosh' OK but a bark bad?

4. ) Why would this all of a sudden start up?



Background:

o Changed oil and fuel filters about 600 miles ago

o Been running Baldwin BHAF and Power Wagon injectors for about 4,000 miles. Noticable performance increase with the injectors.

o Truck currently has 164k

o Just recently I also noticed whitish smoke at WOT (i. e. , throttle absolutely buried to the floor - otherwise no white smoke) at times - but not all the time. I posted a question on this and got some real good info - basicaly the new injector's higher pressure cause the pump to retard somewhat which in turn causes the fuel-air mixture to be heavy on the air side causing the white smoke.



I just would like to make sure the truck is OK, or if not, how serious the 'problem' may be and what's involved in diagnosing and correction!!!



Thanks in advance for any input and help!!



Mike

 

[cerberusiam]

Barking, huffing, groaning, whooshing, or something that sounds like a squirrel with its tail in a meat grinder. Either way you have slid too far down the HP slope to go back now.



A sigh or a whoosh probably isn't too bad. The squirrel thing, definitely not good!



Whatever it's called, it is boost going the wrong way thru the turbo. When its starts stalling the compressor your turbo is not long for this world. Better put the 14 on and see if that will cure it. Or not. Good excuse to get one them there massged HX35 thingys.



What does it sound like if you dump the throttle after a WOT run?

 

[Hunter4x4]

Haven't dumped the throttle after a WOT run yet - I'll try that and let you know.



By 'boost going the wrong way through the turbo' do you mean the compressed air between the compressor side of the turbo and the intake valves is built up and when I let off the throttle it's passing backwards out through the intake system for that brief moment?



And finally, how do I know if I stall the compressor?



Thanks!

 

[Greenleaf]

To say the least, yes. And I think you answered your own question.



GL

 

[cerberusiam]

And finally, how do I know if I stall the compressor?



It differs from truck to truck, but generally the squirrel thing.







As Scott said you answered your own question. Take away the exhaust flow on the hot side suddenly and there is not enough to keep the compressor spinning against the built up boost. Generally means you are out of the map the compressor will function effectively in. Changing the hot side should help but if the boost is beyond the turbo map it will still want to stall the compressor. Add enough fuel and air flow you need to start upgrading parts to handle it.

 

[michigandon]

Does it sound like a super stock pulling tractor shutting down at the completion of its run when you let off the throttle?

 

[Greenleaf]

Same thing, but there is more boost in that application such as 80 plus. We have to hold the fitting together with steel strap and "O" ringed fittings.



Scott

 

[Hunter4x4]

Michigandon - Can't say! I don't think I've ever heard a super stock pulling tractor shutting down at the completion of a run!

 

[Greenleaf]

Generally there is this sudden, loud WHOOOOOOOSSSSHHHHHH and a light haze is seen spewing from the intake pipe. Don't use an air filter, rather a simple pipe with an emergency trap door to kill her quick should a plunger stick. Some use two or even four turbos. 100# boost is not unusual. The turbo's are made to deal with this common occurance.



A bark will also occure if the engine begins to labor suddenly as the tires are getting a good bite. The RPM's will drop and all that boost cannot be used inside the combustion chamber. The air will momentarily reverse.



Scott

 

[JLEONARD]

So the smaller exhaust housing will make it worse as it will further restrict air flow?

I have never heard my turbo "bark"... probably because I have a wimpy stock non I/C turbo with it's 52 mm compressor wheel that is perhaps to small to stall?

But when I modify to the 56 mm wheel from an I/C turbo, will I be hearing the bark... or be more likely to as it will be easier to stall?

Jay

 

[cerberusiam]

A smaller hot side housing should alleviate bark because it will keep spinning with less flow than a larger housing. A larger pin wheel should help also as it takes a bigger bite out of the air and is capapble of building and holding more boost.



If you can get a large enough rpm drop when boost is high you can bark just about any turbo. The manuals are worse for having it happen as the shift points drop rpm's more than the autos at least with a sloppy stock converter.



The Ford 7. 3s have the same problem with the Garret when you open up the exhaust, air intake, and/or add fuel and go beyond a stock setup. Their answer is to upgrade the compressor wheel so it should work the same way with a Holeset.

 

[JStraw]

Ever since I did my bombs I can get the sound you mentioned. I LOVE IT There's no place else for the compressed air to go except to be regergitated.

 

[JLEONARD]

A larger pin wheel should help also as it takes a bigger bite out of the air and is capapble of building and holding more boost.

Not sure I agree. I know in propellers under water (same principle and problem with "stall") this does not hold true.

I would agree that an upgraded wheel as in a different turbine design (different blade angle, blade area,etc) would help.

Anyway I never heard this on mine... . has anybody that is non intercooled had this problem?

 

[cerberusiam]

But, but, but doesn't "bigger" mean its "better"? Size matters doesn't it?





Ok, delete "larger" insert "different". Surface area, blade pitch, blade size will all contribute to the performance or map of a turbo. Changing the map affects the point at which barking, etc will happen.



Jstraw, I don't agree regurtitating the air is a good thing. It indicates a mechanical problem that will lead to a mechanical failure. I agree its sounds really cool but my pocket book can only stand so much cool. Been there done that. :{



Jleonard, not a fair comparison. The 2 mediums have very different properties and there are different obstacles to overcome. Naturally the same principals apply but there is a lot less friction moving air than there is moving a solid object thru water. Given the lack of friction and the fact air will compress there is a lot more wiggle room in the tolerances. In this case "bigger" is a valid and effective performance modifier.

 

[michigandon]

Jstraw, I don't agree regurtitating the air is a good thing. It indicates a mechanical problem that will lead to a mechanical failure. I agree its sounds really cool but my pocket book can only stand so much cool. Been there done that. :{

So, that loud PUHHHHHHHHHHHHHH that is audible when I take my foot off of the gas in the 1st gen house is not a good thing? :{



(FYI-this engine is bone stock except for a 16CM housing, an Afe ProGuard 7 air filter, and a 4" open exhaust)

 

[cerberusiam]

Looking at 2 different perspectives, functional and practical, and addressing Mike's original question leads me to a couple conclusions.



From a functional stand point of engine and turbo operation the barking should have no effect on engine operation and is not a serious problem.



Looking at the practicalities, if the barking is causing unaccounted for stress on mechanical components leading to a failure then it is a serious problem. Grenading the turbo can have some serious effects, one of which is ingesting pieces of said turbo directly into the engine. Obviously the Holeset turbos are overegineered or they wouldn't live as long as they do doing what they do. However, there are limits to what the turbo can take and barking is one that will seriously reduce MTBF.



Jleonard asked a good question, how many non-IC trucks experience this? Are the IC trucks more prone to it because of the larger space for compression and storage of air? Does the shorter route to engine on non-IC truck minimize the problem? Scott said the huffing on the pullers sounds like the same thing. Do the pullers run an IC or are they stuffing the air directly into the manifold?



From a mechanical engineering stand point stalling or slowing the turbo compressor by applying a reverse flow of air has to be a bad thing. Not only does it have to deal with the stress of spinning so fast but it also has to absord the amount of energy applied to stall or slow it.



I think its kinda one of those "do at your own risk" things. My own experience tells me it is a problem that needs to rectified. If I can't completely address it and achieve the performance I want then "I am my own warranty station".

 

[Greenleaf]

The pulling tractors I have wrenched on are all stuffing the air directly into the intake man.



Scott

 

[bgilbert]

Haven't dumped the throttle after a WOT run yet - I'll try that and let you know.

Hunter, this is not recommended. NOT a good test, just to see if you can 'bark' the turbo. If it happens, great, if not great, but don't purposely try to grenade your turbo. It may not damage it with say less than 30psi of boost for instance, but more boost more chance of failure, not to say that 30psi something won't fail, just not as likely.



JL, cerberusiam, yes a nonIC'd baby turbo will bark, run 40psi through it and simply shift gears, yes it will talk to you. WOT, dump the throttle it will REALLY bark. Stock condition, 22psi it was barely noticeable after the stacks were installed, not noticeable without the stacks.

 

[JLEONARD]

Well with my 30 psi gage well against the pin at WOT and released to 0 it still does not bark that I can hear.

Maybe it's the muffler.

Maybe once I get "the parts" and modify the turbo things will change.

Jay

 

[sparks57]

LOL!



WHOOOOOSHHHHHHH: ok

PSSSSSSSSsssssssss: ok

WOOF!!!!: BAD!



:-laf



But seriously, a loud chirp, or a drawn out whislte on deceleration is fine... but a bark is just that... it's a quick "woof" right when you shift or let off.



Woofing the turbo is bad, because it can snap the impeller shaft. The quick reverse torque load can be catastrophic. It's not bad for anything else though.



If you ever listen to a pulling tractor or go to a truck pull... you will see them goose the throttle right when the stop, that's to keep the impellar spinning... when you're making 80-100+ psi of boost, out of a $6k set of compounds, it's not a good idea to let it woof!