Engine/Transmission (1994 - 1998) Turbo bark

[Reddog1]

My turbo barks, unless I really pay attention when I let off the go pedal. I seldom had a barking issue with my stock turbo.



I recently replaced my stock turbo with a PDR 35. My other mods are in my signature. The PDR 35 was not tapped for the wastegate hose, so I ran it for a few days without the wastegate. It spooled very quick (to 30 PSI), and ran real nice through out the RPM range, absolutely no problems, except frequent barking when I let off the pedal.



I then put a "T" in the intake, inline with the AFC Housing hose. I installed a PDR Elbow, which was on my stock turbo. It made no difference in the barking or performance.



It has been a couple of years since I installed my fuel plate, but I think it is in the middle.



I would appreciate input on why it now barks, and what can I do to prevent it from barking.





Wayne

 

[cojhl2]

I think you have to back off power a little slower/easier.



I used to drive a big truck that would stall the turbo consistantly if you wern't careful at shift time.

 

[Reddog1]

Thanks, I am backing off the power a little slower/easier now. I would like to drive it, and not nurse it.

I have done a search, and could not find a specific fix. I really do not think I am the only one that has had this problem. There must be a specific cause and fix.


Wayne

 

[ATaylor]

How about a Blow off valve? I have read on this site about BOV's solving barking. BD makes a rather expensive one.

 

[Reddog1]

I will check out the BOV.

With so few responses, you would think I am the only one that has had this problem. I really doubt it.


Wayne

 

[cojhl2]

I have done a search, and could not find a specific fix. I really do not think I am the only one that has had this problem. There must be a specific cause and fix.

Wayne

The cause is the turbine has let's say 25psig boost to the manifold and you pull the input power away. The turbine does not have the rotating mass to support the pressure against it so it stops and maybe reverses direction. The hi pressure down stream is relieved thru the turbo.



That is why when shifting, take the input power to the turbo off easy so the manifold pressure has a chance to drop preventing the backflow. It only takes an instant.



Always drive a diesel as though you have an egg under your right foot. .

 

[Reddog1]

I understand why it barks, but do not know how to prevent it. Pushing the pedal to the floor is not an issue, it is the letting off that is the problem.

I have driven this truck, with the mods in my signature (PDR HX-35 excepted) for about seven to eight years. Every once in a while, it would bark with the stock turbo. If the upgraded turbo caused the bark, there must be something I am missing to balance the cause of the barking.

I was more up on this stuff eight years ago, than I am now. Amazing just how much you forget.


Wayne

 

[cojhl2]

Hi Wayne,



You are right, flooring is not the prob. I misled by the egg thing.



The prob is as you said, letting up on it. But it's after you built a lot of boost after "flooring" it.



This new turbo probably builds more boost than your old one and additionally may have less rotating momentum. (hence the quick spoolup)



So far as I know there is no solution as it is a matter of physics, pressure downstream of the turbine and no energy to keep it there.



The only way I could not turbo bark my big truck is to back off easy to let the manifold pressure drop before taking all energy off.



I will be watching this thread to learn more. As you are I am sure,, waiting for others to chime in.

 

[Reddog1]

Actually, the new turbo builds the boost much faster. I am not sure it builds more boost.



I have been away from TDR for a while, but I can remember a time a Thread like this would have had 2 or 3 pages of responses by now. Oh well, I guess they have moved up to 3rd Gens.





Wayne

 

[hsmith]

Solved my barking with a swap from the PDR 35 to a Super B. Lowered EGT's a bit also.

 

[TBartlett1]

This is a post I wrote a while back pertaining turbo bark. It was a reply to a fellow TDR member's concerns. So you wouldn't be disappointed by the lack of replies I cut & pasted it just for you.



My 98 does the same thing and is very loud at low speeds. I have twins and an open K&N air filter so the turbo whine is very audible and will (woof, woof, woof) if I release the throttle suddenly at low speeds, let me attempt to explain. When under power and creating boost the drive pressure in the exhaust drives (spins) the exhaust turbine which in turn spins the inlet compressor. As long as these conditions are stable the exhaust drive pressure maintains the energy to turn the turbine wheel creating boost. As soon as you release the throttle no fuel equals no energy from combustion heat which means no drive pressure. In an instant (under certain circumstances) the boost pressure can exceed the drive pressure. Now the airflow (boost) which was being driven into the intake reverses because the air pump (turbo) is essentially shut off. The air flow reverses and can back flow out through the air filter. I'm not a turbo expert but I would say a steady diet of this if excessive is not good for the turbo because the turbine wheels are being slowed down extremely fast which puts excessive loads on the turbine shaft bearings and seals.

The Phatt Shaft turbos are an attempt to eliminate breakage due to this phenomenon.

There is no performance advantage to the larger turbo shaft other than increased durability in extreme situations.



The most likely reason you are just noticing it after the mods is because the air box is modified, it was designed to quiet the inlet noise from the turbo, (noise pollution).

Your signature shows that you have an ATS 5 star TC as I do. This can also contribute in the following manner. When towing you can load the engine and build boost very at low engine speeds, and when the throttle is released your ATS TC slows the engine so fast that the boost air flow reverses.

The performance mods you have, air intake system, chip and very tight TC along with towing heavy combine to make it much more noticeable.



And you are right the 3rd gens don't bark because the electronic throttle slowly ramps the fuel down rather than abruptly shutting the fuel off to control turbo bark or surge. I feel because of this operational characteristic an accident I had where I rear ended a car was more severe than it would have been if the engine had shut down like the old 1st & 2nd gens.



My 2005 suffered $5k in damage but was drivable but the Volvo I hit was pushed in to the truck in front of her and that truck hit the car in front of it and this was at approx 25mph.



The Volvo was totaled @ $18k but the other 2 involved were Illegal & scooted before the police came.



No frame, fender or hood damage. Only bumper, intercooler & condenser. Body shop said the frame on the Dodges needs a really hard hit to damage it.

 

[Reddog1]

TBartlett1, thanks for the post, and the cut and paste. For what ever reason, I did not find your post when I did a search.

What can be done to correct the problem (barking)?

Wayne

 

[Reddog1]

Solved my barking with a swap from the PDR 35 to a Super B. Lowered EGT's a bit also.

What is different about the Super B, that prevents it from barking?



Wayne

 

[fest3er]

TBartlett1, thanks for the post, and the cut and paste. For what ever reason, I did not find your post when I did a search.



What can be done to correct the problem (barking)?

Technically, it's not a problem because the system is performing as designed and intended.



That said, the way to avoid barking the turbo is to pretend you are a chauffeur who will be fired if his driving spills his passengers' martinis.



Or, stated a little more scientifically, control your acceleration instead of your velocity. In other words, instead of matting the go pedal instantly every time, stretch it to 1-2 seconds. And instead of instantly releasing the go pedal, anticipate and take 1-2 seconds to ease off the fuel.



Besides, going from full fueling and boost to zero fueling and boost is hard on the entire drivetrain, not just the turbo.



In 260K miles and almost 12 years of driving my '98, I think I've had to instantly release the go pedal fewer times than I have toes. The rest of the time I anticipate, so much so that I can drive an entire tank of fuel without touching the brakes. And I still make better time than most people. Folks who know me will assure you I do not drive like an old grandma.



If you are unable to amend your driving habits, reinstall the silencer ring and install an air filter that dampens the sound so you don't hear the barking.

 

[Reddog1]

Technically, it's not a problem because the system is performing as designed and intended.

I think I have something wrong with the design, hopefully just a small thing. The stock turbo rarely barked, and my driving habits have not changed. It could be there is nothing I can do to the design.

That said, the way to avoid barking the turbo is to pretend you are a chauffeur who will be fired if his driving spills his passengers' martinis.

I guess I am really going to have to change my role model. I usually hand my wife my beer, and tell her to watch this.

Or, stated a little more scientifically, control your acceleration instead of your velocity. In other words, instead of matting the go pedal instantly every time, stretch it to 1-2 seconds. And instead of instantly releasing the go pedal, anticipate and take 1-2 seconds to ease off the fuel.

It is not an issue everytime I accelerate, but far more often than before the turbo change.

Besides, going from full fueling and boost to zero fueling and boost is hard on the entire drivetrain, not just the turbo.

I agree.

In 260K miles and almost 12 years of driving my '98, I think I've had to instantly release the go pedal fewer times than I have toes. The rest of the time I anticipate, so much so that I can drive an entire tank of fuel without touching the brakes. And I still make better time than most people. Folks who know me will assure you I do not drive like an old grandma.

I am at about 200K miles and 8 years on my '96, with all the mods except the turbo. I doubt the stock turbo barked more than a dozen or so times.

If you are unable to amend your driving habits, reinstall the silencer ring and install an air filter that dampens the sound so you don't hear the barking.

I have not removed the silencer ring. I do not see masking the bark as a solution. My concern is that the barking could cause problems with the turbo.



Thanks again for your input.





Wayne