turbo whistle ???

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22 Sep 2018 18:01 #1 by Chris James
Chris James created the topic: turbo whistle ???
Hello all,for the last few weeks I have had a high pitched whistle from somewhere on the motor of #96. Standard perkins with a Schwitzer turbo as original equipment. It is there under load or accelerating through the gears. When reaching a desired speed and backing off a little to maintain that speed the whistle disappears and reappears when the speed is increased. The turbo was fully rebuilt around 20,000ks ago and has given no trouble since.I don,t know if it is the turbo but I have to start somewhere.All belts are tensioned ok. Any suggestions? Chris

Chris & Shirley 096

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22 Sep 2018 18:22 #2 by Holmz
Holmz replied the topic: turbo whistle ???
It is either audible in the intake snorkel... possibly bearing or other related from the unit itself.
A leak from the turbo to the engine.
Or a leak in the zorst, between the engine an turbo.

Maybe stuff a potato in zorst and see if it makes some exhaust appear somewhere ?

I would think a "vacuum type" of line blown off the intake is also likely.

You probably need an assistant maybe with a stethoscope type of listening tube to Yoda around...

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23 Sep 2018 10:20 #3 by mort
mort replied the topic: turbo whistle ???
Hi Chris,
What you describe it sounds more like your turbo and if so then it is the compressor or turbine wheel scraping on the side of the housing and for that to happen it will be that the bearing is worn. To check take off either the air inlet or dump pipe and see/feel if there is any play either sideways or in and out and that will confirm.
I know you say it was rebuilt so assuming it was done right what is forgotten or not known is to pre oil before start or at least start and idle for some time before reving to allow the oil to lube the bearings first before loading.
The turbo is under load when it is boosting and that is really only when you are accelerating driving under load.
Martyn

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23 Sep 2018 14:02 #4 by mort
mort replied the topic: turbo whistle ???
Hi Chris,
Been thinking a bit more and if it is a distinct whistle and not a screech then it could be just the compressed air leaking from your fittings between the turbo and your intake manifold so if you have an intercooler then check all the fittings and if not then you only have the flexible connection between turbo and manifold.
Martyn

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23 Sep 2018 16:34 #5 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: turbo whistle ???
I've had petrol turbo's for years and as most of them had the wick turned up so to speak they usually had a bit more boost than the factory would design intake connections for and several times I've had the flexible pipe between the turbo and intake delaminate. Usually it would make a farting type noise but once it just whistled and it took me a while to track down where it was leaking, basically it was leaking internally at one end of the hose and externally at the other while some of the compressed air leaked out through pinholes causing the whistling.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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23 Sep 2018 19:10 #6 by Holmz
Holmz replied the topic: turbo whistle ???
I thînk the technical term is "pissing out boost"?
The following user(s) said Thank You: Paul

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23 Sep 2018 19:39 #7 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: turbo whistle ???
Not long after I installed the 6bt and was mucking around changing things getting it going properly I was doing a full throttle acceleration from rest up through the gears (well the auto was) when there was a huge "boom" from the engine bay and it lost power, boost at the time was 28lb and I sXXX myself thinking I had blown the engine.
By the time I'd stopped the truck and opened the engine hatch it sunk in that the engine was still idling and apart from a loud sucking noise it seemed fine, then realised that the hose between turbo and intake had blown off with the boost pressure.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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23 Sep 2018 20:39 #8 by Ralley
Ralley replied the topic: turbo whistle ???
Apparently turbo whistle is to do with balance so a properly balanced turbo will whistle less. The turbo in my cruiser when it was built was balance to a much finer tolerance to normal and it is quiet. The Cummins on the other hand has quite the not to it even at part throttle. It is a bigger turbo. From my experience changing anything on the hot or cold side could change the amount of whistle. Have you changed out a dirty air filter (forgot to put a new one in). Changed the exhaust, fitted an intercooler. Altitude also makes a difference.
If you do check for play in the bearing remember that it will have a little bit of clearance.

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24 Sep 2018 15:57 #9 by Holmz
Holmz replied the topic: turbo whistle ???
They generally spin at ~100k RPM or higher, so a bit of imbalance would likely either result in the centre of mass spinning so that the oil wedge in a plan bearing is not concentric.
Or...
In a roller bearing it results in more of a vibratory force.

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25 Sep 2018 07:13 #10 by mort
mort replied the topic: turbo whistle ???
Hi Peter,
Yes I have had a connection on the pressure side blow on different engines and after you settle down you wonder what has just blown up but the up side is that you know that your heart can still beat pretty fast.
Martyn

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25 Sep 2018 07:22 #11 by mort
mort replied the topic: turbo whistle ???
Hi Holmz,
Yes you are right the turbo will spin anywhere up to and beyond 150,000 RPM so an unbalanced turbo will damage the bearings very quickly then the wheels.
I would think that what is ment is the balance between turbine and compressor wheels...maybe.
Martyn

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25 Sep 2018 07:37 #12 by mort
mort replied the topic: turbo whistle ???
Hi All,
A diesel turbo will whistle and in fact most people who want a good performing and tuned engine will want the whistle where a petrol engine turbo will rearly whistle this is due to the design of the turbo and the difference of the RPM as a diesel will rev lower and achieve peak power well before a petrol engine.
A turbo will suck in the air compress it and push it out this process creates a vortex which gives a whistle.
Chris may have a turbo that is now working fine and for the first time he is hearing a whistle and thinks something is wrong when in fact all is ok so until we get more feedback we dont really know and are only guessing.
Martyn

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25 Sep 2018 09:58 #13 by Chris James
Chris James replied the topic: turbo whistle ???
Hello all, thankyou to everyone for your suggestions and tips, please keep them coming if there are any more. I have been working through them with no result as yet. The one thing that I have not been able to check and it is my main concern is the shaft of the turbo itself. I have the slidon on the tray so no access to the inspection panel on the back of the cab.
To move it I have to make legs etc to lift it a little to move the truck forward a couple of feet so that is my next move,I will report my findings when I have some. Thanks again, Chris.

Chris & Shirley 096

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11 Oct 2018 11:58 #14 by Chris James
Chris James replied the topic: turbo whistle ???
Hello all, not much progress with the whistle as yet but I think I have narrowed it down to the joint between the front of the turbo and the cast U bend to the exhaust pipe, to my mind a very primitive joint.
At that point of the exercise I had a relapse of a fever that I have from time to time, similar to Q fever and just as bad so have been left with the will to continue but not much energy to do so.
Will report back when I know more, Chris.

Chris & Shirley 096

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12 Oct 2018 06:06 #15 by Peter Davis
Peter Davis replied the topic: turbo whistle ???
Hi Chris when you feel up to it you could try some high temperature rope from a furnace/wood heater. Wrap it around the gap a few times and secure with some wire or metal hose clamp. The turbo/dump pipe join is suppose to expand and seal when hot.
Peter

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12 Oct 2018 16:23 #16 by Holmz
Holmz replied the topic: turbo whistle ???
Is that where they get the expression "Ropable" from?

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13 Oct 2018 08:16 #17 by mort
mort replied the topic: turbo whistle ???
Hi Chris,
Yes it does seem like a primitive joint but it is ok. If it wasn't a really sloppy fit when installed then it may be that you havn't fully fitted as there is a sholder inside the dump pipe which should fit right up to the flange of the turbo and sitting square before fitting the bracket that bolts to the back of the dump pipe and block. I have found that sometimes it has been tight and I need to use a rubber mallet or if too tight because dump pipe out of round then used a die grinder to take a fraction off.
The other cause could be that you have a baffled muffler that is partially blocked by soot and carbon causing too much back pressure. You could remove your muffler then see if you get the whistle which would be easier to eliminate that first before your dump pipe and if it is then replace your muffler with free flow muffler or just straight pipe ie no muffler.
Martyn

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20 Feb 2019 17:16 #18 by alanj
alanj replied the topic: turbo whistle ???
Hi there Chris,

Did you manage to fix the whistling problem? Mine also has a loud whistle that comes in around 1000rpm and fades out around 1700. I thought it may be the turbo but I'm not sure.

I'm interested in seeing how you progress.

Alan.

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13 Mar 2019 18:08 #19 by alanj
alanj replied the topic: turbo whistle ???
Hello all,

I thought I would post a bit of progress with the whistling sound.

After some advice from a learned Oka owner, I dismantled the turbo hoses and pipes to look for the problem.

Interestingly, the cast iron dump pipe off the turbo is cracked up near where it connects to the turbo exhaust outlet. I was surprised because it is a big heavy chunk of cast iron.

Has anyone else had a similar issue?

Would anyone out there happen to have one sitting around gathering dust who would love to see it go to a good home?

Alan.

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14 Mar 2019 15:32 - 14 Mar 2019 15:36 #20 by Holmz
Holmz replied the topic: turbo whistle ???
Do you know a welder?

A friend has some nickel-bronze, or nickel-?? Sticks that cost $1200 for a pack, and I could get a stick or two off him.
I recall he used them for building up a gear tooth.

There is also a mob in the US that does some special sticks for cast iron.

The other alternative, which is probably a good idea, is to just remove the pipe, and use it as the template for a pipe welded out of some stainless and mandrel bends.
304,308 are commonly used in heavier gauges (2 to 3-mm) for this type of work.
316 is better, and 321 is the king and allows for thinner gauges, and it used for most aircraft.
The next step up is inconnel 625 and similar nickel alloys, which is more of what F1 and other weight critical motorsports and aircraft would lean towards... often in 0.6-mm thickness!

For the OKA a think 304 is likely ideal, and maybe some Vibrant V-Bands (TM) as connectors...
Then save the drawing as the next bloke will need one too at some point!

Most of the heat is between the engine and turbo, so some ceramic coating on the manifold, or heat shielding asbestos looking tape wrap with stainless zip ties can keep some of the heat inside the pipe. If the parts are out, then it is a better time to do that.
Most pipes do not like more heat, and the thicker gauges, or alloys better with heat characteristics are used.
Keep some heat out of the engine bay might make some sense if you are in there anyhow?
Last Edit: 14 Mar 2019 15:36 by Holmz.

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