Turbo Question

[Chris611]

I have a noise in the turbo if I suddenly cut the throttle when the turbo is spooled up. When I accelerate I can hear the turbo whistle and there is no unusual noise, if I ease off the throttle, no noise. The noise only happens if I suddenly cut the throttle with the turbo whistling. Sorry I don't have any boost readings (gauges sitting in a box waiting to go in). I did the test I found on another post to test the turbo and I think it passed? I warmed up the truck and then tried to move the shaft side to side. I would move some, but didn't appear to touch the sides of the housing. I don't see any evidence that the blades have hit the side of the housing. Anyone have any thoughts on what this could be?

Thanks
Chris

[markrinker]

What kind of noise? If it sounds anything like a bearing squeeling, I'd get it out of there before it grenades, puking shrapnel down your engine's throat...

[Chris611]

Unfortunately it does sound like a bearing, anyway from what limited experience I have with a bearing going out. It isn't squealing, but once I heard the gearbox of a motorcyle that had been run without oil. Sounded like gravel in a blender. This is not quite that bad, but similar. What has me confused is that it only does it when the turbo slows down quickly, not when it speeds up. What causes this? Also what is the best (cheapest) way to replace or rebuild the turbo.

Thanks
Chris

[DmaxMaverick]

The noise could be blow-back. This happens when the turbo has boost pressure built up in the intake, and the exhaust pressure is suddenly taken away, like when you go from WOT to idle quickly while under significant load. The pressure in the intake spins the compressor backwards. I can/could create this condition in every turbo'd vehicle I have and had, including my '01 Duramax. Straight pipes will exaggerate the sound, so what you are hearing could be normal. A malfunctioning wastegate could also cause it to happen when it normally wouldn't. If you had a bearing failure, it would be evident at other times as well. It wouldn't hurt to check the compressor wheel for excess play, though.

[markrinker]

I would also look for a loose heat shield or anything that could be rattling harmonically. From your description, it isn't a bearing failure.

[Chris611]

Thanks guys. I will have to look into any heat shields etc. that could be rattling.

DmaxMaverick, is there a way to tell if the wastegate is malfunctioning. I assume the malfunction would then cause the same counter-rotation of the turbo, hence the noise?

Also, just so I can put it in my memory bank, what does a turbo sound like that has the bearings going out. I have never heard one before (and hope to never), but would like to know what to listen for, so I can fix it immediately.

Thank again.
Chris

[markrinker]

Like a bearing going out. Constant, in relation to speed. Metallic.

[markrinker]

Originally posted by DmaxMaverick:
The noise could be blow-back. This happens when the turbo has boost pressure built up in the intake, and the exhaust pressure is suddenly taken away, like when you go from WOT to idle quickly while under significant load. The pressure in the intake spins the compressor backwards. I think this happened to me today - blew a horrendous cloud of smoke, and set a code 62. Prior to the event, I had my foot in it with trailer and load in tow. Boost was at ~15+ psi and all of a sudden the boost slammed (not dropped) to 0 and it felt like the truck had died. After a few seconds, I was able to re-accelerate, but could recreate the 'event' by flooring it and creating boost >15.

Could a leak at the turbo downpipe seal cause this? I noticed a bit of smoke from near the turbo at cold startup, made a mental note to check further, but hadn't gotten to it yet...

[rjschoolcraft]

The actual technical term is compressor surge. This will make a chirping or barking sound. This happens when the compressor tries to generate too much pressure ratio at a very low flow. When you suddenly pull fuel, under certain conditions, the engine can decelerate very rapidly. The inertia in the turbo charger will sustain its speed briefly so that it is still trying to pump air. However, the engine is "swallowing" less air and the pressure ratio rises rapidly...in this case, taking you out of the operating range of the compressor.

Sustained operation under these conditions can cause blade stress problems, but a "once in a while" occurence will be of little harm

There are some Dodges around here with aftermarket larger turbos installed. Those guys love to accel hard, then cut fuel specifically to generate that sound. They'll usually surge three to five times in a row until the compressor spools down. I doubt that they even know what is happening...they just like the sound. :rolleyes:

[grape]

there is a machining process to the inlet housings that can fix this. When done properly it sounds better than any form of turbocharger noise you've ever heard. The surge thing may sound cool, but like RJ said it's REAL bad. The way the inlet and exhaust wheels are pulling and pushing air makes the turbine shaft crawl towards the inlet side of the cartrige at all times, when it surges it slams the whole assembly back agianst the cartrige which is where the thrust bearings give up. good turbo noise (http://www.inductionperformance.com/newvideo/800hp/tehbeast.mpg)

[ 03-29-2005, 05:25 PM: Message edited by: grape ]

[dieseldummy]

This is what happens whe the turbo surges or "barks" one to many times:

http://img.photobucket.com/albums/v622/dieseldummy/7f67a902.jpg

When it went I definatly knew it, went from 15 psi boost to 0 and the scraping from the fins on the housings was terrible. After barking it on a few occasions out of absolute neccessity in traffic, pulling, ect. it weakeand the integrity of the shaft then under the stress of producing boost it finaly gave it up. If you turbo makes a hollow "woofing" noise from the intake or exhaust take note imediatly...

Justin

[markrinker]

There is absolutely no noise associated with this 'event'. It simply felt like someone shut off the key, and the boost SLAMMED to zero - it didn't DROP to zero...

Also remember the code 62 that was set. The boost sensor has never acted up before - or since. That means it saw -6 lbs at the intake, according to other threads here at the DP...

It took awhile to clear the cylinders, like ingestion of crankcase oil. After rolling 5-10 seconds, combustion sllllowly started again, and the cloud cleared up as the familiar diesel 'rattle' returned.

Remember, I have been experiencing unexplained and higher than normal oil consumption with this truck. Could my turbo have a blown oil seal? How about a faulty waste gate?

The 'cloud' was definately bigger than any diesel cloud either of my 6.5 trucks has ever made!!! We are talking 'can't-see-the-cars-behind-you' kinda cloud...I really think it was crankcase oil.

However the mystery remains: How could crankcase oil find its way into the engine under these circumstances (high boost, hard pull, then immediate no/negative boost), and then return to normal operation just as suddenly as it started?

If I keep my foot out of it, its the same old truck. If I floor it and keep it there, this would happen again.

[ 03-29-2005, 05:57 PM: Message edited by: Mark Rinker ]

[rjschoolcraft]

Mark,

When a surge occurs, the flow reverses, and as Grape said, the thrust forces reverse. If you had an oil seal leak that allowed a sudden increase in quantity (a slug), this could induce a violent surge. Under these conditions, a negative manifold pressure is possible for a very short time.

It is difficult to imagine a seal leak in the turbocharger, though, that could do this. The delta P is such that, if a seal leaks, it will leak air into the sump, not oil into the gas path. This is how labyrinth seals work in gas turbines.

A possible source could be the CDR valve. If a combination of high blow-by (crank case pressure high) and high restriction on the air filter (high vacuum at compressor inlet) is occurring with a bad diaphragm in the CDR, you could see a sudden slug of oil at the inlet to the compressor that could induce a violent surge. Your comments about no noise don't fit with this scenario, though.

Don't know, just some thoughts.

Dieseldummy,

Which turbocharger is that?

[ 03-30-2005, 04:07 AM: Message edited by: ronniejoe ]

[Kennedy]

Originally posted by Mark Rinker:
There is absolutely no noise associated with this 'event'. It simply felt like someone shut off the key, and the boost SLAMMED to zero - it didn't DROP to zero...

Also remember the code 62 that was set. The boost sensor has never acted up before - or since. That means it saw -6 lbs at the intake, according to other threads here at the DP...

It took awhile to clear the cylinders, like ingestion of crankcase oil. After rolling 5-10 seconds, combustion sllllowly started again, and the cloud cleared up as the familiar diesel 'rattle' returned.

Remember, I have been experiencing unexplained and higher than normal oil consumption with this truck. Could my turbo have a blown oil seal? How about a faulty waste gate?

The 'cloud' was definately bigger than any diesel cloud either of my 6.5 trucks has ever made!!! We are talking 'can't-see-the-cars-behind-you' kinda cloud...I really think it was crankcase oil.

However the mystery remains: How could crankcase oil find its way into the engine under these circumstances (high boost, hard pull, then immediate no/negative boost), and then return to normal operation just as suddenly as it started?

If I keep my foot out of it, its the same old truck. If I floor it and keep it there, this would happen again. Sounds like too much boost for the program/chip that you are running. PCM dumps boost first and since it can't control a fully mechanical device, it gets mad and puts you into a limp mode cutting fuel, and likely timing which would explain the smoke.

[dieseldummy]

I Never knew that limp mode changed the timing, learned something new today.

RJ, That's a WH1C Holset...

[markrinker]

Followup:

Today hauled 390 miles roundtrip without incident, after adjusting Turbo-Master to allow 11psi max boost at WOT.

Strange thing is I have put on ~40K miles without adjusting anything. The only change is curiously that that CDR is unhooked and venting to atmosphere, waiting for a new one.

Okay RJ - what is your theory now?

[rjschoolcraft]

Originally posted by Mark Rinker:
Okay RJ - what is your theory now? I guess that I'm not supposed to answer your posts? It is always a bad idea to try to troubleshoot long distance, sight unseen...especially when people don't share all of their observations. But, that's what this board is for... People go out on a limb to help each other. Sometimes the limb gets sawed off by those who are receiving the help. That's life.

As for theorys, I stated up front that it was one possible scenario and that all of what you did share didn't exactly fit. My first post discussing surge wasn't even directed at your issue. I didn't even read your post about a problem until after I had posted the first time. I was responding to and expounding upon the earlier post by DmaxMaverick. I finished reading his post and hit the reply button. Bad move on my part.

It's clear that you have some burr under your saddle toward me... I can't help that, because I didn't put it there. I will continue to extend grace to you and will attempt to answer future questions... knowing full well that I'll probably get smacked again.

With the new information, Kennedy's theory is probably right. There I go, inching out on that limb again.

[gmctd]

Rinker's big smoke event sounds more like
1. the CDR is not functional, allowing large plug of valve cover oil into the intake at high Boost
2. something blocks the compressor inlet ducting, resulting in full vacuum intake draw thru the CDR.

Either one will quickly dampen combustion process - might take a look, from air box inlet to compressor intake.

[markrinker]

If we could only incorporate facial expression, intention, or tone of voice into emails...RJ I was SINCERELY looking for your input...really! You obviously know your stuff.

GMCTD - the original (possibly non-functioning?) CDR was still in place in the valve cover, but completely unhooked from the intake (old brittle rubber tube cracked completely in half a few days ago) at the time of the 'event' described above.

This is the only recent change of any kind under the hood in ~40K troublefree miles with all mods listed below on truck #2, while in search for the source of my high oil consumption.

I am thinking the 'event' described above has something to do with having the CDR in place, yet unhooked from intake vaccuum.

Could the crankcase have pressurized? Seems unlikely, at idle it spews a steady stream of oil vapor (blowby).

How about this theory:

For some reason, the computer desides on this day, under these conditions to drastically pull fuel. As a result, the turbo goes into a surge condition, and for a split second, negative manifold pressure exists, sucking engine oil past the valve guides in enough quantity to stop combustion, creating a huge cloud of blue smoke out the exhaust.

???

[ 03-30-2005, 06:54 PM: Message edited by: Mark Rinker ]

[rjschoolcraft]

I apologize. I read it as sarcasm. Probably a little touchy lately. I'll think about it some more.

[gmctd]

Don't think that's possible - any Boost would pressurize crankcase thru those same valve guides, which would have blown oil out the CDR.

Other possiblilty - water in fuel = heavy black smoke, no Boost, takes a while for a slug to pass thru the Inj Pump, which would also seem like it was clearing out choked up cylinders.
Which, it is.

I'm not really buying into this back-pressurizing the GM-X compressor - could do it against suddenly closed throttle plates, or maybe at 30-45psi, but highly iffy at ~15psi.

Crack open the wastegate and 15psi drops like a shot, partially from air resistance on the compressor wheel, partially because it is driving a dynamic device - your engine.

No exhaust energy - no Boost.

IMO

But, the -6 DTC 62 seems to indicate high vacuum in the intake, indicating the compressor inlet path was blocked

Chris's problem sounds like loose exhaust hangers, heat shields, and such.

[ 03-30-2005, 08:17 PM: Message edited by: gmctd ]

[grape]

it's sucking the air cleaner duct shut at high boost. I bet it's doing it infront of the crankase breather tube inlet into the intake tract........meaning the engine can only breath through the cdr valve for a second pulling all the oil through the turbo.