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Discussion Starter · #1 ·
There have been mentions of possible turbo failures in several threads. Jeff (Sleep_R) told me via e-mail that his turned out not to be the turbo itself, exact cause still TBD.

The Turbo Assembly consists of the turbo (turbine/compressor), wastegate, and integral CBV from the first pass diagnostic POV. I'm guessing that the CBV may be part of the perceived failures.

So does anybody have any factual info on how that works. I don't mean how CBV work in general but rather exactly how the Volvo/KKK integrated one does.
 

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Re: Turbo Failures (JimLill)

With early R's there have been reports about cracking hoses at the nipple situated in the compressor housing. Volvo changed the shape of the nipple after that.

So far no 100% turbo failures have been reported and to my knowledge the CBV has not been part of boost related problems. The turbo pressure solenoid is a part which can malfuction from time to time but overall they appear to be of good and durable quality. Most of the time other failures in the vacuum setup of the engine lead to faultu turbo behavior. The problem with the R's management system is that it has a large margin to compensate for certain failures. What I don't know is how much this compensation affects the durability of the parts which have to work harder or different at that point.

To me the CBV setup doesn't look fragile. It is different from the Mitsubishi type CBV's and also difficult to block with a plate because the CBV is situated inside a sort of chamber. The spring is pretty strong, the used material apppears to be strong also.

The CBV is operated straight from the inlet manifold, no electronics involved.

One more thing, if the management system decides to cut the engine on power, limp mode, OBD will often report an overboost failure because the engine has been cut and not because there is a boost problem. The overboost DTC is a result of the actions taken by the management system.
 

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Discussion Starter · #3 ·
Re: Turbo Failures (Johann)

Great report Johann...

can decsribe how the CBV works in this application. I have heard conflicting POV over time.
 

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Re: Turbo Failures (JimLill)

I will try to make a few pictures later.

The CBV is a channel between the compressor intake and pressure outlet. It is blocked by a rubber cap which in it's turn is backed by a spring. Manifold boost will push the cap shut, vacuum will pull it open bypassing the build pressure to the intake before the wheel.
 

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Re: Turbo Failures (JimLill)

Quote, originally posted by JimLill »
There have been mentions of possible turbo failures in several threads. Jeff (Sleep_R) told me via e-mail that his turned out not to be the turbo itself, exact cause still tbd

Jim or Jeff, Can you clarify if the condition of Jeffs car has been fixed(without knowing what was the cause) and the turbo was not the issue; or is the car still NOT performing as it should?
 

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Discussion Starter · #7 ·
Re: Turbo Failures (Johann)

Quote, originally posted by Johann »
The CBV is a channel between the compressor intake and pressure outlet. It is blocked by a rubber cap which in it's turn is backed by a spring. Manifold boost will push the cap shut, vacuum will pull it open bypassing the build pressure to the intake before the wheel.

What state is it in if the hose or diaphram fails?
 

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Re: Turbo Failures (JimLill)

These are some pictures Johann posted showing the CBV on the turbo.



 

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Discussion Starter · #9 ·
Re: Turbo Failures (Our R)

it's the black thing...

the lower picture only shows the WG flapper inside the turbine cavity
 

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Re: Turbo Failures (JimLill)

Quote, originally posted by JimLill »
it's the black thing...

the lower picture only shows the WG flapper inside the turbine cavity

Here are a few details.

Enjoy!
 

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Re: Turbo Failures (JimLill)

Quote, originally posted by JimLill »
What state is it in if the hose or diaphram fails?
Boost, right? If the diaphragm sees atmospheric pressure, the valve should close, kicking the flow to the manifold. If it fails, same thing. Turbo would then blast away at closed throttle valve. Ouch.

Tom.
 

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Re: Turbo Failures (JimLill)

.
Quote, originally posted by JimLill »
What state is it in if the hose or diaphram fails?
In the event of a hose, nipple, or diaphragm failure, the valve should remain in the non-bypassed mode. Vacuum supplies the force to overcome the spring, and the absence of vacuum should leave the valve closed.

I'm basing this on knowledge of other CBV's. I assume the R CBV is similar.

Don't confuse this with the wastegate, which is the thing that regulates boost. It operates on the other (turbine) side of the turbo.
 

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Re: Turbo Failures (Johann)

Quote, originally posted by Johann »
Enjoy!

I really appreciate your effective use of the digital camera! We learn a lot from your snapshots.
 

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Discussion Starter · #14 ·
Re: Turbo Failures (Dyno)

Quote, originally posted by Dyno »
In the event of a hose, nipple, or diaphragm failure, the valve should remain in the non-bypassed mode. Vacuum supplies the force to overcome the spring, and the absence of vacuum should leave the valve closed.

That's what I assume but have heard that boost closes it too. So I wonder if Johann has practical experience on how the R valve actually works.

Of course what I am getting at is that if it's open with no vacuum/pressure "signal" applied, a failed hose or diaphram would cause reduced boost.
 

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Re: Turbo Failures (JimLill)

Quote, originally posted by JimLill »
Of course what I am getting at is that if it's open with no vacuum/pressure "signal" applied, a failed hose or diaphram would cause reduced boost.

Oh, I see now... Vacuum counteracts spring force to open it, but the design might rely on boost "signal" at the diaphragm to suppliment spring force to hold the valve closed in high boost situations (spring might not be strong enough by itself if boost wants to blow open valve).

You'd have to examine the parts to see if boost from the compressor discharge tends to force the valve closed or open. Can't quite tell from photos.

Good question.

I'd also be concerned about overspeeding the turbo if you were trying to make boost with the bypass open. That could be real ugly.
 

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Discussion Starter · #16 ·
Re: Turbo Failures (Dyno)

Johann IM'd me...

Quote »
If the hose fails the CBV is only spring operated. It should be capable of holding a bit over atm I guess so the car should drive fairly normal but off boost.
 

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Re: Turbo Failures (JimLill)

Quote, originally posted by JimLill »
I believe it is now fixed.... exact cause TBD
Yes, back to full power. The report from the dealer service rep was that a replacement turbo was obtained and that parrallel bench tests were run on the new and the old with exactly the same performance. Previous repot of wastegate not opeing at the correct pressure were incorrect - they did not have the correct specification. So, they replaced the gasket for the exaust manifold (did find a small perforation), "tightened up" the electrical connections at the ECU and ... VIOLA. Crackerjack techs to the rescue.

I will check the service report to see if they did anything else.
In the interim, back to the high performance shop for a custom SS 3" DP with removable cat.

I am not confident that the issue will not resurface, but wil enjoy untl then. http://********************/smile/emcocktl.gif
 

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Re: Turbo Failures (SleepR)

Interesting. I just posted that one of the items for the service dept to look at on my car was loss in power. when accellerating hard, the turbo spools up and the car takes off like it is supposed to. but when it hits about 5500 rpms it feels like it dumps the boost pressure and I loose a lot of power. Is this what others are experiencing? oclv
 

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Discussion Starter · #20 ·
Re: Turbo Failures (oclv)

what gear does the 5500 phenomena occur in? The tach lags reality in lower gears....
 
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