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I thought I'd post this up here as an FYI for other owners to hopefully help them either avoid or at least quickly diagnose the issue should it occur.

Reading today's Autocar I saw their second piece on their long term Quad. In the text it is mentioned that they suffered the CEL and limp mode issue that struck my car. The resolution was to have both sets of turbo overboost valves replaced under warranty.

My strong hunch on reading this is that is exactly what happened to my car. The car failed under sustained hard acceleration and the obd reader showed identical overboost related fault codes on each bank of cylinders.

It seems therefore that the software updates applied to my car were probably not going to cure it and that the problem would quite likely have manifested itself again.

Knowing this now adds further disappointment about the fact that AR customer services were unwilling to have my car examined in the UK post the Swiss misadventure but that's not the point of this thread. Instead I have posted this because it might be something owners wish to discuss with their dealers as cars are going in for software updates, any potential remedy to the ECU covering etc. If there is a TSB issue for example about the valves I would suggest you may want to be pre-emptive especially if you have any sustained high performance driving ahead.
 

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Interesting.

When you say "turbo overboost valve" which one do you mean?

I presume they mean the solenoid that controls the boost, in the VAG world "N75 Valve".

It uses a solenoid to control how much vacuum goes to the wastegates and thus boost...

Not sure whether the QV uses this, or maybe electronically actuated wastegates.
 

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On the 2.0 the wastegate is electro operated solenoid valve, on the Quad its vacuum operated mechanical valves if I am not mistaken. I have the info somewhere, MacGeek also posted about this a ling time ago. I will report back if any corrections.
 
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Interesting.

When you say "turbo overboost valve" which one do you mean?

I presume they mean the solenoid that controls the boost, in the VAG world "N75 Valve".

It uses a solenoid to control how much vacuum goes to the wastegates and thus boost...

Not sure whether the QV uses this, or maybe electronically actuated wastegates.
Sorry MB my mechanical knowledge doesn't stretch that far and have quoted how they described the issue verbatim.

I was told a while ago but have to say I have forgotten all but the fact they are apparently quite hard to reach and it takes several hours but MG has provided some more clarity on the mechanics above.
 

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On the 2.0 the wastegate is electro operated solenoid valve, on the Quad its vacuum operated mechanical valves if I am not mistaken. I have the info somewhere, MacGeek also posted about this a ling time ago. I will report back if any corrections.
OK found some info. I was right about the wastegate.

The actuators that move the by-pass waste gate valve are pneumatic. The waste gate valve is normally open. To be able to close the valve, the pneumatic actuator that moves it has to get a vacuum from the proper void channelling.

The pneumatic actuator has an internal reaction spring that lets the waste gate valve open when the vacuum in the actuator diminishes.

Based on the above info. I would say the "overboost valves" referred to by Autocar are unlikely to be the wastegate, they are possibly the dump solenoid valves (Items 6) in the attached picture of the Qf air intake system. Happy to be corrected if I am mistaken.
 

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I think that might be wrong MG. Mainly because they seem to be quite accessable at the front of the engine. More likely the valves in question are down at the turbo and control the angle of the variable vanes in the turbo itself, thereby controling boost directly. Similar set-up in most diesels for the last 10-15 years. If it is a variable vane set-up that is. But whatever they are, as Brooking says they were hard to access, then they would be down by the turbo.
 

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OK found some info. I was right about the wastegate.

The actuators that move the by-pass waste gate valve are pneumatic. The waste gate valve is normally open. To be able to close the valve, the pneumatic actuator that moves it has to get a vacuum from the proper void channelling.

The pneumatic actuator has an internal reaction spring that lets the waste gate valve open when the vacuum in the actuator diminishes.

Based on the above info. I would say the "overboost valves" referred to by Autocar are unlikely to be the wastegate, they are possibly the dump solenoid valves (Items 6) in the attached picture of the Qf air intake system. Happy to be corrected if I am mistaken.


My only question is...where do I get the technical files on Giulia of which you posted a teaser :)
 

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That is for the 2.0 . If you look at the US Giulia forum , Eurocompulsion are experimenting with various mods on their own 2.0 280HP model and the Gofast Diverter valve is one of them. Not sure if the Qf design actually has this arrangement. The Dump solenoid in the picture sounds like the DV. What I don't know is if it diverts the compressed air back to the intake or "blows off" like the old BO valves. The black tubing from the dump solenoid does seem to have a pipe connected to the turbo intake suggesting it is acting like a diverter valve reicirculating the turbo compressed air back to the intake when the throttle is closed thus controlling compressor stall and over boost? The fact that it is physically located between the throttle body and the turbo intake suggests this is the re-circulating valve (Dump valve, Dump solenoid, Diverter Valve... whatever). Am getting confused by all the different terminology :D

My only question is...where do I get the technical files on Giulia of which you posted a teaser :)
Well I had a 1 week paid subscription to the USA FCA Mopar Tech Authority site from where I painstakingly downloaded some of the info. ;)
 
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Thats how I found it MG, through Eurocompulsions postings. They mentioned the 2.9 has the same set up. And they are fitted beside the turbo.
 

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Thats how I found it MG, through Eurocompulsions postings. They mentioned the 2.9 has the same set up. And they are fitted beside the turbo.
Cool. I have updated my post above as an after thought. Apart from the pneumatic wastegate and the Dump solenoid / Diverter valve, I can't see anything on the turbo/intake system that could relate to the "overboost valve". Can't imagine they would have replaced both wastegates! Either way sounds like Brooking's car could have been fixable if only AR had investigated properly.
 

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It seems the Autocar car was not the only vehicle to have this problem as in this month's Top Gear magazine they reference their long termer as having been to back to the dealer and needing "two new turbo overboost valves fitted".
 

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At least Evo's long termer has only had to go back for wind noise from the drivers door and a small fault with the ceramic brakes. Otherwise, there has been only praise.

I wonder if the turbo overboost valve issue is simply a duff consignment of valves that were fitted to the early cars or if this will end up being a widespread problem.
 

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Discussion Starter #14
At least Evo's long termer has only had to go back for wind noise from the drivers door and a small fault with the ceramic brakes. Otherwise, there has been only praise.

I wonder if the turbo overboost valve issue is simply a duff consignment of valves that were fitted to the early cars or if this will end up being a widespread problem.
Who knows, although it feels like a possible batch issue and my car was of roughly the same vintage as the reported ones. Definitely seems worth owners talking to dealers to see if there has been a TSB issued as this is a classic example of the few pennies part causing the lots of pounds car to fail.
 

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It seems the Autocar car was not the only vehicle to have this problem as in this month's Top Gear magazine they reference their long termer as having been to back to the dealer and needing "two new turbo overboost valves fitted".
I have had a similar problem - twice actually - with one of the solenoid controlled dump valves. Both times, it was the right side bank dump valve (when facing the engine). In my case, neither incident was actuated by hard driving. The first happened on a freeway traveling at constant speed -+140 km/h and constant throttle - CEL light pops up. The second time, I was stationary at an intersection and as I pulled off, CEL on. It seems AR are not sure if the problem if a component problem or a software one. Both incidents happened after the software updates were loaded at about 2000kms on odo. Prior to that, I had no issues. My car now has 5800km. They swopped out the dump valve (10 minute job right at the front of the engine just below the intake plenum left and right legs). From what I have been told, one other QV in SA has had this problem. There are about 40 QV's on SA roads. I have not had the problem recur but who knows...
 

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Lol. Let the conspiracy theories begin.

Blame them there German parts (ZF Box, Bosch Diverter Valves and solenoids)

Although there may be a kernel of truth here somewhere.
 

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These are theories yes, ones that are being postulated based on people's experiences with their cars and to some extent due to the lack of structured fault investigation and information supply by AR. A couple of cars in the US have also experienced similar failure symptoms and needed the Diverter valves replacing. Some of the independent Alfa and Fiat tuners in the states also think the symptoms exhibited by the press cars point toward the Diverter/Dump valves. I can't see where the conspiracy is. This fault scenario is the most logical explanation seen to date for the symptoms shown by the affected cars, admittedly only a handful but occurred none the less.:ponder: ?
 
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