Quote:
Originally Posted by ML
Rob, how are you liking Belgium? I've been a couple of time for work and would love to get back over there for a vacation. Does Ax exist there?
As for your turbo problems, it has to be related to the boost solenoid, diverter/blow-off valve or wastegate. Check (or just replace) all of your vacuum lines that run between the turbo, waste gate, intake manifold, turbo intake pipe and the blow-off valve. All of these lines work under both pressure and vacuum. Cracking in these lines would not be a surprise on a ten year old car, especially around the turbo due to the heat from the turbo. Cracking in these lines can result in the boost solenoid not reacting quickly enough, the waste gate failing to open or the blow-off valve failing to open. If you replace all of the vacuum lines, ensure that there isn't a restrictor pill (typically a brass orifice) in one of the lines running between the wastegate and turbo.
Ensure that your blow-off valve works smoothly. Remove it from the car and actuate it by hand. Clean it while it is off. The blow-off is held closed by a spring and manifold pressure while under boost. As soon as you lift your foot off of the accelerator, the manifold will go from being under pressure to vacuum and result in opening of the blow-off valve to relieve excess pressure between the turbo and the throttle body. Because your problem seems to only be under full throttle, there is little chance that this is your problem. But, it would be worth checking.
The boost solenoid could be messing with the actuation of the wastegate. Checking out the boost solenoid will require access to computer data along with the manifold pressure and the pressure coming out of the the solenoid (unless you have a fixed valve, then it is not actuated by the computer). This can also get tricky to check out since most modern turbo cars will not load the turbo without a load on the engine, i.e., the turbo won't develop boost while the car is parked. This would be a lower probability problem unless the car pumped a bunch of oil through the intake manifold or turbo intake pipe at some point in its life.
The waste gate may not be actuating as expected. The device works under pressure to bypass exhaust gasses around the turbo as the boost target is approached or exceeded and is a function of the manifold pressure. The device is subjected to basically all of the heat from the turbo and is typically actuated by a fabric and rubber diaphragm that is expanded by the manifold pressure as actuated by the boost solenoid, or turbo exit pressure directly. Given the heat cycles on a wastegate and the typical construction of a OEM part, I wouldn't be surprised if one might fail after ten years. The actuator arm should also be checked to ensure that it is not bent and moves freely (assuming that it is an external wastegate turbo).
So that's the brain dump on boost issues and probably stuff you already know. I guess if I were looking at the car, the order would be vacuum lines, wastegate, boost solenoid, blow-off valve. Now, if only you hadn't just moved to Belgium and and had some tools.
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That seems more of an explosion than a dump, but I like it!
Here is a diagram I found that gives a block diagram of the vacuum system and the air/exhaust path.
Here are some further pictures of the turbo that should be in my car:
click me
one sample picture:
I don't believe our turbos have a proper wastegate or a blow-off valve, but I am not too familiar with these things. It does have variable vanes in the turbo to regulate boost, which is one common problem base on what I have read. Often these vanes get mucked up by soot in the exhaust and get stuck. And if they get stuck in the position that would tend to give the most boost, then the ECU can't regulate boost down at high load/RPM because the vanes are stuck.
That being said, my turbo was supposedly cleaned already and should have this problem. The shop thought that the cleaning would fix the problem, but apparently not. So it goes back in the shop at the end of next week...
I believe the N75 valve is functionally equivalent to the wastegate solenoid you mentioned, so it could be that the N75 valve is screwed up... or like you said a hose is cracked. When it was in the shop before, they did replace a number of vacuum tubes, but I don't think they replaced any of the main air-flow turbos for the intercooler or turbo.
Oh well, add that to the mix...
What makes the inability to go full throttle even more annoying is the fact that I am driving to Black Forest this weekend in Germany... so the autobahn will be just a little less fun (not that a 110 hp diesel gives you an ear-to-ear grin anyways).
P.S. Belgium is ok. There are some good things, like 35 vacation days a year and proximity to a lot of western Europe, but also annoying things like the bureaucracy, limited open hours of most everything, not really knowing many people, and not have English as the default language. Once we get traveling it will seem better I am sure. We are heading to Romania/Bulgaria/Istanbul in October, then Barcelona in Nov, and probably Prague/Vienna also in Nov (none of them driving trips though). Gotta use those vacation days somehow!