Boost problems - perhaps

[davelowe]

Okay - I should do research. I intend to, when conditions permit (somewhat distracted by my brother's wedding tomorrow).

Synopsis: 'Check ignition' (might be a misnomer). Clip reveals nothing, but the turbo after cycling through heavy bursts of foot down - lift off, gave the message.

It has chattered for a while - I suspect compressor stall. No idea what the problem is, but the servo that controls the boost makes a loud ringing noise at idle.

No need to answer this: I'll keep you posted.

Turbo spools A OK. Looks like a map situation or a loose hose.

[tomalamix]

have you ever had problems with your map before? (despiste the usual ones before tune-up )

[ikhan]

Just curious (and off-topic as well I guess), but how is the turbo suppose to react on the 106's?

I don't have any problems (that I know of), but I get a slight whistle from the moment I press the accelerators (about 1,200rpm upwards), and at idle, I got this faint 'hum' which I think is the fuel pump?

Are both of these sounds normal?

[davelowe]

This is not 'slight' it is very noisy. I'll check the obvious but nothing comes to bear as yet *disclaimer "I was 'tired and emotional' yesterday" (major hangover!). Boost was reduced, but then it went away. Neither CLIP nor any other protocol will connect to this damned thing.

I'll report back.

TTIA

[davelowe]

Just curious (and off-topic as well I guess), but how is the turbo suppose to react on the 106's?

I don't have any problems (that I know of), but I get a slight whistle from the moment I press the accelerators (about 1,200rpm upwards), and at idle, I got this faint 'hum' which I think is the fuel pump?

Are both of these sounds normal?

Boost is very low revved on these engines. The hum, well, not sure. Depends what you mean...Have you a recording?

[AlexB]

Dave,

It's more likely to be flutter than chatter. The compressor in a diesel wouldn't stall at low revs due to absence of choke. Flutter is about stability of the wastegate or VGT, usually caused by non-linear control elements in the control loop. Sticking actuator or vanes are such elements...

Ringing is not good. Are you sure it is coming from the turbo?

[AlexB]

Ikhan,

Turbos can make all sorts of faint sounds, which are normal, as long as they are faint to the extent that many people would not hear them at all. At idle the turbo is usually silent. When gently driving off on cold engine some rather pleasant sound of spooling up can be emitted. When releasing the accelerator a faint "dumper valve" sound can be heard, although there is no such a valve in a diesel. The most worrying sound is happens when going at full throttle at above 4000rpm, it is a kind of 'w'-'f' sound which makes you feel that the turbo is working at its limit.

Less normal, but still harmless sounds are minor air leaks. They are much louder and can have different pitch. There will be a spot of oil spray around such a leak, as the compressed air carries a small amount of oil from the crankcase ventilation system.

Finally, any loud and scary grinding, ringing, whining sounds from the turbo, modulated by its speed, are not good.

In any case, if you are worried, then change the oil to something like Mobil 1 0w40, oil and air filters. Otherwise, you will keep thinking about a potential failure, which is not fun.

[ikhan]

Thanks guys - that puts my mind at rest somewhat

No oil sprays / residue or anything like that. I'll try to get a recording of the humming sund, but to be honest it probably wont get picked up on any device.

[davelowe]

Right, since we are talking about two very different things here, I'll end my contribution with some brief notes.

The noise I was describing was odd. Not whistling (this being normal), but fluttering/chattering and only when experimenting with WOT and/or suddenly lifting off (and I mean sudden)! When the spanner showed its ugly face, I drove about 3 miles home virtually at idle. I had a good look around all the obvious places, checked all the hoses, play in the shaft, and much else. No oil was leaking, nor was it 'missing'. In short, everything looked good. My CLIP detected all the computers, but would not report a problem. Other protocols including VAG and whatever ELM (I'll check) uses, would not report anything.

In short, the problem has gone away. And in answer to whoever asked, I don't believe the map was to blame. This has been extremely intermittent over a longish period.

Not, so far as I'm aware in Haynes (and other places), is an electrical/vacuum controller. It takes one feed directly from the vacuum pump and is hooked onto the brake fluid reservoir via an electrical connector. I assume the other end finishes at the turbo actuator - the engine design/layout makes this very hard to determine. It buzzes when in use (even at idle) and continues for several seconds after shutting down. This car is a hybrid of all sorts - the electronics don't make much sense (OBD) and neither does the EGR (this design not mentioned in Haynes).

Anyhow, thanks all for your input. Of course should ikhan have further problems, please continue to post. But for the mean time, consider my problem closed.

[direstraits]

I understand your engine has been remapped? Remapping usually means more unburnt fuel (depending on how good your map is) in the exhaust. And that in turn means EGR valve will get more soot and it will eventually become clogged with oil+soot mixture. It is a good idea to check the EGR. Just remember, EGR valve needs to be reinitialised after cleaning, there is a command in Clip (if your Clip has all the options it should have) that should be executed.

[davelowe]

I understand your engine has been remapped? Remapping usually means more unburnt fuel (depending on how good your map is) in the exhaust. And that in turn means EGR valve will get more soot and it will eventually become clogged with oil+soot mixture. It is a good idea to check the EGR. Just remember, EGR valve needs to be reinitialised after cleaning, there is a command in Clip (if your Clip has all the options it should have) that should be executed.

Whenever the weekend weather is good, the EGR comes out. Invariably it is clean. As you say, not all maps mean more unburned fuel. My experiment regarding the map reveal better performance and fuel economy tend to support this.

I will investigate the CLIP commands regarding the EGR - although this is not the source of the noise (it might be the cause of it). The car is odd electronically as I've mentioned - things are present and absent that do not appear in any of the technical notes.

As things stand, all works as advertised. Many thanks for your input. I'll post further here if it deteriorates.

[direstraits]

Can you smell exhaust gasses under the bonnet?

[Skidms9]

Dave, long shot without hearing it but the noise you describe sounds to me like wastegate 'flutter'. Happens on any car with a FG turbo but normally goes un-noticed. Over the years I've seen it's more noticeable on cars running over 7PSI-ish boost and the higher the boost the more the flutter. Can be very loud with modified induction systems, modded panel filters, cones or cold-air-intakes.

Ikhan, your noises don't sound too problematic and I wouldn't lose any sleep over it. You've checked the obvious without any nasties so just monitor it

[davelowe]

I'll bear this in mind - the boost pattern is different to the original car specification owing to the map.

One interesting characteristic that occurs after the map, is that the turbo will spool up fast on overrun/closed throttle - presumably to prepare for performance if needed (and not ex-factory). I'm not so sure that this is good, since at low rpms, the oil pressure lubricating the turbo bearings is lower. However, this has not shortened the life of the turbo or deteriorated since the map has been added.

In essence, I can make the problem happen during non-normal driving conditions, so I'm not so worried about it. More curious if anything...

The wastegate scenario sounds very viable. I'm wondering why the overaction of the wastegate would cause the check engine light. Wondering, mind - not worried!