Another Overboost Thread

[FollowingGhosts]

Hi all,

Is there anything else I need to check/test/replace before falling back and putting a new turbo in.

 

Limp mode only happens when the engine is under high load and usually when it's still warming up.

 

The intercooler has been cleaned, EGR valve is clean, there don't seem to be any hose splits or boost leaks. (I'm assuming a boost leak would cause under rather than over boost)

 

I've checked the actuator and it holds vacuum for a couple of hours with a handheld vacuum pump so I don't think it's a vacuum leak. Actuator has been lubed with lithium grease regularly as well.

 

Turbo actuator moves freely after the Mr Muscle/Forte treatment. Tends to become markedly better after these but I can still put it into limp mode if I push it at high revs.

 

The actuator moves fine with the VCDS test last time I checked it too.

Car is a PD100 1.9 Estate

[sepulchrave]

Adjust the actuator stop screw so you get fractionally less peak boost, problem solved.

[FollowingGhosts]

40 minutes ago, sepulchrave said:

Adjust the actuator stop screw so you get fractionally less peak boost, problem solved.

Do you know of anywhere I can find documentation on how to do that?

 

I've found bits and pieces but nothing concrete.

[bigjohn]

1 hour ago, FollowingGhosts said:

I've cheked the actuator and it holds vacuum for a couple of hours with a handheld vacuum pump so I don't think it's a vacuum leak. Actuator has been lubed with lithium grease regularly as well.

 

 

 

How about the vacuum between this and the brake master cylinder "T" off. Lots of hard and flexible pipes to fail

 

Does the anti shudder valve operate when you turn off

 

 

Edited 27 December, 2017 by bigjohn

[sepulchrave]

Do you really need documentation? The actuator linkage is a very simple mechanism, just adjust it a small amount then test it, rinse and repeat as necessary. Keep track of how much you've moved it, then you can always put it back exactly where it was.

[faboka vrs]

Log group 11 and in 3rd gear do a WOT from from 2500 to 4000+rpm. Save the csv file and open in excel. Put it in a graph to compare actual vs requested to see what’s actually happening.

 

if it’s overbooating and the actuator/n75 is 90+% then the actuator rod is too short and needs lengthening.

[FollowingGhosts]

So, just to be difficult, it seems like I'm actually under boosting now.

 

Which I'm guessing is a loose turbo hose somewhere. It could be that my fiddling around has knocked something loose. 

 

This is from about 10 mins of driving around with the full load moments which you can see with the peaks

[faboka vrs]

Just log a single 3rd gear pull from 2-2500 to 4K and graph actual vs requested. Also graph the n75. Will give you a nice clear idea of how the boost is.

 

[FollowingGhosts]

On 27/12/2017 at 22:28, bigjohn said:

 

How about the vacuum between this and the brake master cylinder "T" off. Lots of hard and flexible pipes to fail

 

Does the anti shudder valve operate when you turn off

 

 

Finally actually checked this,

 

The car shudders when it's turned off, which I assume means the valve isn't working? Is this likely to be the main vacuum line from the brake servo side causing the issue?

[bigjohn]

1 hour ago, FollowingGhosts said:

Finally actually checked this,

 

The car shudders when it's turned off, which I assume means the valve isn't working? Is this likely to be the main vacuum line from the brake servo side causing the issue?

You have a vacuum leak somewhere . Start at the T off the master cylinder vacuum feed -T piece with two large pipes which is the in and out of the brake vacuum + a small pipe feeding the vacuum system which usually crosses the bulkhead on a RHD car (towards the NS/ LHD side) and then goes down to vacuum solenoids operating EGR, Turbo and anti shudder valve.  Disconnect (& reconnect) a pipe at a time and start the egine to see if you can feel the suck of the vacuum (or hear it) at each pipe / stage.  Examine each pipe for damage including the soft and hard ones. The soft flexible ones rot and the hard ones can wear with vibration rubbing / wearing the pipe against something. See attached photo showing the piece of pipe chopped out of one of the hard pipes of my previous pd car with vibration wear - looks a bit like an orgen pipe. Produced similar turbo symptoms and shuddered on turn off.

 

Edited 22 January, 2018 by bigjohn

[FollowingGhosts]

22 hours ago, bigjohn said:

You have a vacuum leak somewhere . Start at the T off the master cylinder vacuum feed -T piece with two large pipes which is the in and out of the brake vacuum + a small pipe feeding the vacuum system which usually crosses the bulkhead on a RHD car (towards the NS/ LHD side) and then goes down to vacuum solenoids operating EGR, Turbo and anti shudder valve.  Disconnect (& reconnect) a pipe at a time and start the egine to see if you can feel the suck of the vacuum (or hear it) at each pipe / stage.  Examine each pipe for damage including the soft and hard ones. The soft flexible ones rot and the hard ones can wear with vibration rubbing / wearing the pipe against something. See attached photo showing the piece of pipe chopped out of one of the hard pipes of my previous pd car with vibration wear - looks a bit like an orgen pipe. Produced similar turbo symptoms and shuddered on turn off.

 

Thanks, just checked all my hoses and they're all holding 20inHg happily so I don't think it's them

 

I've taken each hose off one by one.

 

I took the hose off between the T-off for the master cylinder and the solenoid box and that wasn't holding vacuum when the engine is off. Is that normal or is that a sign the box is done for and needs replacing?

[bigjohn]

1 hour ago, FollowingGhosts said:

Thanks, just checked all my hoses and they're all holding 20inHg happily so I don't think it's them

 

I've taken each hose off one by one.

 

I took the hose off between the T-off for the master cylinder and the solenoid box and that wasn't holding vacuum when the engine is off. Is that normal or is that a sign the box is done for and needs replacing?

That isn't normal

 

How about the hard pipes? The one crossing the engine bay to the other side is a regular fail as it passes over a vibrating engine. This has been added as part of the RHD "conversion" as the resi of the plubing originates from the near side (where the servo would be on a LHD

 

With the small hose off the T disconnected is it hissing/sucking at the T junction?

Edited 23 January, 2018 by bigjohn

[FollowingGhosts]

7 minutes ago, bigjohn said:

That isn't normal

 

How about the hard pipes? The one crossing the engine bay to the other side is a regular fail as it passes over a vibrating engine. This has been added as part of the RHD "conversion" as the resi of the plubing originates from the near side (where the servo would be on a LHD

 

With the small hose off the T disconnected is it hissing/sucking at the T junction?

 

I followed the hose from the T off to the vacuum solenoid box and found that there is vacuum being held in the hose between the t-off and solenoid end

 

However, if I remove the hose from the T-off and leave it attached to the solenoid box, the solenoid box isn't holding vacuum, if that makes sense

[bigjohn]

14 minutes ago, FollowingGhosts said:

 

I followed the hose from the T off to the vacuum solenoid box and found that there is vacuum being held in the hose between the t-off and solenoid end

 

However, if I remove the hose from the T-off and leave it attached to the solenoid box, the solenoid box isn't holding vacuum, if that makes sense

 

On mine (Superb I - pd 100)  after the T off it went to the EGR valve solenoid first then onto the vacuum reserve via a one way valve which then feeds turbo and anti shudder solenoids

 

Posted just for the diagram:-

 

 

Edited 23 January, 2018 by bigjohn

[FollowingGhosts]

So, replaced the vacuum solenoid box with one from a breakers. 

 

It didn't go into limp mode once on the motorway once this time. Even when I was in fifth and trying to coax it to. It seems to have more pull from the turbo too.

[FollowingGhosts]

For the sake of feeling sheepish, it'd help if there wasn't a massive hole in the vacuum line going to the turbo actuator. 

 

Tip: always double check the hoses