307 2.0 Hdi RHR 136 turbo pressure

[tmead]

The car is all back together after repairs, with a replacement turbo repeat sensor. The stuttering at partial throttle seems to be gone, along with the surging at full throttle as the revs rise. However, the peak pressure now is around 16psi. I'm sure pressures of nearer 20 were recorded before, although not constant. I guess that could have been because the ecu was cutting something else back, reacting to what appeared to be excess pressure ?

[EDC5]

Here is a pic of the Turbo pressure of my RHR during acceleration.

The peak measured pressure was 2435 mbar (I assume) so when we subtract the atmospheric reading, 1012, the boost pressure is 1423 mbar or 20.5 PSI

So it looks like yours is a little low.

[tmead]

Thanks EDC, I have felt the car is a little slower than before, which this would explain. MPG is fine, and it runs OK though.

Not quite sure where to look next. Its just good to be back on the road and not to have to constantly worry about getting it back running again !

I did see a message about the DPF being nearly full when I cleared everything to get a fresh start, and at 190K without any record of a DPF change that wouldnt be a surprise..... I'll gather some data about differential pressure etc next. Cant see how this would be different now than before the cam change though.

Graphing doesn't work for me on planet. I just see a black screen. Data is captured, so I can graph later on the PC. I need to check that the turbo repeat is now tracking where it should, so will have to plug in and record some data sets.

[EDC5]

Yeah, you must be relieved that at least it's going again

I suppose a good thing would be to check all of the air hoses for a leak first off.

I'm just thinking a blocked DPF would restrict exhaust flow through the turbo and lower the boost, but as you say if it was working fine beforehand then it shouldn't have changed.

Checking the live data is probably the best next step.

[tmead]

OK, PP now back activated. No idea why it suddenly decided not to just work, but that's the way everything is going right now....

Live data is clearly showing that the turbo repeat is now working as it should ! 12% at key on and engine off.

This is before the change - the lack of response of the repeat sensor is clear, and the ecu is dramatically modifying the turbo position signal, which is reflected in the pressure. This is felt as a series of hesitations on full throttle.

After the change its clear that the repeat value is tracking the request position as well as it can.

Turbo pressure request tops out at 2300, and the actual takes a little while to build to that.

This all makes sense. I need to now check why the repeat value from the EGR is constantly pretty much zero. I didn't think I'd even unplugged it during the work, as even though the peugeot procedure advises removing the EGR and cooler to do the exhaust cam change I didnt think it was necessary to disturb it and didn't ! But maybe I did unplug for access and moving wiring etc to get at stuff and have missed plugging it back in......

[EDC5]

That first graph is really interesting, it suggests that the ECU is trying to 'unstick' the vanes in the turbo by repeatedly applying full vacuum. Very clever.

It appears to have done the trick regardless by looking at the second graph with everything tracking correctly.

Just a suspicion, but maybe your turbo is all coked up with soot. I'm not sure if there is anything you can do about it as it's impossible to get to in practice, but that might be the cause regardless.

do you have any engine faults recorded about your EGR?

[tmead]

Yep, two errors. EGR valve learning and EGR valve circuit, valve position too distant in relation to the reference value. No ecu light though now though, it popped up once and went away. Makes sense that the light came on really, as the repeat value doesn't appear to move from zero....
I did swap the EGR for a secondhand one a while back, as the original stuck open (but blanked) quite frequently. The replacement actuator is decoupled from the mechanism and limited for stroke to about where it should be. However, if it is not reporting correctly I may need to have another go. It doesnt seemt o be hindering things at present, no lights or limp mode.

EGR is blanked, and has been for probably 90K, so the turbo hopefully not desperately sooted up.

I did see a method on a VW forum for putting foaming drain cleaner down the EGR connection in the manifold through a pipe into the turbo and washing it through after a few minutes to clear out soot. The pipe would need guiding along the exhaust manifold with a fibreoptic camera in the RHR exhaust manifold I guess, but then the turbo is lower than the manifold.
Probably not worth it, as I suspect in my case after 190K with vanes that still do work, they will be worn to the point that cleaning the soot away could just make things much worse !

[EDC5]

Yeah I wouldn't worry about the EGR too much. The less EGR flow the better. Truth be told, they are a curse on an engine.

this video might interest you regarding the turbo, it's shown on a volvo but it's a RHR engine nonetheless:

[tmead]

I'd seen a referecne to the oven cleaner method for VW, and assumed it should work for Hdi RHR too. Looks like it would ! I'm not sure its necessary though, as the graph above seems to show my turbo is moving OK.