Engine: D5244: - Ecm 6805 and boost related issues

aland · May 14th, 2018, 13:01

Fuel correction test found - interesting issue - I run VIDA in a Windows 7 VM on a MacBook - the video driver was default and was causing some graphics (like the VC2000 image) to not display properly, hence couldn't see it. Once fixed the image appeared.
Fuel correction test shows an imbalance similar to the values in this post https://www.volvoforums.org.uk/showthread.php?t=236336, with 1,2,3 around 7mm2, 4 at 0mm2 and 5 around 30mm2. I did the same test when the engine is working normally and the results are similar.
It's pretty unlikely cy4 is really perfect on all these engines and that cy5 is miles out also - and the fact that my results didn't change when there is no fault agrees with this.

Regarding the suspected VNT issue, with the engine off, a hand-pump moves the VNT actuator through the range. It reaches the end-stop around 18 in/Hg.
I hooked up a vacuum gauge into the turbo actuator pipe, run into the cabin.
This shows that initially when you boot it, there is around 22 in/Hg vacuum, tailing off to 0 as the revs increase. After a few seconds of 0 it goes into limp mode and the vacuum settles at 6 in/Hg. VIDA shows over-boost (flat-line) a few seconds before limp.
When all is well, it also goes to 0 but no limp (and less boost).
If I hold the release valve on the gauge open (so no vacuum to the actuator), performance is considerably reduced confirming that it needs vacuum to create boost, and that the ECU is correctly attempting to reduce the boost when it's over-boosting, then goes into limp.

So, this must mean that either:
- The engine off VNT test is meaningless, as there is no load on the turbo / VNT mechanism - really need to see if the actuator really moves to the zero position when the vacuum is reduced by the ECU when the turbo is spooled up. Might need a carefully mounted Go-Pro and light to find out!
- Or that the MAP reading is often OTT when cold(er) causing the ECU to believe there is waay more boost pressure than there really is.

As the MAP sensor is cheap and easy to swap, I might start there.

May 14th, 2018, 13:01	#33
aland Senior Member Last Online: Jan 17th, 2024 15:41 Join Date: Dec 2004 Location: Luton	Fuel correction test found - interesting issue - I run VIDA in a Windows 7 VM on a MacBook - the video driver was default and was causing some graphics (like the VC2000 image) to not display properly, hence couldn't see it. Once fixed the image appeared. Fuel correction test shows an imbalance similar to the values in this post https://www.volvoforums.org.uk/showthread.php?t=236336, with 1,2,3 around 7mm2, 4 at 0mm2 and 5 around 30mm2. I did the same test when the engine is working normally and the results are similar. It's pretty unlikely cy4 is really perfect on all these engines and that cy5 is miles out also - and the fact that my results didn't change when there is no fault agrees with this. Regarding the suspected VNT issue, with the engine off, a hand-pump moves the VNT actuator through the range. It reaches the end-stop around 18 in/Hg. I hooked up a vacuum gauge into the turbo actuator pipe, run into the cabin. This shows that initially when you boot it, there is around 22 in/Hg vacuum, tailing off to 0 as the revs increase. After a few seconds of 0 it goes into limp mode and the vacuum settles at 6 in/Hg. VIDA shows over-boost (flat-line) a few seconds before limp. When all is well, it also goes to 0 but no limp (and less boost). If I hold the release valve on the gauge open (so no vacuum to the actuator), performance is considerably reduced confirming that it needs vacuum to create boost, and that the ECU is correctly attempting to reduce the boost when it's over-boosting, then goes into limp. So, this must mean that either: - The engine off VNT test is meaningless, as there is no load on the turbo / VNT mechanism - really need to see if the actuator really moves to the zero position when the vacuum is reduced by the ECU when the turbo is spooled up. Might need a carefully mounted Go-Pro and light to find out! - Or that the MAP reading is often OTT when cold(er) causing the ECU to believe there is waay more boost pressure than there really is. As the MAP sensor is cheap and easy to swap, I might start there. Last edited by aland; May 14th, 2018 at 13:04.

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