Unwanted Overboost

[logic28]

Ok guys,



I am reading 1.65 bar of boost at 4000 rpm and once even 1.76 at 2600 rpm in my recently acquired Megane II 1.5 dci 106 bhp.

Weird ! Sounds way too much ...

But I have no way to find out what its values should be from the factory.

Dunno if someone previously messed around with the mapping or if it's a lazy "variable vane's" return spring or even simply just a dodgy control solenoid.

But then again it could be the MAP or indeed a faulty software.

The fact being that there are no warnings on the dash nor inside the CLIP diagnostic tool.

???????????????????? 1.6 = overboost ? ? or perhaps Renault intended for it to be so high ?

[overs0ull]

I see before on some reanult same boost holding on laguna dci over 1.55 or 1.6 hold and in the soft been the same from factory cause not been mapped 100% sure .
Also have other thibks to be checked .
1-check all vacum pipes for leakege .
2-check the turbo pressure valve.
3-check the car are have good pressure on exaust system cause if have cat and is blocked we get bacl pressure.
4-check the turbo viriable geometry are is not dirty and are is moving 100% perfect

[logic28]

I see before on some reanult same boost holding on laguna dci over 1.55 or 1.6 hold and in the soft been the same from factory cause not been mapped 100% sure .
Also have other thibks to be checked .
1-check all vacum pipes for leakege .
2-check the turbo pressure valve.
3-check the car are have good pressure on exaust system cause if have cat and is blocked we get bacl pressure.
4-check the turbo viriable geometry are is not dirty and are is moving 100% perfect



Thank you for coming in on this :)


You have seen a Laguna "holding" on 1.55 ? Do you mean been on 1.55 for some time ?


Mine doesn't ... it gets there and comes down following the correct pattern... it just seems like a too high thrashold that's why I was thinking of the variable geometry spring being week.


1- no vacuum leakages
2- pressure solenoid (& peressure) follows exactly the pattern of the control voltage received !... having said so it could be over-boosting on the all range ! ? but it definitely comes down to 0 as it should.
3- if the exhaust was partially blocked wouldn't I get a lower boost ? Gasses wouldn't reach the required speed !
4- If the variable geometry was dirty wouldn't it stick either open or closed for periods ? This boost goes up and down in pressure like it should .... just too far up I think ... :torn:

Would be nice to know the max boost values that it's supposed to have.

Take a look here :wink:

[jnoroeste]

Hi M8,
Renault engines usually have very high svbl, in some cases mone than recommended.
They uses the boost to keep torque even at low ranges.
Check if your ecu file is stock, and if all parts ar working fine, then no problem.

Regards.

[logic28]

Hi M8,
Renault engines usually have very high svbl, in some cases mone than recommended.
They uses the boost to keep torque even at low ranges.
Check if your ecu file is stock, and if all parts ar working fine, then no problem.

Regards.


Hi J,


Thanks for your comment,

The VIN of the ecu is original but about the software I have no Idea.


I would like to check the ecu files but I just don't know exactly how to do that with CLIP, do you by any chance ?




Cheers