Hi everyone, pulling my hair out with an ongoing issue that seems to be undiagnoseable.

I have a 2017 4.4sdv8 57000 miles,

Driving around normally keeping the revs below 2500rpm everything is all fine and dandy, however take it above those revs when the 2nd turbo kicks in whether thats booting it or not the car just becomes bogged down and loss of power but you can momentarily feel the 2nd turbo kick in then it just becomes flat as a fart. even if you manually change up a gear dropping the revs back below 2.5k until you lift of the throttle 2-3 seconds then everything returns to normal. Take the revs back upto 2.5k and same again, does it when cold and warmed up. The only thing that changes is a loss of power and a change in the engine note.

Been plugged in to diagnostics no faults at all, have read live data 2nd turbo boosting and operating normally, the car seems to think everything is happening but its not?

Becoming frustrating and wondered if anyone had any ideas on what could be causing this? Or what else to check?

Many thanks, jamie

What diagnostic tool has been used, and who did it...?? Pete

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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Hi pete, think it was a solus pro and a good friend i know, we both sat in the car and went for a drive around monitoring all live data.

Only thing we noticed with the bonnet up in the air and engine cover off was a mechanical chainy type noise coming from what i think is the hpfp not sure if this is normal or not?

Its almost like a boost pipe collapsing and being starved of air or not getting enough fuel but surely both of these would cause some sort of dtc fault?

Just checking on the scanner you used, the Snap On Solus are good so should show something...

Very weird, I would guess fuel and it does sound like a HPFP issue but it's above my pay grade.... Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Thanks for your advice pete, its a very strange issue and driving me insane!

Ill take another look at the live data and focus again on fuel pressure readings 👍

Could it be an air flow meter ? I think that each of the turbos has its own air inlet route which is joined after the turbos on the way to the throttle body an plenum. After each of the air filters on each side there are sensors plugged into the pipework. Whilst I’ve never checked, I’ve presumed them to be air flow meters.

If the MAF for the large second turbo isn’t reading quite right , that could explain the bogging down. For example, when the 2nd turbo spools up and starts drawing air across the sensor, the sensor is sending a low reading cause it’s not working correctly.

The ecu then may see high pressure at the plenum (cause the turbo is working), but low air flow … so might deliver less fuel than is actually needed, and the performance dies.

The scenario may not throw errors as the sensor may be sending a value within spec … just the wrong value for the actual airflow. ( although re reading your post does say you were looking at the turbo values … sorry )

May be worth looking at the air flow readings as you the second turbo kicking in. V8 or else ...

Hi fisha,

Certainly worth another look! Thanks for your reply. Im hoping in the next day or so to get someone who understands the live data allot more than we did to take a look but i will keep you posted 👍👍