Hi,

 

Does anyone know the standard amount of boost for a BXE 1.9 PD engine?

 

I ask because I have recently had a power loss when pulling through the revs, which has since sorted itself, but I suspect sticky VNT vanes, or bad turbo actuation.

 

Previous history: 5000 miles (about a year ago) I popped a boost hose off and encountered similar symptoms, but this hose was refitted and is still secure.  At this time, I also cleaned the EGR and ASV and it's run fine since - although I did not renew the gaskets, I can see no leaks (soap solution on the EGR joins does not bubble).

 

Car does a lot of 20 mile journeys but once a week I get her warm and pull her through the gears until 4000 rpm.  Recently I completed a 100 mile M-way journey which was mostly low throttle in 5th gear.  When near home I pulled out of a services onto the slip road and booted her, she pulled fine until 3500 rpm in third, then felt like she's lost all boost, limped 10 miles home.  No check engine light.

 

Today I fired her up after checking the boost hose from before was still OK, it was.  Vacuum hose from pump looks on OK, vacuum hose to turbo actuator looks on OK.  Car now runs fine even when revved.  I then do another test run with a cheapo OBD-2 dongle wirelessed to phone mounted on the dash, no fault codes show up, and I select "MAP sensor" as a realtime readout.  Car runs fine through the revs and at idle MAP is ~100kPa i.e atmospheric.  At full throttle around 3000-4000 rpm I get 220 kPa i.e 1.2 bar of boost which settles to around 200-210 kPa (1.0-1.1 bar boost).  Again, car feels fine.

 

Questions:

i) What should my MAP/boost be maxxing out at?

 

ii) If overboosting caused by sticky vanes, should I just get her warmed up and intermittently rag her a bit more to work the vanes back and forth?  I'm aware of the Mr Muscle fix but I don't want to disassemble things yet based on an intermittent fault.

 

Cheers  

 

 

 

 

 

 

 

Sounds similar to my experiences, I have a post on it.  Long story short the turbo actuator diaphragm internal return spring had rusted and snapped so I was enjoying overboost performance until things got so bad that sustained foot to the floor of more than a few seconds would trip limp mode without ECL.

 

Easy check, by hand with engine not running ensure the actuator moves smoothly between the stops and returns to a stop with a positive spring action.

I've managed to move the actuator rod by hand (using pliers - its tight behind the BXE and the EGR cooler and actuator bracket don't give much room).

 

Push rod up into actuator~1cm, let go, rod drops back down briskly by itself.  There's a slight squeak which I suspect to be either air moving within the diaphragm or the rod as it enters the actuator.  Seems like there's only 1cm of range and I don't want to force her.  I try pushing rod further *down* and it moves about a cm that way but feels a little gummy, and it stays down, doesn't spring up.  Then back up to the top and it drops back by itself.  Does the vacuum suck the rod "up" on these turbos?  I think there are Garrett and 3K versions, not sure which I have.

 

So the rod's preferred relaxed position might be in the middle of possible ranges.  Hard to say whether it drops back to dead bottom or just to its middle position, it's hard to see the movement exactly because of poor access.  I suppose I could paint a mark on it.

 

Take the car out for a spin, no fault codes.  Car drives fine and on a second and third gear max throttle pull to ~4500 rpm. Pictured: In second, the boost spikes at about 3000 rpm in second to a large 1.35 bar.  However within 1 sec it's controlled to 1bar and stays at 1 bar until I shift.  Third gear, the boost barely exceeds 1 bar (1.05 bar) from 3000 to 4500 rpm.

 

I'm assuming: that at max throttle and max rpm, the VVT vanes would have to be fully open else overboost.  So the fact that it can hold 1bar is encouraging that I have decent range of motion of the vanes.  But I'm spiking boost so maybe the mechanism is a tad sticky which delays response? 

 

Or is 3000 rpm the "naughty spot" where the compressor hits max boost at average airflow, and at higher RPM the turbo can't supply mega boost at mega high airflow so it's easier to avoid overboost there?

 

 

 

 

There's your problem, at rest the actuator should be pegged at the stop, not somewhere between the stops.

Here's the long version: 

 

Thanks.  Tomorrow I will explore the lower travel on my actuator rod again.  I think I had similar millimetres of travel to you  Could be my spring is porked, Could be the vanes are gummed up and the spring isn't meaty enough to push through the gum, in which case hand movement might help.