S40: V40 2.0t '01 Underboosting

[bobe84]

Car performed poorly for about a year.
I had sort of turbo "whine" on acceleration and it lacked middle range torque(1500-3000RPM)
This september turbo started making more horrible noise(compressor just barely touching housing) and turbo went to service. After service everything was super for about 2 weeks.
No turbo whining or perhaps boost leakage.
I have OBD2 cheap chinese elm327, during that period of 2 weeks car was boosting to 155kpa from 95kpa atmosferic pressure. It was able to peak in boost in third at a little over 2000RPM. Really strong pull.
After 2 weeks whining sound started coming back, and started performing poorly in middle range.
Today i tested for boost leaks. I pressurized hose from turbo outlet to the throttle body. Apparently nothing was audible. Had about 1.5bar pressure.


Guys any sugestions?
My observance at cruising and using light to medium throttle i have negative shortterm fuel trim... it goes to -15%
It suggests i have leak but i cant find it.
Now i have to wait to hit peak boost of 60kpa (0.6bar) at 4000rpm. Really laggy medium rpm.
Some directions please for debugging.
Thanks!

Forgot to say, during that period of 2 weeks car didn't misfire and was running really happy at high boost on 40C outside temp.

[Spetsnaz GSh]

Replacing the Turbo Boost Control Valve is always a fairly cheap and effective place to start.

It's located just behind the air box.

[bobe84]

After doing boost leak test, which could be totally inaccurate i noticed more response around 2000RPM so i assume there is boost leak and i couldn't replicate it with my test.

Hose that goes onto turbo outlet seems to have couple of "outside" cracks and it was oily from outside.
Also whine noise is less noticeable now, im lead to assume hose could be source of leak.

Since i dont have time now i will be replacing that hose after new year.
And then we will see.
Also noticed that performance in middle range is down when engine gets up to working temperature.


TCV Valve would not give me -10 STFT on boost right?

[bobe84]

Im attaching screenshot of intake pressure + shortterm fueltrim.

After reattaching hoses i probably tightened them good and lag is less noticable, but there is improvement!

Can brake vacuum hose be leak?
CBV?
I have to make better test for leaking since one of my connections was leaking and i could hear good.

Hose that goes from turbo outlet is oily and has couple of outside cracks. Anyone has experience with that hose?
Definitely when engine all warmed up it is more laggy so im lead to belive that it is hose that starts to leak when warm.

[ww1dm1]

Firstly, you should check the total fuel trims, not just the STFT. If your LTFT is 0 and STFT is -10% then this does not indicate a vacuum leak. On the contrary, the engine wants to run rich.

Anyways, you mentioned that you did a boost pressure test, why are you still chasing around for leaks? Do you doubt the results? If you feel suspicious about tiny cracks on the turbo hose - wrap it in some heavy duty duct tape and see if it makes a difference. Though you should notice such problems during a boost leak test.

Looking at your graph the STFT doesn't seem that bad anyways, +-5% is nothing to worry about. Check your LTFT.

Also, which engine are you talking about? 118/120/147 kW?

[bobe84]

Engine is b4204t3 (2001) it is i belive 120kw.
Longterm fueltrim is 0.8% at whatever RPM/LOAD.

STFT goes -18% at cold start. After driving for some time it settles around -10 to +5%.

Does anyone know at what RPM should i hit full boost in 3rd gear?

[bobe84]

Originally Posted by ww1dm1

Firstly, you should check the total fuel trims, not just the STFT. If your LTFT is 0 and STFT is -10% then this does not indicate a vacuum leak. On the contrary, the engine wants to run rich.

Can you please explain LTFT 0 and STFT -10% why engine wants to run rich?
Does this mean i have bad ignition, inaccurate MAF?

[cheshired5]

What is the MAP reading with engine off, ignition on?

Also, do a graph showing revs and MAP running at the same time.

[bobe84]

Originally Posted by cheshired5

What is the MAP reading with engine off, ignition on?

Also, do a graph showing revs and MAP running at the same time.

MAP reading with engine off key on is 95kpa.

Left graph on the screenshot is infact MAP(Intake manifold pressure)
At idle im showing 30kpa, so atmosferic pressure is 95kpa so it means it is 65kpa vacuum.
Anything beyond 95kpa is boost, i reach about 145kpa max and it is around 50kpa(0.5bar) boost.
Trouble is it is laggy and takes time to build 145kpa.
One thing i tried i disconected TCV line that goes to the wastegate actuator and i could see boost to about 170kpa where i started backing my foot because car started spinning tyres in third gear.
So i belive fuel delivery, ignition spark is all good since it pulls like a maniac with WG hose off.


Left graph shows how the boost is built, it is slow to come on to full bost. In third it takes going over 3000RPM(close to 4k rpm) to reach max.
Looking at fuel trims ltft is constantly 0.8% and stft goes -10 or more when accelerating(on boost). That is why im lead to belive i have boost leak somewhere. Am i correct or am i thinking in wrong direction?

[barrybritcher]

It sounds like it boosted fine with the wg shut. Ie disconnected. So it could be either: tcv, hoses or ecu