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You should never see a negative pressure on a Td5.
Try unplugging the MAP sensor and driving, what does Nanocom show then. Have you fitted a 'manual' boost gauge to see what boost you are getting?
My gut feeling is a faulty MAP sensor, or damage to the engine wiring harness.
with the engine off it shows -0.34BAR, when I unplug it it goes to zero, this really feels like a fubar sensor
as a matter of interest, if there is a faulty pressure sensor, how does the ECU know its in overboost?Quote:
Originally Posted by discorevy
Agree , looking like sensor, it's one of the reasons for a manual boost gauge , to answer your question the ecu should take other readings into account and if one is too far out of range should log a fault , it's still worth looking at the iat as that runs of the same sensor, while too much real boost won't do harm for the sake of a test , unless you blow an intercooler hose , not enough boost will cause higher than acceptable egt which can do harm to the engine
remove the MAP sensor, let it plugged in and blank the hole in the manifold with duct tape then start the engine and see the MAP reading at idle, if this way it's OK it means there is a restriction somewhere before the inlet manifold and that's why negative pressure is created by the engine's suction...if this way the reading is still negative get a new sensor...and use the "inputs fuelling" menu to see the manifold absolute pressure cos in "instrument" mode that "turbo pressure" is calculated by nanocom extracting the AAP reading from the MAP reading not some real thing
I've tried a new sensor and things got very strange
the new sensor is a Tridon TMP1108 which Im led to believe is compatible, has a reading of 1.16bar with the engine off and at idle dropping to zero under load
looking at the fuel inputs this appears as 226 kPa
the original sensor shows 67kPa under fuel inputs and appears to track normally
I know nothing about that sensor of your's, the gist is that in inputs fuelling a good MAP sensor should show similar/extremely close at idle to the AAP(ambient pressure) reading and up to 230(or even 240 with a shortened wastegate rod) under load.... if your's goes up then drops to 0 it's oveboost there which occurs if the MAP exceeds 242. The AAP should only drop a little bit under load and be very close to the real pressure there compared to a barometer. See attached how a fairly well running engine's log should be, i managed to set the forge wastegate actuator as to get 240 MAP just below the overboost at max load(pos 92) Attachment 128054
as about thisif the sensor is faulty the ECU limits the fuelling for default max 1 bar boost so not the case of overboost thenQuote:
Originally Posted by bgkdavis
Don't know about compatibility, but polarities are probably reversed. Try a genuine even if its second hand ( borrowed)and working to test the car
I've checked the Tridon website and according to them this is the correct sensor for a 16P TD5 engine, but yeah I thought the behaviour felt like reversed polarityQuote:
Originally Posted by discorevy
Is this a D2a? Correct me if i'm wrong but the D2a also has a sensor in the air box. I thought the ECU checked this sensor and compared it to the MAP sensor in the intake manifold to calculate boost pressure.
So if this is correct it could be either of these senors.
Just to rule it out maybe unplug the boost regulator and bypass it. So connect the hose from the intake pipe that goes to the intercooler directly to the turbo.
Also check the circlip on the waste gate is still there so when it activates it actually moves the rod.