Thread: turbo boost pressure

with the engine off it shows -0.34BAR, when I unplug it it goes to zero, this really feels like a fubar sensor

Originally Posted by discorevy

Try going to 9 threads , see what your reading is under full boost , you won't harm anything as the ecu has protection if it over boosts

as a matter of interest, if there is a faulty pressure sensor, how does the ECU know its in overboost?

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) Good readings.xlsx

as about this

Originally Posted by bgkdavis

as a matter of interest, if there is a faulty pressure sensor, how does the ECU know its in overboost?

if the sensor is faulty the ECU limits the fuelling for default max 1 bar boost so not the case of overboost then

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

Originally Posted by discorevy

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 polarity