burpod
teh stallionz!!1
- Joined
- Nov 27, 2004
- Location
- cape cod, ma
- TDI
- 82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
i posted on ecuconnections, but maybe someone here might have some answers before i bite the bullet and swap to an alh ecu...
so i thought i had my 4bar map sensor working correctly on my rabbit tune, but as i have been fully testing boost above 2bar (3bar absolute) i realized something isn't right.
compared to my new vdo 3bar boost gauge, and using my air compressor and blocked off boost pipes to check for leaks and compare readings with key-on/engine-off, my vcds readings seem accurate up to around 1.9bar (2900mbar absolute) but then seems to quickly lose accuracy and vcds won't read past 2998 even when pumped up to 2.5bar boost which should read 3500mbar. a while back i thought i found a hard limiter for maximum displayable boost pressure, as i could not read past 3014mbar. i changed a number from 3019 to 4000 and then was able to see readings past 3014 (At least in logs). in logs i have taken where i had seen a maximum boost (Steady for a second or more so vcds would pick it up) of 2.5bar, vcds has read 3350 - a bit low. i know i shouldn't be boosting that much, but because my readings in the upper end seem to be much lower than reality, i had been adjusting my n75 values wrong.
i've checked all my wiring, thinking maybe i'm having a wiring issue, but i think that's all good. i can see 3.8v at the solder joint onto the ecu board using pin #1 on the map sensor as ground. based on the map linearization table, this is clearly above 3000mbar. testing voltage between pin #1 and #3 i see steady 5v - this is all with key-on/engine-off. it will not read past 2998. but when i'm doing vcds logs i AM seeing values as high as 3350mbar. however, compared to what i'm seeing on the gauge, these numbers are low - like the sensor is saturated and not reading correctly.
I have tried swapping to a different ecu (another JB ecu), and also tried another new 4bar map sensor. both are bosch, one is vw-branded, the other just plain bosch. and no change. aside from my crappy cluster that has issues (in any car), i haven't had or noticed any strange electrical problems and everything else seems to read correctly, so i don't think now it is a hardware/wiring issue.
but what gives? why the readings max out at 2998 with key-on/engine-off, but vcds logs i see values >3000, although they seem to be inaccurate? it makes no sense, i can read the voltage the ecu should be seeing at the solder joint on the board for the external map sensor and that is a sane value.
i did have a slight boost leak crop up around 2bar that i'm fixing now, but it holds the pressure long enough that i should see higher readings. but maybe somehow that's contributing to the problem. with the car actually running, perhaps it is enough to mess up the map readings.
so i thought i had my 4bar map sensor working correctly on my rabbit tune, but as i have been fully testing boost above 2bar (3bar absolute) i realized something isn't right.
compared to my new vdo 3bar boost gauge, and using my air compressor and blocked off boost pipes to check for leaks and compare readings with key-on/engine-off, my vcds readings seem accurate up to around 1.9bar (2900mbar absolute) but then seems to quickly lose accuracy and vcds won't read past 2998 even when pumped up to 2.5bar boost which should read 3500mbar. a while back i thought i found a hard limiter for maximum displayable boost pressure, as i could not read past 3014mbar. i changed a number from 3019 to 4000 and then was able to see readings past 3014 (At least in logs). in logs i have taken where i had seen a maximum boost (Steady for a second or more so vcds would pick it up) of 2.5bar, vcds has read 3350 - a bit low. i know i shouldn't be boosting that much, but because my readings in the upper end seem to be much lower than reality, i had been adjusting my n75 values wrong.
i've checked all my wiring, thinking maybe i'm having a wiring issue, but i think that's all good. i can see 3.8v at the solder joint onto the ecu board using pin #1 on the map sensor as ground. based on the map linearization table, this is clearly above 3000mbar. testing voltage between pin #1 and #3 i see steady 5v - this is all with key-on/engine-off. it will not read past 2998. but when i'm doing vcds logs i AM seeing values as high as 3350mbar. however, compared to what i'm seeing on the gauge, these numbers are low - like the sensor is saturated and not reading correctly.
I have tried swapping to a different ecu (another JB ecu), and also tried another new 4bar map sensor. both are bosch, one is vw-branded, the other just plain bosch. and no change. aside from my crappy cluster that has issues (in any car), i haven't had or noticed any strange electrical problems and everything else seems to read correctly, so i don't think now it is a hardware/wiring issue.
but what gives? why the readings max out at 2998 with key-on/engine-off, but vcds logs i see values >3000, although they seem to be inaccurate? it makes no sense, i can read the voltage the ecu should be seeing at the solder joint on the board for the external map sensor and that is a sane value.
i did have a slight boost leak crop up around 2bar that i'm fixing now, but it holds the pressure long enough that i should see higher readings. but maybe somehow that's contributing to the problem. with the car actually running, perhaps it is enough to mess up the map readings.