3 bar map sensor trouble

[aruss99]

Hi all,

Recently finished my turbo ls build, with no major issues except for the map sensor. The motor is a 2003 lm7 5.3l with 80lb injectors. It runs just fine with the stock map sensor, but when I convert to a custom os, (3 bar speed density) the map sensor reads either way high, or way low. (0 kpa at key on, 314kpa when running.) The motor will run for a little bit, then dies. I have gotten it to read correctly once, let it idle up to temperature as it should, shut it down, and the next day, without changing anything, the truck wouldn't even start. I am at a loss as to what to do because all the forum threads I have read have said the only changes necessary is changing the linear offset and the scaling of the map sensor... I have a log of the motor trying to start as well as my 3bar tune. (the IAT sensor was unplugged in the data log, but having it plugged in makes no difference to the results I am having) if anyone has any suggestions on things to try that would be very much appreciated... this is the second 3 bar map sensor I have gotten, so I am confident it is not an issue with the sensor itself.

Link to tune and log files https://drive.google.com/open?id=0B1...mROVDNBTU9SNU0

Thanks

[akdg87]

did you rescale the VE table? are the map sensor parameters correct?

by upgrading to the 3 bar you are taking resolution out of your VE table compare your stock VE table to the 3 bar OS.

Also ensure you have correct injector data

[aruss99]

Originally Posted by akdg87

did you rescale the VE table? are the map sensor parameters correct?

by upgrading to the 3 bar you are taking resolution out of your VE table compare your stock VE table to the 3 bar OS.

Also ensure you have correct injector data

Not 100% sure what you mean by re scaling the VE table. If you mean the table now reads up to 300ish kpa as opposed to 105kpa then yes I have, but that change was made automatically once I switched to the 3 bar tune.. I have not made any changes to the VE table. The two changes I made for the map sensor parameters is the linear setting and the offset. Both of those values came from EFI source which is where I got my map sensor from. I am confident my injector data is correct as it runs like a champ on the 1 bar tune with the stock map sensor.

[akdg87]

Originally Posted by aruss99

Not 100% sure what you mean by re scaling the VE table. If you mean the table now reads up to 300ish kpa as opposed to 105kpa then yes I have, but that change was made automatically once I switched to the 3 bar tune.. I have not made any changes to the VE table. The two changes I made for the map sensor parameters is the linear setting and the offset. Both of those values came from EFI source which is where I got my map sensor from. I am confident my injector data is correct as it runs like a champ on the 1 bar tune with the stock map sensor.

when you switch to the 3 bar it will copy the 1 bar VE table over with its values up to 315 KPA, what you need to do is put the correct VE values at the corresponding KPA VS. RPM. You only have correct data up to 105 KPA (non boost region). 105-315 KPA is a guess until you data log and see what the pcm desires.

From HP Tuners:
The VE table will be full of invalid data. You *must* create a valid VE table before writing the file to the PCM. It is a good idea to copy your previous VE table into the non-boost region and then copy and increase the last row of the VE table to the new boost area. It is important to start tuning on the rich side (higher numbers) and then work back to your desired AFR.

EDIT:
Did your new map sensor require you to cut/splice in a new plug?
at idle it should be around 40-55 KPA
314 KPA when running is WAY to high.

[aruss99]

No, the map sensor plugged right in. The only thing that was changed was in the tune. The offset and linear data. Even if that was wrong though, I would think that the map sensor reading would still change as the motor idles because of the change in load, but the issue I am having is that the map sensor reading does not change at all. From the time I start cranking to the time it dies (if I can even get it to start) it reads 314 kpa. I am at a loss as to what could be causing the problem...maybe a dtc that needs to be changed/removed?

The reason I think it can idle for a short period of time is because I believe that while cranking the motor uses a different table to get the car to start, and ignores the map sensor?? But soon after the motor is running, it switches to the regular VE table, where is sees a 314kpa reading and immediately dies.

[BR3W CITY]

Which GM 3bar sensor? They don't all play the same.
GM 12223861 -14.4PSIg (2kPA, 20mbar) to 31.1PSIg (316kPA, 3160mbar)
GM 12219935 -8.3PSIg (44kPA, 440mbar) to 30.8PSIg (314kPA, 3140mbar)
GM 16040749 -13.1PSIg (11kPA, 110mbar) to 29.3PSIg (303.4kPA, 3034mbar)

[aruss99]

Not sure of the part number, it is a efi source ls1 style map sensor.

[akdg87]

Originally Posted by aruss99

No, the map sensor plugged right in. The only thing that was changed was in the tune. The offset and linear data. Even if that was wrong though, I would think that the map sensor reading would still change as the motor idles because of the change in load, but the issue I am having is that the map sensor reading does not change at all. From the time I start cranking to the time it dies (if I can even get it to start) it reads 314 kpa. I am at a loss as to what could be causing the problem...maybe a dtc that needs to be changed/removed?

The reason I think it can idle for a short period of time is because I believe that while cranking the motor uses a different table to get the car to start, and ignores the map sensor?? But soon after the motor is running, it switches to the regular VE table, where is sees a 314kpa reading and immediately dies.

dumb question but are you logging with the 3 bar map PID in hp tuners?

[aruss99]

Originally Posted by akdg87

dumb question but are you logging with the 3 bar map PID in hp tuners?

Yes I am

[akdg87]

Possible they have a bad batch of sensors, i know they were out for while when i tried to order mine.

Whats your linear and offset values?

Double checked for bent or pushed out pins?

[aruss99]

No pins are bent, guess that leaves the sensor then. Only things that need to be changed in the tune is the linear and offset correct? Because if so then I have done everything correctly and may have to go a different route with map sensors.

Offset is 10.33 and linear is 305

[Hart_Rod]

I don't think you have your scanner setup correctly. You need to upload your configuration file so we can see how you did it. Also, if possible find the part number for you MAP sensor and post it.

[davepl]

Aha... when I did this with my turbo build using a BS3 computer, it automatically "rescales the VE" when you change the MAP range. Now I know what they meant!

I guess if you don't the cell pressure value changes on the axis but the cell contents do not, so you wind up with a nonsense VE table.

[aruss99]

I will post the config file as soon as possible, senior year has just started for me so it's been pretty hectic. I couldn't find a part number for the map sensor I have but here is a link from where I bought it. Hope it is somewhat helpful http://www.efisource.com/shop/ls1-st...ar-map-sensor/