MAP Sensor reading to low for elevation

[75280z]

So just as WigenOut-S30 found out, as well as I did, you can't search for map and Manifold Absolute Pressure doesn't seem to turn up a whole lot.

 

The Car:1975 280z, l28et, MS1v3 MSNSe running 83 turbo dis, Stock Turbo, no IC, stock turbo injectors with resistors inline.

 

The Problem:

 

I live in Denver about 5000 ft above sea level, but my MAP (Manifold Absolute Pressure) Sensor is reading 42KPa with the engine off just at ATMO, where the Megamanual says it should be reading right around 80Kpa. This is the normal MAP sensor that came with MS the 250kpa version.

 

I have taken the board out nothing seems to be distressing the sensor, everything looks very well soldered in I checked the voltages going into/out of the Sensor everything seemed normal. I have unplugged the tube to make sure some how it wasn't something in the tube. The sensor still reads and moves when I start the car, but never even hit 100 Kpa even when under 7lbs of boost which should be somewhere around 130kpa. At idle the car sits at around 18Kpa.

 

The question is my MAP sensor bad, do I need to replace it, or just re tune my table to accommodate the lower values?

[cygnusx1]

I would call DIY and get a new sensor or upgrade to the dual sensor type.

[mario_82_ZXT]

It will read lower the higher in elevation you are because the air is less dense.

 

http://en.wikipedia.org/wiki/MAP_sensor

 

At your altitude you'll be able to run slightly more boost before maxing out the sensor.

[75280z]

I would call DIY and get a new sensor or upgrade to the dual sensor type.

Man I don't want to spend more money, but honestly I mainly don't want to throw money at a problem unless that is the actual solution i am spending money on. Also glensgarage has a much better price on the 2.5bar sensor. I ordered my MS stuff through him several years ago and he was really nice. That being said Matt over at DIY is awesome too.

 

It will read lower the higher in elevation you are because the air is less dense.

 

http://en.wikipedia.org/wiki/MAP_sensor

 

At your altitude you'll be able to run slightly more boost before maxing out the sensor.

I know it will read lower but the megamanual as well as putting in atmospheric pressure here an converting it to KPA should be much closer to 80kpa which means it is reading at half of the value it is supposed to.

Edited September 24, 2010 by 75280z

[Matt Cramer]

Could be a hardware or a configuration problem. Try taking the case lid off, turn the ignition key on, and check the voltage at pin 1 of the MAP sensor (the square hole on the 6 pin header). What voltage do you see with the engine off?

[75280z]

Could be a hardware or a configuration problem. Try taking the case lid off, turn the ignition key on, and check the voltage at pin 1 of the MAP sensor (the square hole on the 6 pin header). What voltage do you see with the engine off?

 

The voltage is 2 Volts from ground to pin 1. I checked a while back to make sure the words written on the sensor were facing out and they were.

[Matt Cramer]

2 volts should be more like 80 kPa than 40. I'd check to be sure this is getting all the way to the processor and that you haven't somehow accidentally set it for a 115 kPa sensor in the Configurator.

[75280z]

You know I hate when people don't come back and update posts so here I am. I got some time to look through my configuration files today. I had changed the values in the basic configuration, but not in the project configuration, and since I was using tuner studio I didn't know how. I learned and checked the settings. Guess what Matt Cramer you were 100% correct the settings in the project were for the 115Kpa sensor. So I changed the values and now my MAP (Manifold absolute Pressure) sensor is reading a correct value of 80kpa with the engine off!

 

Now I can more accurately tune my car and make it more drivable. Thank you every one. Also on a side note if you have problems with your MAP sensor please place the text Manifold Absolute Pressure in your post that way people searching with similar problems can still look in this forum setup.