Some MAP tables for the 3800

[Perforator]

Hi, I need to have the following tables mapped for the 3800. On the PowrTuner they are labeled: MAP_Scaling_Factor, MAP_Sensor_Offset and Default_Max_MAP. These are used to install a 3-bar map sensor. I have one installed now and if I ever want to go back to a 2-bar map sensor, I'll have to keep the PowrTuner because I can't change them in the HP Tuner unless I'm missing something... Let me know if you need any more info.

Thanks,
Mark

[Chris@HPTuners]

i can add the MAP sensor calibration params, but do you realize the PCM code limits the maximum MAP reading to 200kPa? No matter if you rescale for a 3bar sensor or not. ie. Unfortunately, unless you mod the operating system code there is no point putting a 3bar sensor on your car

Also, the Default Max MAP value is only used if the MAP sensor fails and the PCM switches to quasi Alpha-N mode where it estimates the MAP from TPS and RPM. It has no use when the MAP sensor is operating correctly and you don't really need to change it unless you want to calibrate the other 4 tables that are used to estimate the MAP value if it fails.

Chris...

[Perforator]

i can add the MAP sensor calibration params, but do you realize the PCM code limits the maximum MAP reading to 200kPa?
Chris...

Isn't the MAP a sensor? I realize that the tables in the code only go to 200kpa, but that shouldn't limit what the sensor actually reads???

[Chris@HPTuners]

Isn't the MAP a sensor? I realize that the tables in the code only go to 200kpa, but that shouldn't limit what the sensor actually reads???

Sure the MAP is a sensor, but the code that reads the sensor limits the maximum read value to 200kPa. Often GM does this, eg. the GM LS1 code limits the MAP Sensor reading to 105kpa. You can put any sensor in there you want but the maximum MAP the PCM can ever see is 105kPa until you change the harcoded limits. Even worse the 4cylinder code actually hardcodes the scaler and offset values making things even more annoying.

GM likes to have fun don't they?

[Perforator]

Sure the MAP is a sensor, but the code that reads the sensor limits the maximum read value to 200kPa.

How does it do this? If the MAP sensor value is greater than 200kpa it replaces the value with 200kpa? Is that actually in the code?

[Chris@HPTuners]

How does it do this? If the MAP sensor value is greater than 200kpa it replaces the value with 200kpa? Is that actually in the code?

yes

[Perforator]

Well that stinks, lol.
Any other sensors you know of that the pcm does this for?

[Chris@HPTuners]

most values in the PCM are clamped at certain limits, sometimes its the internal binary decimal limit, sometimes it is something lower as in this case.

Not many are important, but the MAP is for FI apps and generally so is the upper limit on MAF, VE Airflow and associated Cylinder Airmass limits. In the V6 code the MAF and VE airflow limit is 512 g/sec and cannot easily be changed.

How much boost are you running?

[Perforator]

I'll have to check my old logs. I know I was getting close, that's why I installed the 3 bar. I haven't really done anything to the car or scanned since the summer...

[Perforator]

How much boost are you running?

Chris, I just checked and the highest MAP reading I had was 198...

[Foghorn]

Chris, I just checked and the highest MAP reading I had was 198...

Very interesting info Chris, something we PT guys never knew.

In the past I've seen up to 205 kPa with a 2.8" pulley, interesting to learn I was in the Twilight Zone.

Cheers,

[johnh]

lol...I've seen 201 kPA, but never anything higher...

[Perforator]

Well that doesn't make sense in light of what Chris said now does it lol.

[devildog9999]

One all of the scans I have ever done, even on turbo applications, the max MAP values are 200, regardless of boost or sensor type.

[Perforator]

Chris, I was thinking about this and had an idea. The portion of code you are referring to that limits the MAP reading, is it possible the code is doing some kind of table lookup or airflow calculation? I'm thinking that the PCM would indeed have to limit the MAP value when doing table lookups or airflow calculations but when we scan, it reports the actual value returned by the MAP sensor??? Does that make sense, lol?

[Chris@HPTuners]

no the value is limited right after it is converted from a voltage to kPa. The MAP (SAE) PID is limited to 200. This 200 kPa limited MAP value is used throughout the entire PCM code.

you could scan the MAP voltage PID and create a user defined PID that converts the MAP voltage to kPa if you really wanted to see values higher than 200 in the scanner

[Perforator]

you could scan the MAP voltage PID and create a user defined PID that converts the MAP voltage to kPa if you really wanted to see values higher than 200 in the scanner

Now that's a good idea!
Thanks Chris...

[Perforator]

you could scan the MAP voltage PID and create a user defined PID that converts the MAP voltage to kPa if you really wanted to see values higher than 200 in the scanner

Chris, what would be the formula to convert the MAP voltage to kPa?
Thanks!

[Chris@HPTuners]

for a 2bar sensor try something like

kPa = 39.73 V + 9

for a 1bar sensor it is usually:

kPa = 18.87 V + 10.33

[Perforator]

Thanks Chris, what about a 3 bar sensor?
Also in that formula, is it 39.73 * V?