GM Map Sensor Gain/Off Set

[lazaris]

Does anyone have the gain and off set values for the GM 2 bar map sensor for XFI?
I want to use it to log crank case vacuum.

 

[RmvBfrFlght]

Interesting application. It would also show any crankcase pressure. Here is the transfer function for the GN 2-bar MAP, which also matches the small form factor 2-bar sensors (09350899 & 16235939):

Vout = Vref * (KPa * .005 - .04)

Vref being the power supply to the MAP sensor voltage (typically 5.0 or 5.1 volts).

RemoveBeforeFlight

 

[lazaris]

Anyone?

 

[RmvBfrFlght]

Anyone?

Did I misunderstand which MAP sensor you want to use?

RemoveBeforeFlight

 

[lazaris]

Did I misunderstand which MAP sensor you want to use?

RemoveBeforeFlight

I'm going to use the stock 2 bar GM map sensor. I have to input the gain and off set values in the XFI to make it read correctly.

 

[RmvBfrFlght]

OK, the transfer function I posted is correct for that MAP sensor. Just need to swap it around to go from voltage to KPa.

RemoveBeforeFlight

 

[karolko]

2bar Map sensor:
Sensor Gain: -12 Sensor Offset: 30 Sensor High: 30 Sensor Low: 0 Decimal Places: 0

my contribution for the week.

 

[bison]

You should try and find a 1 bar for higher resolution.

 

[karolko]

1 Bar will not allow for Boost pressure, only vacuum.

Personally, I feel that it is a relative value that we are looking to see, weather C.Case pressure is increasing or staying stable during a run, and being able to compare it to when you are not using a pump.

That being said I run a LT1 pump strickly to control oil leaks, not for power and I can clearly see a change in vacuum during a run. I use a 2 bar

Adrian

 

[kidglok]

If it's .5-4.5v output it would be
Gain 7.5
Offset -18.75

 

[lazaris]

2bar Map sensor:
Sensor Gain: -12 Sensor Offset: 30 Sensor High: 30 Sensor Low: 0 Decimal Places: 0

my contribution for the week.

Thank you. Will those settings read in inches of vacuum or pressure?

 

[HighPSI]

The values I texted you last Monday were to display vacuum in inHG. It will actually display pressure in negative inHG. Like I texted you earlier, if you want it to display the pressure in psi, then it will display the vacuum as negative psi.

 

[lazaris]

The values I texted you last Monday were to display vacuum in inHG. It will actually display pressure in negative inHG. Like I texted you earlier, if you want it to display the pressure in psi, then it will display the vacuum as negative psi.

Yes I know, I was curious as to Adrians settings since he didnt say how it read and they were different from yours.

 

[HighPSI]

The gain and offset are the same. What I gave you will just display one more decimal place. I could be mistaken, but I think Adrian got his values from me also

Posted from the TurboBuick.Com mobile app

 

[lazaris]

The gain and offset are the same. What I gave you will just display one more decimal place. I could be mistaken, but I think Adrian got his values from me also

Posted from the TurboBuick.Com mobile app

Lol. Thanks again Cal.

 

[karolko]

Hey Guys, sorry for the response,

Yes the numbers I listed were originally from Cal Hartline. They are in InHg and like Cal said, InHg are positive values.

I run a LT1 pump and I see 2 InHg of vacuum when the pump is on, and it stays stable when it is on.

I activated it with one of my Aux outputs and that's it.

I am logging from the passenger side valve cover and pulling from the drivers side.

I never really took the time to tweak the sensor so it is perfect, but it is on my list of things to do over time, but to me honestly it only needed to give me a relative reading and I can see if I am getting major blow-by.

I will say that I ran the car once with the pump on and once without and the log did show that without the pump I was getting more crankcase pressure.

A

 

[lazaris]

Hey Guys, sorry for the response,

Yes the numbers I listed were originally from Cal Hartline. They are in InHg and like Cal said, InHg are positive values.

I run a LT1 pump and I see 2 InHg of vacuum when the pump is on, and it stays stable when it is on.

I activated it with one of my Aux outputs and that's it.

I am logging from the passenger side valve cover and pulling from the drivers side.

I never really took the time to tweak the sensor so it is perfect, but it is on my list of things to do over time, but to me honestly it only needed to give me a relative reading and I can see if I am getting major blow-by.

I will say that I ran the car once with the pump on and once without and the log did show that without the pump I was getting more crankcase pressure.

A

Actually the numbers you listed were different from Cal's. The Gain and Off-Set values are reversed.

 

[karolko]

deleted post not to confuse anyone in the future

 

[HighPSI]

Karolko's values are correct. They should be:
Gain= -12
Offset= 30

I must of reversed them when I texted them to Ralph

 

[lazaris]

Ok np thanks.