Forum » General Tuning Discussion » Jaguar V 12 map sensor install

Jaguar V 12 map sensor install

General Tuning Discussion

Forum Posts



Tech Articles

Discuss all things tuning in this section. News, products, problems and results. 

= Resolved threads

Page 1

Hello people.

This topic has come up and I have seen people nod their heads that they understand. Now I don't. So bear with me. My current project is 1986 Jaguar xjs v12 5.3 naturally asperated. Stock motor internals, modify intakes, exhaust, standalone ecu ( Omex 710) and much more. With their help and being a gold member of HP Academy you folks have help me so much. To increase my knowledge of what ecu's are capable of. For my application I'm probably only using 20% of what this 710 can do. Now my issue. I have decided to install a map sensor to assist in the idle and light throttle transition area. This map sensor is a 1 bar ( GM 16165793 ). The ecu is looking for:

Load scalar

Load offset

I have searched the internet, Read manuals, consumed vast amounts of vodka and still.....

Build picture and Omex tab in question attached.

Thanks for any help

Attached Files

Additional info: Pressure In Hg / kpa Voltage

Atmospheric ( basically sea level ) 0/0 4.91

-5/16.9 3.89

-10/33.863 2.97

-15/50.795 2.06

-20/67.727 1.17

-25/84.659 0.27

This my tested info with vacuum pump and voltage meter.

Since the sensor has a linear output, the line is defined by the equation Pressure = Scaler * Voltage + Offset (this is the classic Y=A * X + B, but using their terminology).

From High School Algebra, we solve this first by determining the slope (Scaler).

That is Rise / Run (y2 - y1) / (x2 - x1) or using first/last points:

(-5 - (-25)) / (3.89 - 0.27) = 20 / 3.62 = 5.524 (units are inHG / volt).

To calculate the Offset, we just solve for B using one of the data points (let' used the first one 3.89, -5), let's rearrange the equation:

Offset = Pressure - (Scaler * Voltage)

Offset = -5 - (5.524 * 3.89) = -5 - (21.49) = -26.49

So, your scaler for inHG is: 5.52, and the offset is -26.49

Thank you very much David.

I will work the math to verify I understand how you reached the values. I was in high school in the mid 70's so my math skills were confined to mainly ounces lol. Thanks again