# Absolute Air Pressure senor MAP Bosch 0261230266 how to plot in excel?

#### huramentzefix2

Joined Apr 12, 2024
26
I have an Absolute Air Pressure senor MAP Bosch 0261230266 that I want to use for a "Speeduino" project to meassure absolute pressure and the temperature of the intake manifold of my car.
If the data which I have found is correct then it is the following:
11-245kPa (absolute)
250-4750mV

This is the sensor, klick for information on the link
Pinout:
#1 GND
#2 NTC
#3 +5V
#4 Pressure output in mV

I was trying to come up with a spreadsheet but can't get the formula right.
I am pretty much at sea level, probably 20-30m elevated. My airpressure should be 101.4kPa + the altitude which I will confirm via GPS.
Via the spreadsheet I wanted to confirm whether or not my data for the sensor is correct but I am not getting the formula right.
If I remember correctly then I was getting a reading of about 1700mV.
Can someone help please?

#### LowQCab

Joined Nov 6, 2012
4,309
The precise Pressure vs Voltage-level is basically irrelevant unless You are actually
using it to operate a Precision-Gauge of some sort, that must be extremely accurate.

Mega-Squirt, and Micro-Squirt, both have built-in "Models" that come pretty darn close to accurate,
and I would think that Speeduino would have a similar arrangement for common Sensors,
especially one so vital as a MAP-Sensor.

And in any case, the Engine must be tuned with whatever Data it normally receives,
and, of course, only the end-result is what really counts.
.
.
.

Last edited:

#### Jerry-Hat-Trick

Joined Aug 31, 2022
590
Not sure if I’ve understood your question correctly but the first point I’d make is that atmospheric pressure at sea level typically varies between around 98 and 104 kPa so you can’t rely on that as your reference.

looking at the specification, if the sensor is linear between 11 and 254 kPa (not 245) with an output of 250mV to 4750mV then a pressure difference of 243 kPa gives a voltage difference of 4500mV. 4500/243 = 18.52mV per kPa. Your 1700mV suggests a pressure of (1700 - 250)/18.52 + 11 kPa = 89 kPa but I would not rely on that. The sensor is probably fairly linear but the offset will vary between sensors

But I wouldn’t worry too much about accuracy at this stage, you’ll need to calibrate a working system. To target a stoichiometric mix you have a range of about +/- 10% fuel between lean and rich so approximate values of pressure drop will get you started. Most vehicle EFI systems are more primitive than they’d have you believe, relying on a complex mapping arrangement where fairly simple machine learning software would allow them to “map” themselves