look at it this way. The factory sensors are designed to read 2.5 bar absolute pressure which is 36.2594 PSI. boost pressure is relative to the barometric pressure. lets sat 21PSI boost pressure. at sea level barometric pressure is ~14.696PSI. add those 2 numbers together and you get the absolute pressure of 35.696PSI.
That being said the Bosch sensors do have a little bit of wiggle room. the 2.5 bar sensors are designed to output 4.65 volts @ 2.5 bar.
we can use this equation to find out what the actual maximum pressure the sensor is able to handle.
x_pressure = (((voltage - min_voltage) * max_pressure - min_pressure) / max_voltage - min_voltage) + min_pressure
where
min_voltage = minimum the sensor is able to output for a voltage . gotten from the sensor data sheet
max_voltage = voltage output from sensor at rated pressure (2.5 bar). gotten from the sensor data sheet
min_pressure = minimum rated pressure. gotten from the sensor data sheet
max_pressure = maximum rated pressure. gotten from the sensor data sheet
voltage = the voltage the sensor is going to output for x_pressure
Bosch has these numbers for the sensor.
0.40 volts @ 0.2 bar (2.90075 psi)
4.65 volts @ 2.5 bar (36.2594 psi)
so if we use 5.0 volts for "voltage" the result is ~37.75 PSI. That is the absolute upper limit of the sensor.
Lets see what 24PSI added to barometric is at sea level. 38.696PSI... That is above what the sensor is going to be able to report. While the sensor reading in and of itself is not used to calculate air fuel ratios. It is used to check the consistency of the data reported by the mass air flow sensor. There is the potential for the ECM to register an error and put the vehicle into limp mode because of it. Chances are this is not going to happen but I can tell you that running the sensor above it's rated output can and will cause the sensor to prematurely fail. Would you constantly hit the rev limiter on your vehicle?? Probably not. Why not? Because it's not good for the engine. If you revved the engine to 6987 RPMs (487RPMs above the red line) how many times of doing that before something not so good happens? Well 487 RPMs is 7.5% higher which is what the sensor would be if it is being pushed to the 5.0 volt output. 7.5% higher then it's rated maximum. Think of the pressure rating as the rev limiter, there is a reason why it is there and pushing past it might not be a fantastic idea.
You also have to think about this.
Why would GM put a 2.5 bar sensor in a vehicle that when stock it produced 14PSI of boost at sea level (28.696 PSI absolute) which is 80% of what the sensor is capable of reading? Then you have GM putting in a 3.0 bar sensor for the GMPP tune which increases boost to 19ish PSI at sea level (33.696 PSI absolute) which is 78% of what that sensor is capable of reading. GM feels the need to not exceed 80% of what the sensor is rated for. I wonder why....... Ahhhh I know why. that's because the sensor may not be fed 5.0 volts. if it is fed say 4.8 volts the whole thing changes and you start loosing resolution and range and the rated maximum pressure lowers. so on the 2.5 bar sensor (36.2594 PSI) there would be a loss of 4% if the sensor is fed 4.8 volts instead of 5 volts. That puts the rated maximum at 2.4bar (34.809024 PSI). A 0.2 volt deviation is an acceptable deviation according to SAE. It is the allowed deviation for the accelerator position sensor and also the throttle position sensor and is a fantastic number to use in this scenario because it is an allowed change.
Again the sensor failing or not reading correctly is NOT going to destroy your engine. But it can make your drive a whole lot less enjoyable when you can only boost to 5 psi. And we all know that's going to happen. it's when that Honda pulls up next to you and wants to run.
Man ooo man not gonna live down losing to a Honda. RFLMAO.
$140 for the MAP and the TMAP sensors with the correct o-rings and also the adapters so no cutting of wires needs to be done. simple to install.
www.performanceautowerks.com
