This is a great explanation. I think I now know what the sensor thing is all about....Thanks.To understand whether or not you need or would want the GMPP MAP sensors you have to understand their job and what they do.
The LNF from factory comes with 2.75 bar MAP sensors and the GMPP sensors are 3 bar sensors. 1 bar of air pressure is equal to 14.7 psi of air pressure. Air pressure at sea level isn't 0 psi, it is about 14.7 psi. Thus anything under 14.7 psi is vacuum and anything above is boost. Thus 1 psi of boost is 15.7 psi of air pressure. 14.7 psi of boost is 29.4 psi of air pressure or 2 bars.
The MAP sensor measures air pressure in the intake manifold (hence Manifold Air Pressure or MAP sensor). The stock 2.75 bar MAP sensors can read up to 40.425 psi of air pressure. Subtract 14.7 for ambient pressure at sea level and you are left with a sensor that will read up to 25.725 psi of boost. At the extreme range of the sensor, the data from it is less reliable. This is why you see a maximum boost reading of 24 psi in your DIC.
A 3 bar MAP reads up to 44.10 psi of pressure which translates to 29.40 psi of boost.
When you up the boost pressure of the K04, 24 psi is about the max you want to run. However, with the stock sensors, if you run 24 psi, the ECM reads 24 psi. if you run 28 psi, the ECM reads 24 psi. This means if you really want to max out the turbo and get the most power out of it, you have no idea if you have gone too far. 3 bars will let you know (though not through the DIC, it will still only read 24 psi but the ECM will now see the true number).
Trifecta and most other tunes for a stock LNF don't push the K04 turbo that hard. 22-24 psi is the range it runs and so the stock sensors are fine. IF you have ANY thought about upgrading the car later and pushing more than 23 psi of boost, the 3-bar sensors are a beneficial upgrade. They don't help make power, they are there to make even more power safely if that is the route you want to go. That route usually includes a bigger turbo, btw.
From everything I have learned on the matter since my initial post about retuning, is no. The stock settings on the ECM are not calibrated for the 3 bar sensors. Also without a tune why would you have an inclination to change to the 3 bar sensors?
I have seen people do that (use GMPP sensors, thinking it was 'racy', somehow) and screw up the stock tune of the car.Also without a tune why would you have an inclination to change to the 3 bar sensors?
Both sensors use the same voltage range to communicate with the ECM (JohnWR can correct me on this if I'm off but this is my understanding of it), This range is roughly from 0-5V This is the same regardless of how many bars they read. So 2 volts on a 2 bar MAP is not the same as 2 volts on a 3 bar MAP.
Unless your MAF fails. LOLI talked to Trifecta about it and they said they could tune for either sensor, but that there was no reason to switch to the GMPP sensors when you wanted a Trifecta tune, even for a larger turbo etc.
You are CORRECT, sir! The accepted range is to 4.75V though, after which the sensor readings go nonlinear. The following is the range data for the GMPP Bosch sensors:Both sensors use the same voltage range to communicate with the ECM (JohnWR can correct me on this if I'm off but this is my understanding of it), This range is roughly from 0-5V This is the same regardless of how many bars they read. So 2 volts on a 2 bar MAP is not the same as 2 volts on a 3 bar MAP.