Engine/Transmission (1998.5 - 2002) MAP sensor

[JCyrbok]

Hooked my Quick Check II up today and it is pretty cool. One thing that I quickly noticed was WITH THE ENGINE OFF Quick Check said I was making 14PSI of Turbo boost. NOT Bad, LOL.



When I fired the engine up My SPA Boost Gauage ran normal and the Quick Check said that I hit 32 PSI at 100 % throttle, SPA said 20 PSI.



My question is where does the ECM get its boost info from, I'm guessing the MAP sensor? IF so does this indicate that my MAP is not functioning right. I worry about the ECM defueling at pretty low boost due to the bad sensor. If the MAP does not give boost info to the ECM where does it come from? BTW no codes have been set.



One down side to the Quick Check II, atleast on my 2001 is that it does not support the FUEL RATE function of the Quick Check. This sucks as this was one of the major reasons I got it. Back to the drawing board on how to measure fuel rate on my declining LP.



Thanks in advance

J-

 

[ihegdal]

The MAP sensor is an absolute pressure sensor ( Manifold Absolute Pressure ). The normal atmosphric pressure at sea level is about 14. 5 psi. Boost pressure as displayed by the SPA gauge is calibrated to show pressure with the reference set to normal atmosphric pressure and the MAP sensor indicates relative to an absolute vacumn.



I recently read my throttle position sensor using the "Car Code" software and was getting readings of ~10% at idle and ~70% at full throttle from the "TPS %" (APPS) data point , does your Quick Check II allow you to read similar values, or give any indication that your throttle position readings have been scaled so that 10% = 0 and 70% = 100?



Ian

 

[JCyrbok]

Throttle position w/ quick check

Yeah the Quick Check reads throttle position in %. At idle I was at 0% and WOT was 100% it read everything inbetween too. I would reset your APPS and see how your % come out.



It also reads engine load, output torque and abunch of other things too. Its pretty cool. It also reads fault codes and other engine info such as serial number and calibration numbers.



As for the Turbo boost, are you saying that 14PSI on the Quick Check would equal to aprox 0 PSI on my SPA? or am I missing something here?



Thanks

J-

 

[ihegdal]

"are you saying that 14PSI on the Quick Check would equal to aprox 0 PSI on my SPA"



Yes, Since the MAP sensor is an absolute reading sensor it will read about 14. 5 psi with the engine off or at idle. The typical automotive boost sensor/gauge is a relative pressure reading device. They read the the pressure difference relative to normal atmospheric pressure. Since with the engine off or at idle the pressure in the intake manifold is about the same as outside the intake manifold the relative pressure difference is 0 , they indicate 0. AS the turbo builds pressure the SPA goes from 0 to say 20 psi and the MAP will go from 14. 5 to 34. 5.





In your case the the SPA went from 0 to 20 and the MAP went from 14 to 32. So the is a couple of psi unaccounted for, maybe the SPA indicates a little high or the MAP a little low. The SPA is easy to calibrate if you have the 200 series indicator.



Ian