I just got an AEM 3.5 bar MAP sensor and, using the voltage to pressure specs included with the sensor, it is reading almost 3 psi lower than my Defi D boost gauge and almost 2 psi lower than my electronic boost controller.

Do you really just need to take the enclosed calibration with a grain of salt and derive the proper conversion table from an accurate reference source?

All 3 boost gauges are tee'd off the same vacuum line from the manifold and the most distant one from the manifold is reading the highest and the closest one is reading the lowest.

 

Well, generally boost gauge sensor (cheap) arent as good as a nice map sensor. I used to have 3 things tapped to my boost line and they all read a few PSI from eachother. Where do you have the AEM MAP sensor connected?

 

The Defi boost gauge is mechanical. Boost line to the AEM is tapped off the factory vacuum line from the intake manifold to the BOV.

 

Have you tried testing all 3 independently? Is there no pressure loss with multiple taps?

 

I had the Defi boost gauge first when the car was fairly stock. Boost peaked at 19 psi and fell to about 16 psi by redline. Seemed about right. Then I added a Blitz electronic boost controller tapped off the same line. The Blitz reads about 1.2 psi lower than than the mechanical gauge, but the line to the Defi gauge is longer, so I would have assumed that any pressure loss would make the Defi read lower, not higher. The AEM map sensor is the closest of all to the boost source and I've seen no change in the reading of the Defi and Blitz ebc from adding the AEM MAP sensor.

 

Noted. I'm not sure then...you'd think the MAP was more accurate. It may go back to your original thought of boost being relative to the observer. Maybe you are seeing ACCURATE boost pressure, whereas everyone else THINKS they are running higher boost. I'd like to hear the conclusion of this...

 

I would trust the EMS map sensor over anything else. Especially over a mechanical gauge and an EBC display.

besides, boost pressure is only a relative thing anyway. who cares what boost pressure your actually running? Just run the most you can get away with in your tuning variables. If that ends up being 20 or 22, or 24 on one gauge and 20 on another..what differance does it make in the end.

 

The map sensor is medical grade and accurate to 1/10 or so of 1 psi. All of the regular boost gauges I have seen, read a little off and too high at higher psi. Rely on the map if you want to know what you are really boosting too...

 

Well, one thing would be the life of the turbo...

 

i was told by a few supra and evo buddies of mine not to tee off of the same manifold vacuum source too many times as this could possibly cause inaccurate readings. i have my hks evc and defi boost gauge tee off of 2 different vacuum lines and they read almost dead on with each other. i could be wrong though just my 2 cents.

 

Funny thing - the AEM reads low on boost

Compare the sensor voltage as logged by AEM and sensor calibration (sensor manufacturer) and you will see what I am talking about

I refer to AEM boost as a seperate measure

 

with the car off and the ignition on, what is the aem 3.5 bar giving you for a reading in the parameter window? mine seems to be reading .2psi for some reason. something might not be correct in the calibrations somehow.

 

I was under the impression that map sensors need to be tapped off the manifold? Perhaps the rre adapter?

 

You may also need to calibrate it for the software using it. Depending on your sea level it will change.

 

With the car off, the sensor is reading 1.58 volts, which equals -1.2 psi using the calibration table included with the sensor. Hmmm...