MAP sensor range

CurtisF · Aug 9, 2011

What is the actual physical range that a stock MAP sensor can see in terms of gauge PSI. Since I don't have test equipment to check myself, I'd like to find out from some folks who do know for sure. After all, I can only get AE to display boost up to a certain point. And it doesn't match the boost gauge beyond that.

BBottoms · Aug 9, 2011

My AE flat lines manifold pressure at 28psi, so assuming a 14.7psi Barometric reading, the MAP is maxing out at ~42-43 psi. I can check some data logs when I get home to make sure but I think this is correct.

Gearhead · Aug 9, 2011

Factory MAP sensor is done at 25PSIg and shows the full 5 volts. The computer freaks out and thinks the sensor is bad at above 4.7 volts so that's where the overboost error comes from.

CurtisF · Aug 9, 2011

Gearhead said:
Factory MAP sensor is done at 25PSIg and shows the full 5 volts. The computer freaks out and thinks the sensor is bad at above 4.7 volts so that's where the overboost error comes from.

Ok, that's what I've always thought.

Problem is, I can run up to and at 30 psi of boost, and no overboost error. Hit higher than that, and I get a code and the check engine light on.

So that's why I wanted to double check. Next step is figuring out why.

cowboy_dan · Aug 9, 2011

Some information from the TDS archives for the OBS:
Frequency 111hz = 14.7PSIA.
130=20
167=30
203=40
Set code 0237 at 54.7PSIA, which is roughly 256.71 hz.
Also set code 0235 at 5.7PSIA, which is roughly 78.13 hz.

I could have sworn I had the same information for the SD trucks, but I can't find it.

BBottoms · Aug 9, 2011

I just checked mine with AE. The MAP reading maxes at 43.5psi on my OBS, which equates to ~29psi of boost/gauge psi at sea level (same as the data logged "Manifold Gauge Pressure" which is boost)

I believe SuperDutys run a MAP that output a straight voltage versus a frequency like the OBS MAP sensor. Not sure if this changes the maximum reading on the SDs versus the OBSs.

tbolt · Aug 10, 2011

My e99 sets a light @ around 24-25psi. Which is about out of range for my small turbo.

Gearhead · Aug 10, 2011

yeah the OBS trucks are different that the SDs. You really need a mechanical fooler on the OBS trucks because sometimes the sensors will freak out and go to zero boost if you bring the boost up too fast.