Map Sensor Question

[neverkickn]

When looking at manifold absolute pressure on AE should I see atmospheric pressure plus gauge pressure? Reason I ask is cause I just did a run where I had 20lbs on the boost gauge in the pod but the manifold pressure readout on AE was at 18 or so.

I also selected manifold gauge pressure and was only reading 5 lbs with AE and around 20 on the gauge in the pod.


Is my map sensor toast or am I fuzzy on how the data is calculated into a number on AE?

 

[907DAVE]

MAP sensor reads in "gauge" pressure, not absolute.

EBP sensor reads absolute (BP+Baro).

 

[neverkickn]

MAP sensor reads in "gauge" pressure, not absolute.

EBP sensor reads absolute (BP+Baro).

I just assumed that it was reading absolute because the readout for the map sensor was at 1atm at idle.

AE also has a gauge pressure readout that I assumed did the math and subtracted atmospheric pressure from the readout.

So this is incorrect, the map reads gauge pressure for sure?

 

[907DAVE]

Atmospheric pressure is usually ~14.7.....

 

[neverkickn]

I would see 14.7 on the AE readout at idle, but when I showed 20 lbs of gauge pressure on my analog boost gauge the AE readout only increased to 19lbs or so.

 

[Tom S]

Seems to me AE has both reading available.

 

[neverkickn]

So since my map reading and my boost gauge reading dont line up does that mean that I have a bad map sensor?

 

[907DAVE]

I dont think ~1 psi is anything to worry about.


What make you think it is not your mechanical?

 

[neverkickn]

It is not it is not a 1psi difference it is a 15 psi difference. The map sensor is reading 19psi absolute and the mechanical gauge is reading 20psi gauge pressure.

I just didn't know if that meant the sensor was bad for sure or if there was something else that I need to look at.

 

[neverkickn]

I put on a new map sensor and it there was still a descrepency in my analog gauge and the map readout on AE. That is until it just magically started reading right for a couple of minutes. It is intermittent it seems so I guess I am looking for a short.

 

[neverkickn]

I can hit 30 lbs and my map sensor is still only reading 19 to 20 lbs. It seems that it will only register the first 5 lbs that I make accurately and after that it doesn't see anymore. I did get an overboost code today though when I didn't have the scanner hooked up so I know that it is working some of the time. So I'm guessing I have a short. Any ideas on how to pinpoint the short?

 

[907DAVE]

Map sensor will only read a touch over 20 psi, in my experience.

Whats the truck doing?

 

[neverkickn]

I was having a problem spooling my charger from cruising speeds. Basically anything below 2k and I had to downshift or roll into it really slow or I would smoke out the road. I had a 1.15 exhaust housing on my charger so I tried going back to a 1.0 and it helped tremendously, but I had been told that the problems that I was having with running the larger housing weren't really common.

So I hooked up the scanner and noticed the map readings and wondered if that might be causing my problem. The charger is a stocker with a 66mm intake and a 1.0 exh.

I already checked for boost and drive pressure leaks. I have new uppipe gaskets and the uppies looked good when I had em out.