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Discussion Starter #1
Just for the heck of it I was watching the MAP readings yesterday on my Edge CTS readout. At idle I was showing 12.0 psi. Driving down the road, I read anywhere from 14 to 18 psi. These seem low to me...does anyone know what normal MAP psi readings should be?

Thanks,

Griz
 

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how hard did you step n the pedal to get 18?

i think he most you will see through the map is 21-22
 

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Discussion Starter #3
how hard did you step n the pedal to get 18?

i think he most you will see through the map is 21-22
Not really that hard...it was pretty must normal highway speeds going up a hill. I am probably wrong on this but isn't atmospheric pressure at sea level around 14.7 psi and you can calculate boost by taking the MAP minus atmospheric pressure.

Griz
 

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That's right - so, a baseline reading of 12 means you are either in the mountains, or your MAP sensor is screwy. 7.3s don't generate a lot of boost until you are working them, so cruising down the road don't expect more than 2-3 psi boost. If you have a trailer hooked up and you floor it to get up to speed, it should hit 17 psi stock and 22-25 with a tuner.

Edit - OR you are generating some vacuum secondary to a restriction - like a clogged air filter or a raccoon's nest in the cold air intake. See what it is key on engine off compared to idle.
 

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Discussion Starter #5
That's right - so, a baseline reading of 12 means you are either in the mountains, or your MAP sensor is screwy. 7.3s don't generate a lot of boost until you are working them, so cruising down the road don't expect more than 2-3 psi boost. If you have a trailer hooked up and you floor it to get up to speed, it should hit 17 psi stock and 22-25 with a tuner.

Edit - OR you are generating some vacuum secondary to a restriction - like a clogged air filter or a raccoon's nest in the cold air intake. See what it is key on engine off compared to idle.
RT...KOEO I read the same as when I am idling...12 psi. My air filter is new and I don't see any raccoon nest in my intake so I suspect the MAP sensor is bad.

Griz
 

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Right- if it's the same running or not, that eliminates restriction as a cause- sounds like a bad sensor.


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ya should be 14.7 with KOEO...
 

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Discussion Starter #8
Right- if it's the same running or not, that eliminates restriction as a cause- sounds like a bad sensor.


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Do you know where a good place to buy a MAP sensor at?

Griz
 

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It depends if you insist on a Motorcraft sensor or don't mind a standard motor products version. I don't mind standard products personally. I would get it from Rockauto or Tousley.


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ya should be 14.7 with KOEO...
I've seen quite a bit of variation from 14.7 psia on both BARO and MAP sensors. I chased what I thought was a MAP sensor problem, changed it out and found essentially no difference in KOEO readings from the original. I don't believe that MAP sensors go bad that often.

Griz - Be sure you check the sensor tube at the spider to be sure it isn't plugged. Also check the hose between there and the sensor. Any restriction can cause a low boost reading.
 

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Discussion Starter #11 (Edited)
I've seen quite a bit of variation from 14.7 psia on both BARO and MAP sensors. I chased what I thought was a MAP sensor problem, changed it out and found essentially no difference in KOEO readings from the original. I don't believe that MAP sensors go bad that often.

Griz - Be sure you check the sensor tube at the spider to be sure it isn't plugged. Also check the hose between there and the sensor. Any restriction can cause a low boost reading.
klhansen...If I had a clog wouldn't the key ON engine OFF reading be different from when I am idling? The MAP reading seem to work normal other than the starting point of 12 psi. Cruising down the road at 63 mph I read 14 psi. It goes up from there depending on the terrain.

Griz
 

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Not necessarily. A clog in the sensor tubing would basically retard the reading as the pressure leaked thru the clog. At KOEO, the sensor would read atmospheric, and SLOWLY increase as pressure built in the intake, and SLOWLY decrease when it dropped.

If the clog was in the intake as RT suggested, then the reading would be different KOEO vs idling.
 

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Discussion Starter #13
Not necessarily. A clog in the sensor tubing would basically retard the reading as the pressure leaked thru the clog. At KOEO, the sensor would read atmospheric, and SLOWLY increase as pressure built in the intake, and SLOWLY decrease when it dropped.

If the clog was in the intake as RT suggested, then the reading would be different KOEO vs idling.
Okay I'll check the tube and hose before I order a replacement for the MAP sensor.

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DO you have a tuner? Some tuners skew the MAP reading. The actual sensor output is spot on, but the calculated MAP (what you see on the readout) is wrong. If you have a tuner, load your stock program and recheck before you go spendin a lot of money.
 

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DO you have a tuner? Some tuners skew the MAP reading. The actual sensor output is spot on, but the calculated MAP (what you see on the readout) is wrong. If you have a tuner, load your stock program and recheck before you go spendin a lot of money.
Okay will do.

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Discussion Starter #16
DO you have a tuner? Some tuners skew the MAP reading. The actual sensor output is spot on, but the calculated MAP (what you see on the readout) is wrong. If you have a tuner, load your stock program and recheck before you go spendin a lot of money.
YT90SC you were right. I returned the tuner to Stock program and it reads 14 psi. When I switch to any of the other programs it reads 12 psi. Why do they skew the MAP readings like that?

Griz
 

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possibly to prevent defueling in their higher hp tunes.
only thing i can think of.
 

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Griz, I am not sure at all why. blue might be right, or they might drop it to prevent overboost codes or keeping the wastegate closed longer or... or... maybe some of the tuner guys might weigh in on this...
 
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