View Full Version : map sensors or make your DETROIT RUN

01-22-2013, 11:07 PM
i ordered 1 for my 94 think they are all blown or close to being blown

my 90 which i just sold was doggy~
i checked the old sensor and it was blown as it didnt change when vacumn was applied.

the interesting thing is the factory sensor on the 90 and my 94 and don bartletts are are 2 bar sensors--our 8v require a 3 bar sensor.

i bought this here is what i used

the 90 40 wb was a hot rod~! ask the new owners~~


to explain here is some information via
the logic module uses the manifold absolute pressure (MAP) sensor to determine the absolute pressure (not the relative to atmospheric pressure) of the air inside the intake manifold and the atmosphere (barometric pressure).
This information is used to determine the density of the air entering the combustion chamber (in conjunction with the IAT(Intake Air temperature) sensor), which is used when calculating the proper air/fuel mixture for the engine, especially at WOT since the system is not in closed-loop at this time.
It is also used to help adjust the IAC(Idle Air Control) motor during idle.
It uses a silicon wafer that is thinner in the center (0.001") than around the edges (0.045"), which causes it to act as a diaphram.
It is mounted with a perfect vacuum beneath the chip so that the air pressure from the other side flexes the chip.
This flexing causes a change in resistance and the circuitry inside the sensor converts this to a voltage ranging from 0.02V to 4.94V when the output is pulled up towards 5V by the ECM(Electronic control module).

1 Bar MAP sensors are used on NA(naturally asperated) vehicles.
2 Bar MAP Sensors are used on forced induction vehicles(Turbo & Supercharged). They can measure up to 2x the apmospheric pressure(29.4psi), so that means it can measure up to 14.7psi boost(the atmosphere is 14.7psi + 14.7psi from the turbo/supercharger).
3 Bar MAP sensors can measure up to 44.1psi, which translates to 29.7psi boost from a Turbo/supercharger.

01-23-2013, 10:40 AM
OK Woody, you've got me curious. I want to check mine. Were are they located? Paul

01-23-2013, 11:34 AM
Didn't even know about the MAP sensor on a 8v92. Now I have to know!
What do I do next?
If the sensor is bad, is it an all or nothing thing, or can the engine run progressively poorly until the sensor is replaced?

01-23-2013, 01:00 PM
Mary and I purchased Woody's 90' "Northern Lights" and he is correct. This Bird with the 8v92 wanting to run as we were cruising at 70 mph most of the way home right at 2000 RPM and she still wanted to run faster which was something we had to watch with all the troopers we saw.
The idle is very smooth and the response off the line was excellent, even towing Mary's Taurus on a tow dolly.
Fuel consumption was close to 5.5 mpg which we are very happy with.

It was fun watching everyone who passed us, waving and even had some Japanese tourists, hanging out the windows of their car taking pictures. Just proves how wonderful these great machines are. We even had a car from Alaska pass us waving and blowing their horn so we opened up the duel air trumpets to return the hello.

We have her currently in secure storage as we are having a new 10-12" concrete parking area installed next to the garage so we have easy access for service, loading/unloading and ensuring she gets taken good care of.

Mary and I want to again THANK WOODY, for being such a great individual, patriot, and we hope a friend for the rest of our lives as he is welcome in our home always.

01-23-2013, 08:28 PM
OK Woody, you've got me curious. I want to check mine. Were are they located? Paul

locate a 1/4" line off pass side intake
the map is at the end of this hose:)

01-23-2013, 08:29 PM
Didn't even know about the MAP sensor on a 8v92. Now I have to know!
What do I do next?
If the sensor is bad, is it an all or nothing thing, or can the engine run progressively poorly until the sensor is replaced?

i dont know but for sure they give low boost when not working

im a believer in changing them on ford diesels when they get older

the engines in out units are not any different;)

01-23-2013, 08:51 PM
Detroit Diesel SENSOR SERIES 60 #23527829 TURBO BOOST PRESSURE map.



Detroit Diesel TURBO BOOST SENSOR 8V92 DDEC ~ GM MAP 12219935 ~ 28182633 - 16070629 (http://www.ebay.com/itm/Detroit-Diesel-TURBO-BOOST-SENSOR-DDEC-GM-MAP-12219935-28182633-16070629-/160835316620?pt=Other_Vehicle_Parts&hash=item2572882b8c&vxp=mtr)


Hope this helps

04-18-2013, 09:31 AM
According to the .pdf below, the vacuum port needs to be pointed downward. Blue Bird mounted the GM Factory style MAP with vacuum port in the horizontal position. Pointing the port down will allow liquid or condensate in the line to drain away from the sensor cell. This may affect longevity?


Note: Prior to our ownership, W.W. Williams of Phoenix, replaced the MAP sensor on our '88 WB 8V92 and I found 4 items that were troubling.

1. 5/16" vacuum hose used instead of 1/4", resulting in leaking connections at the supercharger as well as at the MAP.

2. A 2-BAR MAP was installed instead of a 3-BAR.

3. The electrical connector at the MAP was broken is 3 places and was zip-tied; I have replaced with a new MAP #12223861 and pig tail.

4. MAP was reinstalled with vacuum port horizonal instead of vertical per the Delphi .pdf drawing. Read note #4 in the .pdf below.


04-21-2013, 09:01 AM
The MAP sensor has a 1/4" diameter ribbed plastic nipple, and this hose connecting to the nipple is subject to swelling or splitting at the MAP sensor. Any loss of vacuum/pressure at the MAP sensor will send erroneous data to the MAP sensor and/or the ECM. Replacing the cheap MAP sensor hose with a piece of 1/4" internally reinforced fuel hose will improve the connection both at the MAP sensor and at the barbed nipple on the roots supercharger.

I suggest installing new Corbin type clamps on each end of the new hose running between the blower (supercharger) and the GM factory style MAP sensor.

Some pics of the GM factory style MAP sensor used on my 1988 DDEC I equipped 8V92 Detroit diesel.