DDEC IV PID Intake Manifold Temperature

[travelite]

Folks,

My VMSpc diagnostics shows the following code:

ABS PID 105 7 Intake Manifold Temperature Not Responding 11/13/10 16:59

My VMSpc has never been able to display a correct value for the Intake Manifold Temperature; it usually displays 0x00 and on occasion 0xFF. I think I may have a loose or corroded connection. The intake manifold temperature sensor is new. I have a couple of questions:

1) Does DDEC IV do anything useful with the output of this sensor?
2) Can any one share the ECM connector and pin number for this sensor?
__________________

[Jon Wehrenberg]

David, My brain is unencumbered with facts but I suspect the intake manifold temperature information as used by DDEC is intended to help DDEC determine the fuel that should flow through the injectors for optimal performance.

As the intake air is heated, it is less dense and therefore the amount of fuel that would be ideal for either performance or economy at cooler temperatures would be excessive at higher temperatures. Conversely on a sub zero day when intake air temperatures are low, the amount of fuel flowing through the injectors must increase otherwise the mixture in the combustion chamber will be too lean. At least that was my reaction when I read your post even though I have no clue as to if what I just said was true.

Just how important that sensor is is beyond my pay scale.

BTW, in the performance charts for my plane which is turbocharged, and lacks computerized controls such as our coaches have, are fuel flow values at specific outside air temperatures and altitudes. I am not sure our coaches see exhaust gas temperatures that would be damaging, but on my plane for example insufficient fuel flow at a given power setting could result in severe engine damage.

[lonesome george]

David, looked up the Air Temperature Sensor in the DDEC III/IV ECM manual. "The air sensor is located in the air intake manifold and monitors the air temperature entering the engine. The ECM adjusts the engine timing to reduce white smoke, improve cold starts, and provide engine protection."
This information is in the engine harness section: air temperature - wire #132 - cavity N-2 - wire color white. Fault Code 27 is ATS low, Fault Code 28 is ATS high.
The test procedure and description in the manual is 18 pages if you like I can copy and fax or scan and email them if you like. I have never done this test, so I'm no help beyond having the manual and an interest in what you find out.
lonesome

[travelite]

George,

Thanks, That's exactly what I'm looking for. I PMed my email address.

Jon,

Thanks for your help.