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Mother

MAF and seperate IAT sensor ground wire

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I wish to add a separate IAT (inlet air temp sensor) to my SC rather then the one in the MAF, however wondering about the ground wire for a 2000 - 996. Would it be "Grounded" by "T" off the BRN/WHT wire and cut and use the BLU/GR as the sensor temp or is the sensor grounded to frame or another way?

post-4095-0-82285600-1315944821_thumb.jp

Edited by Mother

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I would think the ground you are looking at is sufficient. You could test this easily with a multi-meter.

Another way would be to take ground from a separate ground point since you are adding another air intake sensor.

The car only has one "ground" system AFAIK, eventually everything is grounded to the chassis.

Let us know how it goes.

Edited by logray

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Another way would be to take ground from a separate ground point since you are adding another air intake sensor.

Logray,

Sorry for confusion I am actually removing the MAF temp sensor (by cutting the wire) and just relocating it to separate IAT sensor in the IC for the SC I believe it will be a more accurate reading of true air temp for DME. Thanks for feedback.

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No problem, yes I think I understand what you were asking.

And my answer is pretty much the same.

The car only has one ground system with many ground points.

Everything, the engine, the DME (multiple pins), instrument cluster, lights, radio, etc. etc. etc. all share the same ground AFAIK.

I don't think you will encounter any problems using that ground for your new sensor from an electrical perspective.

I'm not sure how the computer will cope with a different sensor, but assuming it provides the same voltage and impedance ranges as the orig sensor I don't see why it wouldn't work.

Perhaps 1999Porsche911 would chime in, although I haven't seen him here for a long time.

Edited by logray

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Perhaps 1999Porsche911 would chime in, although I haven't seen him here for a long time.

Yes, hope he is well, however just say the magic word "OIL" and see what happens.

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I think the temp sensor share an internal ground path with the mass air flow sensor through the engine ECU but I am curious as to where you are going to locate the new sensor in the engine compartment that you think will give more accurate readings?

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I take back what I said earlier about using a separate ground for this case. Let's say you create a better or different path for ground, it might be possible to create a ground problem and damage something. Going back to your diagram I think you should be fine.

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Please excuse the protype intake it has been changed, however the IAT would be relocated on the IC on the out port after the cooling takes place from compressed air before entering throttle body. I was concerned about using eng grd and seemed that it should be grounded thru the MAF ground wire.

post-4095-0-92271300-1316027926_thumb.jp

post-4095-0-36941100-1316028714_thumb.jp

Edited by Mother

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I would ground through same connection ( DME) that the existing sensor uses. IMO, this should prevent any sort of ground loop or better path to ground situation.

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You mentioned checking resistance for plus and minus and was wondering if IAT sensor is not marked which is the positive using meter?

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I maybe wrong and it might not be possible but wouldn't it be better to relocate the MAF to after the cooler. That way the MAF is as close to the throttle body as you can get it and then you wouldn't need to rewire for a seperate IAT. It looks like you have already gone to a lot of trouble modifing the intake so maybe that is another option.

Jermmy

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You mentioned checking resistance for plus and minus and was wondering if IAT sensor is not marked which is the positive using meter?

As for checking which terminal of the sensor is positive, did it not come with color coded wires or a marking? Perhaps it doesn't matter which goes to which in that case, as long as one side is grounded. You could connect a multimeter to the terminals and measure ohms. Blow some air on the sensor and observe the change in resistance. If it doesn't change then you have the wrong terminals. Or flip the leads around and repeat the test - confirming whether it matters which pole is positive and which is negative.

That comment I made was meant more along the lines of making sure the IAT you select provides the appropriate resistance based on the temperature and what the computer expects to see.

Otherwise if it gives the wrong impedance values, the IAT might be feeding the computer the wrong temperature, which is counter productive to what you are trying to achieve.

Example (I'm not sure what the 996 DME expects, this is just an example for GM):

Temperature Ohms

48 degrees F 7000

87 degrees F 1930

146 degrees F 560

Edited by logray

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I maybe wrong and it might not be possible but wouldn't it be better to relocate the MAF to after the cooler. That way the MAF is as close to the throttle body as you can get it and then you wouldn't need to rewire for a seperate IAT. It looks like you have already gone to a lot of trouble modifing the intake so maybe that is another option.

Jermmy

The only measurement taken by the MAF in my case will be the intake Air Flow and does not matter where it is located as long as it before the compressor and as we know there is not much room in the engine comp to move much around.

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Logray,

I just ordered the sensor and comes with no wires and have to make my own harness. Good idea with blow dryer or maybe my Durametric scanner shows intake air temp and if wires are reversed I would guess it will show a neg number I hope. Trouble also if finding a connector.

post-4095-0-71071200-1316039424_thumb.jp

Edited by Mother

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That temp sensor will take a standard Bosch connector which you can get from any wrecker. My local auto parts store also has new connectors but I can't remember the company that makes them. Bosch used that connector style one fuel injectors,cold start injectors,warm up regulators,O2 sensors,etc...etc.

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I agree with wvicary and would certainly try to source a proper connector and harness for that instead of trying to make your own. I bet you could take that to your local parts counter and they would have a connector and wire setup for you in no time and for very little money.

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I agree and will wait for sensor to show up and head to parts store or salvage yard. I tried searching online parts and what a pain.<_<

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I agree and will wait for sensor to show up and head to parts store or salvage yard. I tried searching online parts and what a pain.<_<

Steve, you've got PM. Sent you some info on the connector for the sensor. Basically a Bosch EV1 fuel injector connector will work. PM me your email and I will forward you a copy of the wiring info from VF.

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mec0t0

Got it and thanks for the everyone's help "Many hands make light work". The wire colors are different, however the above schematic MAF color codes are correct for a 2000 996 and knowing that the ground "is" taken from the MAF connector ground wire. :)

Edited by Mother

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I think the temp sensor share an internal ground path with the mass air flow sensor through the engine ECU but I am curious as to where you are going to locate the new sensor in the engine compartment that you think will give more accurate readings?

Installed today just the sensor but gives idea of location please pardon phone pics.

post-4095-0-49121200-1316233952_thumb.jp

Edited by Mother

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Follow-up: Sensor connected via above diagram and works good tested with Duramatric scanner and hair dryer.

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Waiting on new SC pulley belt which just found out today was lost by post office however will let you know when I get results. I have some original excel Durametric spread sheets to use as comparison.

Edited by Mother

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Mother,

Bringing this back from the dead.  I cant find info anywhere online about this topic.  What was the sensor sourced from?  By the pic it looks like possible VW VR6?  The largest importance is ensuring the temperature curve is the same as the IAT in the MAF.

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