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Old 03-17-2011, 05:48 AM  
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Joined: Apr 2003
Location: Long Beach, CA
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"Does the location of the sensor make a difference?"

Originally Posted by Jltrd View Post

With the booster plug I'm not quite sure if I have the air temp sensor in the best spot. Does the IICE Air also have an air temp sensor that will need to be placed somewhere on the bike?
I have been waiting for that question "Does the location of the air temperature sensor make a difference?" The short answer is, no, it doesn't.

When the bike is moving, the sensor always sees the ambient air temperature.

It's easy to imagine that putting the sensor up near the steering head gives it a supply of cool air. Though just because it's easy to imagine doesn't make it true. I admit I wanted it to be true.

Seems like a reasonable question. I mean, seeing as how some of the competitor products have the sensor mounted up near the steering head/instrument cluster. Of course I had to find out.

It was a mild evening last August. The plan was to make a high speed run on the freeway, then take some temp measurements while the bike was idling. Ambient temperature was 70F, and since it was evening there would be no influence from solar radiant heating.

I set up for the test and took off on a run up the 405 freeway from Long Beach to UCLA/Westwood. The 28 miles of freeway in 19 minutes, so the motor was good and warm.

I pulled off the fwy and quickly pulled into a waiting garage. The door was shut to eliminate any breeze, and the bike was left idling on the centerstand while we started logging measurements.

In preparation for the experiment, I had relocated the original Intake Air Temp sensor from the airbox to the area in front of the steering head.

First thing after pulling into the garage the bike is put on the centerstand, then pull off the saddle and connect to a waiting GS-911 and laptop to take temp readings. No cooling fan was used.

The setup process took no more than 30 seconds. The ambient temp in the garage was 70F but already the IAT reading was 86F. Remember, this was the ECU's reading from the relocated IAT sensor, mounted in front of the steering head.

The motor idled along happily with the headers turning red while the ECU gave these temp readings via the GS-911.

   86.0    228.2
   87.8    230.0
   91.4    230.0
   93.2    231.8
   93.2    233.6
   95.0    235.4
   96.8    237.2
   98.6    239.0
   98.6    242.6
  100.4    242.6
  100.4    244.4
  102.2    244.4
  102.2    248.0
  104.0    248.0
  104.0    249.8
  105.8    249.8
  107.6    253.4

I shut it down at that point, figuring 250 degrees was hot enough for the oil.

So there it is. Ambient air temp was 70, and after a few minutes the relocated sensor was reading 38 degrees higher at 107.6

For comparison, I did this experiment 2 more times. Once with the IAT sensor in the factory location in the airbox. And once more with the sensor resting on top of the airbox, with the saddle in place.

Result: The ECU sees the same temperature regardless where the sensor is mounted.

Wait, that's not entirely true. With the sensor placed on a table 5 feet away, the ECU always reads the same intake temperature. (I actually did that with an extension wire on the sensor.)

Conclusions: No matter where you put the sensor, there's no way to escape the heat when you come to a stop.

And once the bike starts moving, the hot air that collects when stopped is immediately replaced by moving ambient air.

When the bike is moving, the sensor always sees the ambient air temperature.


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Poolside screwed with this post 11-08-2011 at 12:34 AM
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