Howdy...Well I don't know either, I'm not sure anybody does. And YES! exactly...both the engine ind the IAT use the same chart....but of course the engine sensor uses mostly conduction it's gonna be steady and reliable, where as the IAT is subject to lots if variables. Got figure the puter knows that.

The stupid net just erased 1/2 of typing!!!!

(I'll do it again with more flames!)

 

the chart is here > http://www.lunghd.com/Tech_Articles/...iagnostics.htm

 

ANYWAY, IN THE TEXT THAT VANISHED, I MENTIONED THAT I GOT NEARLY 22 MPG ON A TRIP THIS SUMMER, AFTER REPLACING MY IAT WITH A 225 OHM RESISTOR,on MY 90 WITH OVER 225K. Also I went to 280 155 746 injectors... https://www.cherokeeforum.com/f2/199...r-swap-163105/ and did my O2 sensor>
https://www.cherokeeforum.com/f2/ren...ce-rms-133153/

AND removed the air restriction in the air-box that is between your air cleaner and the throttle body. You can rip it out with pliers.

 

Yes. It's reading the air temp inside the intake manifold.

It's still hot in there.

 

I don't believe the IAT uses multiple variables. That's why it has the tip it does--to read AIR temp only.

 

Yes, I know that. I just thought he'd like to know what the ambient air temp was as a reference. It will obviously affect it differently if I were in freezing weather. My reading was done with the engine running BTW.

yes in a perfect world the sensor will only read the air temp, but it is obviously affected by other sources albeit less than the air convection. I believe we are all basically in agreement that the air temp readings is higher in the manifold vs outside the manifold. I mean you moved the sensor outside for a reason, because the air is hotter in the manifold. Well, what is the reason the air is hotter in the manifold? Because of the conduction and radiation. So if conduction and radiation affects the air, why would it not affect the sensor as well. The plastic cage design is not immune to those heat sources, but it is designed to minimize their effects. The question is whether or not the Renix ECU programmers took that into account or not.

 

I agree....but it had to be set to deal with where it goes. I'm not sure I'd move mine to cool plastic and expect it to do the same as it would in hot metal. (conduction there). Then of course surrounded by plastic radiant heat to it would be less as well. Of course you could suspend it in a magnetic field in a vacuum with heat shields. Then you could say conduction and radiation are not a factor!

Anyway it seems to me a minor player. I've been runnen great for months with just the 225 ohm resistor. Here "cold" is just freezing. We shall see what happens then....