Intake Air Temp resistor experiment.

[diamondlarry]

Originally Posted by cfg83

diamondlarry -



That's why I was imagining a dial that "clicked" into each position. I am imagining in my head a dial on the cockpit that had an OFF position and then X number of R(esistor) positions. In the off position, the real IAT input would go to the ECU/PCM. In the other R positions, you could have a breadboard with different (and changeable!!!) resistors of your choice. That way, there would be no "jumpiness", but you would still have control over the range of IAT temperatures.

Hrmmmm, sounds like a kid's electronic project to me. Where's my crystal radio kit!?!?!?!?!?!?

CarloSW2

I think you may be on to something. A different value for different stages of engine warmness.

[LxMike]

Originally Posted by cfg83

diamondlarry -



That's why I was imagining a dial that "clicked" into each position. I am imagining in my head a dial on the cockpit that had an OFF position and then X number of R(esistor) positions. In the off position, the real IAT input would go to the ECU/PCM. In the other R positions, you could have a breadboard with different (and changeable!!!) resistors of your choice. That way, there would be no "jumpiness", but you would still have control over the range of IAT temperatures.

Hrmmmm, sounds like a kid's electronic project to me. Where's my crystal radio kit!?!?!?!?!?!?

CarloSW2

Go for it buddy! you could market it as a mileage/performance chip for any vehicle and make millions selling on ebay!! J/K!!!!!

I'm gonna see about doing this mod myself. maybe not with as low a resistance as usedgeo or diamondlarry. just to see if my car would respond to something like this.

[basjoos]

Originally Posted by diamondlarry

I tried a potentiometer when I first started messing with the IAT mod. It was difficult to control down near the bottom of the range; very jumpy.

Get an audio taper pot, which adjusts along on log scale rather than on a linear scale as do normal pots. In general, the more expensive the audio taper pot pot, the more log-like the output curve.

[LxMike]

well shucks! the haynes manual for my car shows where the iat is but when i went to look there was nothing there. all i found was a lil flat area on the intake tubing where it should have been. now i'm gonna have to go searching for it on my day off when i have more time and light.

[cfg83]

basjoos -

Originally Posted by basjoos

Get an audio taper pot, which adjusts along on log scale rather than on a linear scale as do normal pots. In general, the more expensive the audio taper pot pot, the more log-like the output curve.

Thanks, I didn't even know they existed. Here's some URLs describing them :

All About Audio Amplifiers
http://www.angelfire.com/electronic/...mp-Volume.html

The Secret Life of Pots
http://www.geofex.com/Article_Folder...s/potscret.htm

The following diagram shows the three main kinds of pot tapers, along with one common approximation to an audio taper. Curve 1 is linear taper. If we clip one lead of our Ohmmeter (Hey! There he is again!) onto the leftmost lug, and the other lead on the center lug, then the resistance we read as we rotate the pot clockwise will fall on the curve that goes diagonally upwards. The proportion of the total pot resistance we traverse as we turn the pot is linearly proportional to the amount of rotational travel we turn.

Curve 2 shows what happens with an audio or logarithmic taper. As we turn the shaft, the proportion of resistance we traverse increases slowly at first, more slowly than the percentage of rotation. As we get past half the available rotation, the rate of resistance traversed speeds up as we get closer to the furthest rotation. This compensates for the human ear by increasing sound levels very slowly at first, then faster as the ear's sensitivity falls off at higher sound levels.

When we buy "audio taper" pots, we usually get something like Curve 3. For less expensive pots, manufacturers use a two or three-segment approximation to Curve 2. It's not perfect, but it usually works OK. Curve 4 is the typical resistance versus rotation curve for reverse log pots. In real life - that is, if you ever found one of these in real life - it is usually a two or three segment approximation, too.

If you have an unknown pot, you can figure out what taper it is. You measure the resistance from end to end, then turn the pot exactly to half its rotation and measure the resistance from the counterclockwise lug. The crosses on curves 1, 2 , and 4 show the most probable values. If the resistance is 50% of the total resistance, then the pot is linear. If you measure only 10% to 20% of the total resistance, the pot is an audio taper. If you measure 80%-90% of the total resistance, the pot is a reverse log taper.

CarloSW2

[repete86]

Okay, I bought the resistors in order to start experimenting weith this project, but I'm having some problems under the hood. I can't seem to find anything that could be an IAT sensor. Is this an OBD2 thing? My car was built in '93.

[cfg83]

repete86 -

Originally Posted by repete86

Okay, I bought the resistors in order to start experimenting weith this project, but I'm having some problems under the hood. I can't seem to find anything that could be an IAT sensor. Is this an OBD2 thing? My car was built in '93.

Check this out :

Where is __________? (on 4th Gen Honda Accords)
http://www.mycb7.com/bb/viewtopic.php?t=53

Intake Air Temperature Sensor (TA): Left rear of engine, on intake manifold

This "mycb7" website is dedicated to your Honda Accord, so I think this will be a place that you troll for all the grimey details of your 4th gen Accord.

CarloSW2

[repete86]

Originally Posted by cfg83

repete86 -



Check this out :

Where is __________? (on 4th Gen Honda Accords)
http://www.mycb7.com/bb/viewtopic.php?t=53


This "mycb7" website is dedicated to your Honda Accord, so I think this will be a place that you troll for all the grimey details of your 4th gen Accord.

CarloSW2

Nice. Thanks alot.

[repete86]

Okay, I installed the resistor. I had some major problems, and my mileage plummeted. The car wouldn't shift lower than 3k rpm, and my check engine light is now on. I'm going to take a closer look at it tomorrow to see if I can fix it. I used a 1/2 watt 150 ohm resistor. It looks like on the cable that connects to the IAT sensor, there are three connections. One is the ground, and maybe I ran the resistor into the wrong holes, or maybe I need more than 1/2 watt.

[LxMike]

maybe your car just doesn't like that setting. resistors are cheap so you might have to try a few diff ones.

i done some checking around and have found that my iat is integrated with my mass air sensor. i found a site that shows a pot (potentiometer) installation, but i'm not into cutting wires. oh well can cross that exp off my list now.