Intake Air Temp resistor experiment.

[zpiloto]

Originally Posted by repete86

I would have been doing this with the intention of reducing emissions. I'm going to have to do more research to find a way to fix this problem. My mileage improvements have been done for environmental, not economic reasons.

I applaude your decision. It's the same reason that I run a E15 blend.

[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.

[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.

[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

[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

[cfg83]

LxMike -

Originally Posted by LxMike

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.

There are already "dialing" performance mod chips on ebay. But maybe they only cover the "performance" end of the spectrum, or are (cheapy) audio pots.

Hrrrrmmmm, maybe I'll get one and perform an autopsy .

EDIT : Here's one on ebay for $30 !!!!!!
88-95-96-97-98 99-04-05-06 Saturn SC/SL/SW Chip Module
http://cgi.ebay.com/ebaymotors/88-95...QQcmdZViewItem

EDIT : Oh, brain fart on my part. Nowwwww I see the J/K.

CarloSW2

[usedgeo]

This mileage is just too darn good. It cannot be true. Here is an unpleasant hypothesis.

What is the chance that the ScangaugeII incorporates the IAT temperature into its fuel use calculation?

Maybe I am fooling the scangauge not the car. I am doing well on this tank but the scangauge is showing 2.1 gallons used. This is about the 5th tank of gas I have used in this car and the gauge is quite accurate. I have driven 130 miles now and the fuel gauge looks like I have used 2.5-3.0 gallons. That would be right in line with my last fill up of 46 mpg.

I won't be fueling up for a couple weeks unless I take a trip. The suspense is killing me.

Yes, I will keep you posted.

Ernie

[usedgeo]

Originally Posted by usedgeo

What is the chance that the ScangaugeII incorporates the IAT temperature into its fuel use calculation?

I wrote to scangauge asking this question.

I called and a local dynamometer emission test would cost $100 minimum. I won't do that yet. I might pay for a 5 gas no load emission test, but I think I will wait a while first. 5 gas. CO, CO2, O2, HC, NOx.

There has been some discussion about Exhaust Gas Temperature comparisons. I have experience with airplanes and trucks that used such instrumentation. This is a good idea. I might by a cheap gauge for comparison purposes. I wonder if my infrared thermometer would be useful for this.

A standard catalytic converter is never going to clear up NOx. At least as far as I know.

I have come up with a really nice sounding theory for what is going on in the engine but I am going to wait until it is more clear that I really need such a theory.

If I missed a question hit me up again.

Ernie