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03Dak
Dodge Dakota
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8/28/2003
00:53:27
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 Subject: IAT mods
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Today I finally modified my TPS and my IAT which sounded like a good idea now that I have an improvment from my home brewed intake it probably needed a little more fuel.
So I did the TPS mod. It was .56 VDC before and after I got it to .72 VDC so that's where I left it.
Then I took my IAT sensor (which I allready had mounted a few feet downstream on the intake tube) and did some experimenting to see what resistance values I read at different temps.
So basically the colder the temp, the higher the value. I also found an online chart which seems accurate. For example at 89 degrees ambient temp resistance = 7 k ohms. At 73 degrees it is 11k ohms, at 109 degrees it's down to 4.7 k ohms, etc.
So in hopes of en riching my fuel mixture to enhance my intake mods I installed a resister inline to re calibrate the signal. Increasing the resistance tricks the computer as if it is colder out than it really is, so more fuel.
So far after resetting the PCM (battery wire off) I had only driven it a few miles after these two mods and I think I may have an improvment. I'll really find out next time I go up the large mountains I frequent.
While doing this mod my bro in law has a 2000 RAM with the 318. Slightly different than my 2003 Dak with the 4.7
He has the threaded in IAT in his aluminum intake.
While experimenting we found something interesting. We both do Air Conditioning. We took a outdoor temperature sensor from a Trane heat pump used for a defrost control. I also had a chart plotting resistance versus temperature.
Funny a$$ crap is that there must be some sort of a standard for thermisters because on the charts and by testing we get the very same readings. So what he is going to do is use this sensor from the A/C unit and mount it in his home brewed intake tube and leave in his threaded one on his intake plenum with no wires on it.
I'll have to let everyone know what the results are after a few days but I just wanted to share what we found during the latest adventure on our trucks.
I do work on electronics as a hobby so you wont find me wasting money buying "black boxes" to adjust sensors when I can just make something on my own. PLus I'll always share info here as many others do to help each other.
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jbro1000
Dodge Dakota
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8/28/2003
22:43:36
| RE: IAT mods
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What size resistor did you use. I just put a 1K ohm 1/4 watt inline on my 4.7. I can't really tell any difference.
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03Dak
Dodge Dakota
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8/29/2003
01:49:43
| RE: IAT mods
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I wanted to start small, so I used something like a 560 ohm. That would only lower the reading a few degrees. I think I should use about a 2.2k next time, that would be approx 10 degrees. My home brewed intake should deffinitely be giving a more dense charge so I assume I could use the adjustment to be sure it isn't leaning ot out.
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GraphiteDak
GenIII
8/30/2003
19:52:59
| RE: IAT mods
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I replced the 560 ohm resistor with a 2.2k ohm one today. Drove it around some today but not sure if it helped or not. That should trick my computer into thinking it's approx 10 degrees colder than it is. With my home brewed intake I hope this helps. I'll let you know.
Formerly known as 03Dak
2003 Graphite QC 4X4 4.7 Auto 3.55
Home Brewed Cold AIr Intake, Flowmaster 40 series, Modified TPS to .72VDC, Modified IAT to compensate for home brew intake
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GGalarmtec
Dodge Dakota
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8/31/2003
03:05:37
| RE: IAT mods
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Try using a 15k ohm resistor.That will trick the
computer into thinking it's approx. 58 degrees.
14.36k=60
14.97k=59
18.32k=54
26.64k=37
Good luck.......
GGalarmtec
02 flame red QC 4X4 cold air 4.7 3.55 .76 TPS IAT.
removed fan. switched electric fan 180 therm.
My other car: 95 ZR1 corvette, factory hemi, 16 fuel injectors second set of injectors turned on via a key switch. factory rated@405 HP.TPS 180 therm.gibson. Dyno@488 HP. Best 1/4 run 11.58. Top speed well over 177 mph. Cant take a Viper, or King cobra,
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jbro1000
Dodge Dakota
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9/02/2003
22:30:56
| RE: IAT mods
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After referring to my Haynes manual I learned that my 1K resistor isn't doing squat. According to the chart in the manual if your intake air temp is 140* the sensor gives a reading of 2400 ohm. Adding a 1K resistor would trick the PCM into thinking the air is about 122* Using an 8K resistor would bring it down to 75* which is about what you would want. Trouble is you have to start with an accurate measurement of what the intake air acually is. And this will be different when running and when sitting in traffic. Any guesses on what intake air temp would be on a 4.7 with cold air intake and 180 Tstat on a 90 degree day? There has to be some heat soak from the manifold, so I would think maybe a 30* increase while running and maybe as much as 60* while sitting in traffic. Anyway, I'm going to splice in a 4.7K, 2.2K and 1K in series for a total of 7.9K and see how it works.
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GraphiteDak
GenIII
9/03/2003
00:03:57
| RE: IAT mods
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jbro1000 just leave your stock IAT sensor connected and splice in a 2.2k ohm or whatever resistor to offset the reading to whatever you want. I don't understand why people are removing the IAT alltogether for a constant and fake reading when you can just add a little resistance to offset the reading.
That 2.2k resistor I added simply tells the PCM it's 20 degrees or so colder than it really is, but at least it still adjusts for different conditions.
So when I'm in Phoenix and it's 110 degrees, it says shows approx 90 degrees. Therefore giving more fuel than it would have with the true reading. So, when I drive up to Payson where it would be 95 degrees, it says approx 80, but at least it adjusted for temp change.
And when I drive to Payson in the winter and it's 20 degrees, it says approx 10, etc.
See what I am saying. I'm adjusting the mixture to suppliment my home brewed intake system, while allowing the sensor to make NEEDED adjustments in different climates.
I think removing the IAT and installing a fixed reading is deffinitely not the thing to do unless you change it on a day to day basis and only use it at the track!
I have always tried to study and build my own electronics, so this is just me sharing my .02
2003 Graphite QC 4X4 4.7 Auto 3.55
Home Brewed Cold AIr Intake, Flowmaster 40 series, Modified TPS to .72VDC, Modified IAT to compensate for home brew intake
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jbro1000
Dodge Dakota
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9/03/2003
08:45:02
| RE: IAT mods
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I am not disconnecting the sensor. I am doing the same thing you did but using 7.9K ohms of resistance instead of 2.2K. The resistors will be in series spliced into the black/blue wire with sensor remaining in it's original location. The ohms/voltage ratio changes dramatically with temperature changes. For instance, if intake air is 140* a 2.2K resistor will make the PCM read about 118*, approx. 20* difference. But if the intake air is 86* the 2.2K resistor will make the PCM read 76*, only a 10* difference. And lastly if the intake air is really hot, like sitting it traffic, say 194* the 2.2K will make the PCM read approx. 125* making a 70* difference. Under these same conditions with 7.9K of resistance instead of 2.2K the PCM will read 140/77, 86/55 and 194/79.
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GraphiteDak
GenIII
9/03/2003
22:25:45
| RE: IAT mods
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You're right.
Looking at the chart, the colder you get, the less the difference making this type of a mod very good.
After a few days I think I can now feel a difference.
The other day I ran my friends (FWD V6) Chevy that we fixed up a little (home made ram air, etc that made HUGE gains). We got his Chevy to keep up with my 5 speed Nissan Altima that would beat every V6 Honda and Acura 3.2 TL and most trucks etc that I raced. Not saying that is too much but that's where it stands. I traded in my Nissan in so I couldn't run my truck against that. Anyway, it seems to be dead even out of the hole to my friends car. I am sure I will soon be taking his after more work.
Last week I saw two Honda Civic's race off at the light. One had the usual fart can. I jumped into the empty 3rd lane and kicked both of their ass's with my 4X4 QC truck. You should have seen their faces especially when my exhaust outlet was aimed right at his open window giving him a taste at what a good V8 sounds like over his weed eater! I thought that was cool for a start and that was before the last mods.
2003 Graphite QC 4X4 4.7 Auto 3.55
Home Brewed Cold AIr Intake, Flowmaster 40 series, Modified TPS to .72VDC, Modified IAT to compensate for home brew intake
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jbro1000
Dodge Dakota
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9/04/2003
08:21:12
| RE: IAT mods
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I still think you need to use more resistance to take full advantage of this mod. I think slightly less than 10K ohms will keep your PCM reading between 70 and 80 degrees and out of open loop at virtually all times at the temps where you and I live.
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resistor???
Dodge Dakota
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9/04/2003
10:49:02
|  RE: IAT mods
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I went to Rat Shack to get a 2.2K resistor. What wattage resistor would I need? 1/4 watt?? 1/2 watt?? or does it make a differance.
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jbro1000
Dodge Dakota
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9/04/2003
20:19:16
| RE: IAT mods
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1/4 watt from what I understand.
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GraphiteDak
GenIII
9/05/2003
00:06:33
| RE: IAT mods
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A 1/4 watt would be fine just to be sure that sucker doesn't break under normal vibrations. Other than that virtually no power goes thru the circuit. I'm sure i'ts just a simple reference voltage from a resistor divider circuit given to another comparitor circuit in the PCM.
12VDC devided by a total of 10k ohms itself would only be .0012 amps or .0144 watts!
You could use a really small surface mounted resistor that you could barely pick up with a needlenose plyers!!!
Enough of that idea, use the 1/4 or 1/2 simply to make sure it's RUGGED enough not to BREAK!
2003 Graphite QC 4X4 4.7 Auto 3.55
Home Brewed Cold AIr Intake, Flowmaster 40 series, Modified TPS to .72VDC, Modified IAT to compensate for home brew intake
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resistor???
Dodge Dakota
JOIN HERE
9/05/2003
10:44:05
| RE: IAT mods
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Message:
Thanks for the info. Time to go back to Rat Shack.
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Just a though
Dodge Dakota
JOIN HERE
9/05/2003
18:53:34
| RE: IAT mods
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I know a lot of people here are interested in keeping there gas milage. So I have an idea. How about wiring up the inline resistor for the IAT with a switch so you can switch between normal mode and with the extra resistance.
Sorry about the cheesy graphics
-----
| S | ---resistor-- IAT
| W |
| I | ------------- PCM
| T |
| C | ------------- IAT
| H |
-----
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GraphiteDak
GenIII
9/05/2003
22:19:12
| RE: IAT mods
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Message:
That might be a good idea, especially for those who are doing this to a stock set up.
2003 Graphite QC 4X4 4.7 Auto 3.55
Home Brewed Cold AIr Intake, Flowmaster 40 series, Modified TPS to .72VDC, Modified IAT to compensate for home brew intake
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jeremy03cc RT
Dodge Dakota
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9/09/2003
11:57:50
|  RE: IAT mods
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HUH????????
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Aden
Dodge Dakota
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9/09/2003
21:50:00
| RE: IAT mods
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this all sounds very good but how would ya splice a little thing like that[not good at sparks]
i thought resistors are really small or they were when ilast whent to school a few yrs ago.any pics or info would be good
also i have a 4" air tube ported stock tb
dyno max out the side which is always black so it must still be running rich , correct me if iam
wrong
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GraphiteDak
GenIII
9/09/2003
22:15:21
| RE: IAT mods
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If your running rich, I would think this mod would be completely out of the question LOL!
This mod should be used to add a little more fuel for the extra air flow (if any).
Simple and quick method to adjust the IAT. The more inline resistance you add, the colder it thinks it is. The colder it is outside, the denser the air, the more fuel it will add.
But no reason to do this mod with a stock intake or air tubes that takes HOT air from under the frigging hood!!!!!!
By the way, there will be no "sparks" from this mod. Very little current goes thru this circuit. It's just a reference voltage devided by another internal resistor and the IAT (thermistor / variable resistor) I'm sure.
2003 Graphite QC 4X4 4.7 Auto 3.55
Home Brewed Cold AIr Intake, Flowmaster 40 series, Modified TPS to .72VDC, Modified IAT to compensate for home brew intake
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TexasTodd
Dodge Dakota
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9/10/2003
16:02:42
| RE: IAT mods
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So if you have one of the IAT Adjusters, that Bernd used to sell, it's got a reostat, what range is it running, min to max I mean. As someone mentioned, it also has an on/off switch.
I usually always have mine turned off, last time I used it, after awhile, the check engine light came on. Turned it off, and after awhile it cleared itself.
Bernd used to talk about the 2001's and up being so sensitive, that when it senses any difference in the temps, the check engine light comes on.
Anyway, keep up the good work, hell, maybe I';ll turn mine back on!
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GraphiteDak
GenIII
9/10/2003
21:19:30
| RE: IAT mods
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I don't see the reason to keep playing with the settings. I wouldn't mess with it at all on a stock intake.
I'm "guessing" my home brewed cold air intake may be getting a more dense fuel charge than the stock air intake tube.
I don't even know for sure if my IAT adjustment helped or not. It does feel a little stronger. That could very well just be in my mind for all I know. Next time I go out of town up the same large mountains I always drive over I may definitely know if it helped. That's one reason I did this, to tow over large mountains. Not that the truck doesn't allready do a bad job stock.
2003 Graphite QC 4X4 4.7 Auto 3.55
Home Brewed Cold AIr Intake, Flowmaster 40 series, Modified TPS to .72VDC, Modified IAT to compensate for home brew intake
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