IAT Modification

[simple guy]

Did a search and didn't find that anyone did this to their 3.0L and reported results.

I saw a writeup that a 5.6K ohm resistor was used in line of the IAT sensor. I live in San Diego and the air temp around here is usually around 50-80 deg. F where I live. SO with that said has anyone done this mod to their IAT (by adding a resistor), what size resistor(s) did you use, and which provided the best results?

 

[Bob Ayers]

What are you hoping to accomplish? A lot of work went into the EFI system to make it as efficient as possible, including telling the PCM what the correct air temp is entering the engine. Why would you want to screw it up?

 

[Wicked_Sludge]

+1

"fooling" sensors is never a good idea. your PCM is programmed to give you best fuel economy when you want it, and best power when you need it. feeding the PCM falsified information will only lead to problems.

this isnt a deisel engine. more fuel does not mean more power. gasoline engines will only run properly on a narrow ratio of gas-to-air mixtures and deliberatly tampering with the mixture is going to cause a drop in mileage, fouled plugs, plugged cats, carbon build up in the combustion chambers, etc etc.

 

[simple guy]

Why, It pings, I opened up the intake system, and need a little more fuel. Read that this mod helps with pinging. Plus if I wanted more performance I understand the end results. My question was have you done this and if so what did you use for resistors. I understand mechanics and the results of such.

Bob and Wicked question for you, why install aftermarket exhaust or taller rearend gears to toy with performance? Shall I critized your mods or reason for? No need because I can appreciate people and their experience when modifying regardless of the mod and outcome.

Bob, very nice pics on your site, hummers are awesome
Wicked nice looking machine "candy" on your site. I'm a low rider guy but can appreciate lifts.

 

[Wicked_Sludge]

Plus if I wanted more performance I understand the end results.

im sorry, but if you think adding more fuel is going to increase horsepower, then you DONT understand.

your engine determins how much fuel to feed the engine by activly monitoring the amount of oxygen in the exhaust. if you increase the amount of oxygen going into the engine, this will show up as a lean mixture in the tailpipe and the computer will compensate accordingly by adding more fuel. in short, "opening up the intake" will automatically be adjusted for by the PCM.

aftermarket items such as intake and exhaust systems are supposed to work (we'll talk about them later) to increase the amount of AIR the engine can move...which, when increased, will be supplimented with more fuel by the PCM. your wanting to increase the amount of FUEL going into the engine, without increasing the amount of air...leading to a rich mixture, fouled plugs, plugged cats, carbon...and all those other nasty things i mentioned.

pinging is a mechanical problem and should be properly repaired, not band-aided by fooling the PCM (which will actually lead to further carbon fouling of the chambers and thus, more pinging).

im not trying to be rude, but your obviously misinformed and dont quite grasp how a modern fuel injected engine works. me and several other members of the site will be more than willing to help "iron out" some of the urban myths surrounding the operation of your engine if you give us a chance.

and my truck is stock height BTW.

 

[jimd1050]

Chevy Trailblazer

Disclaimer: I'm only posting this because I saw it myself!

One of the mechanical production guys at work (I'm in Medical Electronics) asked if I could get him a 1 watt, 5.6K resistor for his MAF. He has a V8 Chevy TrailBlazer. I asked why and he told me to improve fuel economy. I said "How?" He said I am supposed to put the resistor across pins "x" and "x" (I don't remember now) of my MAF/IAT sensor plug and it is supposed to increase fuel economy significantly. In short, we did it and he went from 15 mpg to 21 mpg! He ran the test on several tank fulls to be sure and it worked! We had no schematics so I'm not sure if it was changing the "air flow" value or the "air temp" value but it frickin' worked!

FM, I guess!

 

[Wicked_Sludge]

my initial reaction is to doubt your friends ability to accurately calculate mileage.

but barring poor mathematics, one can always sacrifice power for mileage, or vica versa. how was his truck for power after running the resistor? (dyno sheets please, "butt dynos" dont count).

attempting a mod on a whim without any method of control or understanding of the logistics behind it is foolish. without knowing what actions the PCM took to compensate for the resistor (leaning the mixture, retarding the timing, lowering the fuel and timing curves etc), theres no way for him to know if his "mod" really did work. theres also the distinct possibility that he unintentionally and unknowingly "repaired" his motor with the resistor...thus covering up low fuel economy symptoms due to...oh, say...a vacuum leak, failed ECT sensor, bad MAFS, etc.

on top of that, running lean is VERY dangerous and VERY bad for an engine. i have to wonder what the long term ramifications of his little "chip" will be (hint: it involves pulling the heads).

 

[shadetree]

Plus, Ford computers have "adaptability." The computer is constantly monitoring all sensors. As the sensors age, and the parameters change, or the sensor developes a problem, the computer will see this. If the change is within the capability of the computer, it will adjust to the change and keep everything operating normal. If outside it's range, it will ignore the sensor, and operate off it's own internal settings.

When you install the resistor, it may make a small change for a while, but after a few starts, the computer will see a change at the IAT sensor, and re-adjust to normal conditions. If outside it's range, it will ignore and set a code and CEL if you have one. So, you are back where you started.

As stated before, the computer is perfectly capable of handling anything your engine needs in stock form. It perfectly computes for the correct stoichiometric ratios of fuel/air. If you modify the engine, you also have to modify the computer, not the sensors.shady

 

[Bob Ayers]

Why, It pings, I opened up the intake system, and need a little more fuel. Read that this mod helps with pinging. Plus if I wanted more performance I understand the end results. My question was have you done this and if so what did you use for resistors. I understand mechanics and the results of such.

Bob and Wicked question for you, why install aftermarket exhaust or taller rearend gears to toy with performance? Shall I critized your mods or reason for? No need because I can appreciate people and their experience when modifying regardless of the mod and outcome.

Bob, very nice pics on your site, hummers are awesome
Wicked nice looking machine "candy" on your site. I'm a low rider guy but can appreciate lifts.

"Opening up your intake" was your first mistake! First off, the OEM air filter, airbox, and intake will flow way more air than the engine can pull, so you won't get any more air with an increased diameter intake! What you did do,
is decrease the velocity of the air across the MAF sensor, and now it isn't
accurately measuring the air flow any more. It's measuring less air than is actually flowing, causing a lean condition, and pinging!! The fix for this is to
re-install the OEM setup.

Thanks for the compliment, I'm glad you enjoyed the hummers!!

 

[Cat_Pappy_01]

Usually the goal in this situation is to trick the ecm into believing the air is colder than normal to give you a more aggressive timing curve.

 

[bigredrangero]

That's a real old school shade tree mod, but it can definitely work. My 2006 Taurus ran like a beast but I had to take the extra resistance out every time I started it. My 96 ranger runs great with the extra resistance.