IAT Sensor relocation/modifying?

[Doug99RS]

So I've been doing some thinking lately about intake air temperature sensor location and voltage. I work with a guy who has unplugged his IAT sensor and put a resistor in the circuit and claims some decent performance enhancements from it. While I don't think this is the rought I want to go I have been thinking about something similar.

The IAT is mounted in the intake manifold on my 2gnt. Naturally it's connected to the engine and so it reads hotter air than what's coming in next to the air filter. My question is what are the other changes people have done to this area of fuel management WITHOUT the use of any additional computers or gauges? I'm in a bit of a dry spell for cash and so spending money on an AFC, A/F ratio guage and the like is not a possibility. On the plus side I do have a scan tool and can monitor upstream o2 at WOT.

The IAT is a negative temperature coefficient thermistor-type sensor. It has two wires. One is sensor ground (shares a ground with other sensors and also goes back to the PCM), the other is the IAT signal wire. As temperature goes down, the voltage signal goes up. And as the temp goes up, the voltage goes down. So... my next question is related to everyone's desire to lean the a/f ratio out quite a bit. Cold air tells the computer to supply more fuel. Hot air means less fuel. So am I right in thinking that I would want to install a resistor in-line (still leaving it connected so it can adjust to changes in intake air temp) on the signal side that will drop the signal voltage by x% which would mean that the air is hotter and the air/fuel mixture should be leaned out?

And now that I've totally confused myself... wouldn't this mean that the cold air intake was a waste? Other than the smooth piping and higher flowing air filter? I mean... first I'm giving it colder air, higher o2 content. Higher o2 content means more gas is thrown at it... then I take it back away with this resistor?
Doug

 

[ChanJr.]

Sounds like the intake temp gauge works just like the O2 sensor: more heat = less resistance.

With no other mods on your car, I would recommend a timing advance gadget. I know a friend who found one for his J-body Cavalier and he got significant gains. You can find this on e-bay.

 

[kpt4321]

Don't replace it with a resistor. The IAT sernsor is there so that you get the right amount of fuel, even at different temperatures. With the resistor might just happen to work in one small temperature range, it won't work all the time.

Adding a resistor will, I believe, cause the ECU to add more fuel. I'll have to check that though.

The whole point of an intake is to supply more air. Air is power, it's as simple as that. Since you're getting more air, the ECU has to add more fuel, to keep the desired A/F ratio.

Don't screw with the A/F ratio if you don't have a real way of minitoring it. An O2 gauge doesn't cut it.


....Kyle T.
93 TSi AWD "TURBO4"
14b - 12.8 @ 108

 

[Doug99RS]

Originally posted by kpt4321


Adding a resistor will, I believe, cause the ECU to add more fuel. I'll have to check that though.

---With this particular IAT sensor, a resistor will lower the voltage. A lower voltage would equate to hotter air. Hotter air means less fuel.

The whole point of an intake is to supply more air. Air is power, it's as simple as that. Since you're getting more air, the ECU has to add more fuel, to keep the desired A/F ratio.

---Yes the intake supplies the air inlet source. The intake air temp measures the temp of the air and adjusts some minor air/fuel changes. Colder air is densor meaning a higher oxygen content. A higher oxygen content would require more fuel to maintain that pre-programed air/fuel ratio the computer is designed for. However, the object of a resistor in line, not in place of, would be to lie to the computer about the temperature of the air. Enrichen or lean the air/fuel ratio. I'm thinking a resistor would give a voltage difference that is linear to the true intake air temperature. So the computer would still be able to adjust a/f ratios based on air temp changes BUT the difference would be the signal voltage would be 95-90% of the true temp. Follow?

Don't screw with the A/F ratio if you don't have a real way of minitoring it. An O2 gauge doesn't cut it.

---An o2 gauge would be sufficient for moderate changes like what I'm thinking here. I'm not talking about leaning out the system by 40%, spraying Nitrous or a turbo and only monitoring a/f ratio based on a PDA scan tool software. Just looking to lean out the air/fuel ratio by a couple 1/100ths of a volt. I'm also looking for input on what other modifications like this have been done and what the outcome was.
Doug

 

[kpt4321]

All I was asking was why that would have anything to do with a cold air intake being a waste.

If you only plan on modifying the A/F ratio a couple hundredths of a volt, then why even bother? That's like, 2 molecules less fuel for the same amount of air. That won't make you run 10's.

Actually, an O2 gauge is much better for monitoring large changes than it is for monitoring small ones. It does not have the resolution or the consistiency to monitor little tiny useless changes like the ones you suggest.

It can be done, and people have done it. My opinion is that it is not a good way to go about it. That's it.


....Kyle T.

 

[Doug99RS]

Well, as I thought I made it clear I was NOT looking for massive gains. So dropping my 1/4 times to 10's is not only going to be very difficult but also NOT what I was shooting for with this thread.

And a couple of hundredths of a volt is what many people tune by. That's 0.XY volts. The Y being 1/100s of a volt position. Many people tune their cars by 1/100's of a volt on a daily basis using things like AFC's and DSMLink.

If there's anyone that has any USEFUL information about this type of mod please feel free to pipe up. If all you want to do is criticize my asking questions on the subject then your input is not needed. I'd like responses from people that have seen or done this mod or at least some rational responses about the effects this type of mod would have. Thanks

 

[ChanJr.]

I took time to read your enormous post and responded in a logical manner. The conclusion is not one you wanted, so therefore I wasted YOUR time? I think others reading this post would agree that mods should be done right or not at all.

 

[Doug99RS]

Originally posted by ChanJr.
I took time to read your enormous post and responded in a logical manner. The conclusion is not one you wanted, so therefore I wasted YOUR time? I think others reading this post would agree that mods should be done right or not at all.

Um, none of my responses were directed towards you so I'm hoping you didn't take any offense to my comments. While you did not add anything IAT sensor related I did still take your comments in to account.

My question however still remains IAT sensor related and does not involve the purchase of much more than a resistor or other small component to change the voltage signal of the sensor signal. I'm sure this timing component you're referring to will cost more than the option that I was looking in to. So my question remains unanswered.
Doug

 

[LandoAWD]

Doug..the "timing thing" on E-bay is just a resistor.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33557&item=2419175811

 

[Doug99RS]

This seems to be along the lines of what I'm thinking about. I'm guessing Kris and ChanJr are talking about the same thing. Now we're getting somewhere.

I've talked with Kris and this sounds like it takes the place of the IAT sensor and holds a constant signal (temperature as the computer will interpret). It's really close to what I'm thinking of but I'm actually looking for something that still changes with the ambient temperature changes only on a linear scale difference of a couple percentage difference.

Beuler, Beuler, Beuler....

 

[pneumo]

Radio shack has variable resistors, called potentiometers really cheap. Like $3. So you can try your idea and your not stuck with one resistance value. You can try a setting and retune it.

One thing I'm concerned about is if the ECU uses intake temps to adjust timing as well as A/F ratio. Cold air means more fuel and more timing. Hot air gives you less fuel and less timing. The IAT mod can't separate the two, what if you need more timing and less fuel?

 

[Doug99RS]

Now THAT is the kind of response I've been looking for. I don't have all the answers and so that's why I posted the question in here. I'm hoping some more people will pipe up and either expand on your ideas or provide info to explain maybe that timing is pulled ever so slightly but the effects of leaning out the timing overcome the down side. Either way... I'm still kicking the idea around.
Doug

 

[pneumo]

It looks like it would work best if you trick the ECU into thinking the air is cold so that you get more timing. Since you don't need the extra fuel that comes with it, how about modding the airflow sensor to make it run a little leaner? and since the ECU sees less airflow it will add a little more timing again.
Just make sure you have some way of closely monitoring the engine and sensors to make sure you don't run super lean with way too much timing because that could make less power and/ or blow up your engine.

-Pandora's Box has been opened, Proceed with caution.

 

[Doug99RS]

The 2gnt does not have a Mass airflow sensor. However, the equivalent would be the MAP. And a change in map voltage may do the same thing. This is all speculation though so maybe some research in to the MAP sensor operation is in order for tonight and this weekend.
Doug

 

[nine5raptor]

you use the potentiometer in a series (or in parallel) with the IAT depending on whether you need greater or lower (respectively) resistance. You can also affect the barometric pressure the ecu sees to make changes.
essentially this:

"The value that would be the easiest to change would be the barometric pressure sensor. We’re going to add resistance to this value so that the ECU will see less barometric pressure than what there really is. This will also lean the car out so you should see a performance increase as well. Depending on the car and altitude you might need to add more fuel with an AFC.

So let’s get started, Parts needed:

A 10K potentiometer (although a 5K would probably do just fine). These are available at any electronics store, if you go to Radio Shack ask for a volume control knob because they don’t know what a potentiometer is

Wire strippers

Soldering iron

Step 1: Remove the access panel on the driver’s side of the center console. You should now see four plugs with a ton of wires going to them.

Step 2: Pull out the top plug, it’ll be the one that’s the hardest to reach. Locate wire #85. It’s orange with a white stripe.

Step 3: Cut the orange wire in half. Solder one end of the wire to the center peg of your potentiometer. Solder the other end to either the left or right leg, it doesn’t matter which. Turn your potentiometer all the way counter-clockwise.

Step 4: Plug the harness back in and start up the car. It should sound like it did before you did any modifications. If the idle is choppy or the car won’t run you turned your potentiometer the wrong way.

Step 5: Add resistance to the barometric pressure sensor by slowly turning the knob on the potentiometer. Drive the car around; if you get a CEL then add some more resistance. Keep doing this until you no longer get the CELs.

That’s it, special thanks to Marco for pioneering this mod and to all the guys on the DSM1gina2g Yahoo group for all the discussion, ideas, etc.

-Blake Heisler"

off of magnus motorsports's page.

 

[powells85]

I raced a friend's mx6 with the IAT mod and his 1-2 shift and 2-3 shift shot him foward a lot!. I'm really interested in this, anyone have a definite answer on what to do?

 

[Doug99RS]

Well, I did do a slight mod and at least noticed a temperature change. Unfortunately, it's on the neon.

My intake air temperature sensor connector also fits my battery temperature sensor (measures heat of the battery to aid in correctly charging it supposedly). In the process of reinstalling the transmission I accidentally broke the sensor end off of the battery temp sensor. Looked at it, saw it was basically the same as the intake air temperature sensor and also plugged right in. So I zip tied the new sensor to the radiator and plugged the harness in to it.

Now I've got about a 10 degree difference between the true intake air temperature sensor and what I'm actually using instead. This was of course going 60+mph down the road. Under hood temps will reach well in to the 140-150 degree temps on a 90 degree day here. The factory intake system draws air from basically right at the middle of the engine bay up at the hood so I know it is still getting the hotter air. Eventually I'll be able to get a cold air intake. I'll then do another comparison to see if it's colder at the filter or where the fake sensor is at.
Doug