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paul
Dodge Dakota
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7/12/2005
15:06:50
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 Subject: RE: iat relocation- more HP ?
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thank you somebody here has a lick of common sense. tricking your pcm into a richer mix does NOT give you more power, it gives you emmissions problems and a busted cat.
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Android287
GenIII
7/12/2005
16:49:37
| RE: iat relocation- more HP ?
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The IAT sensor mod or inline resister mods are used when the outside temperature is warmer than 80 degrees. Have you ever noticed that your truck seems to run faster on cooler nights that are around 60 degrees? This is because when its cool the engine runs a little richer and advances the timing slighly. All these mods do are trick the computer into thinking its about 60 degrees out and advances the timing slightly. There have been dynos charts in the past on here where the resisters have made roughly 5HP at the wheels. I don't see how this would ruin our emissions equipement when our trucks' PCM does this automatically when the air is cooler in the fall, winter, and spring. You can run too cold with the resisters. Usually a resister that runs 30-40 degrees cooler works best. Othrs have tried the resister mod in the cold winter and fall and have noctices no gain. So again this mod is only for use in hot temperatures.
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N56629
Dodge Dakota
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7/12/2005
18:21:30
| RE: iat relocation- more HP ?
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"Othrs have tried the resister mod in the cold winter and fall and have noctices no gain. So again this mod is only for use in hot temperatures."
I run this mod during the winter and get a minimum increase of 1.5 and up to 2 mpg better. This is done by making the computer think the air at the manifold warmer than it really is thus leaning it out. It also seems to fool the computer into going into closed loop earlier which also a leaner condition than open loop.
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N56629
Dodge Dakota
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7/12/2005
18:26:59
| RE: iat relocation- more HP ?
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"Relocating the IAT sensor to a colder climate merely richens the air/fuel mixture. Granted, you get a bit more power that way, but soon your tailpipe, and O2 sensors, and catalytic converter will be coated with a fine layer of soot. It's from unburned hydrocarbons, and is electrically conductive - not a good thing for the O2 sensors."
Doug, what do you think the computer does with all the information that O2 sensor is feeding back. Do you think it just sits there and says "Wow this is really rich," and then go back to doing whatever it was doing? Of course it doesn't it adjusts timing, pulse width and whatever else it can do to return everything to normal.
The only way I can see this working in the long term would to be to ditch that sensor and install an O2 simulator.
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Tim S
Dodge Dakota
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7/12/2005
23:30:51
| RE: iat relocation- more HP ?
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In reference to running better after a rain....
I've been noticing that since 1972, when I 1st got my permit, so I don't think it has anything to do with computers at all, but air temps and water content, possibly friction or air resistance, but not a program....
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Doug
Dodge Dakota
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7/13/2005
00:42:04
| RE: iat relocation- more HP ?
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"Doug, what do you think the computer does with all the information that O2 sensor is feeding back. Do you think it just sits there and says "Wow this is really rich," and then go back to doing whatever it was doing? Of course it doesn't it adjusts timing, pulse width and whatever else it can do to return everything to normal.
The only way I can see this working in the long term would to be to ditch that sensor and install an O2 simulator."
OOPS! I missed a few details. Here's some of it:
IAT SENSOR
The IAT sensor provides an input voltage to the Powertrain Control Module (PCM) indicating the density of the air entering the intake manifold based upon intake manifold temperature. The PCM uses this input to calculate the following:
- Injector pulse-width
- Adjustment of spark timing (to help prevent spark knock with high intake manifold air-charge temperatures)
O2 SENSOR
The upstream sensor (1/1) provides an input voltage to the PCM. The input tells the PCM the oxygen content of the exhaust gas. The PCM uses this information to fine tune fuel delivery to maintain the correct oxygen content at the downstream oxygen sensor. The PCM will change the air/fuel ratio until the upstream sensor inputs a voltage that the PCM has determined will make the downstream sensor output (oxygen content) correct. The upstream oxygen sensor also provides an input to determine catalytic convertor efficiency.
The downstream oxygen sensor (1/2) is also used to determine the correct air-fuel ratio. As the oxygen content changes at the downstream sensor, the PCM calculates how much air-fuel ratio change is required. The PCM then looks at the upstream oxygen sensor voltage and changes fuel delivery until the upstream sensor voltage changes enough to correct the downstream sensor voltage (oxygen content).
TPS
The PCM needs to identify the actions and position of the throttle blade at all times. This information is needed to assist in performing the following calculations:
- Ignition timing advance
- Fuel injection pulse-width
- Idle (learned value or minimum TPS)
- Off-idle (0.06 volt)
- Wide Open Throttle (WOT) open loop (2.608 volts above learned idle voltage)
- Deceleration fuel lean out
- Fuel cutoff during cranking at WOT (2.608 volts above learned idle voltage)
- A/C WOT cutoff (certain automatic transmissions only)
MAP SENSOR
The PCM uses the MAP sensor input to aid in calculating the following:
- Manifold pressure
- Barometric pressure
- Engine load
- Injector pulse-width
- Spark-advance programs
- Shift-point strategies (certain automatic transmissions only)
- Idle speed
- Decel fuel shutoff
IAC
The PCM uses the IAC motor to control idle speed (along with timing) and to reach a desired MAP during decel (keep engine from stalling).
CAMSHAFT POSITION SENSOR
Engine speed and crankshaft position are provided through the crankshaft position sensor. The sensor generates pulses that are the input sent to the powertrain control module (PCM). The PCM interprets the sensor input to determine the crankshaft position. The PCM then uses this position, along with other inputs, to determine injector sequence and ignition timing.
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Doug
Dodge Dakota
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7/13/2005
00:46:58
| RE: iat relocation- more HP ?
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And one more thing.
The PCM controls the air/fuel ratio of the engine by varying fuel injector-on time. Mass air flow is calculated using the speed density method using engine speed and manifold absolute pressure (IAT is a modifier in Speed Density).
Different fuel calculation strategies are used dependent on the operational state of the engine. During crank mode, a prime shot fuel pulse is delivered followed by fuel pulses determined by a crank time strategy. Cold engine operation is determined via an open loop strategy until the O2 sensors have reached operating temperature. At this point, the strategy enters a closed loop mode where fuel requirements are based upon the state of the O2 sensors, engine speed, MAP, throttle position, air temperature, battery voltage, and coolant temperature.
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Josh
Dodge Dakota
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7/13/2005
00:59:55
| RE: iat relocation- more HP ?
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N56629 wrote "...it adjusts timing, pulse width and whatever else it can do to return everything to normal."
So we relocate out IAT sensors which, according to Doug, richens up the mixture, and then the PCM leans it back out again based on O2 sensor outputs?
What's the point, then?
Must explain...
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N56629
Dodge Dakota
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7/13/2005
11:16:21
| RE: iat relocation- more HP ?
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Well, Josh, I've been asking that question for a long time myself. This subject concerns both the IAT and TPS sensor mods that everyone does.
I think it is quite possible that you see improvements in some engines and not others for the simple fact that there is a range of air/fuel ratio and timing that the PCM finds acceptable. If you are on one end of that spectrum you will see an improvement and if you are on the other end the PCM will bring them back into an acceptable range.
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Idano
Dodge Dakota
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7/13/2005
12:08:56
| RE: iat relocation- more HP ?
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Josh, N56629;
It's my understanding that WOT throws the PCM into an open loop condition. The PCM would then ignore the O2 sensor and base the A/F ratio and timing curve on presets determined by the AIT, MAS, RPM, and Coolant temp.
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N56629
Dodge Dakota
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7/13/2005
12:58:38
| RE: iat relocation- more HP ?
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That's right but I doubt that too many people drive around at WOT. Most are looking for better throttle response of idle. I doubt that any of the sensor mods, other than the crank sensor, accomplish much at WOT.
As you can see from the explaination on TPS, adjusting the voltage has limited value. Eventually the PCM "learns" the new minimum value or the closed position of the throttle plates.
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Idano
Dodge Dakota
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7/13/2005
17:28:20
| RE: iat relocation- more HP ?
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N56629,
You and Josh aked what's the point.
That's the point about moving the IAT.
Fool the PCM into reading colder air under WOT, colder air = richer A/F mixture from the factory presets. Richer mixture will usally = more power.
Yes it only works under WOT conditions.
I doubt most people looking for performance mods are looking for better response off idle. I haven't seen a V-8 Dakota that won't smoke the stock tires off the line.
I've been lurking around here for about 2 years,
(Right after I bought my used 98 RC 2wd), and most of the questions I've seen in this area are about max power for the least amount of money to make their truck quicker in WOT situations.
It's not very often you see someone ask about low end grunt in this section of the board. That would probably be more prevalent in the 4x4/off-road section
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N56629
Dodge Dakota
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7/13/2005
22:10:14
| RE: iat relocation- more HP ?
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I think that I would buy the WOT part but that doesn't seem to be mentioned in most of the treads on this subject.
How much horsepower would I gain if I dropped it in a container of ice water? I guess I'll have to give it a try some day. I'll probably have to figure out how to keep the wiring dry though, huh?
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