After some theory discussions with the other mechanics and the service manager at my work, Ive decided to switch back to the stock air intake setup over the winter.

The general idea is.... in cold weather the engine reads the air intake temp, and adjusts, adding more fuel to compensate for the cold air not just at start up, but the whole time in winter.

We have been seeing -10 degrees to 10 degree for the last week.

I have seen my milage decrese the last week, so im going back to the stock setup through the winter.

Ill let you guys know in a week or so when I have had a chance to see what is happening to milage.

 

do you have the 5.9L?

 

nope, 4.7

Souldnt matter though, in theory this should apply to ALL cars

 

I'd like to see the results, but I don't think it's going to make much of a difference. Whether stock intake or aftermarket, it's still sucking in cold air.

 

I don't think it makes a great difference, I think your mileage thing is more of now getting the sucky "winter blend" gas. However, when I lived in upstate NY, I knew more than one guy who removed his CAI and cooler thermostat for winter use, putting both back in the spring time...

 

true, but the stock setup is more restrictive thus allowing the air going into the engine to be slightly preheated, unlike an aftermarket CAI.

The "Hemi hat" (which is also on the 4.7l) is basically a preheating box in the winter time.

 

In theory, you are absolutely correct. In real world, it might make a difference, or not.

The IAT (intake air temperature) sensor measures the temp of the air inside the intake manifold, just past the throttle body. When you first start the motor, it is in warm up mode, or "open loop". During this period, the computer richens the air/fuel mixture, and advances the ignition timing. Once the IAT gets up to temp, the computer will then lean out the A/F ratio, and retard the timing.

With that being said, if your IAT is constantly stuck in "open loop" you will have a rich A/F mixture at all times. Keep us updated on the results you find. I'm interested to see if the CAI really makes that much of a difference as far as air temps go.

Lucas

 

i have never had problems with my cai in cold winter weather. im in MA up in new england. my mileage always drops in winter due to winter gas blends ( i installed intake mid winter and had same mpg with stock and volant intake.) In the spring it goes back up to normal mpg averages.
my iat sensor is in the intake tube not the throttle body. is that what you meant my past throttle body???

 

The IAT sensor is before the throttle body on most engines...on the hemi it's in the silencer when stock and with a CAI you put it in the tube. Maybe the 4.7 is different I dunno..

Open/closed loop is controlled by various sensors and the IAT isn't one of them...you'll go into closed loop even with 35* air intake temps. Open/closed loop is more controlled by the coolant temp sensor and the o2's...even though the o2's are bypassed when in OL as far as a/f ratio goes.

 

I stand corrected. I wasn't aware that the IAT was located in the air tube on the newer engines. Back in the day it was plumbed directly into the intake manifold. A lot of jeep, ram, and dakota guys would pull it out of the manifold, plug the hole, and relocate it to the air tube. This would essentially trick the PCM into richening the A/F ratio.

I'll be honest, I've been out of the performance game for a while. I still haven't even looked under the hood of my 08 quad cab 4.7l. So I'll take your word for it when you say it's now in the air tube. When the IAT used to be located in the intake manifold, moving it would trick the PCM to stay in "warm up mode" all the time. I had my jeep rigged up with a resistor on the IAT, and a toggle switch in the cab. With the flip of a switch i could go into "warm up mode", and you could definitly tell the difference in the seat of the pants.

I guess Dodge has made things a little harder for us now.

Here's how we used to do it:



How to relocate your IAT Sensor

The IAT Sensor is located on the #2 Intake Runner (3.9/5.2/5.9L) or under the Throttle Body, in the manifold (4.7L) - Big Brass looking sensor with two wires (Grayish connector)

Remove the IAT sensor from the manifold and plug the hole with a 1/4" NPT Pipe Plug (Home Depot)

Drill a 1/2" hole in the intake tube and thread the IAT sensor into the hole (use some silicone if you want...not required though) - You may have to extend the wires about 6-12" in some cases (use 16ga. wire)



Open and Closed Loop Operation:

There are 7 different modes (conditions) that are used (besides Key-ON and Key-Off mode). Here is a table of what sensors are monitored and what determines the mode. One thing to remember, under OPEN LOOP Operation, the O2 Sensor(s) are ignored by the PCM.


Engine Start-Up Mode (OPEN LOOP)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp (IAT)
MAP
TPS
Starter Motor Relay
Cam Position

Engine Warm-Up Mode (OPEN LOOP)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp (IAT)
MAP
TPS
Cam Position
Park/Neutral Safety Switch (Automatics Only)

Idle mode (Once at Operating Temp: CLOSED LOOP)
A/C Select (if equipped)
A/C Request (if equipped)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp (IAT)
MAP
TPS
Cam Position
O2 Sensors
Park/Neutral Safety Switch (Automatics Only)

Cruise Mode (CLOSED LOOP)
A/C Select (if equipped)
A/C Request (if equipped)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp (IAT)
MAP
TPS
Cam Position
O2 Sensors
Park/Neutral Safety Switch (Automatics Only)

Acceleration Mode (OPEN LOOP)
A/C Select (if equipped)
A/C Request (if equipped)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp (IAT)
MAP
TPS
Cam Position
Vehicle Speed Sensor
Park/Neutral Safety Switch (Automatics Only)

Deceleration Mode (OPEN LOOP)
A/C Select (if equipped)
A/C Request (if equipped)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp (IAT)
MAP
TPS
Cam Position
Park/Neutral Safety Switch (Automatics Only)
Vehicle Speed Sensor

Wide Open Throttle - WOT (OPEN LOOP)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp (IAT)
MAP
TPS
Cam Position

Lucas