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Old 02-25-2011, 10:30 PM
Mopar1973Man's Avatar
Mopar1973Man Mopar1973Man is offline
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Default Experimental MPG Fooler for Dodge Cummins

There is some high fuel prices coming to some of us.... I'm offering up an idea on how to gain a few extra Miles Per Gallon (MPG's) for your 1998.5 to 2002 Cummins Bosch VP 44 Dodge truck.

Full article here.
http://mopar.mopar1973man.com/cummin...mpg-fooler.htm

Theory Of Operation
The IAT (Intake Air Temperature) sensor, senses the air within the manifold of the head entering the cylinders. The actual location of the IAT sensor is at the rear of the head close to #6 on the driver side. The IAT is a basic measurement of air density. So, going back to known facts that colder air produces more horsepower and torque. But if you reverse this, you gain MPG's, because as far as the ECM and VP44 are concerned, the air is less dense so less fuel is required to burn completely. IAT also effects the timing of the Bosch VP 44 injection pump. So, if I increase the IAT sensor temperature up to summer-like temperatures, you should be capable of getting close to summer-like MPG's. Now, looking at this winter weather in Idaho ranging from -25*F to 45*F, you can see the wide range of temperatures, and how cold air decreases MPG's. But the diesel engine requires a certain amount of heat to fire the fuel properly, so when is the air too cold for good performance?

Normal IAT Temperatures
The IAT sensor in a 24 Valve Cummins is located near a coolant passage so the numbers are a bit skewed. But you can figure your IAT on a offset figure. In fairly mild weather, say between 30*F and 80*F, the offset is 40*F plus the outside temperature, will be the temperature in the manifold. Below 30*F, the offset of 50*F plus will be closer to the mark. Then temperatures above 80*F outside will produce a offset of 30*F plus.

Comparing To Other Cummins Models
The IAT sensor in the 12 Valve Cummins (1989-1998) were all in the top of the manifold cover. Then, the Common Rail to current are also in the top of the manifold plate. Its only the 24 valve Cummins that placed the IAT sensor in the back of the head near a coolant passage.

Experimenting
So, what I've been doing, has been experimenting throughout this winter with different IAT values by using a rheostat and my ScanGauge II to monitor the IAT. In all the experimenting I've found, the warmer air (IAT) does help increase the MPG's back to summer-like values. But, also finding out that using a winter front to aid in getting the engine to full temp as quickly as possible is a big help too. Currently, I'm using a 2.2K ohm resistor in the IAT plug which translates to 143*F IAT temps.

IAT Values and Temperatures
These are tested values from actually plugging each resistor into the IAT plug and checking the IAT temperature reported by the ECM. I don't suggest using any resistor below 2.0K ohms these temperature are just way to high and totally out of normal operation. More than likely, performance issues will result in overheat temperatures in the manifold, thereby setting a code in the ECM.

Conditions
I've been keeping my driving style fairly constant when testing, I've been using 55-60 MPH as a average speed. No fuel additives, other than my standard 128:1 Ratio of 2 cycle oil. Weather has been ranging from -25*F to 45*F so far.

Results
Results have been ranging around 19-21 MPG with the 2.2K ohm resistor (143*F IAT) and with winter front. Without the fooler, it drops to 15-16 MPG. Without the winter front and Edge Comp, I was at a low of 12 MPG. With the IAT set at 143*F, I noticed the turbo spools quicker, and produces more boost than with normal sensor operations. Smoke seems to be reduced quite a bit with the IAT fooler in place over the normal IAT sensor.

Other Thing To Be Aware Of
If you are using a resistor or rheostat in the IAT plug, this will force the ECM into believing the manifold is already warm at start up, so there is a problem of no grid heater present on cold days. What I figured out was if I just set my High Idle fooler on, I can get my grid heaters to function. But, if you forget and turn the key on before the High Idle Fooler, then you are stuck without the grid heater. But I found a trick to that too, turn the key off and flip both the ECT and IAT switch of the high idle and ECM assumes a different run period and will now allow the grid heater to operate again.

The other odd thing is, if the engine is already warmed up to operating temperature of 190*F, and you stop at a store and pick up a soda pop or whatever. When you start the engine again the grid heaters will operate still. Huh? The IAT is at 143*F (fooled) and the engine coolant temperature is at 180-190*F. Still can't explain this one as of yet.
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Michael Nelson - AKA: Mopar1973Man - Forum & Articles
2002 Dodge Ram 2500, 5.9L Cummins Turbo Diesel, 5 Speed NV4500 transmission, 4x4, 3.55 Gears, AirDog 150 fuel pump with 1/2" Big Line Kit, Stock Bosch VP44 Injection Pump, Bosch RV275 Injectors +40HP, Edge Comp Performance Box, BHAF (Big Honkin' Air Filter), Stock Holset HX35W Turbo, Straight 3" Pipe Exhaust, Crankcase Vent Mod, High Idle Mod, MPG / IAT fooler Mod, ScanGauge II, 25% Tinted Windows, DiPricol Gauges (Fuel pressure, Boost, Pyrometer), 235/85 R16 tires mounted on 16x7 Aluminum mags (weighing 62#), Custom Fog Lights, Custom Backup lights, Silverstar Headlights, 23-24 MPG

1996 Dodge Ram 1500, 5.9L Magnum V8 Gasoline Engine, 46RE Automatic Transmission, 4WD with CAD axle with 3.55 Gears, Mopar Performance PCM, Gutted Kitty, ScanGauge II, 35% Tinted Windows, 16-17 MPG


Last edited by stodg73; 09-16-2012 at 03:51 PM.
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Old 02-25-2011, 11:06 PM
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dknaks dknaks is offline
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Nice writeup. I also run a pot for my IAT and have usually run mine at 114 degree setting in the winter (except when running with the chip turned up or stacked). Not only does it increase mileage but you can physically hear the engine run to a better tune. I seemed to find my best results at 114, which is odd coincidence thats the number the truck defaults to if per say it looses the sensor reading (and throws a code).
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Old 02-26-2011, 09:30 AM
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Mopar1973Man Mopar1973Man is offline
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Funny part is I'm also on a rheostat as well set at 140*F and with todays weather at -3*F this morning I could still get 19-21 MPG with even winterized fuels.

But your right it does seem to run better with a hot IAT temp vs. the sensor pulling down to -3*F... (Rattle bucket)
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Michael Nelson - AKA: Mopar1973Man - Forum & Articles
2002 Dodge Ram 2500, 5.9L Cummins Turbo Diesel, 5 Speed NV4500 transmission, 4x4, 3.55 Gears, AirDog 150 fuel pump with 1/2" Big Line Kit, Stock Bosch VP44 Injection Pump, Bosch RV275 Injectors +40HP, Edge Comp Performance Box, BHAF (Big Honkin' Air Filter), Stock Holset HX35W Turbo, Straight 3" Pipe Exhaust, Crankcase Vent Mod, High Idle Mod, MPG / IAT fooler Mod, ScanGauge II, 25% Tinted Windows, DiPricol Gauges (Fuel pressure, Boost, Pyrometer), 235/85 R16 tires mounted on 16x7 Aluminum mags (weighing 62#), Custom Fog Lights, Custom Backup lights, Silverstar Headlights, 23-24 MPG

1996 Dodge Ram 1500, 5.9L Magnum V8 Gasoline Engine, 46RE Automatic Transmission, 4WD with CAD axle with 3.55 Gears, Mopar Performance PCM, Gutted Kitty, ScanGauge II, 35% Tinted Windows, 16-17 MPG

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