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Old 05-14-2016, 01:02 PM   #1 (permalink)
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Ideal iat

The truck is a 24v 2nd gen dodge diesel. It has an iat sensor that tells the computer to retard the injection timing if the air is too cool. Retarding the timing gives you a big hit on economy. Without the computer intervention, I would think the engine would be more efficient with air as cold as possible. Cold dense air hurts economy from an aerodynamic standpoint, but cold dense air should make the engine more efficient. Someone help me understand this better. Alot of people want to warm the air going in, I want to cool it as the turbo heats it up by compressing it.

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Old 05-15-2016, 01:41 PM   #2 (permalink)
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Bump so some diesel folks see this.
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Old 05-15-2016, 05:40 PM   #3 (permalink)
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I do have the stock intercooler now, but am planning to build a water to air cooler that can drop iat more than the air to air intercooler. I can fool the computer into thinking it's a nice warm sunny day by bypassing the iat sensor with a resistor (2.2k ohm I think). The ecu will then keep the injection timing advanced, giving me beter performance and economy. I think the stock programming retards the timing for emission durring cold engine operation, but the winters in Colorado get cold enough to keep the engine in that mode. My mileage takes a hit all winter. Some of that winter mileage is do to winter fuel (diesel) has a higher cetane rating to make the diesels eisier to start, but higher cetane means lower heat content. The iat fooler was developed by a guy on cumminsforum.com who has the same generation dodge I have. He regularly gets in the 20 to 23mpg range. My understanding of the systems on my truck are rudimentary, but his understanding of 2nd gen dodges is extensive. I believe if you can get around the computer, the engine will be more efficient with cold dense intake air. I might be able to prove (or disprove) that with my 2 dodges. One runs with the stock injection pump (vp44) controled by the ecu. My other truck I put the previous gen (p7100) injection pump in that doesnt respond to any of the sensors or ecu input. It gets tunned by old fashioned mechanical adjustments. That is the truck I plan to do experments with. Aba testing on each truck seperatly should give some more insight.
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Old 05-16-2016, 12:51 AM   #4 (permalink)
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Diesels with mechanical injector pumps and no air temp intake adjustment improve in efficiency down to 0 degrees F or lower. Don't sweat a thing about cold temps with a modern computer controlled diesel.
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Old 05-16-2016, 12:05 PM   #5 (permalink)
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That's good to know. There are many threads on warming the intake air, but I've been thinking about cooling it as much as possible. I want to tap into iat data with a scangauge on the obd2 port and see how the instant mileage is affected by iat. Is that the right product to use? On my 99 with the p7100, the ecu and all the sensors are still functional, just don't control anything but gauges and charging.

Btw With so many people on this furum looking to heat intake air, they might look into getting the grid heaters off a diesel from the junkyard. Some performance diesel guys remove them from the airstream for better flow. I wouldn't ever remove mine as I would never get the truck started in the winter.

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