Well gang... I've been playing with theories and ideas for long enough now its time to put them into a design and see if it actually works. We all know the 24V's seem to take a good tumble in MPG's as the winter sets in well ISX proved that with the 12V engines with static timing that MPG's don't change. Well if you look at it the only thing that could be tossing this out the window is the IAT sensor on the 24V is changing the VP44 performance. Most know that colder air produces better HP/TQ because colder air is denser and requires more fuel to keep balanced. Well if you reverse this and warm the air (in theory) the VP44 should retune and burn according to the manifold temp. So what I've done tonight is fished through my resistor pile and found 3 I'm going to use for test candidates. Orange - White - Red - Gold = 3.9K Ohm = 116*F IATRed - Violet - Red - Gold = 2.7K ohm = 132*F IATRed - Black - Red - Gold = 2.0K ohm = 148*F IAT So now tomorrow I'm going to pull 3 test runs on the same piece of highway... Seeing if the highier the IAT temp increases the MPG or not... I'll can give you something to think about... Grid heaters are NOT controlled directly by the IAT... With the 2.7K Ohm resistor in place before even starting the grid heater still where hitting as normal. So there is more to the grid heater that the IAT temps... ... On the cutting edge again...

I just did another run with the fooler on. I think I have a 143* resistor on mine and I got 18.92 mpg. I used 14.986 gallons and went 283.5 miles, and these are corrected miles due to larger than stock tires. 90% of this was highway driving at 80 mph. There was very little idle time with this also. Some stop and go in town traffic:banghead:.

I see what your doing. I think you will have a very hard time hitting the proper marks with a 50K pot. I think there is a code for too cold as well. I would just put it on a switch so you can revert back to normal IAT operation. As for the winter front thing, I think that needs more testing. It was like 10F when I got the same 27mpg as I got in summer and that was without a winter front. My truck has more power and is responsive as all get out. You put the winter front on AND set the fooler for 140F, you didn't try it without the winter front with the IAT at 140. I went 45mph for a week or so a month ago when it was freezing out, the EGT's were 300F the majority of the time. I got 25mpg (I think lugging the engine like that (outside the turbos range) made it a little less efficient, plus going so slow) which proves that even with cold EGT's, the engine is fine. I believe EGT is just one factor, internal combustion temps are another. If it were really 300F then the engine would not run since diesel has to be over 400F to combust. According to my calculations, at 0F IAT, the heat of compression with 17.9 CR and 16.3 CR (which both could be wrong as we know these numbers are thrown around) is only a 50F difference, which is 1000F and 950F. The combustion process is adiabatic (however thats spelled) which means it happens too fast for heat to be lost through the combustion walls or anything like that. I think some heat is still lost, but hardly. At 600RPM the piston is hitting TDC 10 times a second. Now think about how long it takes to heat a block of iron up with a torch.

I don't suggest using a rheostat (pot) for the fooler unless you have a way to monitor the IAT temps. Because it doesn't take much to go either way... But 100-120*F is a good normal starting temperature and work your way up. I think 140*F is going about the high mark of normal.

I don't suggest using a rheostat (pot) for the fooler unless you have a way to monitor the IAT temps. Because it doesn't take much to go either way... But 100-120*F is a good normal starting temperature and work your way up. I think 140*F is going about the high mark of normal.

Thanks Mopar, ISX, and Sasqch for the info. I have a Maxitrip auto computer, a Chinese version of the Scan Gauge with a few glitches but not a bad unit for 59$ at Princess Auto (Canadian version of Harbour Frieght). For testing I will use the 10k pot then once a common resistor # is agreed on then likely a resistor and a switch like Sasqch mentioned.

I believe EGT is just one factor, internal combustion temps are another. If it were really 300F then the engine would not run since diesel has to be over 400F to combust.

Please don't confuse EGT numbers with combustion temp numbers. My 93 12 valve idles with egts in the 250* range. Remember that as the piston moves down after combustion and the space in the chamber gets larger which has a cooling effect to the high temp high pressure gasses so in a no load condition most of the compression heat and some of the ignition heat is lost through expansion. If it was not cooling as the volume increased the pistons and exhaust valve would melt and the idle EGT temps would be over 1700* if they were the same as combustion temps.

According to my calculations, at 0F IAT, the heat of compression with 17.9 CR and 16.3 CR (which both could be wrong as we know these numbers are thrown around) is only a 50F difference, which is 1000F and 950F. The combustion process is adiabatic (however thats spelled) which means it happens too fast for heat to be lost through the combustion walls or anything like that. I think some heat is still lost, but hardly. At 600RPM the piston is hitting TDC 10 times a second. Now think about how long it takes to heat a block of iron up with a torch.

Just a minor point that came to mind

--- Update to the previous post...

For testing I will use the 10k pot then once a common resistor # is agreed on then likely a resistor and a switch like Sasqch mentioned.

I suspect that as testing continues we will find that the "best" resister value will change with the outside air temps. It may need to be higher with warmer air temps. That's why I am using a pot instead of a resister. If it turns out to be just one value is best, I can set it and forget it.

Jim

Just a minor point that came to mind

--- Update to the previous post...

Jim

I know the difference between EGT and combustion temp, I have a calculator showing exactly what the heat of compression is. The point I am trying to make is that I think the winter front is degrading performance/mpg. Maybe not mpg, but definitely performance. I didn't dyno it or anything, but with it off and me just driving around with frigid temps, I was constantly wondering what was going on. I know the feel of the power it has very well and I was expecting the usual power, so when the butt-meter spiked, I knew something was going on and all I had done was taken the winter front off. I need more solid proof but the colder it gets, the faster it is. It was -10F a while ago and that thing was an absolute animal. I never got that kind of power with the winter front on. Remember that mine is completely static, so the only thing that changed was colder air going into the engine.

Another thing to think about with cold temps, the engine is at 200F or so, I don't think your going to lose any heat to the cylinder walls at operating temp.. You lose a little bit or else the engine wouldn't have the thermostat open, but hardly. I believe it is well within it's range to burn the fuel efficiently. According to my calculator, going from 0F to 100F is means going from 1000-1300 on compression temps, still well above 400F. This would mean the colder temps (1000) would take more time for the fuel to ignite, retarding timing. I think that is why the 24V spends so much time advancing it. As the fuel gets hot, it ignites faster, so timing advances. I think the 24V determines how much to advance it based on IAT. This is why on really cold days, it knocks really bad, but in summer it is not as bad. Now, fooling it brings our mileage back up, but how if it has cold fuel that is being shot in way to late. I think the fuel gets warmed up a lot, up to the same point as it gets to in the summer (since the engine is 200F in both instances) so the fuel goes in at the same temp.

In other words, I think the programmers of the engine screwed up. Now there might be something with emissions for cold temp driving that they did, so they might have not screwed up. I think they did though, if the mileage drops THAT much in winter, you can't tell me it's not a screwup. I also don't see how it screws up so badly as to drop you more MPG than I do pulling a 4k lb enclosed trailer. I think they just thought "oh the fuel is cold, lets advance the timing a lotttt so it has time to ignite, to the point that it is very inefficient". They should have tested more.

Well I babied this truck and my UG read 17.5 average mpg and I fill up to see 14.:banghead: Granted, I didnt get the tank to the tip top on the prior fillup but it was pretty close because my needle pegged to full, it may have been 1 maybe 2 gallons off at the most. So now I am just gonna drive it like usual and with the new tires its gonna suck it up even quicker.

Still holding a constant 21-22 MPG every trip to McCall, ID now...

Don't say that to us Mike:doh: I'd be so tickled with mileage like that I wouldn't have even thought of an mpg fooler:lol: I've come across a guy about an hour from me that works on these trucks a lot and he says his dad has a 99 that is getting 29-31 mpg. The first chance I get I'm heading to his shop to find out what he does. From my own testing lately I get 2-4 mpg better by driving in Drive instead of Overdrive. Running at 2100 rpm is better than 1400.

I've come across a guy about an hour from me that works on these trucks a lot and he says his dad has a 99 that is getting 29-31 mpg.

Hard to believe that high...

(I'd love to dig up a article for ya but my internet is in LIMP MODE... Really slow)

That's why I'm heading up there asap, to see what he does:cool:

I know what he does, he goes by the overhead.

First tank with the new tires was about 15.4 but I picked up a pack of 2.2k ohm resistors and my intake went to 143.6 and my mileage on the ug also went from 15.? to 19.5. I dont imagine its that high but it would be nice to be between 15 and 19.5.

First tank with the new tires was about 15.4 but I picked up a pack of 2.2k ohm resistors and my intake went to 143.6 and my mileage on the ug also went from 15.? to 19.5. I dont imagine its that high but it would be nice to be between 15 and 19.5.

What is a UG? Get some hand calculated numbers. I bet you are getting 19.5 though. Thats the same resistor I used on stodg's truck and it bumped his way up there too.

Glad to hear 98whitelightnin. I'm just waiting for the soldering iron to warm up so I can incorporate a 5k ohm POT into my idle fooler and maybe enjoy those numbers too:thumb1: And, ISX, a UG is an Ultra Gauge. Basically a Scangauge by a different company.

Haven't read this in a little while .... but Guessing this is going to make little difference to someone running a truck in warm climate like AZ,TX or most places in summer - where IAT's are going to get 10+ pretty quick and stay there ? :shrug:Really only for you snowboyz ? :P

Well I went for a drive and about the only difference I could notice was the engine sure was quieter with the IAT dialed in to 140-150:banghead:

When I decided to build the IAT fooler, I wanted it to be removable so I didn't have to cut the factory wiring harness. Mike pointed me to Casper electronics who sells a IAT extension. I also wanted to be able to switch between the IAT and the fooler. I also wanted the fooler to be adjustable.To this end I bought the extension, a double poll double throw mini dip switch (on-off-on), a 5K potentiometer, and 10 foot of18ga 3 wire cord. I built the control housing box from ABS plastic sheet I already had in the shop.

So have you noticed improved mpg's or am I the odd man out who didn't see any improvement?

What is the Casper part number for the extension harness, please?I am confused about the resistor value desired. I'm looking at the chart: IAT Sensor Resistance Values Am I missing something?(Deleted chart as more up to date information posted below)