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...

So far it has helped me. It may help only in the winter time, but I am not sure yet, as I haven't run it in the summer. So, currently time will tell.

Yeah I have it sitting at 143 all day long with a resistor. We are between 70-95 degrees since I have had it on - no noticeable difference in mpg.

:hyper::hyper:I'm excited, I ordered my iat/mpg fooler today!!! Hurry up an ship it ProWelder...:lmao::lmao2:

:hyper::hyper:I'm excited, I ordered my iat/mpg fooler today!!! Hurry up an ship it ProWelder...:lmao::lmao2:

I will in the morning about 10 am!

What is a average MPG for these trucks, I have a 98.5 24v with 200,000 miles on it. I get around 13-14 mpg and was wondering if this is a normal number or if I should be getting better mileage. I have never replaced the injectors and was wondering if that would boost my MPG up?

What is a average MPG for these trucks, I have a 98.5 24v with 200,000 miles on it. I get around 13-14 mpg and was wondering if this is a normal number or if I should be getting better mileage. I have never replaced the injectors and was wondering if that would boost my MPG up?

That's about right for town driving. Highway should see high-teens, at least. Sent from my EVO Android via Tapatalk Pro

That's about right for town driving. Highway should see high-teens, at least. Sent from my EVO Android via Tapatalk Pro

Well, I'm seeing about the same for both highway and city maybe a few more mpg's on the highway but not much. Would new injectors help?

Well, I'm seeing about the same for both highway and city maybe a few more mpg's on the highway but not much. Would new injectors help?

New injectors may help a little if you stay stock or go to RV275 injectors, but usually only if your current injectors are worn out or very dirty. Tire size, tire pressure, and tread design make a huge difference. Driving habits make the most difference, if you drive like a nearsighted grandma easy on the fuel and slow on the brakes using the techniques the big rigs use you will improve your mileage the most. Automatics get worse mileage than standard transmissions unless you high rev the engine in every gear with the standard. Automatics get poor mileage until the TC lockup happens then they get better mileage but still not as good as a standard because of more internal friction in the trans. Rear end ratio makes a difference also. The condition of the vp44 and fuel pressure to it also make a difference. A clean air cleaner makes a huge difference. All of the above and much more contribute to your mileage. Average????? no one is average. Jim

I got the mpg fooler in and installed that I got from Winslow! Was working on some numbers for a 3500 truck, but all that got cancelled due to my tranny going out! Going to take the tranny out prolly tuesday and see if the dude is going to replace it! After that I will get some numbers!

New injectors may help a little if you stay stock or go to RV275 injectors, but usually only if your current injectors are worn out or very dirty. Tire size, tire pressure, and tread design make a huge difference. Driving habits make the most difference, if you drive like a nearsighted grandma easy on the fuel and slow on the brakes using the techniques the big rigs use you will improve your mileage the most. Automatics get worse mileage than standard transmissions unless you high rev the engine in every gear with the standard. Automatics get poor mileage until the TC lockup happens then they get better mileage but still not as good as a standard because of more internal friction in the trans. Rear end ratio makes a difference also. The condition of the vp44 and fuel pressure to it also make a difference. A clean air cleaner makes a huge difference. All of the above and much more contribute to your mileage. Average????? no one is average. Jim

Well yes it is an automatic with 33" tires, and I drive more like Dale JR. the a gramma. SO that all makes good sense but heres my question. After reading on new injectors, DDP claims to give you a 2-3 MPG increase with their 75hp injectors, is that a realistic number if a person drove relatively sane?

Well yes it is an automatic with 33" tires, and I drive more like Dale JR. the a gramma. SO that all makes good sense but heres my question. After reading on new injectors, DDP claims to give you a 2-3 MPG increase with their 75hp injectors, is that a realistic number if a person drove relatively sane?

Keep in mind that you can tell when a salesman is not telling you the truth, because his lips are moving. Of course the sellers of a product will make claims of bigger better etc. they are trying to sell their product. Will they guarantee it and give you your money back + the cost of shipping when you don't get better mileage? No, they will say you are driving differently because you have more power now and that is what is affecting your mileage or ask you to prove worse mileage. Usually once the sale is made they don't want to hear any more about it. I have had +80 injectors and lost mileage, I currently have RV275 (about +40) and got some mileage back. My best mileage was with stock injectors. That's my experience with larger injectors. The larger the injector the more fuel they dump in when they fire, stands to reason as they have larger holes in them or more holes. the VP44 puts in more fuel by increasing the length of the injection cycle, not by changing the pressure. At a given pressure only so much fluid can be put through an injector in a given amount of time, so the larger the hole size the more fuel will be injected. Some say they gained mileage with larger injectors maybe they have I don't know and it has not been my experience. If they have there had to be some inefficiency in the engine setup that the larger injectors solved to give better mileage. No two engines are exactly the same and most of the people on the forum have modified their setups for more power which usually results in poorer mileage. It takes fuel to make power and less fuel to make better mileage, you can't have both at the same time. That's one reason the programmers are so popular, they only increase fuel consumption (more power) when you ask for it. bigger injectors give more power all the time. That's my worth. Jim

I think it depends on the specifics of the injectors. If the holes are to big to properly atomize the injection, or the injectors aren't balanced/pop tested to match eachother, economy will suffer and there will be more black smoke from the exhaust. Mildly bigger injectors (RV275's) or those with more similarly small holes, but more of them should do well mainitaining or slightly improving (through better atomization) fuel economy. The plus is that when you want the extra power it's available. If you aren't using that extra power, it shouldn't cost you any more fuel. It's just my opinion, I'm not an engineer. This is good conversation though.

My understanding is that the higher hp injectors let more fuel in earlier, effectively like advancing the timing. This is only valid to a certain limit in that the steel injector lines are somewhat elastic and act like an accumulator absorbing some fuel volume with the smaller OEM hp inlectors. That "stored" fuel injects later (after pop-off)in the combustion cycle. Put in the bigger injectors and that stored fuel volume gets in the cylinder more directly and earlier. This all assumes the exact same pop-off pressure. Usually the higher hp injectors just have 5 holes instead of the OEM 4 holes (or similar). Once the hp of the injector gets above a certain limit the fuel often does not atomize as well and can black smoke at idle and reduce mileage. The above "stored fuel" is the main reason why all 6 injector lines are designed to exact same length so there is a perfect firing balance between cylinders.

My understanding is that the higher hp injectors let more fuel in earlier, effectively like advancing the timing. This is only valid to a certain limit in that the injector lines are somewhat elastic and act like an accumulator absorbing some fuel volume with the smaller OEM hp inlectors. That "stored" fuel injects later in the combustion cycle. Put in the bigger injectors and that stored fuel volume gets in the cylinder directly and earlier. This all assumes the exact same pop-off pressure. Usually the higher hp injectors just have 5 holes instead of the OEM 4 holes (or similar). Once the hp of the injector gets above a certain limit the fuel is inserted over a longer duration and can even cause black smoke at idle when the turbo is not working much.

The injector is purely mechanical and cannot affect timing unless the pop pressure is lowered below 300 bar. below 300 bar the injector opens earlier in the cycle (read nanoseconds) and will marginally affect the timing to be earlier. earlier timing is NOT necessarily a good thing and can cause poorer mileage because the explosion has to fight the upcoming piston. It can also cause overheating of the piston. Injectors with more holes have slightly smaller holes than injectors with a lesser number of holes. If you dump in more fuel than there is air to burn it you ger the black smoke. But good luck with it.

Well I'm going to be taking the TT out in the next few day's I'll bring along the video camera and such and document a run down to Boise, ID...

SASQCH: I explained that poorly. I looked it up again and I found "more holes" makes a shorter injection impulse duration. The fuel starts injecting at the same crank angle but terminates earlier and makes for more efficiency in that peak combustion starts at an earler crank angle. Efficiency also comes from better atomization and swirl with five or six holes instead of OEM four holes.

SASQCH: I explained that poorly. I looked it up again and I found "more holes" makes a shorter injection impulse duration. The fuel starts injecting at the same crank angle but terminates earlier and makes for more efficiency in that peak combustion starts at an earler crank angle. Efficiency also comes from better atomization and swirl with five or six holes instead of OEM four holes.

balsip: I think you are making the assumption that the vp44 somehow meters the volume of fuel being injected and only injects that volume regardless of the injector size or duration of the injection cycle. I think with further checking you will find that the VP44 injects the volume of fuel based on an injection cycle time. Therefore, with bigger injector holes or more holes more fuel is injected in the same injection cycle time frame. The ECM regulates the injection cycle time frame based on several sensors one telling it the engine RPM (CPS) and the other telling it the throttle position (APPS) it uses these readings to locate in the fuel map how to change the injection cycle time frame to achieve the RPM requested by the throttle position. So in essence what you are saying is true but not in the way that many people would think. There are other factors that affect atomization than just the number of holes or hole size. Hole position, smoothness, and angle are important for proper atomization and probably have the greatest effect. Earlier timing of the injection does not necessarily mean better efficiency and mileage. I think that Mike has proven that with the IAT fooler. With colder intake temps the ECM advances the timing in an effort to warm the engine (combustion occurring earlier causes the engine to fight the compression stroke and retain more heat). When the fooler comes into play and feeds the ECM info that the intake air is over 130 degrees the ECM retards the timing giving better winter mileage. As I've said before some claim better mileage with larger injectors but many get worse mileage. I would like to think that those of us that get worse mileage just don't have as good of driving technique as those that get better mileage. I for one just cannot seem to get as good mileage readings with larger injectors than stock no matter how carefully I drive. Jim

some claim better mileage with larger injectors but many get worse mileage. I would like to think that those of us that get worse mileage just don't have as good of driving technique as those that get better mileage. I for one just cannot seem to get as good mileage readings with larger injectors than stock no matter how carefully I drive. Jim

My I have had stock, RV275 and now +75 CPP. I keep hand calc in my book each time I fill. Best overall mileage was with the RV275 (for city and highway). I added the +75's and I can still hit my best mileage (not by much) ABOVE the RV275's -> when I cruise in Cruise Control and in OD for most of it on hwy. Its much awash tho. I do lose 1-2 mpg in start stop traffic when I try to use my foot though. So yeah - I agree with Jim - hard to get better mileage out of a bigger injector - just due to driving requirements ...... but the bigger injectors can perform well **OH** check out the terrain (all AZ) from Greer => Alpine => Clifton => Phoenix to see where I just pulled 20.1 mpg on a camping trip home ......... including about 15 miles of 4x4

I installed the IAT fooler harness yesterday. I'm not about to take it off to redo, but if I was starting from scratch I'd pay better attention to make the leads come out to exact equal length because we're cutting the leads it's an extra detail. I'd also Y the splice joint rather than Ting the way I did. It would just make the end product slicker & the final dressing of the harness neater. I ran the harness up & over the brake to the gromet to keep it safe. When I'm done, I'm going to slide split loom over it & zip tie it to the other harness on the cowel edge along with the XZT+ harness. The only thing left to do is solder the switch in... Already soldered the 2.2K resistor to the switch.I will run the IAT fooler alone, first, before using the XZT+ so that I can ~scientifically separate the effects. I place this update here on this thread, to help those others who follow after. Russ

It rained really hard lastnight and I guess my resistor got wet because my iat's were all over the place. My 3cyl high idle kicked in with a 2.2k ohm resistor. It got down to -40 degrees

Well I'm going to be taking the TT out in the next few day's I'll bring along the video camera and such and document a run down to Boise, ID...

Drat... The weather got me pinned for about 1-2 weeks till the wind lets up... :banghead: