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...

"As for the fuel blowing up inside the injector, I wonder if that would happen since there is no oxygen in there, kinda like water wont boil if there is a lot of pressure."

Sorry, I didn't mean to imply that the fuel would ignite inside the injectors and HP lines. Obviously it won't because as you point out there is no O2. I was thinking more that it would flash into a gas and raise the pressure in the lines to beyond their burst point. When water flashes into steam it expands 10,000 times in volume. I don't know how much diesel fuel expands when it flashes into a gas. I do know that when water boils and flashes into steam it absorbs a tremendous amount of latent heat and that's why the whole volume of water don't turn into steam instantly when it reaches 212*F at 14.7 lbs absolute pressure (sea level). The heat source has to supply the heat the gas absorbs when it flashes. So the greater the heat source the faster the water boils and flashes into steam.

You are correct that water will boil at lower or higher temps depending on the pressure on it and when it does it contains more or less energy depending on the pressure and temp. The high pressure steam driven ships the NAVY used before nuclear systems, used superheated steam from a pressure vessel (boiler) at temps and pressures exceeding 1200psi and as high as 1000*F, because the steam contained more energy and could drive the steam turbines much harder.

Just tidbits from my past.

Jim

  SASQCH said:

"As for the fuel blowing up inside the injector, I wonder if that would happen since there is no oxygen in there, kinda like water wont boil if there is a lot of pressure."

Sorry, I didn't mean to imply that the fuel would ignite inside the injectors and HP lines. Obviously it won't because as you point out there is no O2. I was thinking more that it would flash into a gas and raise the pressure in the lines to beyond their burst point. When water flashes into steam it expands 10,000 times in volume. I don't know how much diesel fuel expands when it flashes into a gas. I do know that when water boils and flashes into steam it absorbs a tremendous amount of latent heat and that's why the whole volume of water don't turn into steam instantly when it reaches 212*F at 14.7 lbs absolute pressure (sea level). The heat source has to supply the heat the gas absorbs when it flashes. So the greater the heat source the faster the water boils and flashes into steam.

You are correct that water will boil at lower or higher temps depending on the pressure on it and when it does it contains more or less energy depending on the pressure and temp. The high pressure steam driven ships the NAVY used before nuclear systems, used superheated steam from a pressure vessel (boiler) at temps and pressures exceeding 1200psi and as high as 1000*F, because the steam contained more energy and could drive the steam turbines much harder.

Just tidbits from my past.

Jim

  ISX said:

Ah, very interesting.

Expanding on this:

I was reading yesterday about how cold liquids have their molecules clump up and move around, whereas hotter fluids have their molecules moving around individually. That was water but maybe fuel is the same, and if it were the same then it stands to reason that hot fuel would atomize better since there are no "clumped" molecules.

So in theory we should be getting the fuel as hot as possible without having it blow up.

I don't think the fuel temp should be raised above the flash point of 62ºC (62 ºC = 143.6 ºF). If it goes above the flash point some of the fuel may flash into a gas and interfere with the injectors working properly.

Hmm, I have an idea since it is cold here. If I used a heat gun on the injectors for a while before the morning start, it would theoretically start better. I think that a heat gun isn't going to do much against that 1,000 lb heat absorbing chunk of iron called the cummins engine.

I would aim it away from the block but at the injectors and that should transfer all the heat through the fuel. Would be a neat test to do anyways.

  SASQCH said:

That's what is holding me back from just slapping together a simple heat exchanger using engine coolant. I need some kind of adjustable temp controlled valve to regulate the coolant flow to keep the temp of the fuel below 140*F automatically once it is set. Jim

  ISX said:

Yeah I was wondering how much of the heat would just go straight into the block. I think if I got it hot enough I could start it before all of the heat transfered.

John's 24V had a fuel temp on the edge module and if you drove it and let it sit for a long time, the temps would get to 150-160F. I wonder if being contained inside the fuel system like that would keep all of it from turning into a gas. Yes, I think so only some of the fuel would flash to gas thereby raising the pressure and raising the flash point. Just like boiling water in a closed high pressure vessel. As it flashes into steam the pressure goes up preventing more to water to flash until more heat is added to reach the new flash temp of the pressurized fluid. Interestingly if you remove the heat source from the boiler and allow it to cool back to it's starting temp the pressure also drops due to the steam condensing back into a fluid. I suspect that diesel fuel follows the same thermodynamic laws.

His fuel also didn't get hot too quickly while driving, might have got to 30 over ambient, which in the winter would mean it stayed cold, though I would like to hear from someone who has watched it in the winter. You would think the VP44 would then be more efficient since it is full of fuel, hence heating it up more. The only fuel mine sees is what it puts in the plungers.

Another thing to think about is the density of fuel changes with temp. You might have to step on it more with hot fuel than cold fuel, unless it is more efficient with the hot fuel. Yes, I think you are right here, I don't know how much the volume changes. But I do know it changes, go to a fuel station early morning after a cool night and fill your tank to the brim and wait for it to warm up with the day temps. You will have fuel running out by 5 or 6 PM.

So many factors

  JOHNFAK said:

Once you get your fuel gauge - sell the EZ and get a COMP/JUICE/ADRENALINE more timing and power ......... 2-3+mpg generally

  SASQCH said:

Yes, I think you are right here, I don't know how much the volume changes. But I do know it changes, go to a fuel station early morning after a cool night and fill your tank to the brim and wait for it to warm up with the day temps. You will have fuel running out by 5 or 6 PM.

  Mopar1973Man said:

Yes that one is true I got called on a fire run for a HAZMAT spill. What had happen is exactly that the owner had filled his fuel tank totally rim top full and parked the truck on the street and it went from 55*F in the morning to over 115*F in the afternoon and the diesel fuel was perkin' right out of the fuel cap.

Needless the say the owner got slapped with a heavy fine...

Oh if I want to see IAT over 130*F all I got to do is find a grade drop the exhaust brake and bam! IAT temp rocket up and stay up till I turn off the exhaust brake. But as for the rise at low boost I see the same thing but rolling into the boost pressure I typically see a fall in temps about 5-10*F typically. I think because at low velocity the air has time to pre-heat in the manifold since there is a coolant passage the runs along the bottom. But under boost your pushing air through so fast its not pre-heating as much... (My thought on it )

The IAT is slow to react. I noticed it when I took it out and was testing resistance values of it in water and stuff. You would put it in ice water, and it wouldn't do anything for a couple seconds then slowly start to figure out it was cold. I got more info from the physics wizards and indeed the boost and atmospheric pressure have NO effect on the temp rise you get when the piston compresses. Compression ratio and IAT are the only determining factors. Now more boost usually comes with more heat from compression in the turbo itself, so the IAT would be warmer due to that which would in turn create more heat during compression. But if the IAT was always the same, it doesn't matter what boost or atmospheric pressure is, the temp rise from the piston compressing will always reach the same point. So more compression means more heat, and higher IAT means more heat, that's it. More pressure in there from more boost means more volume and air molecules in there to burn, so the volumetric efficiency shoots up. Obviously colder air increases this efficiency further.

After reading your post ISX it seem to be that if I can find the high point for MPG and just use a fixed IAT resistor that's all it matter then right? So as long as the ECM thinks in a nice warm summer day I should be good all the time right? (Trying to understand your math)

  SASQCH said:

Yup, I think self serve fuel stations should have signs warning of this hazard and telling people not to over fill their vehicles. ........... Jim

  Mopar1973Man said:

After reading your post ISX it seem to be that if I can find the high point for MPG and just use a fixed IAT resistor that's all it matter then right? So as long as the ECM thinks in a nice warm summer day I should be good all the time right? (Trying to understand your math)

With fuel prices around here high... I don't ordinarily worry about topping up. I plead guilty however to topping right up the spout... fortunately my tank & fill are tight with no seepage... before hooking up to head out on trip. It's far enough home that I'm down close to a gallon, just getting there. I have been paying attention to the previous posts on this topic & have not topped up since... If/when I get a Draw-Straw I'd be concerned about seepage from the gromets. It would hurt to waste fuel at these prices, even if no one caught us. Russ

  dracozny said:

even in a non self serve state, the attendants automatically top off, around here anyways.

Mine leaks at the grommet... But since I drilled the wrong size hole from what I found out that explains part of it. I was a unlucky person missing part of the manual explaining that part, no extra spring, no warranty card, no sticker, etc... But I'm happy with my AirDog 150 still going strong...

  SASQCH said:

Yup, I think self serve fuel stations should have signs warning of this hazard and

telling people not to over fill their vehicles.

Jim

  Rogan said:

Around here, they DO say "do not top off fuel tank" on the pumps.. On another note, I was able to get a little info on the piston differences between the 12v and 24v, and related to compression changes. The 12V has a 60cc bowl, and the 24v has a 64cc bowl, thus a touch less compression ratio. And while picking up my exhaust yesterday morning, he got a 12v and 24v piston out, so I could take a pic and show the physical differences of the bowls.. On the left, is the 24v with it's centered 64cc bowl. The right one is the 12v's offset 60cc bowl (since the injector is off to one side, rather in the middle.)

What are the 24V HO pistons like, are they the same as the SO pistons?

Also, the pistons for the H.O. are different shapes than the S.O. due to the different injection pattern.

  JOHNFAK said:

Nice - thx So why the difference - I would have assumed the compression ratio's if they impacted performance would be pretty constant between years ?? To whatever was best ?