mm3 ???

[Killerbee]

What kinda truck do you operate that only requires this volume of fuel at a cruising range.

what do you use on your tune? Maybe its more.

See depending on what you do with the fuel tables, 20 mpg could 40, or 60, or 5, or most any number. Just depends on your histograms.

It has been a long time since I ran a stock tune, so to address Bens statement, we need a baseline 75 mph cruise mm reading. Let's say it is 20 mm^3. IIRC there are 4 pulses per rev in a 4 stoke 8 cylinder. At 2000 rpm, that comes out to 160,000 mm^3 per minute, 9,600,000 per hour. There are 3,800,000 mm^3's in a gallon. That comes out to 2.5 gallon per hour.

At 20 mpg I know I use 75 mph/20 mpg= approx 4 gallon per hour. So I'd say the stock tune is not very representative of accurate fuel use.

Our stock 20 "reference" should actually be more like 32 mm^3

 

[Mike]

what do you use on your tune? Maybe its more.

It has been a long time since I ran a stock tune, so to address Bens statement, we need a baseline 75 mph cruise mm reading. Let's say it is 20 mm^3. IIRC there are 4 pulses per rev in a 4 stoke 8 cylinder. At 2000 rpm, that comes out to 160,000 mm^3 per minute, 9,600,000 per hour. There are 3,800,000 mm^3's in a gallon. That comes out to 2.5 gallon per hour.

At 20 mpg I know I use 75 mph/20 mpg= approx 4 gallon per hour. So I'd say the stock tune is not very representative of accurate fuel use.

Our 20 "reference" should actually be more like 32 mm^3

I would grab a log of your trucks tune driving down the road. With the calculations used by the o/s to give an approximation of mm3 Flow and Flow2, we'd have a start. Just remember that part of that pumping the cp3 is doing will be returned to the tank. especially when not in pe mode.

 

[Killerbee]

I would grab a log of your trucks tune driving down the road.

that's where I got 15. But everyones tune is different, and with that, so will that logged number be different. This is also why we have a DIC correction table.

 

[Killerbee]

Timing and boost won't have any impact on the mm^3 disparity, though it does change motor efficiency, and mpg.

I understand what you are saying. Most folks just add to the WOT section of things, and leave most of the tables alone. Just to be clear, on one of my tunes, my pressure table is not even left alone. it is somewhat different (lower) in many areas, for noise emissions reasons. With that, my pulse ends up longer for the same load.

That could have the effect of seeing larger fuel qty numbers on the log, although mpg may be identical.

I feel a little like this thread has been hjacked, so we can discuss off-line or start another.

 

[Mike]

Timing and boost won't have any impact on the mm^3 disparity, though it does change motor efficiency, and mpg.

I understand what you are saying. Most folks just add to the WOT section of things, and leave most of the tables alone. Just to be clear, on one of my tunes, my pressure table is not even left alone. it is somewhat different (lower) in many areas, for noise emissions reasons. With that, my pulse ends up longer for the same load.

That could have the effect of seeing larger fuel qty numbers on the log, although mpg may be identical.

I feel a little like this thread has been hjacked, so we can discuss off-line or start another.

Seems as this lower pressure and higher pw will cause rail problems.

I will say the impact from timing and efficiency is less throttle position, less mm3.


Mike

 

[McRat]

Who runs 23000???

Yeah, we lie to the computer to make more power.

If the factory says it takes 1500 microseconds to squirt 100mm of fuel, we lie to it, and say it takes 3000 msec so it squirts in far more fuel when the throttle pedal requests 100.

HOWEVER... The actual fuel going into the cyl at this point is unknown. I think we are in for a surprise.

 

[Mike]

Who runs 23000???

Yeah, we lie to the computer to make more power.

If the factory says it takes 1500 microseconds to squirt 100mm of fuel, we lie to it, and say it takes 3000 msec so it squirts in far more fuel when the throttle pedal requests 100.

HOWEVER... The actual fuel going into the cyl at this point is unknown. I think we are in for a surprise.

Well Pat, we little tuners with little fuel capabilities have to run little pressure.


I know you run 26k plus but heck I can't afford to make provisions to run with you guys.

I'm with you concerning the surprise....

 

[Mike]

FWIW, I did find that 1 gallon [US, liquid] = 3 785 411.784 cubic millimeter using the conversion from http://www.onlineconversion.com/volume.htm .

So your more like number did come down a bit.

 

[JoshH]

Timing and boost won't have any impact on the mm^3 disparity, though it does change motor efficiency, and mpg.

I understand what you are saying. Most folks just add to the WOT section of things, and leave most of the tables alone. Just to be clear, on one of my tunes, my pressure table is not even left alone. it is somewhat different (lower) in many areas, for noise emissions reasons. With that, my pulse ends up longer for the same load.

That could have the effect of seeing larger fuel qty numbers on the log, although mpg may be identical.

I feel a little like this thread has been hjacked, so we can discuss off-line or start another.

How would having a longer pulse with a lower pressure cause a higher fuel quantity number. The main injection pulse table is scaled to reflect mm3 and pressure so if pressure goes down the cell used moves on the pressure axis, not the quantity axis, or am I misunderstanding what you're saying?

 

[Killerbee]

How would having a longer pulse with a lower pressure cause a higher fuel quantity number. The main injection pulse table is scaled to reflect mm3 and pressure so if pressure goes down the cell used moves on the pressure axis, not the quantity axis, or am I misunderstanding what you're saying?

perhaps a misunderstanding. It is also worth noting, fuel quatity reduces with the square root of pressure, or linearly with pulse. So a reduction in pressure has less of an effect on quantity delivered, than pulse.

To be clear about the highlighted statement: if I reduce the fuel pressure table, then a longer pulse will result for a given load, say 75 mph cruise. This is the truck seeking enough power (fuel) to offset the drag forces, the driver being the variable input using speed limit signs. With the longer pulse, and advanced timing, the truck becomes quieter, with no measurable loss in economy. The slower burn has lower pressure front clatter.

 

[JoshH]

I understand that, but what I am saying is, is the total amount of fuel different or just the amount of time it takes for it to be injected?

That could have the effect of seeing larger fuel qty numbers on the log, although mpg may be identical.

This is the portion of the post I was having the problem with. I'll pull some numbers out of the air as an example to illustrate my point. Say at 30 mm3 with 120 MPa of rail pressure you have a pulse time of 800 uS, but if you drop down to 80 MPa your pulse time extends to 950 uS. You are still injecting 30 mm3 of fuel and it is still logged as 30 mm3 of fuel unless you've modified the main injection pulse table, in which case it is worthless to go off mm3 for any form of quantity measurement (which may be the point you are trying to make).

 

[Mike]

I understand that, but what I am saying is, is the total amount of fuel different or just the amount of time it takes for it to be injected?This is the portion of the post I was having the problem with. I'll pull some numbers out of the air as an example to illustrate my point. Say at 30 mm3 with 120 MPa of rail pressure you have a pulse time of 800 uS, but if you drop down to 80 MPa your pulse time extends to 950 uS. You are still injecting 30 mm3 of fuel and it is still logged as 30 mm3 of fuel unless you've modified the main injection pulse table, in which case it is worthless to go off mm3 for any form of quantity measurement (which may be the point you are trying to make).

Is it possible the log is showing the mm3 value as it corresponds to throttle position? Na, mm3 in the log must be a calculation from knowns such as pulse and pressure. xx mm3 can be injected in xxxx ms. Influences can be cylinder pressure, timing ( as fuel injects and flashes cylinder pressure increases and therefore less quantity as cylinder pressure increases ) rail pressure as injection takes place ( falls if quantity is not present ). If we knew the amount of mm3 through the injector at a given pressure and time, we could check the log for accuracy. Is anyone aware of a lbs/hr chart for the multiple dmax injector types?

 

[Killerbee]

I understand that, but what I am saying is, is the total amount of fuel different or just the amount of time it takes for it to be injected?This is the portion of the post I was having the problem with. I'll pull some numbers out of the air as an example to illustrate my point. Say at 30 mm3 with 120 MPa of rail pressure you have a pulse time of 800 uS, but if you drop down to 80 MPa your pulse time extends to 950 uS. You are still injecting 30 mm3 of fuel and it is still logged as 30 mm3 of fuel unless you've modified the main injection pulse table, in which case it is worthless to go off mm3 for any form of quantity measurement (which may be the point you are trying to make).

if you were to reduce the pressure table across the board (just an example), then the to maintain the same load, pulse will increase, just because that same amount of fuel is required for that load.

If the tables are "correct" then 30=30. Lower pressure, increase pulse, and vice versa, to maintain the same "quantity". I think you understand same as i do.

 

[Killerbee]

Is it possible the log is showing the mm3 value as it corresponds to throttle position?

YES, though the torque and maf limits, etc may limit it further. Logged mm3 may have no real accuracy, because it is neither derived from real time measurements, or from a pressure/pulse algorithm. That is why I don't like it, and feel EFI should not have labeled it mm3.



Na, mm3 in the log must be a calculation from knowns such as pulse and pressure.

NO, logged mm3 may, in fact, be completely wrong if the tun is changed from stock. This is what McRat is saying

The mm3 that is preloaded into the tables, comes from correlations determined from experimentation.

xx mm3 can be injected in xxxx ms. Influences can be cylinder pressure, timing ( as fuel injects and flashes cylinder pressure increases and therefore less quantity as cylinder pressure increases ) rail pressure as injection takes place ( falls if quantity is not present ). If we knew the amount of mm3 through the injector at a given pressure and time, we could check the log for accuracy. Is anyone aware of a lbs/hr chart for the multiple dmax injector types?

That would an interesting find.

 

[Mike]

if you were to reduce the pressure table across the board (just an example), then the to maintain the same load, pulse will increase, just because that same amount of fuel is required for that load.

If the tables are "correct" then 30=30. Lower pressure, increase pulse, and vice versa, to maintain the same "quantity". I think you understand same as i do.

But, will the lower pressure cause a reduction of the flash potential? I thinks so.

 

[Mike]

That would an interesting find.

" Na, " answers the previous question I asked, the question just before the "Na"

the " , " was a punctuation error on my part and should have been a "." sorry for that error.

As far as mm3 in the log, I think this " value " is a reflection of the data value in the tbiq for the cell referenced.

 

[Killerbee]

But, will the lower pressure cause a reduction of the flash potential? I thinks so.

I do not know what you are asking? What is "flash potential"?

 

[Killerbee]

" Na, " answers the previous question I asked, the question just before the "Na"

the " , " was a punctuation error on my part and should have been a "." sorry for that error.

As far as mm3 in the log, I think this " value " is a reflection of the data value in the tbiq for the cell referenced.

I got all that. Your conclusions were not correct, so my red comments were in reply

 

[Mike]

I got all that. Your conclusions were not correct, so my red comments were in reply

"YES, though the torque and maf limits, etc may limit it further. Logged mm3 may have no real accuracy, because it is neither derived from real time measurements, or from a pressure/pulse algorithm. That is why I don't like it, and feel EFI should not have labeled it mm3."

Hmm... Not sure exactly why you would think this has no calculation impact? Where do you think pressure and pulse width are controlled? What else would EFI call fuel quantity?

"The mm3 that is preloaded into the tables, comes from correlations determined from experimentation."

So, can a calculation not have been used to determine the actual mm3 used at a specific "load"? I feel the above statement maybe "Hypothetical". There are too many knowns to have to experiment to come up with mm3.

 

[Mike]

I do not know what you are asking? What is "flash potential"?

Flash, dealing with the compression ignition engine, means the ability to ignite the fuel/air mixture. The Idea is to atomize the fuel in a manner that will cause the air and fuel to become stoichiometric and burn causing expansion and therefore force the piston down.