Alright I am working through the process of creating a true instant MPG meter.   

 

 

In theory, I love that word, we should be able to know how much fuel is being burned.   We know commanded duration, we know speed, we know rpms.  

 

Below is the rough draft #1 for my testing, I am not concerned about it being %100 accurate. 

Quote

 

building the equation

 

A 4 stroke 6 cylinder engine should have 3 power strokes per rev, so power strokes, or injections, per minute will be RPM * 3. 

 

Mph to MPM would be MPH / 60 = miles per minute

 

we need to get stroke converted into gallons. 3785410 mm3 = 1 gallon

 

The last thing we need is a MM3 of fuel per stroke in the vp44.  

 

After a good bit of reading I have come to the vp44, in stock form, producing 125mm3 of fuel per stroke max.  

 

Now we throw some fuzzy math at it and say that duration % is linear to stroke. 

 

 

If we plug that equation into excel and input duration, rpm, and mph into it we get output mpg's that match, considering fuzzy math, a vp44 truck.  

 

IE: stock, 55 mph, %20-%25 duration 1460 rpm = ~22-24 mpg in a perfect world.   

 

 

So my Question is when it comes to injectors in the VP44 system.  If the vp44 can produce 125mm3 of fuel per stroke in stock form, what happens when you increase injector size?  Does having larger injectors mean the vp44 will produce more fuel, IE 200 mm3 of fuel?    Or is the 125mm3 the vp44 is spec'd to produce a constant unrelated to the injectors?  

 

@jlbayes @mopar1973man @carbur8tr and anyone else that has an input.

I like it, my theory would be -
It would still make 125mm3 of fuel per stroke due to the fact that the pump is untouched and the delivery demand for the pump is left the same. The only thing changing is the amount of fuel injected by the injector, which is completely mechanical and a computer wouldn't adjust for that hence why bigger injectors on a stock truck smoke so much. So the fuel per stroke would be a constant in this situation. With the overflow valve  it would simply recycle less unused fuel with a bigger injector because the pump can still supply adequate fueling required by the injector demand. But we would need to know the amount of fuel actually injected on each injector and figure out how much fuel it injects per pop to get an accurate variable to make the mathematical equation.

Edited September 15, 20177 yr by Cronus577

So the theory is then that 125mm3 of fuel or 125 cc per 1000 strokes is enough for 650 hp.  Is that true?

 

That 125cc number is too low in my mind for 650 hp.  

 

 

28 minutes ago, Me78569 said:

So the theory is then that 125mm3 of fuel or 125 cc per 1000 strokes is enough for 650 hp.  Is that true?

 

That 125cc number is too low in my mind for 650 hp.  

 

 

That's where a wire tap would come in commanding the vp44 to fuel more than stock. But if we're talking about an untapped vp44 with nothing more than larger injectors there's no way it would reach 650hp. But once you tap the vp44 I would no longer say that it's "stock with injectors" because a tap would imply a tuner that handles above stock fueling. If you see what I'm saying

Edited September 15, 20177 yr by Cronus577

I would also say the stroke will be a constant being you need XX amount of HP/TQ to roll the truck. Regardless of the size of the nozzles. So larger nozzles just means YY mm3 of fuel is injected quicker.

The volume of fuel injected is dependent on the nozzle size. If you go to bigger nozzles you are injecting more fuel, hence the more power and more smoke :-) 

 

The 125mm3 is part of the OEM calibration of the ECM/VP44. They know that at OEM power the commanded volume of fuel is 125mm3, it doesn't mean it's always 125mm3 or that it can't inject more than 125mm3. 

 

 

Edited September 15, 20177 yr by AH64ID

I'm kinda thinking the same thing as well, but what do I know. Out of all the people here you (Nick) would be the first one I'd ask about it, lol.

33 minutes ago, AH64ID said:

The volume of fuel injected is dependent on the nozzle size. If you go to bigger nozzles you are injecting more fuel, hence the more power and more smoke :-) 

 

The 125mm3 is part of the OEM calibration of the ECM/VP44. They know that at OEM power the commanded volume of fuel is 125mm3, it doesn't mean it's always 125mm3 or that it can't inject more than 125mm3. 

 

 

The calibration is considering the injector size.  125mm3 is oem command and bosch duration through an oem nozzle?

33 minutes ago, Dieselfuture said:

I'm kinda thinking the same thing as well, but what do I know. Out of all the people here you (Nick) would be the first one I'd ask about it, lol.

Haha i dont know that much, i am just bull headed enough to look until i find out.

It would be interesting to see if one of the businesses that pop test injectors (if any) could actually weigh the amount of fuel that comes out of an injector. That would give a more accurate volume especially over time.  That was just my first thought and I could be totally out in left field on that.

 

L8tr

D

10 minutes ago, SilverMoose said:

It would be interesting to see if one of the businesses that pop test injectors (if any) could actually weigh the amount of fuel that comes out of an injector. That would give a more accurate volume especially over time.

 

I know for Common Rail Injectors they measure the amount of fuel over time. I'm pretty sure all injector builders can do it but most don't. 

13 minutes ago, SilverMoose said:

It would be interesting to see if one of the businesses that pop test injectors (if any) could actually weigh the amount of fuel that comes out of an injector. That would give a more accurate volume especially over time.  That was just my first thought and I could be totally out in left field on that.

 

L8tr

D

 

I know that the CR injector test machines do this. 

 

22 minutes ago, Me78569 said:

The calibration is considering the injector size.  125mm3 is oem command and bosch duration through an oem nozzle?

 

 

That is my understanding. As soon as you increase the nozzle size the flow will increase above 125mm3. 

 

Without knowing the exact internal working of the VP I cannot comment as to how efficient it is... i.e. does a nozzle capable of 2x the fuel on a test stand actually flow 2x the fuel in the truck.

Edited September 15, 20177 yr by AH64ID

1 hour ago, AH64ID said:

 

Without knowing the exact internal working of the VP I cannot comment as to how efficient it is... i.e. does a nozzle capable of 2x the fuel on a test stand actually flow 2x the fuel in the truck.

 

Being you are attempting to spray from a pressurized injector into a pressurized cylinder (boost plus compression) I'm going to bet that it does not flow the same in the engine versus the test stand. Being there is no compression pressure during the time of the test stand.

 

Thank you AH64ID made me think it out just a bit more. 

Edited September 15, 20177 yr by Mopar1973Man

The design of my mpg meter will handle efficienties, I just needed to know if that 125mm3 was for a system that includes the injectors being stock.

 

I am pretty close here.

2 hours ago, Me78569 said:

The design of my mpg meter will handle efficienties, I just needed to know if that 125mm3 was for a system that includes the injectors being stock.

 

Long story short.... yes.  

Edited September 15, 20177 yr by AH64ID

Well I have working instant MPG meter in the Quad now.  Now I need to figure out a Trip MPG meter....ugh

I am going to test using a routine that fires 1 time per second to add up a mm3/sec reading and convert to gallons.  

 

We will see if this is accurate enough to show a true gallon used reading.

Is there a way to calibrate this for different size injectors? I wonder if you could use a known amount of fuel injected at 800rpm idle while up to operating temps to calibrate a larger injector, since you can likely know to a certain degree of accuracy how much fuel every truck will use in that situation.

10 hours ago, kzimmer said:

Is there a way to calibrate this for different size injectors? I wonder if you could use a known amount of fuel injected at 800rpm idle while up to operating temps to calibrate a larger injector, since you can likely know to a certain degree of accuracy how much fuel every truck will use in that situation.

the ecm should be doing this already.  It will only give as much fuel as needed for idle.  

 

What I have noticed is if I try and alter idle state fueling by %5 then the ecm just gives a fueling command of %5 higher.

11 hours ago, kzimmer said:

Is there a way to calibrate this for different size injectors? I wonder if you could use a known amount of fuel injected at 800rpm idle while up to operating temps to calibrate a larger injector, since you can likely know to a certain degree of accuracy how much fuel every truck will use in that situation.

 

11 minutes ago, Me78569 said:

the ecm should be doing this already.  It will only give as much fuel as needed for idle.  

 

What I have noticed is if I try and alter idle state fueling by %5 then the ecm just gives a fueling command of %5 higher.

 

This is why the IVS (Idle Validation switch) inside the APPS sensor. When the IVS is in IDLE state the APPS value is totally ignored and the ECM idle software kicks in. Then it attempts to hold 800 RPM's using on board software watching tach signal and coolant temperature. Colder the ECT temp the higher the idle. As long as the APPS reports IDLE position then it completely ECM controlled idle. 

Edited September 16, 20177 yr by Mopar1973Man

1 hour ago, Me78569 said:

the ecm should be doing this already.  It will only give as much fuel as needed for idle.  

 

What I have noticed is if I try and alter idle state fueling by %5 then the ecm just gives a fueling command of %5 higher.

 

That's what I mean. Every truck should need X amount of fuel to maintain 800 RPM. With respect to fuel being burned, your X and my X should be the same. So let's say you have stock injectors. Your X is the X for a stock truck. X = final injected fuel amount at 800 RPM. Y = commanded fuel at 800 RPM. Say your X = Y because you have stock injectors.

 

I also have X = final fuel injected at 800 RPM. But my commanded fuel at 800 RPM = Z. Knowing that X = Y, we can solve for my Z. This could be the calibration procedure for final MPG on your truck to match my truck.

 

Thoughts?

oh I get you.  No the idle state fuel is not stable enough long term to base a calculation on.  I see a 200 or so bounce in canbus fuel at idle.