VP44 info needed

[Me78569]

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.

[kzimmer]

Yeah that makes sense. This is unrelated, but what would happen if you commanded a fix value for canbus fuel? Would the truck idle like crap?

[Me78569]

Yea,  idle fueling needs to be dynamic.   it would idle good in a perfect situtation, but that never exists

 

 

[Mopar1973Man]

5 minutes ago, Me78569 said:

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.

 

I see a flow rate from 0.2 to 1.0 GPH fuel flow or 5% to 18% engine load depending on what is running on the truck and the coolant temperature. So idle fuel usage is very dynamic...

[kzimmer]

2 minutes ago, Mopar1973Man said:

 

I see a flow rate from 0.2 to 1.0 GPH fuel flow or 5% to 18% engine load depending on what is running on the truck and the coolant temperature. So idle fuel usage is very dynamic...

 

Balls. So there isn't really a way to compare without a doubt how much fuel one truck uses compared to another with different injector nozzles.

[Me78569]

Nope,   I will publish at general % offset per injector size once I get it figured out.  Still working on the Gallon used trip meter,  that's gonna take time to figure out if I have it close enough.

[Mopar1973Man]

I sat in the truck and started playing with different things to load the engine. Turn on the A/C on high fan can put nearly a 20 HP load on the truck increasing idle fuel flow at least 0.5 GPH. Stack on the 200w worth of lights and my HID's I can tip 1.0 GPH fuel flow at idle. Then engine temperature will vary the fuel commanded to keep the idle at 800 RPM's. 

 

Then if you want to toss high idle 3 CYL and exhaust brake you can push upwards of 9.0 GPH idling at 1,200 RPM's. 

 

Too many things to vary idle fuel flow...

[kzimmer]

1 minute ago, Me78569 said:

Nope,   I will publish at general % offset per injector size once I get it figured out.  Still working on the Gallon used trip meter,  that's gonna take time to figure out if I have it close enough.

 

Yeah just a manual adjustment would be fine with some guess and check.

 

That's the trouble with an open loop fueling system.

1 minute ago, Mopar1973Man said:

I sat in the truck and started playing with different things to load the engine. Turn on the A/C on high fan can put nearly a 20 HP load on the truck increasing idle fuel flow at least 0.5 GPH. Stack on the 200w worth of lights and my HID's I can tip 1.0 GPH fuel flow at idle. Then engine temperature will vary the fuel commanded to keep the idle at 800 RPM's. 

 

Then if you want to toss high idle 3 CYL and exhaust brake you can push upwards of 9.0 GPH idling at 1,200 RPM's. 

 

Too many things to vary idle fuel flow...

 

Ok, now find me a way to load the truck up to 25% on jack stands so I can do some tuning, lol.

[Mopar1973Man]

I know the ScanGauge II and Dash Command both use a fillup routine to calculate offset amounts. 

[Me78569]

That's prob what will happen.  You will set your offset to %100, then burn a tank of fuel and compare how much fuel you used on the screen vs at the pump and calculate from there.

[kzimmer]

This is cool, I like this.

[Mopar1973Man]

On 9/16/2017 at 10:20 AM, Me78569 said:

That's prob what will happen.  You will set your offset to %100, then burn a tank of fuel and compare how much fuel you used on the screen vs at the pump and calculate from there.

 

Missing a step... On ScanGauge & Dash Command when you do the fillup process it will display what fuel you burn and then you change the offset to match the gallons pumped. It automagically does the math for you so no calculations required. Now just hit done and everything is calibrated. 

[Me78569]

that's not something that would be programmed into the box under the hood.  I could go through the work to do that, but it owuld require 3 more data items to push across the bluetooth.   Each of those would need to be coded in and then set to be used somehow.    

 

The easier solution would be to put it in the app itself, but for the beta testing of this manual calcs are required.  UI interfacing code needs to be left up to the app and not the box under the hood.

[TFaoro]

I like it. I'm skeptical, but I like it.

I wonder how bad different timing will throw it off?

Say you calibrate everything for cruising empty, then hook a big trailer up. Could the timing difference make that big of a change in MPG vs what it's calibrated at?

[Me78569]

The MPG info is directly related to the canbus fueling amount.  Doesn't matter what timing is doing canbus fuel will always be 1:1.  Timing will adjust how much canbus fuel is used, but won't change the relationship to mpg

[TFaoro]

Just now, Me78569 said:

The MPG info is directly related to the canbus fueling amount.  Doesn't matter what timing is doing canbus fuel will always be 1:1.  Timing will adjust how much canbus fuel is used, but won't change the relationship to mpg

So you're saying the efficiency will be seen in the amount of fuel injected regardless of timing - Hmm. If you get this setup well it could really help with tuning timing for MPG purposes.

[Me78569]

the relationship of fuel burned is static compared canbus regardless to the timing command   As you get better mpg, related to timing changes, the canbus message will drop,  but is still related to the canbus 1:1

 

 

I have the instant mpg working well, now I am workign on a gallons burned calc.  

[kzimmer]

I think the only uncontrollable source of error would be related to pump health and injector health. A wearing injector could change the amount of fuel actually being injected. Same with a weak pump. However, these things don't change overnight, and that's why you'll have the offset % adjustment. Any truck should be able to be offset to be close.

[Me78569]

One thing I am curious about is if the relationship between fuel into the engine vs the fuel return out of the back of the head.  

 

Is that a 1:1 relationship between the duration command and how much actually gets injected?  in theory it should be because the injectors are not smart enough to control flow.  I would guess that the bigger the injector the less fuel is pushed out hte back of the head at a given duration.

 

I am guessing, wildly, that this is where that 125mm^3 of fuel comes from.  The injectors are passing that amount but the remaining ~350 mm^3 of fuel the vp can supply is pushed out the back of the head.

[jlbayes]

Time to get a flow meter and measure the return. And find someone with a bench you can measure nozzle flow on. Orrrrr talk to a certain builder as he has flowed a few nozzles.