Fuel consumption via injector impulse

[ned]

Now that the com and intercom have been released, maybe you will have time to work on integrating fuel injector impulse to the EMS for fuel usage monitoring. Would be a great improvement over using two flow meter/transducers and trying to get the k factor set. Anyone else having need for this? AS of now, one has to use brand M fuel monitoring for this service. Pleeease!

 

[mmarien]

Ok - you peaked my interest. Can you explain a bit more about how this works and which fuel injection system it works on. PM me if you want to start a discussion on it.

 

[ned]

ULPower ECU has an output wire that sends a 0-100 signal with 100=48litre/h to what should be Skyview EMS but the EMS is not programmed to accept this data.

 

[dynonsupport]

The theory is this:

Any electronic fuel injection engine has to pulse the fuel injectors to inject fuel. A fuel injector flows some amount of fuel per minute (it's usually stated in something like 850cc/min). So, you can theoretically hook to one injector, measure the total amount of time the injector is open, and then multiply by the number of injectors you have.

As someone who just put new injectors on their car last week and is still trying to get it running right, I can tell you the reality is not the same as the theory. We can measure the electrical signal going to the injector, but the injector is an electro-mechanical device, and nothing mechanical happens instantly. Thus, there is a latency (delay) from when you ask the injector to open with electricity and when it actually does. More than that, this latency is highly dependent on fuel pressure and battery voltage.

The latency can be much longer than the amount of time you want the injector open. Latentices are generally in the 1-4ms range, but at idle, you may only want the injector open for .5ms. Thus, the computer may apply electricity for 2.5ms because it knows it won't get fuel for 2ms. So while you actually only got 0.5ms of fuel, SkyView would think you got 2.5ms (5x as much!)

Of course, now your EMS needs to have all this data to know to ignore the latency, and it needs a table of voltage and fuel pressure against latency. I'm guessing very few customers have this table available.

So, while it's all possible, it's not as easy as it sounds (or we can do it the easy way like other companies do and end up with big errors). Fuel flow senders are proven, reliable, accurate, and not that expensive. Given the number of EFI engines our customers appear to have, we're talking about lots and lots of engineering time in order to save a few customers $200 on a fuel flow sender and that doesn't pencil out.

We're happy to hear there is more demand than we thought and will consider doing this. There is also the option that you can get your ECU manufacture to change their output from PWM to frequency (it's "just software" for them as much as it is for us). Someone could also design a pretty simple PWM to frequency converter that would allow our standard system to work.

 

[mmarien]

Thanks for all that guys

Out of curiosity I read the ULPower install manual and did the research on the internet about PWM to analog. Seems simple enough in theory and probably a good project to learn a few more expletives if I had the time. I checked with the manufacture of my system (EFII) before and they said the output is proprietary except for the RPM pulse and check engine light - which I have connected to a EMS contact. If I want any other info it's only available on their i/o device. Bummer :-/.

The two red cubes are giving me good results so I'll leave it at that. How is the ULPower working out for you otherwise?

 

[spudlyhallam]

ok can I add my name to the list I have a ul power and have bought the skyview for its excellent functions but am at a loss with the fuel flow.
Surely a software update is a better bet than sticking two fuel flow transducers and a K factor?
I am happy to pay for the update as it is better than bodging into my fuel lines.
Come on Dynon do your stuff and help us out after all thats why we have invested in the great bit of kit.
Pleeeeeaaaasssseeee

 

[stede52]

I too would love to see this, I've got a UL350iS in my Highlander with the two red cubes, granted I've never had an issue with them in 280hrs but it would be nice to utilize all the ECU's capabilities and remove possible failure points. There was a RV builder who actually had a circuit board design to read the K factor from a D180, see the attached document.

 

[Skee]

I too would love to see this, I've got a UL350iS in my Highlander with the two red cubes, granted I've never had an issue with them in 280hrs but it would be nice to utilize all the ECU's capabilities and remove possible failure points. There was a RV builder who actually had a circuit board design to read the K factor from a D180, see the attached document.

Dynon, just copy tha shit and sell em as a ULPower sensorkit !!

than ill buy one in a year o two when its my time.

 

[pborton]

Put me on the list of UL users.

A couple hundres dollars in sensors isn't much after factoring in all of the other costs in a build. You're right about that, but adding more fittings is adding more chances for leakage and/or failure.

If its "just software" for both Dynon and UL, how about working something out that makes sense to everyone?

It seems short sighted to think that Dynon customers won't be building more than one aircraft...and using the advancing technology that goes along with building experimental. I don't think fuel injection is going away anytime soon, and I'm not saying Dynon's perspective is wrong. If there is a better, more accurate, and safer way to measure consumption (without adding the chance of a fuel leak), someone should develop it. I would think people will pay for it...

 

[Skee]

ULPower manual syas this about fuel consump sensor.

Output fuel consumption
Use the white/green colour wire.
The output signal is a duty cycle. 100% is equal to a fuel consumption of 48 litre/hour
(12,7 USgal/hour).

How does this work?

 

[mmarien]

Check out PWM on Google.

Basically electronic fuel injectors change the mixture or fuel flow by the duration of how long they stay open. If they are open all the time (100%), it equals 48 lph. If they only stay open half the time it's equal to 24 lph. The signal on the wire is the same as it supplies to the injectors which is a pulse with a duration (PWM). As noted in Dynon's answer above the EMS can only read voltage ranges, not PWM which is what the UL Power supplies.

 

[alschief]

I agree it is time to incorporate the PWM into the fuel consumption measurment as an option over using two fuel flow devices. RV 12 with UL Power 260iS

Now that the com and intercom have been released, maybe you will have time to work on integrating fuel injector impulse to the EMS for fuel usage monitoring. Would be a great improvement over using two flow meter/transducers and trying to get the k factor set. Anyone else having need for this? AS of now, one has to use brand M fuel monitoring for this service. Pleeease!

 

[mmarien]

I agree it is time to incorporate the PWM into the fuel consumption measurment as an option over using two fuel flow devices.

I think if you do the investigation and review Dynon's explanation above you'll come to the conclusion that using the duty cycle isn't all that accurate. The short answer is that it's NOT measuring fuel flow. It's measuring how long the injectors stay open which is only part of the equation. How much fuel flows through during that time depends on lot's of other factors.
I'm thinking if you want accuracy, measure the flow directly. :-?

 

[pborton]

The little red box(es) are going on regardless of my thoughts/feelings/complaints.

I received them today as a matter of fact. I didn't spend much time looking the red box over, but the first thing I did was pull the "in" plug and see what looked like a pinhole compared to the opening.

One can only assume that isn't the only passage for fuel if these can handle up to 60gph...

 

[dynonsupport]

Interestingly enough, we've had reports that the 912iS output, which is literally a digital number like "9.8 GPH" isn't very accurate, even though it comes out of a fully certified ECU and it has the ability to apply all the corrections that are hard for us to do.

Also, to re-iterate, frequency for fuel flow is an industry standard. Every EFIS in the world accepts this. Very few accept Duty Cycle. UL power decided to use the non-standard duty cycle. It's worth asking them to change their software to frequency instead of duty cycle which would magically make them compatible with every EFIS rather than having every EFIS write special support for them. It's just as much "just software" for them as it is for us. As a bonus, this output from them could easily contain all the corrections to their signal that would be almost impossible for us to implement, so this would likely be a much more accurate solution.

 

[dynonsupport]

One can only assume that isn't the only passage for fuel if these can handle up to 60gph...

You'd be surprised at how small of a hole is required to flow 60GPH at 2 PSI. It's only about 4mm.

 

[purlee]

The only really accurate way to measure fuel flow is to measure the fuel which is flowing!

If 15 gallons an hour is going up to the injectors and 5 gph is going back to the tank, the fuel usage is 10 Gallons an hour, and you can bet your life on that, (and sometimes you do).

There are just too many variables with trying to calculate it from Duty Cycle and impulses.

Simplicity is a great thing and one of the great lessons you learn as an engineer is that just because you can, does not always mean that you should!

All we are seeking to do here, it seems to me, is to create a complex and inaccurate solution, simply to avoid the possibility of a bit of bad plumbing.

 

[ned]

The 2nd generation ULPower ECU has a new terminal for fuel consumption.
70litre/hr = 170hz (170) pulses/sec
Will this work with the Skyview EMS?

 

[Dynon]

As long as that output looks like a floscan/EI fuel flow sensor, it would work. I'm not sure whether it does or not.

 

[brs]

Are there any updates on this?  I'm about to convert my 914 to fuel injection (sdsefi.com for info) and would like to use the injector pulse.

I've a MGL Xtreme on another aircraft that does this.  The way the MGL works is you connect the injector pulse (to the same wire as a fuel-transducer I believe) and configure fuel-flow for "injector" then you have a "K" factor that can be adjusted/calibrated based upon real usage.  Just create a correction each time you carefully fill up to full.  It's simple to use and works well.

Don't see why Dynon can't do this.