Fuel Flow High

[SkippyDiesel]

I have two fuel flow red cubes. One on main/delivery hose. One on return to tank hose.
Followed Dynon instructions, I provisionally set both for recommended Rotax 912ULS pulses (70000??).
Over several flight & refuels, to same level (full), I made adjustments to number of pulses on the main/delivery line cube and now have good level of accuracy - fuel used and fuel remaining.
I did not adjust/alter the return line provisional setting. My understanding being, whatever fuel flow it registered, would be subtracted automatically from the main fuel delivery line flow.
BUT! my in flight fuel flow seems to be high by about 7L/minute - how can this be?

• Should I be adjusting the return line pulses?
• If so, will the adjustment to the return line pulses, effect the main line pulses accuracy?

 

[SkippyDiesel]

Very disappointed - had a few "Views" but not a word of advice.

 

[SV_Classic]

nevermind, I think I answered my own question

 

[chriscalandro]

They both need to read accurately. The red cube should have some sort of documentation of how many pulses / gallon.

Nothing g about the engine or engine recommendation should fall into that equation. You only care about the red cube pulses and the red cube pulses alone.

 

[SkippyDiesel]

They both need to read accurately. The red cube should have some sort of documentation of how many pulses / gallon.

Nothing g about the engine or engine recommendation should fall into that equation. You only care about the red cube pulses and the red cube pulses alone.

Thank you for your comment.

You have addressed the first part of my question BUT what of the second.

"....will the adjustment to the return line pulses, effect the main line pulses accuracy""?

 

[chriscalandro]

Again, they both need to be entered in accurately. Fuel flow to the feed gets calculated, then fuel flow to the return is subtracted from that. The result is net fuel flow.

They both need to be accurate.

 

[SkippyDiesel]

No offence Chris, you are not addressing the second part of my question - "....will the adjustment to the return line pulses, effect the main line pulses accuracy?"

IE When I start changing the pulse rate of the return line cube, will I also have to adjust the pulse rate on the mainline cube - remember the actual fuel used/remaining read out, is now very accurate, it's the in flight flow rate which is incorrect by about 7L/hr

 

[chriscalandro]

I don’t think I can make how this works any more clear or any simpler.

If you can’t figure out what I wrote and how it pertains to your question you should have a professional set these configurations for you.

I have absolutely answered the question asked.

They both need to be configured accurately.

 

[SkippyDiesel]

I am sorry that you seem to be taking offence - perhaps you don't know the answer to my question.

Will adjusting one cube pulse rate effect the reading of the other cube????

 

[chriscalandro]

I am sorry that you seem to be taking offence - perhaps you don't know the answer to my question.

Will adjusting one cube pulse rate effect the reading of the other cube????

I have answered your question several times.

I can assure you I’m not offended. I can also assure you, since you don’t understand the answer you have been provided, that you seek help from a qualified professional and do not attempt to change settings on your own.

To get a reliable accurate result, both red cubes need to be calibrated properly using the information provided by the manufacturer and supplied with the individual red cubes.

 

[SkippyDiesel]

I disagree - I have been specific in my question, you have been very general in your repeated response ie not addressing the question.

I think you can infer from the information I have given, that I know how to change/adjust the calibration - I have achieved a satisfactory level of fuel used/remaining accuracy (calibration) BUT my fuel flow (in flight) is not accurate. I suspect this may be because I have left the return line red cube initial calibration, as advised by Dynon.

Yes I can change the return line fuel callibration, WILL THIS THEN EFFECT THE MAIN LINE RED CUBE CALIBRATION?

It's a very simple question - NO IT WONT or YES IT WILL

 

[chriscalandro]

Again you show a fundamental misunderstanding of how this works. Fuel used/fuel remaining is independent of the fuel measurement and specifically relies on the fuel flow data. If that information is accurate, then the fuel flow itself must be accurate.

You have 2 red cubes. They MUST BE CONFIGURED SEPARATELY AND INDEPENDENTLY.

 

[SkippyDiesel]

"If that information is accurate, then the fuel flow itself must be accurate"

Exactly what I would have expected, that does not seem to be what is happening. Read my opening statement.

"They MUST BE CONFIGURED SEPARATELY AND INDEPENDENTLY."

Once again you avoid the question - what impacted/effect does one cubes adjustment have on the others reading? ie Cube A is adjusted so that the Fuel Used/Remain readout is accurate. I now start to "play" with the pulse rate of Cube B - will the changes made effect the settings of A?

 

[chriscalandro]

It sounds like you might be confused how addition and subtraction works….

 

[SV_Classic]

hey guys, let's try to keep it civil and get Skippy's problem worked out.

@chriscalandro I understand how to calculate the K factor and how to adjust it based on calculated fuel flow vs actual fuel used but what instructions are you referring to for the return fuel flow calibration?

@SkippyDiesel have you tried contacting Electronics International about recommended procedures for calibrating the return fuel flow sensor? I don't see a specific starting K value for Rotax engines, only a specific plumbing schematic. In a couple of places the manual says 68,000 should be the initial starting K value.

You might have to run fuel into a bucket (disclaimer; lots of ventilation, no ignition sources nearby, etc. ) and measure how long it takes to pump a certain number of gallons and calibrate the sensor based on that process as monitoring fuel used through each of two sensors in the same fuel system won't be as straightforward as the guidance I'm finding for installations with just one sensor. Once you get acceptable flow measurement performance from the return sensor using the bucket method, do the same for the supply sensor. Then, as you start flying again, you can tweak the k factor for the supply sensor using the instructions in the manual (similar to a one sensor system) and probably just leave the return sensor's k factor alone.

When I get my plane back flying I'll have to work through finding the right K value while we finish off the Phase 1 hours, I'm really happy to have just one sensor after reading this! lol

 

[SV_Classic]

Once again you avoid the question - what impacted/effect does one cubes adjustment have on the others reading?

the K factors don't affect each other, the two cubes are acting independent of each other and the EMS-220 is subtracting return fuel from supply fuel to display the fuel flow being used by the engine. if one is accurate but the other is not, the EMS will show an inaccurate instantaneous engine fuel flow number when it does the math.

 

[SV_Classic]

I'm thinking about this some more, you might be able to set the return K-value to the initial 68,000 value and then just tweak the supply side k value using the standard method with the result being the correct fuel flow being calculated by the EMS. The EMS-220 is measuring the difference between the two, having both off a little but the difference being accurate, that might work. I'd check with Electronic International's tech support to see what they say. Are they pretty good about responding to questions?

 

[chriscalandro]

In order for all the data points to be accurate, both red cubes must be accurate.

It’s really not that difficult and the procedure of using the pump into a bucket is a good plan.

Again, based on the responses, I’d strongly urge seeking outside help.

 

[SV_Classic]

In order for all the data points to be accurate, both red cubes must be accurate.

you're saying for the fuel flow number to the engine to be accurate at all RPM settings, the individual k-values have to be accurate instead of fixed for the return and tweaked for the supply.

@SkippyDiesel are you the original builder of your plane?

 

[chriscalandro]

you're saying for the fuel flow number to the engine to be accurate at all RPM settings, the individual k-values have to be accurate instead of fixed for the return and tweaked for the supply.

@SkippyDiesel are you the original builder of your plane?

Yes. If one or the other is off either fuel flow or usage will be incorrect.

For them both to be correct both cubes need to be accurate.

You would be either calculating too high a usage, or too high a return. (Or low) which would shift the numbers in each metric. They are only both correct when the red cubes calibration are both correct.