Dynon fuel computer

prkaye · #1 10-05-2011, 07:38 AM

I have the Dynon D-180. I have the float fuel senders and did the calibration procedure, but the fuel gauges just don't provide me with any level of accuracy, and when they just start to get into the yellow region my tanks are almost empty. I do have a fuel flow sender and use the Dynon for Fuel flow display.

I hadn't got around to looking at using the Dynon "Fuel Computer" until recently. I had *hoped* that the fuel computer would use the fuel flow value to continuously subtract the appropriate quantity from the full value, thereby providing you with a much more accurate fuel quantity information. Of course this would require you to tell the dynon which tank you were running off at all times. From what I read in the manual, the Dynon fuel computer does *not* do this, however, and it appears I am stuck with the fuel gauges. Have I missed something?

Cadstat · #2 10-05-2011, 08:23 AM

I think you are begining to understand that you never know exactly how much is in the tank until the engine starts to cough. Reserve is always suppose to be just that, held in reserve. Most gauges are not that great be it GA or experimental. The sight gauges were nice in some old a/c but there is unusable in every system. Learn the settings that give you 7.5 gph or 8.5 or 14.2. We are supposed to fly by time. Trying to fly down to the last 20 minutes of total fuel is a fools game. I lost a friend in an aircraft who bet his life on that and lost. John Denver took off in a long eazy that could fly 10 plus hours on a load of fuel and crashed trying to switch to fuel in another tank. My -6 will fly for 4 hours easy with reserve. Why push your luck? The weather 500+ miles from your departure airport is seldom the same and you must always have fuel to reach an alternate.

prkaye · #3 10-05-2011, 08:36 AM

Funny how so many threads quickly fill-up with common basic safety principles being rehashed in as many different ways as people can find words to articulate them.

Clearly, flying till you're out of gas is a bad idea and everybody knows that a pilot should always visually check the fuel level before takeoff and not plan to fly longer than the known fuel allows with a healthy reserve. Everybody learns this as a student pilot, and we get reminders of the importance of this principle when accidents happen like the ones you mentioned.

However, I think everyone can agree that having reliable in-flight fuel quantity information can at least sometimes be a good and useful thing

. So getting back to the actual topic of my thread, which was the Dynon Fuel computer system... am i correct that the Dynon does not provide the feature I described? Do later versions of Dynon products provide this?

schristo@mac.com · #4 10-05-2011, 08:36 AM

Do you have a fuel flow sensor installed? If so the Dynon totalizes the flow very accurately to display gph, mpg, fuel used, fuel remaining... Assuming you start from a known level, typically full. The totalizer does not interact with the level sensors. The level float arms might be sticking on the indents that make up the rheostat, or perhaps more likely they were a bit sticky when you did the initial calibration giving you bad data... take a look at the resistance values throughout the float range (generaly 0-16 gallons) and graph them... it should be reasonably linear... You should be able to edit the sensor data in the Dynon directly to reflect a best fit from your graphed data to adjust for any recorded points that are obviously in error.

prkaye · #5 10-05-2011, 08:41 AM

Quote:

If so the Dynon totalizes the flow very accurately to display gph, mpg, fuel used, fuel remaining...

This is what I was looking for. Yes, as I mentioned in my original post I do have a fuel flow sensor (it's a Red Cube) and I display my fuel flow on the EMS at all times. However, I couldn't find anythign in the manual describing how to tell the Dynon which tank it is using at any given time so as to display fuel remaining in each tank independently, based on fuel-flow computations and not on the fuel level sender. Does the Dynon not allow you to do this?

schristo@mac.com · #6 10-05-2011, 08:56 AM

The totalizer needs a known starting point that YOU provide... The fuel computer does NOT use the level sonsor data. You set up what your total fuel is and then indicate when the tanks are full... the totalizer does not know or care where the fuel comes from... it is just accounting for the fuel that flows through it.

prkaye · #7 10-05-2011, 09:01 AM

Right. That's what I suspected. It would be nice if it allowed for independent totalizers for each tank, with a way to select which tank you're running on at any given time. You tell it when you fill both tanks, and you always tell it which tank you're running on. Then it would do exactly what you describe except it would do it for each tank independently. This would be an easy thing to add to the software (doing exactly what you describe, except for each tank independently). The only downside would be if you switch your fuel selector and forget to change the setting on the dynon, the dynon would be subtracting the fuel value from the wrong tank.

TX7A · #8 10-05-2011, 09:05 AM

Page 6-14 in the install manual...
Is this what you're looking for?
http://dynonavionics.com/downloads/I...tion_Guide.pdf

hydroguy2 · #9 10-05-2011, 09:05 AM

Quote:

Originally Posted by prkaye

........ However, I couldn't find anythign in the manual describing how to tell the Dynon which tank it is using at any given time so as to display fuel remaining in each tank independently, based on fuel-flow computations and not on the fuel level sender. Does the Dynon not allow you to do this?

Correct. Dynon does NOT do this.

schristo@mac.com · #10 10-05-2011, 09:09 AM

I think that you have an issue with your floats... my tank floats display within a gallon or so in their range; plenty accurate for tank level... my totalizer is accurate to about a tenth of a gallon. Check your float calibration.