V

vette_guy

Member
My D-180 has recently started indicating fuel flow above what it should be by about 2 gal./hr. I've adjusted the "k" factor above and below the 68000 recommended in the Dynon manual when the original tag specific to the transducer is not available. Fuel slow during taxi: 4.5 gal/hr; takeoff: 8.8 to 9.0 gal/hr. Normally it is 2 gal/hr. less. This figure then distorts the fuel used/fuel remain figures on the -180. Dynon tech service said change the "k" factor which I did and still the erroneous fuel flow #. Anyone had this problem? Any solutions?
 
If the fuel flow changes with engine RPM, and other engine readings are normal, then it would be unlikely that the D180 is malfunctioning. But it is also odd that it would suddenly start reading high if once it read correct. More than likely your fuel flow sensor went bad. I suggest you contact our support, discuss it further with them, and probably replace it.

-Robert
Dynon Marketing
 
bad fuel pump?

I am not saying that engine driven pump is definitely the cause of high fuel flow, but it is a possibility. Check the pump weep holes for signs of fuel leakage. Air leaking into the fuel system can cause high fuel flow. And so can little fuel vapor bubbles that form in the fuel lines (aka vapor lock).
Joe Gores
 
Mine was the same way. Started out at a k factor of 68000 and made two adjustments up(now at 85000) and got the numbers pretty close, less than a gallon. Then two loads of fuel later and it is telling me I should increase it to over 90000. The last fill up was right on at the old k factor. I think the transducer is the culprit for me. Same with fuel pressure it is all over the place too.
Phelps
 
Which one do you have?

Remember there are two different transducers. Which use way different K-factor numbers. The second version transducer was red (FT-60)and the first version was not Red(Floscan). So check to see which one you have. The 68000 start point was used on the first version(floscan) and I think that 99,999 is the start point for the FT-60. :confused:
 
Flowscan default is 30000
RedCube is 68000

Normally the red cube is pretty much bullet proof up to a couple thousand hours. I would look for air/trash trapped in it or something like that.
 
RV-12 ROTAX 912 ULS - -

After the Dynon update, I had to adjust mine. IF - IF you are in a sparsely populated area, I found I could adjust while flying at a fairly high alt. ( for safety ) At about 5150 RPM, I show 4.8 - 4.9 GPH. That works out about right. Glance outside often, or land and do it on the ground, then go up and see how it does. I think I ended up in the 55000 area. Seems to be fairly good. If I fly for an hour at 5150 RPM, I seem to use roughly 5 gallons of mogas. I have the Flo-Scan.

John Bender
370 plus hours.
 
LIKE MITCH SAYS....CHECK YOUR FUEL PUMP FOR LEAKAGE! Remove the top cowling and turn on the electric fuel pump. Check the weep holes for leakage. My pressures were all over the place when my fuel pump failed. Its odd that both the fuel consumption went up and the fuel pressures went hay wire at the same time.


Gary
 
My techique for setting K Factor

Gentlemen,

Here is my method for getting the best possible fuel flow readings. Keep in mind that you will never get perfect results, unless you were to install a second transducer in the return line to the tank. That is an expensive option that in my view is not warranted in an RV-12. Also keep in mind that in all likelihood individual K Factor setings will vary considerably from one instalation to another, due to variations in the sensors, plumbing, etc.
However, quite accurate results can be obtained by the following:

1. With engine off and a fully charged battery (preferably with a charger attached to simulate alternator operation, as in flight) run the electric fuel pump and watch the fuel flow indication on the Dynon.

2. Go into the fuel flow sensor setup menu and adjust the RETRN parameter until the fuel flow gauge zeros out. You have now told the Dynon what the nominal return flow volume is.

3. Set the K Factor to some nominal setting - say 68000.

4. Fill the tank, and fly for a while - the longer the better.

5. Refill the tank, and use the calculations in the Dynon manual to refine the K Factor setting.

6. Repeat Step 5 at every fill up, until the actual amount of fuel added matches closely to what the Dynon tells you was used.

You will eventually reach a point where the accuracy is quite good - not perfect, but acceptable.

BTW, my first FT-60 went dead within an hour of first installation. The replacement has been working fine for about 75 hours since. Oh yes, and I had one of the early fuel pumps as well. Even though it showed no weeping, it was clearly defective as indicated by unreliable readings as others have reported. I replaced it with the new design. Rotax (Lockwood) ignored my request for a warrantee refund, but the cost was well worth having consistent pressure and flow readings and peace of mind.

Happy calibrating!

John
 
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Please do not proceed with out verifying that you don't have a defective fuel pump. I experienced 7 gal / hr. fuel burn and low fuel pressure alarms on a cross country. My fuel gauge verified the fuel consumption. When I got on the ground I found large quantities of fuel bleeding from the pump weep holes. Turn your electric fuel pump on and observe the weep holes. The frightening thing is, the fuel spills onto the exhaust pipes......

Gary
 
jersey said:
Please do not proceed with out verifying that you don't have a defective fuel pump. I experienced 7 gal / hr. fuel burn and low fuel pressure alarms on a cross country. My fuel gauge verified the fuel consumption. When I got on the ground I found large quantities of fuel bleeding from the pump weep holes. Turn your electric fuel pump on and observe the weep holes. The frightening thing is, the fuel spills onto the exhaust pipes......

Gary
Click to expand...

In my humble opinion, all those earlier model fuel pumps should have been replaced by Rotax, at no cost to the customer. But they were not, for whatever reason. Once again, IMHO it is worth the price to just go ahead and do it on your own, for safety and peace of mind. That's what I did, and the new pump has worked flawlessly, and I don't have to worry about raw fuel on hot pipes!
 
How do you tell?

What does the new fuel pump look like.
I would like to know if mine is a new one or older style.
 
Check valve

John,
I saw you had posted a question on the Rotax-owner site about the need for a check valve with the new pump. Did you ever get an answer to your question and if so what was the result? thanks
 
Hal-san said:
John,
I saw you had posted a question on the Rotax-owner site about the need for a check valve with the new pump. Did you ever get an answer to your question and if so what was the result? thanks
Click to expand...

Check valve not required in the RV-12 implementation.
 
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