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Fuel Flow "K" Factor - Initial settings

B

BigJohn

Well Known Member
Here's a question for those of you who have built some flight time on your '12.
After refinement, what values did you end up with for the K factor? I would like to take an average of your values and use it for my start point. I have the red FT-60 sensor.

Inspection scheduled for 1/21!
 
Just start with the "K" factor they tell you to use. It's pretty close. Mine is different because I installed a shut off switch to the electric fuel pump so it is not running all the time.

Good luck on the inspection!
 
I can make you feel better ...

Just so you can feel good about not having a K-factor value to enter, I didn't either and had to call Dynon to get it. When I received shipments from Van's, it was my habit to quickly inventory pieces-parts and put them in their various homes in the shop. When I came to my fuel flow sensor, it had a paper tag hanging from a string. I promptly removed this and deposited it in the trash.

When it came time to install it, I THEN read the instruction to NOT throw away that tag, as it had the calculated K-factor value for that particular sensor recorded on it! :eek:

A call to Dynon solved the problem, as they gave me an approximate value which was surprisingly accurate. I have since narrowed it some, but it was pretty close.

D'oh. :rolleyes:
 
K Factor for RV-12 "Red Cube"

BigJohn said:
Here's a question for those of you who have built some flight time on your '12.
After refinement, what values did you end up with for the K factor? I would like to take an average of your values and use it for my start point. I have the red FT-60 sensor.

Inspection scheduled for 1/21!
Click to expand...

John,
The Dynon installation manual specifies a K factor of 68000 for the "red cube" to start with. That is way off for the RV-12 probably because so much fuel is bypassed back to the tank. I found by trial and error that I needed a K factor of 96500. Other RV-12ers in previous posts have similar findings.

One possible issue is that the maximum value you can use for a K factor is 99999 on the Dynon.

With software version 5.4 the system is defaulted to something like 54000, as I remember, and this gave me a high fuel flow alarm when I took off without checking the fuel flow factor. If you are seeing 4 or 5 gph at idle the K factor is way off. If you take off on your first flight with that setting you will probably get a fuel flow warning and have to land to check for leaks!

Make a note of your final value because every time you upgrade the software the fuel factor is set back to a default value. Same happens with magnetic intensity, magnetic inclination, and possibly others of your unique settings; keep notes on these values.

Good luck on your inspection, but I expect you to pass with "flying" colors :).

Tony
 
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Thanks for the info so far. Yes, I saw 4 or 5 gph readings at 2000 - 2500 RPM. I know that is wrong, hence the question. Anybody else to weigh in? For now I am going with Tony's number.
 
Geico266 said:
Just start with the "K" factor they tell you to use. It's pretty close. Mine is different because I installed a shut off switch to the electric fuel pump so it is not running all the time.

Good luck on the inspection!
Click to expand...

Larry,

I don't want to drive the thread off topic, so if this gets too far off please reply with a private message.
What I am wondering about is how the switch would affect the K-factor. Is it because without the pump running, the fuel return flow is minimal or none and as there is only a flow sensor in the supply line the return flow is silently computed into the K-factor? Which then would mean that without the pump being on the K-factor is off by the amount of the return line flow.
I'm just asking because I am planning to put in a switch for the pump as well and only use the pump during take-off and landing.
 
Hm, I just realized that I installed the transducer two weeks ago and there was no tag on a string or anything attached to it that looked like a K-factor!
The bag it came in shows serial number and some other stuff that does not look like a K-factor. The tag on the wires attached to the transducer just repeats the serial number and a testing signature and a '220'.
IMG_5170sml.jpg

So how do I get my initial number now? Any ideas?
 
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The K-factor that came with mine was 29890.

While breaking in my new engine I was pumping over 16 GPH through it and was able to update the factor to 32755. Now to find out if that is close to my actual fuel flow.
 
K factor number

So how do I get my initial number now? Any ideas?
Click to expand...
Chances are that number will be way off anyway because part of the flow is returned to the tank. I would use a K factor number that others have used as a starting point. And use trial and error from there.
Joe
 
MacPara said:
Hm, I just realized that I installed the transducer two weeks ago and there was no tag on a string or anything attached to it that looked like a K-factor!
The bag it came in shows serial number and some other stuff that does not look like a K-factor. The tag on the wires attached to the transducer just repeats the serial number and a testing signature and a '220'.
IMG_5170sml.jpg

So how do I get my initial number now? Any ideas?
Click to expand...

Well, one idea is on page 6-14 of the Dynon Installation manual :eek:. I know, I know, the manual is a last resort ;). If you don't have the manual yet they are available online. Here is the one for the D180 installation. You may be getting the Skyview, so download that manual to see what K-factor you will start with. It tells us that the Floscan sensor (which was furnished with early kits) has a tag attached with the K-factor. Also, it says if you have the FT60 (no tag) to use a starting factor of 68,000.
 
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That's true, Tony. Although I thought ahead, I didn't actually read ahead :). The Avionics is way away at this point, so I didn't even think that I might find anything about this in the manual. Thanks for checking this for me! I just thought that tag might have fallen off before shipping or was missing since bagged or something.
 
red cube k-factor info

Hi MacPara
I have the info from Electronics International regarding the Red Cube (FT-60 ) setting if you like that.

I could send you the info if you send me an e-mail address via PM..

Their basic K-Factor is 68000 if you wanna try that.

Hoping that might help you

Bruno
[email protected]
 
MacPara said:
Larry,

I don't want to drive the thread off topic, so if this gets too far off please reply with a private message.
What I am wondering about is how the switch would affect the K-factor. Is it because without the pump running, the fuel return flow is minimal or none and as there is only a flow sensor in the supply line the return flow is silently computed into the K-factor? Which then would mean that without the pump being on the K-factor is off by the amount of the return line flow.
I'm just asking because I am planning to put in a switch for the pump as well and only use the pump during take-off and landing.
Click to expand...

You are correct sir! IMHO the switch is a nice upgrade.
 
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More on the illusive "K Factor".

Took my first real cross-country this past week and checked my Dynon fuel used numbers against actual usage for both legs.

First leg:
Dynon: 7.6
Actual: 6.1

Second leg:
Dynon: 8.1
Actual: 6.5

OK, so this is telling me the Dynon is measuring more fuel flow than is actually occuring. Acording to the Dynon manaual, I am to divide the Dynon number by the actual fuel used, which I did, and in both cases this comes out to a factor of about 1.246. Instructions then say to multiply your present "K Factor" by this number, and increase the "K Factor" to the new amount. Here's the rub. My K Factor was already set to 96,500, the number I got from Tony T. and used as my original setting. After multiplication the new factor comes out to 120,239. Oops! The maximum allowed by the Dynon is 99,999.

Not quite sure where to go with this. Will Dynon increase the size of this field in a subsequent release of the software? Should I try to use the "Return" value that is currently set to zero?

Opinions requested.
 
Set it to 99,999

Hey John,

Although I have an AFS system, I too had to increase the K factor.

It didn't take much one I started to tweak it up.

Why not push her up to the max and then go fly?

At least you will see how close you will get.

You never know, you may be closer then you think.

And if not.....well...flying is never a bad thing!

Good luck,
 
Use the RETRN FLOW

BigJohn said:
Should I try to use the "Return" value that is currently set to zero?

Opinions requested.
Click to expand...

Sigh, finally, someone else has seen the issue with the FT60 and the D180. I thought I was the only one. You will have to use the RETRN FLOW". Here is the previous thread on this:
http://www.vansairforce.com/community/showthread.php?t=69372

Basically, you have to estimate the return flow to the tank. I used an estimate of 2 gph and multiplied that by the theoretical K of 68,000. Then set the RETRN FLOW to that value. Then do the trial and error process with the K to optimize.


Tony
 
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My technique for using K factor and RETRN parameter.

To Tony and others interested in more accurate fuel flow indications,

I posted the following today in the Dynon forum. You can read the entire thread at: http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1306605633/0

Dynon Support - Thanks for the reply and the explanation. Armed with that information, I went to the airport today and did the following:

1. Set the K factor back to 68000, the recommnended value for the FT-60.
2. Went into the RETRN field and while running the electric fuel pump, with engine off, noted the fuel flow indication.
3. Began incrementing the high end of the RETRN field. As I did this the indicated fuel flow went down. When the RETRN value reached 130000 (one hundred thirty thousand) the fuel flow indication was down to zero.
4. Ran the engine. I calculated that at 4000 RPM I should see a fuel flow of about 3.5 GPH. While holding 4000 RPM, I adjusted the K factor to achieve an indication of 3.5 GPH. This value turned out to be 79000.
5. I flew the airplane. Indicated fuel fows were very close to what I believe they should be at various power settings.

I realize this method may not yield perfect results, but I think I am pretty close - certainly closer than before with the K factor at 99999. On my next cross-country flight I will compare calculated fuel burn to actual, and tweak the K factor further as specified in the manual.
 
My latest method - -

Not an exact science, but it seemed to work well. UNDERSTAND, I fly in an open area where you can fly for 2 hours and not see another plane. I knew about what fuel I was burning based upon time and actual usage. I adjusted mine while flying in an open area. I adjusted the K-factor and kept adjusting it until it read what I wanted it to show at that given RPM. Actually don't remember what that figure is now, but it reads very close to what I think it is actually using.

John Bender
 
Just curious John, was there enough range in the K factor so you could get an accurate setting, or did you too have to adjust the RETRN parameter? In Tony's and my cases, the K factor could not be set high enough - that is why we had to figure out how to use the RETRN field.

Will we be seeing you and Marty at OSH again this year?
 
Hey BigJohn - -

Been so long, I don't even remember which one I have. I was able to adjust the k-factor to get it to read what I want it to read.

254.7 hours.

John Bender
 
BigJohn said:
Just curious John, was there enough range in the K factor so you could get an accurate setting, or did you too have to adjust the RETRN parameter? In Tony's and my cases, the K factor could not be set high enough - that is why we had to figure out how to use the RETRN field.

Will we be seeing you and Marty at OSH again this year?
Click to expand...

John,

JB and I have the FloScan, and, I believe you have the FT-60 fuel flow sensor. Our k-factor is near 50000. As such, we do not have to mess with the return flow value.

Of course we will be at OSH. The campground opens on June 24 and I will be there early on the 24th to rope off our campsites.
 
clucier said:
Marty you camping a month early :) I know they are expecting a crowd but ....
Click to expand...

Have been going there day the campground opens, since the mid-eighties to rope off our area under the trees in Paul's Woods. (First day you can do it.) Then pull the travel trailer up there one to two weeks before the show to volunteer. You would be surprised to see the number volunteers helping out now (beginning of June).
 
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