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K Factor going from a Shadin MiniFlo to a JPI 930


LANCECASPER

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The avionics shop is putting the final numbers in my JPI930 and needs the K factor. I'm going from a Shadin MiniFlo to a JPI 930 and the shop is staying with the transducer that came with the Shadin.   It is not stamped on the transducer. The display unit has "-1" stamped on it. Has anyone done this change and what did you come up with?  Thanks

 

Follow Up: I called and spoke with Greg at Shadin Avionics and he said that this was the old method they used. It should start out at a K-Factor of 88 and then -1 should be 87.0. We'll try that and see.

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1 minute ago, LANCECASPER said:

The avionics shop is putting the final numbers in my JPI930 and needs the K factor. I'm going from a Shadin MiniFlo to a JPI 930 and the shop is staying with the transducer that came with the Shadin.   It is not stamped on the transducer. Has anyone done this change and what did you come up with?  Thanks

In October I had a JPI 900 installed.  It turned out that the K factor written on the JPI transducer was way off. It is very easy/quick for the pilot to adjust the K factor. What I did was pick a low number (27.0) to assure that the 900 was showing that I used a lot more than was actually used and then adjusted the K factor up 0.5 to see how much 0.5 affected the quantity "Used" and then slowly adjusted the K factor up until the JPI "Used" value was correct. I realize you don't have the JPI transducer but this procedure gets you to the correct K factor quickly and accurately.

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13 minutes ago, LANCECASPER said:

The avionics shop is putting the final numbers in my JPI930 and needs the K factor. I'm going from a Shadin MiniFlo to a JPI 930 and the shop is staying with the transducer that came with the Shadin.   It is not stamped on the transducer. Has anyone done this change and what did you come up with?  Thanks

This is probably for a fuel pump engine so start with 30.00.  For a gravity system start with 20.00 and you will be close.  If the FF indication is way out, then you will have to change the FF transducer.  (some of the other FF systems have a completely different output).

Then fly a few hours and generate some data from your refuelling slips and the JPI, and follow the instructions in the book on resetting the K factor.

Don

 

 

 

 

 

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Both Shadin and JPI use Floscan 201B transducers. 

http://www.floscan.com/html/blue/aviation.php

JPI acquired Floscan a couple of years ago. These transducers have a K-factor range of 28,000 to 30,000 pulses per gallon and are individually calibrated at a 16.0 gph flow rate. Floscan claims that the transducers are accurate to 0.5% down to a flow rate of 3 gph. If all this was correct, setting the JPI for the transducer K-factor should be very accurate. But most find that getting accurate fuel used requires tweaking the K-factor. Since it was very accurately calibrated at the factory (my transducer came with a tag showing 28,989) this can only mean that, installed in the aircraft, the flow rate measurement is not completely linear. By adjusting the K-factor to match actual fuel used averaged over many flights, I can get it within 5%. It will vary depending on the length of the flight (more time spent at constant flow rate on longer flights). I suspect that the installed accuracy is affected by vibration.

These things do wear out. If it's the original transducer, I would replace it when upgrading from the Shadin to the JPI. They are not expensive and it's a pain to go through the calibration procedure again if it needs replacement. You can tell when they are shot because measurements become erratic and then sometimes go to zero. Some try soaking them in solvent to "rejuvenate" them, but I found this to be a temporary fix. After all, they spend their life soaked in gasoline which is a pretty good solvent.

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I recently calibrated a gravity flow transducer in a C172.  I kept records from my summer trip (42 hours) and did one correction and it has been accurate to within 0.5 to 1G (roughly 1-3% on the 'safe' side).

On my trip I had one refuel that was 4G out (out of about 32G consumed), but all the rest were close.  I went back to that airport on the way back and the numbers were close.  I don't know what happened, I suspect a billing or fueling error (not starting from zero?), but it was a reminder to look at the refusers gauge every time, not just rely on fuel slips.

And then the crazy looks when you call the truck back to squeeze another 1.8G in the tanks (4.5%). Another reminder to look.

And that was with an 'easy' C172.  A Mooney with long range tanks (settling issues), recessed filler caps, etc. introduces far more room for error in your calibration, so pay attention and be consistent, follow the JPI resetting procure and all will be good.

 

Aerodon

 

 

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In October I had a JPI 900 installed.  It turned out that the K factor written on the JPI transducer was way off. It is very easy/quick for the pilot to adjust the K factor. What I did was pick a low number (27.0) to assure that the 900 was showing that I used a lot more than was actually used and then adjusted the K factor up 0.5 to see how much 0.5 affected the quantity "Used" and then slowly adjusted the K factor up until the JPI "Used" value was correct. I realize you don't have the JPI transducer but this procedure gets you to the correct K factor quickly and accurately.

The transducer needs to be installed correctly: horizontal, out on top, secured and no 90° bends close to the transducer, etc.
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3 hours ago, ArtVandelay said:


The transducer needs to be installed correctly: horizontal, out on top, secured and no 90° bends close to the transducer, etc.

I did all that. The Mooney factory installed the transducer on M20Js mounted to the sump upside down (wires coming out bottom). I even went to the trouble to build a new mounting bracket and flip it over. It made absolutely no difference. (The reason for mounting wires up is so that the vent can allow vapor bubbles to evacuate, but if you don't have air leaks in the fuel system, this doesn't seem to be an issue according to JPI). I also removed the 45 degree elbow from the inlet side and replaced it with a straight fitting. No difference. Somewhere, (I think it was in a Floscan installation document for boats) they mention not to mount it to the engine. That's the only thing I haven't tried.

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