JPI 830 Fuel level

[Oscar Avalle]

I heard that the new software upgrade for the JPI 830 would allow to have Fuel levels measured too (ie. direclty from the tanks). I have been trying to find out if that was true, but I have not been sucessful. Somebdoy knows anything about this?

 

Oscar

[jlunseth]

I don't know anything about the software upgrade Oscar, but the general issue with measuring the fuel in the tanks is not what you have on the panel, it is the senders.  Most of our planes have the factory original senders and they are not very accurate.  The 830/930 or panel gauges can only tell you what the senders tell them.  There are better senders on the market, but aside from the cost of the senders, installation is not cheap and the issue I never got answered when I looked into it, was whether the modern senders were compatible with a JPI.

 

I have the 930.  My left tank gauge likes to stick until the tank is down about a third, so I will fly along at full for about an hour and a half, and then the gauge will say I have 20 gallons (I start with 37.5).  The senders are not very accurate at lower full quantities on either side.  The 930 says I have zero when I usually have about 5-7 gallons useable in a tank.  That may not sound like much, but on a long flight the gauges will be saying empty when I have an hour's worth of total fuel left, or about 14 gallons total.

 

I use the fuel flow which is much more precise.  On my 930, it is within .1 gallon for a fuel usage of 50 gallons.

[Alan Fox]

The 830 is not certified as primary , where the 930 is.... 

[Oscar Avalle]

thanks guys. I know that the 830 is not certified. But is is always nice to have the information in one place with alarms, etc. I also rely more on the fuel flow, than the tank leves (my senders get stuck too), but having two tanks can confuse you if don't keep track how much you consumed from each one. thus it would be nice to have that information too.

[N601RX]

I have the 830 and have been considering adding on of these for fuel level. It seems to be the most accurate option available.

http://www.aerospacelogic.com/index.php?dispatch=products.view&product_id=56

[jlunseth]

The resistive senders are indeed supposed to be more accurate than our factory analog senders, but when I was looking into this no one would say that they would be compatible with the 930, rather that it would be for the installing A&P to make that determination.  I would want to know that before going through the throes of an installation, and would not want it left to an A&P to take a guess.

 

On fuel flow, I have tested the fuel flow in my aircraft by filling the tanks myself, taking three flights of about two hours, then refilling the tanks again myself to the same level, and comparing the actual usage with the 930 readout.  I have done that a couple of times so I know the result is good.  Then, when I take a long flight where exact fuel matters, I either refuel myself or supervise the line guy.  It takes some patience and rocking of the wings to get the tanks truly full, which is 37.5 gallons each side.  Many times, line guys have filled my tanks, I have looked at them and told the line guy they can both take 5 gallons more, and indeed they take 5 gallons more. 

 

Once I am certain the tanks are truly full, I set up a chart during the flight.  I start with 37.5 in each tank, and as I switch tanks I do the math to determine how much was used and subtract that.  So for example I run on the left tank until I reach altitude, which for me may be 35-45 minutes at full fuel flow of around 22 gph.  Once I get set up at cruise altitude and power I switch tanks, noting the fuel flow.  Lets say that is 15.2 gallons.  I subtract that from the left tank so I know I have 22.3 gallons left.  I fly for say two hours on the right tank and switch.  Lets say the fuel flow says I have used a total of 40.6 gallons.  I subtract the 15.2 from the 40.6 so I have used 25.4 from the right tank.  Then I note the 25.4 in the right tank column and subtract it from the 37.7 the tank started out with.  So now I have 12.3 left in the right tank and 22.3 in the left. And so on until I land. 

 

I have an iPad and keep all my charts on the iPad and take all my notes during the flight just using my fingtip to draw on the blank screen in Foreflight.  The only piece of paper I carry is a folded over 8 1/2 x 11 that I write this fuel flow on with a pen, so I always know exactly where I am at on both tanks.  It is also useful to take a rough comparison of fuel used, to the fuel flow I have been seeing on the display during the flight.  So have used 25.4 from my right tank in two hours, I would expect to have been looking at a fuel flow of around 12.7 gph during those two hours.

 

It takes alot less time to do it than for me to write it, but it is far and away the best method of tracking fuel for a long flight.  As I noted at the start, this method is with .1 gallons out of 50 gallons on my 930.  The tank gauges on the other hand, will show empty with anything from 5 - 10 gallons left in a tank. 

[Bob_Belville]

I have a 930. Installation was just finished in Dec. We discussed alternatives to the analog float senders but in the end we had to send the old units to Lock Haven for rebuilding. The shop calibrated the JPI as they gradually filled the tanks. But in the end the info is near useless. In my case the right tank reads full until it is half empty. Sometimes. OTOH the Fuel Flow feature is very precise as it was with the JPI 450 I replaced. (I ran out of avgas once, years ago, and I doubt I've landed with less than 15 gallons since.) But if I had to stretch, I'm confident the FF "USD" quantity is right. BTW, the 930 is much more intuitive than the 450 though not all that friendly until you memorize which 2 buttons pushed in sequence or together, arbitrarily, invokes the mode you want.

[M016576]

Does the 930 require tweaking of the K-factor, like the 830? Just when I think I've got my 830 FF dialed in, I get an "outlier" fuel burn, readjust, and start over. Maybe I'm just getting too close to the actual K-Factor value? My 830 fuel burn is within a gallon of actual fuel burn after about 3 hrs of flight... Is that what others are seeing?

[Oscar Avalle]

Does the 930 require tweaking of the K-factor, like the 830? Just when I think I've got my 830 FF dialed in, I get an "outlier" fuel burn, readjust, and start over. Maybe I'm just getting too close to the actual K-Factor value? My 830 fuel burn is within a gallon of actual fuel burn after about 3 hrs of flight... Is that what others are seeing?

I calibrated my 830 and mostly the data looks good and accurate. When I get an outlier in many cases it is because I just did not fuel the tanks correctly  ... Not really full, etc. 

What I started doing is simply burn 10gal per tank based on the fuel flow and then switch tanks, instead of switching tanks every 30 min or hour.

[Bennett]

I noticed a logbook entry to the effect that the k factor was adjusted by the previous owner and/or his mechanic. While I had a total panel rebuild done after purchase, the original 830 was retained, but recessed. If I supervise the filling of the tanks to the same place each time, I am seldom off by more than a gallon, (say in 50 gallons or so) and generally less than that. In two and a half years of doing this, I have never seen an outlier. I have forgotten to enter "full fuel" before starting the engine, and this of course invalidates the fuel used, required, and reserve figures

[Bob_Belville]

In my bird the 450 was "extremely" accurate. The prior owner told me it was within "0.1 gallons of actual fill quantity." That is of course far more precise than the physical filling will be. Since we usually won't know within a gallon or 2 what is "full" on any given fill-up, particularly when out of town, for practical purposes the FF USD is the number to trust. When I'm topped off at home it is in my hanger with the plane in exactly the same spot each time and probably by the same line man. He carefully fills each side but does not rock wings or make a second visit to each wing as has been described here elsewhere.

 

Based on the relatively few flights I've made since the swap out, I suspect the FF on my new 930 is off, perhaps 1-2%, to the conservative side. When I have accumulated enough data to confirm that I will tweak the K factor. 

[M016576]

Just out of curiosity- what are your guys k-factors?

Mine is 30.56 (as of the last 60 or so gallons)

[N601RX]

29.22    It may vary considerably depending on the install. How close it is to hose bends, if the flow exits uphill, ect.  I've saw some installs on here that did not even attempt to follow the STC.

[Bob_Belville]

My K factor is 29.65 where the installer set it..But as I mentioned I am pretty sure it is reading a little high. A fill up at PDK today took 23.7 gallons vs. 24.7 USD. That overstatement matches earlier data. I'll see if I have enough contiguous info to make a factor change.  

[MB65E]

I just received an email today from Jpi answering some questions I had about prior installs. I too have seen the flow sender mounted in places it shouldn't be. Lyc fuel injection and carbed engines needs to be mounted on the left side after the pump before the servo. Clearly states this in the stc. Must be continental techs not reading instructions and mounting it on the metered side of the lyc. Jpi responded with the stc instructions as an attachment. Pretty clear... No return lines on the lyc. However some Shadins I have seen right next to the Spider. Go figure.

-Matt

[Bob_Belville]

I now have enough data to fine tune my K factor. In 13.3 tach hours of flight I have burned 125.2 gallons. The 930 has logged 130.3.gallons. JPIgal/Act.gal = 1.041 so my K factor should be 30.86 instead of the current 29.65. JPI recommends moving it only half way at a time to avoid chasing so I should set it at 30.25 and gather more data.

 

(I hope the JPI manual instruction is correct. I would have assumed raising the K factor would have increased the indicated flow.)

[Oscar Avalle]

Bob 

 

The JPI manual is correct. My K factor is also 30.86... what a coincidence...