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  #41  
Old 07-10-2017, 06:04 AM
rv7charlie rv7charlie is offline
 
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Quote:
Originally Posted by tspear View Post
To me a fuel totalizer is making up for bad fuel tank measurements. Would it not be easier to fix the problem of the fuel tank measurements then add one more bandaid?

Tim
Right. And a GPS is just one more bandaid for poor pilotage.

;-)
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  #42  
Old 07-10-2017, 07:15 AM
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DanH DanH is offline
 
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Originally Posted by Flandy10 View Post
Its the injector pulses that introduce a stutter to the incoming fuel stream causing the flow through the cube to be jumpy. Its still flowing 48gph, just not a smooth flow that the turbine meters like.
Below, red cube rotor, and the cover plate with what appears to be an optical sensor.

The rotor is some sort of plastic, very low mass, probably so it is easy on the bearings in a vibrating environment. System seems to work by breaking the light beam, so if the rotor reverses just a tiny bit due to a pulse, the count goes up.

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  #43  
Old 07-10-2017, 07:52 AM
rv7charlie rv7charlie is offline
 
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And....That's why I suggested a diesel FloScan sensor. They all appear to work the same way, but the ones made for diesel marine engines seem to work OK. It would make one wonder whether FloScan did something like add mass to the turbine wheel to make it less sensitive to pump impulses. Is there a fundamental difference in the fuel delivery system of a typical marine diesel & the one in the a/c?

At any rate, there are often diesel FloScan sensors available on ebay for cheap. Electrically, it should hook right up to the existing electronics in the a/c. In the overall cost bucket, a diesel sensor & a couple of pressure dampers should be a cheap experiment. The dampers are easy to make, with extra plumbing fittings.

Or maybe I'm off in the weeds, and diesel boat drivers don't worry about low load/rpm errors.

Charlie
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  #44  
Old 07-10-2017, 12:05 PM
Flandy10 Flandy10 is offline
 
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The 172 (CD-155) uses the FADEC supplied fuel flow number and the canceled C182JTA (SMA 305) used a derived FF from the servo control computer (I asked after searching the Cessna parts manuals and finding no FF meter). None of the SMA STCd C182s actually measures the FF except for the tests I mentioned.

As for the G3x reading digital, that would take a hardware redesign. Tim/Mike/John (TEAM X) have been extremely helpful as I've worked through some of the differences the EMS required.
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  #45  
Old 07-10-2017, 12:26 PM
Flandy10 Flandy10 is offline
 
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Quote:
Originally Posted by rv7charlie View Post
And....That's why I suggested a diesel FloScan sensor. They all appear to work the same way, but the ones made for diesel marine engines seem to work OK. It would make one wonder whether FloScan did something like add mass to the turbine wheel to make it less sensitive to pump impulses. Is there a fundamental difference in the fuel delivery system of a typical marine diesel & the one in the a/c?
Charlie,

I believe the FloScan sensors are identical for both boats and planes. The difference is the diesel systems add the canister that looks like an oil filter. It is a flow homogenizer/ pulse dampener- that's the key to making this work. I will admit I totally forgot about looking on Ebay.

The biggest problem with these systems is WEIGHT. The transducers weigh 10 ozs but the rest of the marine equipment adds up. And yes, I plan on doing more testing of different ideas- I've not given up yet, just running out of calendar days before OSH.

I appreciate ALL the ideas people have put forward, keeps me thinking about alternatives.
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Last edited by Flandy10 : 07-10-2017 at 12:29 PM.
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  #46  
Old 07-10-2017, 01:00 PM
rocketman1988 rocketman1988 is online now
 
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Default Maybe...

Any chance you could use an arduino to do digital to analog conversion?
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Aerospace Engineer '88

RV-10
Structure - 90% Done
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EFII System 32 - Done
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  #47  
Old 07-10-2017, 01:21 PM
tspear tspear is offline
 
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Quote:
Originally Posted by rv7charlie View Post
Right. And a GPS is just one more bandaid for poor pilotage.

;-)

No. GPS is a fundamental change in how you navigate in a radio based environment. (pilotage is not the correct comparison, VOR and NDB are).
In this case a fuelntotalizer and a fuel tank gauge are providing the same service. How much fuel is remaining. Fuel totalizers largely came about because of inaccurate fual gauges. Fuel gauges have historically been inaccurate because of FAA lighting and other requirements constrained possible solutions. We do not face such constraints. So why continue with the bandaids?

Tim
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  #48  
Old 07-10-2017, 02:01 PM
rocketman1988 rocketman1988 is online now
 
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Default So...

How do you propose we deal with fuel gauges then? For example, in the RV-10, the fuel gauge senders cannot read accurately above a certain amount due to the dihedral in the wing...consequently, the tank will read Full until it reaches a point where it can measure accurately.

The totalizer will tell you exactly how much you have used and what is left in the tank from top off to empty.

I know you will say that you would rather be accurate on the bottom than the top, and I agree with you.

I guess I would prefer to have both quantity and flow, if possible...
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Bob
Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
297 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...

Dues+ Paid 2019,...Thanks DR+
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  #49  
Old 07-10-2017, 02:36 PM
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airguy airguy is online now
 
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The totalizer also can give you estimated fuel left at destination when tied into your GPS (assuming it's calibrated correctly) which greatly assists in making the decision about a fuel stop or push on.
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Greg Niehues - SEL, IFR, Repairman Cert.
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N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #50  
Old 07-10-2017, 02:51 PM
tspear tspear is offline
 
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Quote:
Originally Posted by rocketman1988 View Post
How do you propose we deal with fuel gauges then? For example, in the RV-10, the fuel gauge senders cannot read accurately above a certain amount due to the dihedral in the wing...consequently, the tank will read Full until it reaches a point where it can measure accurately.

The totalizer will tell you exactly how much you have used and what is left in the tank from top off to empty.

I know you will say that you would rather be accurate on the bottom than the top, and I agree with you.

I guess I would prefer to have both quantity and flow, if possible...
The way boats deal with it. Two senders, one at each end or the tank. Then draw a line between and determine capacity or measure as you fill.

Tim
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