Setting fuel pressure on Garmin G3X

>>>My only question now is, is a 50 PSI gauge safe? its very close to the work pressure <<<

The Kavlico P4055-50G is Proof rated for up to 100psi, and Burst rated at 150psi Minimum.

Burst is where the sensor element is permanently damaged,  not where the sender explodes!

The 912iS fuel pumps internally bypass at ~100 psi.  So not a safety issue.

The sender will output its maxumum voltage for anything over 50 psi.

So if your pressure ever reached 75 ps, your display would still be showing 50.

It is a non-issue,  Any pressure over 46-48 would warrant immediate investigation, and 50+ would be a No-Go situation until resolved.

50 psi or over means you have a blocked fuel filter. 

50?, 60?, 70?,   It is only academic to know how bocked it is.

Your respose will be the same in all cases.

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There is nothing particulary special about these senders.

For any pressure between 0 and 50 psi, the sender outputs 0.5 to 4.5 volts.

You just tell the display that 4.5 volts is 50 psi, or anything else, and it scales to match.

Equivalent senders are available from other manufacturers.

e.g.  A UMA N1EU70G Sender would be a 70psi substitute.  (They don't offer a 50psi version) 

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The 912is pressure is 3 Bar above MAP, which is always lower than ambient, so near Idle the gauge might be only seeing 35psi Gauge plus the 8 psi Absolute that the Map is reporting yields the 43psi on the Display.

Now if this was a 914/915 with 10 psi of turbo boost available,  the 70 psi Sender would be required.  100 psi even better!

REPLACE KAVLICO PRESSURE SENSOR!

Dynon has advised that the P4055 has failed in service and leaked fuel. Please read and follow their service bulletin.

https://www.dynonavionics.com/bulletins/support_bulletin_050620E.php

Hello Bill

Thank you for the reassuring response

Uri

Uri,

I’m glad you are headed in the right direction.  Once you start flying at higher altitudes you may have to alter the offset a bit to keep the pressure in the green. Like I said, the Garmin formula does not seem to properly correct for pressure changes due to altitude. I think their formula is too simple to do that.  

  I started with my offset at 1 bar, but ended up at .86 bar in order to be in the green during all flight conditions.  This may be different for your aircraft.  Unfortunately, this ends up being a compromise between accuracy at sel level and your max altitude, but you can get it acceptable.  Essentially, I set mine to be accurate at 4500’, which is .86 bar on a standard pressure day.  It’s kind of a strange system actually, you would think that since the G3X has inputs for both static air pressure and manifold pressure all this could be automatic and much more accurate.  

Like Bill says, the 50 PSI sensor is just fine, that’s what I use. 

I had to designed my installation from a clean sheet.

I selected a UMA N1EU70-D Differential Sender.

It is identical to the G version except the rear, Ambient Reference Port is threaded.

I Installed an 1/8" Barbed fitting on the Airbox (Easier said than done.)

It would have been easier to Tee into the small hose from the Airbox to the Fuel Pressure Regulator, but why do it the easy way?  

This way there are no calculations or corrections needed.

The Sender reports differential Fuel/Airbox Pressure directly.

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The Correction factor makes no sense.

The air box pressure may drop at altitude but the MAP sender does not know the difference between climbing and closing the throttle.

The engine idles on the ramp because the MAP is at 5"hg; About the same as being at WOT at 45,000 ft.

It would appear that the Ambient pressure is being included in the calculation where it should not.

The senders are accurate to +/- 2.5%.

Assuming both the MAP and the Fuel senders were opposite worse cases you should need a correction of no more than 5% worse case.  ~2% typically.

A 14% correction is very suspicious.