On 2010-04-17, at 10:21 PM, Jon Socolof wrote:
A low or high unmetered fuel pressure would indicate the engine is not being supplied with enough or too much fuel and this seems like the more critical information. The gauge port on the flow divider for metered fuel pressure seems to be used primarily to drive a pressure type fuel flow gauge not applicable in my case.
The port can be used to connect a fuel pressure gauge to setup the fuel pressures per the SID referred to by Dennis. My IO-550N use a flow transducer for measuring flow during flight but the ports are used for the setup and maintenance checks. I'm sure others have plumbed pressures into the avionics but you will need to confirm full power fuel flows and pressure alone can't do that. In your first email, I thought you were doing a setup of the fuel pressures and not plumbing to a Garmin system for permanent indication in flight. I was referring to the setup of pressures in the SID.
I will be re-plumbing to measure unmetered fuel pressure as this is what Garmin values are set to on the G900 EIS for Continentals (Garmin measures metered fuel pressure on Lycoming engines). I hope this makes sense.
That plumbing plus $1.00 will get you a cup of coffee and nothing else. The metered pressure is what is delivered to the cylinders. There is a lot of good information on this subject on the web. The first is describes the continuous flow system and how the metered and unmetered pressures connect to each other.
(This magazine is good for maintenance and you can get it online now and subscriptions can be free)
Plus, there is a TCM video on the subject hosted on the same site where you will see two parts to the continuous flow setup:
Lastly, there were good comments on LML on the location of the transducer to avoid bends and turns. There was an excellent note on the plumbing of the return line as well to the Andair selector valve. I don't know if this helps or not but I enjoyed reading it again.
Paul
N357V