Question about Silverhawk.

Chappyd · #1 03-13-2009, 05:28 PM

I was poking around in the shop tonight, wondering what to do next , and started examining the fuel injection system. All I have done to this point is install the fuel servo and the mechanical linkages on the servo for throttle and mixture. I was looking at the spider, or flow divider mounted on the top of the engine and noticed a fitting with a plastic cap. As it sits now, there is one firesleeved line coming up through the cylinders on the right side that appears to be attach to the fuel divider, then the lines out to the 4 cylinders. Looking down from the top of the engine, the fuel line is at 3 O'clock, and this capped fitting at 2 O'clock. a quick search through the literature that came with the engine and a visit to Precision airmotives website didn't offer any answers. What is this fitting for? It's only capped with a plastic cover, so it must do something. Where can I find this info

TIA

rocketbob · #2 03-13-2009, 06:04 PM

fuel pressure gauge.

Chappyd · #3 03-14-2009, 04:33 AM

Do I need 2 fuel pressure gauges? Following Van's drawings, I have one line coming up from the mechanical fuel pump to the manifold mounted on the firewall. The transducer is mounted to that, then wired to the fuel pressure on my Dynon unit. Is that wrong?

And where would I find that info? There must be a source somewhere.

Don at Airflow · #4 03-14-2009, 02:00 PM

What your looking at is the ?GAGE? fitting on the flow divider. Back in the day, before all the cool electronic flow meters were avialable, this port was connect to a pressure gauge that was calibrated in GPH. This port is cross-drilled into the nozzle port next to it, and measures nozzle backpressure. Since the size of the nozzles was known (on certified planes they were always the same) there is a relationship between nozzle back pressure and fuel flow. It?s not very accurate for low flows, but it works pretty well at higher flows and cruise fuel flow.

In your case, if you want fuel flow information and are not going to use an electronic flow meter, you would use this port. Otherwise just plug it. If you were to use it, you would have to find one of the old fuel flow/MAP gauges for your engine application, or we can supply you a nozzle vs. fuel flow backpressure chart.

I wonder why Precision doesn?t tell you guys how their stuff works???

Don