Bill Dube <bdube@al.noaa.gov> wrote:
 
"""
         Do you need the fuel flow transducers? Doesn't the EFI system
 display the fuel flow through the injectors?
"""


The data from the ECUs isn't readily available without hooking up a laptop to their RS232 ports, something that I'm doing currently to verify that our display sensor set matches the data that the ECUs gather from their dedicated sensor set to run the engine.  Consequently we have an EI fuel flow/pressure instrument in addition to the data being available on the SFS EFIS/EAU. Getting the single transducer pair to talk to both instruments was a real treat... entailed sitting in the airplane with an oscilloscope describing transducer signal waveforms to the chief engineers from both EI and GRT while I added and subtracted resistors from a breadboard... resulted in my building a new circuit board to provide the transducers' required bias voltages and split the signals off to both instruments that needed them (schematic attached <g>).  I would much rather have had the data available directly from fuel flow calculations based on the EFI part of the ECU, but the quote we got for the black box that would take all of the ECU data and make it available for direct display on the EFIS was over 15 grand.  Purchasing and installing a complete set of duplicate sensors to drive the displays turned out to be way cheaper. Ain't life grand.

  <Marv>

PS... decided to test the prop today to see if the governor was doing its job. At 2000 engine RPM (<1150 prop rpm) I could only get a 300 engine RPM drop when I pulled to coarse pitch.  Apparently the prop gov works based on prop RPM, so there wasn't enough pressure being developed to get the blades to full coarse.  At 3000 RPM (1740 prop),however, it was a totally different story... a pull to coarse pitch pulled the engine down to 2000. Yee-haaaa!!  That's because ACI (prop mfr) has the coarse angle on the blades around 25 degrees, instead of the 12-13 degrees they do for the TSIO550.  All I can tell you is that at 3000RPM (75% power, or about 450HP) I was getting cramps in my legs from how tightly I had to hold the brakes. I'm pretty sure that if I'd dialed in another 300-400 RPM I'd have been skidding down the taxiway.  That thing is AWESOME!!!!