FAB spacer pros and cons for FI?

RickWoodall · #1 02-07-2010, 09:44 AM

Looking to start my FAB on my VERTICAL INDUCTION FI engine. In searching builders sites, it seems some have built a 1.25 spacer block to stand off the FAB from the bottom of the silverhawk, to better line up the air flow and alleviate some of the mixture arm interference.

Any comments or suggestions? Not sure if its wise or not to go to all the trouble of building this. Pics, pros cons welcome...just trying to figure out what makes the most sense.

Greg Arehart · #2 02-07-2010, 03:54 PM

Rick,

I did not add any spacers etc. and my box seems to line up just fine. If I added more than about a quarter inch, I would probably have trouble getting things to line up. I do have a small bit of interference with the mixture arm and the cowl when in the full rich position, but that would not be changed by adding the spacer.

My suggestion is to build per the plans and once you get the cowling fit you can determine if any spacer is necessary.

cheers,
greg

Fedico94 · #3 02-08-2010, 09:37 PM

I am at that stage in my RV9A and I have a 1/4 inch phenolic spacer supplied by Van's with the VA-182 control linkage bracket. It set the SilverHawk injection servo at the correct height for my vertical induction IO-320. This was of course dependent on the position of the FAB box assembled and mounted on the engine servo (which is another long story). This was aligned with lower cowl with proper intake scoop (O-360) that had been placed in its permanent mounting position with the cowling attach mounting plates in place for the MilSpec rceptacles.

Guy Prevost · #4 02-09-2010, 08:22 AM

I made the decision based on how my FAB sat relative to my cowl. With my IO-360 on the 8A with Precision Silverhawk injection, adding a an ~1" spacer between my FAB and injector servo made the FAB line up with the hole in the cowl perfectly. It also let my mixture arm clear the FAB without any weird notches in the FAB or buying a reversed mixture arm servo.

Since you have an IO-320 and a 9; see what it looks like you need. Maybe nothing, maybe a bunch. There are so many possible variations, you might have a hard time getting the right information for your plane here.