Precision Airmotive FI - hose routing

[Rupester]

I?m puzzling over the best fuel hose routing for my vertical draft Aerosport IO-320 with Precision?s Silverhawk FI. The toughest one is the longish #4 hose from the servo up to the spider, which sits between cylinders 1 and 3. The best routing seems up around the aft side of cyl #3, but w/o the baffles it?s hard for me to tell how that will work. Previous posts evidenced some who planned to come up between the cylinders on the R side, but I see that as a likely [assured?] vapor lock issue when the engine is shut down in hot weather, i.e. small fuel line surrounded by hot cylinders with no airflow.
I could use advice from any of ya?s who have piped the Precision FI on either a 320 or a 360 ? photos would be WUNderful.

[shuttle]

Hi Terry,
I too have a Silverhawk FI but on a different engine (TMX-IO-360-M1B).
Mattituck ran my FI servo-to-spider #4 hose up between no. 1 and no. 3 cylinders.
My spider sounds like it's in the same place as yours - top of engine, just right of centreline between cylinders 1 & 3.

[shuttle]

Terry,
I searched my photos. This is the best one for showing the route up between the cylinders.
The hose was not fitted at the time but you can clearly see the hole in the intercylinder baffle below the cylinders.

Steve

[ninerhawk]

I have noticed from pictures that the "spider" can sit in a different spot above the engine on the IO-320 vs the IO-360.

On my my subject engine as received from Lycoming the fuel hose is routed and clamped in 2 places behind the #4 cylinder. Having mounted the baffles, I plan on adding a simple grommeted hole into the rear baffle on that side to accommodate the anticipated routing and supplied hose. I am going to postpone drilling that hole until I mount the fuel servo and determine how the fuel hose connection fitting and routing to the Precision Airmotive fuel servo will work in conjunction with cowl and linkages - haven't quite got that far yet. Would be curious if any others have made this combination work or if I have to anticipate a different routing.

You can use this link to visualize by model the top view location of the fuel spider.
http://www.lycoming.textron.com/supp...dfs/SB342E.pdf

[Rupester]

Howard,
If the hose is routed behind cyl #4, is your flow divider located between cyls 2 and 4 ?

My flow divider looks like Steve's above, except the 90 degree ell fitting is turned aftward, rather than downward ... hence the logic of bringing the hose up aft of cyl #3. I'm surprised at the clear indication Mattituck runs the hose up between the cylinders. Still seems like a natural hot spot.

[ninerhawk]

Flow divider and mounting bracket appears to be the same parts on my Van's/Lycoming YIO-320-D1A. It is assembled/mirrored on the other side of the case, between cylinders 2 and 4. A straight in fitting is installed in the inlet port, and as mounted on my engine, it appears to point directly at left (pilot, top) motor mount.

[shuttle]

Terry,
On the -M1B the FI servo is positioned bottom front of the engine so the fuel hose to the spider either has to go up infront of and over the top of no. 1 cylinder or behind it. Routing up behind no. 1 looks to be the 'cleaner' option and offers the shortest hose length.

By the sounds of it, with your engine the options differ - either fore or aft of no. 3 cylinder - so the relative merits of either routing will differ too.

The 'between the cylinders' route is clearly deemed acceptable.

[ronschreck]

Mine is routed between cylinders 1 and 3 with good results for 850 hours now. Actually the base of the cylinders is considerably cooler than the cylinder head. I'm sure it's hot enough to vaporize the fuel in the line after shut-down on a hot day, but that's what purge valves are for. I have never had a problem with vapor lock in flight.

[Rupester]

... to all. This is helpful. It tells me:
a) The aft-of-cyl#3 hose route is used sucessfully by others
b) the between-the-cylinder hose routing is successfully used by others, regardless of my fears of heat concentration there.