FI Hot Start Question ?

Larry DeCamp · #1 01-31-2018, 06:36 PM

I am putting an AFP FM-150 system on my 360. Don says the latest system does not need a purge valve and if properly installed, there are no idle issues. I read that insulation on lines FWF dont always solve problems. My question is: why wouldnt taxing around to cool the fuel lines after a heat soak for $100 hamburger or 100LL solve the problem without a purge valve/return line ?

tim2542 · #2 01-31-2018, 07:49 PM

The purge valve is installed between the servo and the flow divider, so it can’t purge fuel in the injection lines as they are downstream of the valve.
Tim Andres

Jesse · #3 02-01-2018, 06:20 AM

Quote:

Originally Posted by Larry DeCamp

I am putting an AFP FM-150 system on my 360. Don says the latest system does not need a purge valve and if properly installed, there are no idle issues. I read that insulation on lines FWF dont always solve problems. My question is: why wouldnt taxing around to cool the fuel lines after a heat soak for $100 hamburger or 100LL solve the problem without a purge valve/return line ?

The heat soak happens when you shut down the engine and let all of the exhaust and engine heat just sit idle in the cowl and heat everything up. A long taxi would help to cool the engine, possibly, but usually you land with a fairly cool engine. Lot es of engines heat up while taxiing because there is so little airflow.

Electrogunner · #4 02-01-2018, 07:49 AM

opening the oil door after parking would help.

Toobuilder · #5 02-01-2018, 09:48 AM

Quote:

Originally Posted by Larry DeCamp

I am putting an AFP FM-150 system on my 360. Don says the latest system does not need a purge valve and if properly installed, there are no idle issues. I read that insulation on lines FWF dont always solve problems. My question is: why wouldnt taxing around to cool the fuel lines after a heat soak for $100 hamburger or 100LL solve the problem without a purge valve/return line ?

Though even at best, the Bendix style FI is not going to start or idle like a modern car, it's hard to call the behavior of a nominally performing system a "problem". You will learn how to reliably start the engine regardless of heat soak, and you will also learn to accept the sometimes chugging and spitting as normal ops. It's not unsafe, it's not a problem, and it clears up as soon as you flush the system with fuel on takeoff.

airguy · #6 02-01-2018, 09:59 AM

Quote:

Originally Posted by Electrogunner

opening the oil door after parking would help.

Unless you're using an engine plenum instead of baffles.

Larry DeCamp · #7 02-01-2018, 02:51 PM

I guess I was thinking of Toolbuilders solution to move some air over the injector delivery tubes in the plenum until it runs safely on the ground. Apparently I need to go to Don's seminar and learn how to avoid the transient rough idle condition since Don says a properly installed system won't do that.

bullojm1 · #8 02-01-2018, 03:39 PM

Larry,

I had the typical FI issues with my IO-360 - engine coughing on the ground while taxing, in the pattern occasional roughness when coming in for a landing, etc.. I added a second layer of fire-sleeve over my fuel lines, and voila! All my issues went away. The engine runs great on the ground and in the air now.

This doesn't cure the hot-start issue - that comes with technique, which isn't a big deal once you understand what's going on with the Lycoming engine pump

Before:

After:

Larry DeCamp · #9 02-01-2018, 03:54 PM

I thought folks were having trouble with vapor in the small lines after the flow divider. Obviously your solution works, Thanks...Larry

Toobuilder · #10 02-01-2018, 04:46 PM

Yes, the injector lines are a big part of the behavior, but understanding that is a big step toward managing it too. Airflow and fuel flow make the behavior go away, while high heat and low flow will bring it back. For example, you can "cure" the behavior with a runup (lots of fuel movement), but it will come back with a long wait at the end of runway.