REFLECTOR: Engine backfiring

Wed Aug 16 10:11:28 CDT 2006

Ok - I thought it was called a sniffle valve?

John

	-----Original Message----- 
	From: reflector-bounces at tvbf.org on behalf of Scott Derrick 
	Sent: Wed 8/16/2006 9:42 AM 
	To: Velocity Aircraft Owners and Builders list 
	Cc: 
	Subject: Re: REFLECTOR: Engine backfiring

	I thought it was called a whiffle valve?

	Dave Dent wrote: 

		Your right I have seen this before.  Some call it the riffle valve. Manifold 
		drain valve.  I have encountered this valve missing and one time causing a 
		fire.  The fuel didn't drain out and it back fired and lit off.
		Good Call Andy
		Dave
		----- Original Message ----- 
		From: "Andrew Ellzey" <ajlz72756 at yahoo.com> <mailto:ajlz72756 at yahoo.com> 
		To: <velocity at davebiz.com> <mailto:velocity at davebiz.com> ; "Velocity Aircraft Owners and Builders list" 
		<reflector at tvbf.org> <mailto:reflector at tvbf.org> 
		Sent: Tuesday, August 15, 2006 9:44 PM
		Subject: Re: REFLECTOR: Engine backfiring

			Dave,

			I had a Mooney M20E that had this engine and flew it for 15 years and 
			about
			600 hours. This engine is known for this problem. The first thing I would
			look at is; there is a 45 degree AN fitting on the bottom of your engine
			that is supposed to be your airbox drain. This 45 degree fitting is 
			supposed
			to have a check valve internal to this fitting. You would never know it is
			installed unless you know that it is there. This is the problem, most 
			people
			think it is a standard AN fitting and will install a new fitting without 
			the
			check valve at overhaul. With the check valve missing your engine sees 
			this
			as an air induction leak and will idle rough and make the backfiring 
			worse.
			A easy way to tell if your valve is working properly is to put your finger
			over the drain line with the engine running and see if you engine lowers 
			its
			idle speed. I have also seen these check valves stuck open and just needs
			cleaning. I tried to order a new check valve when I found that mine had 
			been
			changed out to a standard fitting after fighting this problem for 8 years. 
			I
			never could get a good part number to order one and had to make my own. If
			yours is missing or gone bad I can tell you how to make one. Or you can
			install a PVC valve inline with your drain and it will work just as well.
			The PVC valve should close as your engine sucks air out of your airbox. 
			This
			valve was supposed to drain the excess fuel that drains out of you 
			injectors
			and into your airbox when you shut down your engine and suck closed when 
			you
			start your engine.

			Andy Ellzey

			----- Original Message ----- 
			From: "Dave Philipsen" <velocity at davebiz.com> <mailto:velocity at davebiz.com> 
			To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org> <mailto:reflector at tvbf.org> 
			Sent: Tuesday, August 15, 2006 10:38 PM
			Subject: REFLECTOR: Engine backfiring

				Here's a question perhaps for some of the engine experts:  I've got a
				STD FG with IO360-A1A engine.
				It has one standard magneto and one Jeff Rose electronic ignition.  The
				engine and oil cooling are not a
				problem even with OATs in the low 90s. But, I have a problem (it's not a
				huge problem) with backfiring
				during taxi *after* I land.  Taxiing before takeoff seems to be ok.  The
				backfiring happens maybe once
				every 30 seconds or so.  The engine also seems to run a little rough at
				this time.  I've tried running lean,
				running rich, running on just the magneto, running on just the
				electronic ignition.  None of these seems to
				prevent the backfiring during taxi.  The engine never seems to have
				problems before or during takeoff or
				during cruise or descent...just taxiing back after landing.

				I'm starting to think it's a vapor lock problem or something since the
				fuel flow is way down and the fuel is
				sitting in the lines longer and heating up.  I had the cowling off the
				other day and was checking the routing
				of the fuel injector lines and they don't appear to be routed near the
				exhaust manifolds or anything like that.
				I was thinking of maybe experimenting with some insulating material
				around the individual injector lines as
				well as the main fuel line.  Any ideas?

				-- 
				Dave Philipsen
				STDFG
				N171SP

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