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<TITLE>RE: YS 140 DZ going lean in -ve g maneuvers</TITLE>
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<P><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>Thanks for all the tips.</FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>I will try these suggestions over the weekend.</FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>Peter</FONT>
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<P><FONT SIZE=2>________________________________</FONT>
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<P><FONT SIZE=2>From: Earl Haury [<A HREF="mailto:ehaury@houston.rr.com">mailto:ehaury@houston.rr.com</A>] </FONT>
<BR><FONT SIZE=2>Sent: Friday, 14 May 2004 05:04 AM</FONT>
<BR><FONT SIZE=2>To: discussion@nsrca.org</FONT>
<BR><FONT SIZE=2>Subject: Re: YS 140 DZ going lean in -ve g maneuvers</FONT>
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<BR>
<P><FONT SIZE=2>John</FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>It's likely that the DZ isn't any more susceptible to air in the fuel supply than any other engine, just that the "standard" YS pressure system is very good at preventing those sort of problems. I've run 3 DZ's in a couple of different airplanes with a variety of fuel systems. Generally, they all work well and include a bladder, an open vent / foam clunk, check valved vent / foam clunk, pipe pressure / regular clunk, combining for around 100 gal. of fuel or so. I've settled on an open vent / foam clunk system with the vent routed behind the tank, then forward (1/8" aluminum tubing) to exit.</FONT></P>
<P><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>All the various systems work well, however any configuration that doesn't relieve expansive pressure (say, from sitting in the sun), as well as bladder systems or a high tank, will flood the engine unless some form of positive fuel shut-off is incorporated.</FONT></P>
<P><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>I've seen a couple of systems where the tank was solidly mounted for use with an L that would result in a lean stoppage a couple of minutes into the flight with a DZ. Our old friend - fuel foaming. These systems will generally run OK on the ground as vibration is damped by holding it. Go back to basics and isolate the tank from vibration, the foam clunk may reduce this problem but not fix it.</FONT></P>
<P><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>If a high time DZ begins to sag on uplines as the tank nears empty it's likely that there is wear between the upper pushrod and the pump housing. It's simply easier to draw air from the high pressure area of the rocker cover plenum than fuel from the tank a foot or so below the pump. These engines will also tend to load up during sustained idle as fuel is leaking, via the same route, into the (now) low pressure area of the rocker plenum. Replacing the upper intake pushrod and pump housing fixes this. This is not likely a problem with an engine not having used 50 gal. of fuel.</FONT></P>
<P><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>Earl</FONT>
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<P> <FONT SIZE=2>----- Original Message ----- </FONT>
<BR> <FONT SIZE=2>From: Lees,John W <<A HREF="mailto:jlees@mwdh2o.com">mailto:jlees@mwdh2o.com</A>> </FONT>
<BR> <FONT SIZE=2>To: 'discussion@nsrca.org' </FONT>
<BR> <FONT SIZE=2>Sent: Thursday, May 13, 2004 11:33 AM</FONT>
<BR> <FONT SIZE=2>Subject: RE: YS 140 DZ going lean in -ve g maneuvers</FONT>
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<P> <FONT SIZE=2> I thought DZ's were crap, had several different tanks, clunk's, ect. Not until I went to a Bladder tank{no air in media} did the engine run flawless. Since then it has never even hick-upped. </FONT></P>
<P> <FONT SIZE=2>It is of my opinion that the DZ will not tolerate any air in the fuel delivery system. --john</FONT>
</P>
<P> <FONT SIZE=2>-----Original Message-----</FONT>
<BR> <FONT SIZE=2>From: PENNISI Peter [<A HREF="mailto:Peter.Pennisi@publicworks.qld.gov.au">mailto:Peter.Pennisi@publicworks.qld.gov.au</A>]</FONT>
<BR> <FONT SIZE=2>Sent: Wednesday, May 12, 2004 5:29 PM</FONT>
<BR> <FONT SIZE=2>To: discussion@nsrca.org</FONT>
<BR> <FONT SIZE=2>Subject: YS 140 DZ going lean in -ve g manoeuvres</FONT>
<BR>
<BR>
<BR> <FONT SIZE=2>Hi all,</FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2>My DZ has only returned from holidays in Japan were it was repaired by YS from another cam failure.</FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2>The engine is running absolutely superb except when you pull high negative g manoeuvres like the reverse humpty bump it gets a little lean for a few seconds put it does come good.</FONT></P>
<P> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2>I have re-plumbed the model put the problem is still there. </FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2>Running</FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2>APC 16 x 12</FONT>
<BR> <FONT SIZE=2>OS F plug</FONT>
<BR> <FONT SIZE=2>Tetra 20 oz tank with OS sintered(Spelling) bubble less pickup.(Yes the expensive one)</FONT>
<BR> <FONT SIZE=2>Hatori exhaust (698 pipe)</FONT>
<BR> <FONT SIZE=2>Coolpower 30% heli blend</FONT>
<BR> <FONT SIZE=2>Model is ZN-LINE Alliance.</FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2>Any suggestions</FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2>Peter</FONT>
<BR> <FONT SIZE=2> </FONT>
<BR> <FONT SIZE=2> </FONT>
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