[NSRCA-discussion] YS140DZ idle question-answer

Tue Aug 1 05:46:53 AKDT 2006

How critical is tank location?

John Ferrell    W8CCW
"My Competition is not my enemy"
http://DixieNC.US

----- Original Message ----- 
From: "Earl Haury" <ehaury at houston.rr.com>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
Sent: Tuesday, August 01, 2006 7:50 AM
Subject: Re: [NSRCA-discussion] YS140DZ idle question-answer

> Bob gets the award for proper description of the YS D engine series fuel
> system. Yamada san is a very innovative designer!
>
> As Bob states - fuel is "sucked" from the tank on the pump piston 
> downstroke
> (low pressure in the pump results in atmospheric air pressure "pushing" 
> fuel
> from the tank). Appropriate inlet / outlet check valves within the pump
> provide for incoming fuel draw or outgoing fuel injection.
>
> The pump is a positive displacement piston pump, ingeniously fitted into 
> the
> intake valve pushrod which provides motion that is timed to the intake
> stroke of the engine. The output of the pump is determined by pump size /
> stroke and pump rate (engine rpm) - this output is controlled by the 
> needle
> valve (high end) and the throttle barrel slot. As with all positive
> displacement pumps transferring fluids (non-compressible), there must be
> some way to accommodate excess volume (i.e. closing the throttle at high
> rpm) or parts will break! A spring vs. fuel pressure against a diaphragm
> regulator provides an internal return path from the pump outlet to the 
> pump
> inlet - recirculating excess fuel. Another ingenious YS design application
> is that the regulator spring pressure is modulated by crankcase pressure
> (against the spring side of the diaphragm) - increasing pressure at high
> rpm. Because of this - idle mixture can be changed by adjusting the idle
> fuel pressure with the tension of the regulator spring. Of course - 
> changing
> the spring tension also affects the high end pressure (CC + spring) and 
> must
> be accommodated with appropriate needle valve changes.
>
> For those still convinced that the regulator on the front of the pump is
> actually "the pump" - I suggest that you remove the crankcase pressure 
> line
> between the regulator and the engine and run the engine (it'll lean out at
> WOT but can be richened with the needle) - fuel will still be pumped just
> fine!
>
> Earl
>
>
>
>
> ----- Original Message ----- 
> From: "Bob Kane" <getterflash at yahoo.com>
> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> Sent: Monday, July 31, 2006 10:14 PM
> Subject: Re: [NSRCA-discussion] YS140DZ idle question-answer
>
>
>> No. The DZ series does not use a pressurized fuel
>> system. The fuel is "sucked" from the tank by the fuel
>> pump on the down stroke of the intake pushrod (valve
>> closing), and "squirted" out to the injector as the
>> intake valve pushrod opens the valve. The regulator on
>> the front of the fuel pump limits the fuel pressure by
>> opening when the fuel pressure is sufficient to
>> overcome the spring tension in the regulator. The
>> spring is much stiffer than the spring in the FZ/L
>> series motors. There is no low end adjustment on the
>> carb in the DZ series, so the regulator is used to set
>> the idle mixture. Start the engine, set the high end
>> needle as you would on any other YS, pull the throttle
>> back to idle. If the engine slows down and dies, it is
>> rich, turn the regulator out to lean it. If it speeds
>> up and dies, it is lean, turn it in to richen it.
>> Recheck the high speed needle.
>>
>> These engines will not tolerate restrictive fuel
>> filters. I am currently using a Sullivan Crap Trap to
>> keep the big boulders out of the fuel system and it is
>> working well. I'm still playing with using a check
>> valve on the vent side of the tank. It works well
>> without it but I get some leakage out of the vent.
>>
>> I have recently been through an extensive learning
>> experience with the pump system on these engines. If
>> the fuel lines past the pump blow off the fittings,
>> the pump regulator is set too rich or is sticking
>> closed. If you are having trouble with the adjustments
>> it might be time to have the pump/engine serviced.
>>
>> I will say the power of the 160DZ is incredible, way
>> more than what is needed to pull my Temptation through
>> the Masters sequence. I'm running an APC 18.1X10 prop,
>> the thing pulls like a locomotive and slows down as if
>> you threw the anchor out. Vertical uplines, even with
>> rolls are just over half throttle. The only possible
>> disadvantage is the prop is heavy and will probably
>> cause more rapid conrod wear.
>>
>>
>> --- vicenterc at comcast.net wrote:
>>
>>> Eric,
>>>
>>> I got a new YS 160 DZ.  Is this procedure equivalent
>>> for both engines?
>>>
>>> Thanks,
>>>
>>> Vicente "Vince" Bortone
>>>
>>> -------------- Original message -------------- 
>>> From: "Grow Pattern" <pattern4u at comcast.net>
>>>
>>> Michael,
>>>              The big and first thing to remember is
>>> that the DZ uses a pump. If you keep thinking about
>>> the pump as a regulator it may not help you set your
>>> engine. Unfortunately the instructions call it a
>>> regulator. The fuel is metered out to the carb by
>>> the pushrod action and the "pulsating" crankcase
>>> pressure operates the pump side.
>>>
>>> The next thing is that the carb does two things. It
>>> controls the air flow to the inlet valve and the
>>> fuel supply to the injector. Even though the needle
>>> effects all of the fuel flow it is not the right
>>> thing to use to get a good idle. Many people
>>> accidentally/unintentionally override the pump
>>> settings with the main needle to get a good low-end
>>> rpm.
>>>
>>> The "regulator" screw restricts the primary fuel
>>> flow and is the one that you must use to set an idle
>>> and transition. If you get the big brass screw set a
>>> bit too rich it will keep dousing the plug,
>>> especially at low rpm.
>>>
>>> The trick to a good setting is to keep closing the
>>> pumped fuel supply until the engine will not run any
>>> more.
>>>
>>> You do this by turning the big brass screw clockwise
>>> about 1/8 of a turn and then start and warm up  the
>>> engine. Keep the main needle at about 1.5 turns or
>>> more and don't worry if it runs a bit rich as you
>>> open the throttle about half way, in short bursts.
>>> Do this again and again until the engine will not
>>> start or keep running at idle or open up.
>>>
>>> You are now very close. Turn the brass screw back
>>> anti-clockwise about 1/8 of turn. and see if the
>>> engine will start and idle. It should be able to go
>>> as low as, and hold about, 1.500 rpm.for about a
>>> minute. If the throttle smoothly increases the rpm
>>> you have a good low-end setting. (Go more "open" on
>>> the brass screw if it is needed to keep it running).
>>>
>>> Now is the time set your top-end needle. It may need
>>> more or less fuel so please open up carefully and
>>> listen for the warning "bark". Richen the main
>>> needle if it barks. If all goes well, set the
>>> high-end needle for max rpm and then richen it back
>>> about 500 rpm.
>>>
>>> After that it should run like a Swiss-watch, start
>>> better, and last a good while. It should not quit in
>>> the air or on the ground.
>>>
>>> Please let me know if this worked for you.
>>>
>>> Regards,
>>>
>>> Eric.
>>> ----- Original Message ----- 
>>> From: Michael Cohen
>>> To: NSRCA Mailing List
>>> Sent: Sunday, July 30, 2006 2:31 PM
>>> Subject: [NSRCA-discussion] YS140DZ idle question
>>>
>>>
>>> OK list, I have a question for you.  I have a 140DZ
>>> that will not idle below 2300ish RPM.  Richard
>>> Lindberg and I have adjusted the regulator, but it
>>> appears to have little or no effect.  I might be
>>> able to get one flight in, but eventually, on a down
>>> line, it will die and 7 dead sticks are not that fun
>>> to try.   Full power seems to hold just fine.  We
>>> figured there might be an air leak, and that is why
>>> it seemed to idle worse after a warm up flight, so I
>>> replaced the valve cover gasket and the other
>>> gaskets at the backplate, but that did not seam to
>>> make a difference.  Anybody got any ideas besides
>>> the usual OS/Webra/Mintor/E-power/power slope
>>> soaring comments?
>>>
>>>
>>>
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>>
>> Bob Kane
>> getterflash at yahoo.com
>>
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