[NSRCA-discussion] YS140DZ idle question-answer

Tue Aug 1 05:42:43 AKDT 2006

FYI  - I  got the pump screw directions backwards.

Out is lean and in is richen. Said another, way, out" is less effective and 
"in" is more effective as regards the fuel supply rates.

Eric

----- 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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