[NSRCA-discussion] YS-160 setting

[Troy A. Newman]

Jas,

lean the pump a little bit about 1/4 turn and see if the motor starts to go 
lean in the transition.
The way this engine works is the pump pushes the same amount of fuel all the 
time. Every stroke it pushes the same volume of fuel. If the engine is at 
idle and not using the fuel then pressure builds up in the injector line 
until it gets to that magic pressure where the pump pressure screw allows it 
to bypass back to inlet of the pump. So everything the engine doesn't need 
gets pushed back around to the inlet of the pump for the next gulp.

If you are at idle, and the pressure control on the pump is too tight 
meaning not allowing enough to loop back around it will got in and get burnt 
and come out as lots of smoke at idle. Yet when you are at full power or at 
least upper end power the HS needle is set and the mixture is correct.  So 
what is happening is you have too much going to the engine and not enough 
bypassing around.

Lean the pump...CCW. If you get to lean on the pump is will start to 
detonate on throttle up or will sit and surge at idle. To be honest the pump 
setting are actually pretty broad and the engine will run correctly with 
many different setting. The key is the pump always moves the same amount of 
fuel. You are not adjusting pump pressure, you are adjusting the pop off 
pressure. Meaning the pressure which the little diaphragm will allow fuel to 
loop back to inlet. So adjusting the pump richer means more pressure on the 
spring and diaphragm so the pressure it takes to allow bypass is higher and 
as result more fuel goes to the engine. Less spring pressure on the 
diaphragm and the lower the pressure in the injector line needs to be to 
allow the bypass and the less fuel goes to the engine because the little 
pressure valves open sooner.


If it always pumps the same volume of fuel, and more is going to the engine 
it will burn and turn to smoke especially at idle and below 1/3 throttle.

Now that explanation was for everyone else. Here is the Jason answer.

Turn the little brass screw on the front 1/4 CCW and see if it helps! if it 
surges at Idle you went too far.

Troy


----- Original Message ----- 
From: "JShulman" <jshulman at cfl.rr.com>
To: "NSRCA" <nsrca-discussion at lists.nsrca.org>
Sent: Thursday, March 08, 2007 5:06 PM
Subject: [NSRCA-discussion] YS-160 setting


> Hi all,
>
> I've got my friends DZ and the high end needle is 1 1/8 turns out. The reg
> is somewhere around flush. It smokes and bunch, smooth transition, but 
> 20ozs
> in less than 8 minutes if I'm not careful. I remember hearing (being told)
> that there is a less consuming set-up that I haven't done yet. Anyone know
> what it is? Gonna fly again tomorrow and try it. Thanks.
>
> Regards,
> Jason
> www.jasonshulman.com
> www.shulmanaviation.com
> www.composite-arf.com
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