YS DZ160s... OS-160 EFI

Wed Jan 21 08:08:07 AKST 2004

That's an excellent observation, Ed.
Since it seems to be impossible to add a voice to this (sometimes) argument without declaring what side you are on: let me say that I was very happy with my very reliable four-cycles, and after a fair amount of experimentation, I am now happy with the two-cycles. I have always harbored suspicions about the aerodynamic effects from the huge chins that are required to package a four-cycle. I think that electrics may offer the ideal, but for now ...

I used to prop my reworked 120ACs down to 7,200 RPM, with a narrow-bladed 16-13.
Of course, that RPM was with a rich setting, as required to prevent pre-ignition with the necessary 30% nitro.
The quiet was great! The flexibility to run large diameter and or very high pitch props was welcome.
When the two strokes became legal, I was pleased to find that I could easily run in the mid-sevens.
The FZ 140 (still a sweetly behaved engine) really needed to be propped just under 8,000 RPM, provided the prop would allow the engine to unload to about 8,500 or above. It wanted 12 pitches, not 13s: it needed to unload with P/D ratios more like 77% (think 15.5 X 12) rather than the 85% (15 X 13 wide or 16 X 14) that was my typical with the AC. The quiet suffered, some. Remember, my home field has a 92 dB limit on chicken wire topped table. It appears to be equivalent to a 94 dB limit on pavement.

When it comes right down to it though, there is no substitute for cubic inches, and we are interested ion power-to-weight.
Big engines can still be light, as proven by Yamada, Mintor, Webra, and most dramatically Jett (with their built for CL Stunt RoJett 40 ... now that little critter is practically weightless!)
Regards to All,
Dean P.

-----Original Message-----
From: Ed Miller [mailto:edbon85 at optonline.net]
Sent: Wednesday, January 21, 2004 6:09 AM
To: discussion at nsrca.org
Subject: Re: YS DZ160s... OS-160 EFI

What's interesting in the 4c vs. 2c comparison is the fact that as the 4C YS
has evolved, it needs to be propped to spin faster than the older generation
YS 4C's to stay on it's power curve. Although Yamada has increased the
displacement to the practical limits of the existing case size, he still
needed to compress and time the engine for a higher rpm range in order to
increase power output at the expense of some low end grunt. By comparison,
the newer 2C's seem to be very content to run at 8K to low 8K range which is
nearly silent with 15" 3 blade props. I can remember some older YS 120's
being propped at a very quiet 7500rpm hauling around some very large ( mid
90's over 2meter Omen ) and over 10lb airframes. One would think the 4C
would have the "torque" to spin a heavier load at a lower rpm than the 2C,
but not so when you factor in the natural tuning affect of a pipe/muffler on
the current crop of  2C 's. There is no question in my mind that the 140DZ
is not in the same league top end power wise as the OS140's, 160's, Webras
and Mintor's provided they are on a PIPE and or a very large volume muffler,
in either case something that provides some tuning affect.  Blow a coupler
on a piped 2C at the wrong part of the FAI schedule and watch all that power
disappear. Watching Danny Landis fly the 140 DZ in a 10 3/4 lb Partner in
2003 and a Smaragd in 2002, what disturbed me most about the 140DZ was it's
violent shaking and fuel appetite. What surprised me was Danny's 140DZ's
could not spin the APC/Lockhart 15.75x11 3 blade that the OS and Webra 2C
spin effortlessly.. Fuel consumption I can deal with but hopefully the 160DZ
will be somewhat smoother and more powerful than the 140. It's amazing that
the YS has come from that small valve 120 version first seen here in the
late '80's to the 140 and now 160 fuel injection version today and yet it
still occupies the same footprint as the original 120. Quite an engineering
feat.
Diehard YS fan going OS 2C in '04 but keeping a watchful eye on 160DZ's for
'05.
Ed M.

----- Original Message -----
From: "David Lockhart" <DaveL322 at comcast.net>
To: <discussion at nsrca.org>
Sent: Tuesday, January 20, 2004 11:17 PM
Subject: Re: YS DZ160s... OS-160 EFI

> And...as long as the 2C contingent is speaking up........
>
> The modified 3 blade that I run has been tried on a number of different
> engines - OS140 EFI, OS 140 RX, OS 160 EFI (Jason's, along with some other
> props as he mentioned), Webra 145/160, and YS140DZ.  The 3 blade runs
quite
> nicely on the 2Cs w/ 15-20% nitro.  The 140DZ won't handle the prop even
> with 30% nitro.
>
> Regards,
>
> Dave Lockhart (no engine sponsorship here!!)
> DaveL322 at comcast.net
>
> PS - I've seen several 160 FX and EFIs run well - but none would keep up
> with "THE ONE" Jason has - that particular sample must be the one were all
> the tolerances are just perfect.
>
>
> ----- Original Message -----
> From: "Jason" <jasonshulman at cox.net>
> To: <discussion at nsrca.org>
> Sent: Tuesday, January 20, 2004 10:55 PM
> Subject: RE: YS DZ160s... OS-160 EFI
>
>
> >
> > Chips DZ 160 was close, but not as powerful as my OS-160 EFI. I don't
have
> > #s cause we never ran the same props, and I don't usually tach my
motors,
> > but it didn't seem to have the same pull. For fun at the TT I asked Dave
> > Lockhart to pitch UP a 15.75x13 3-blade and ended up with a 14.75 pitch.
> It
> > flew my 10 3/4 pound Shadow....and I was amazed. Although it was way too
> > fast, it still went through the sequence fine. I flew it again a couple
of
> > weekends ago to learn the new patterns and it's just unbelievable the
> power
> > this thing has. It's more powerful than the 1.70 I had in it's twin, and
> > different power from the electric. If I get my pipe fixed and it doesn't
> > rain this weekend, I'll tach it this weekend.
> >
> > Jason, the lonely sponsored 2-stroke (& electric) pilot
> >
> >
> > -----Original Message-----
> > From: discussion-request at nsrca.org
> > [mailto:discussion-request at nsrca.org]On Behalf Of Jerry Budd
> > Sent: Tuesday, January 20, 2004 8:48 PM
> > To: discussion at nsrca.org
> > Subject: Re: New YS DZ160s
> >
> >
> > Hi Troy!
> >
> > >We already know the 140DZ can keep up with any of the 2 strokes...
> >
> > Any?  Not exactly.  And certainly not mine (for that matter, neither
> > of the two YS160's flown at last years Nats came anywhere close
> > either).  Prop for prop I was turning 300-500 rpm more than ANY four
> > stroke I came across.  How do I know?  I asked their owners.
> >
> > The simple reality is that most non-sponsored pilots are running 2
> > strokes, and most (but not all) sponsored pilots are running four
> > strokes.  I'll leave it to the audience to speculate as to why that
> > is...
> >
> > Jerry
> > --
> > ___________
> > Jerry Budd
> > mailto:jbudd at qnet.com
> > =====================================
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> > #
> >
> >
> > =====================================
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> > #
> >
>
> =====================================
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