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ulflyer(at)verizon.net
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 Posted: Fri Feb 19, 2010 7:12 am Post subject: Valley Engineering Big-Twin - Any one flying with one? |
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Hey guys, we know about Rotax's - I want small - light would be nice
4-stroke engine. The HKS is too pricey, even the small Rotax's are
becoming over priced. What I'm looking for is experience reports
from any folks running the Valley Engineering Big Twin. (The Big
Twin is a customized Genac engine with a reduction drive added, not
a half VW. I've flown behind a Global version of the half VW, don't
care to repeat that experience again. I know there are couple Kolb
running this engine but not much feedback as to their experience
especially if compared to Rotax on that same type of plane.
I don't expect the Big Twin to have the performance of a 503, or 477
for that matter but with the redrive it should out perform a half VW
solution. I know the Stark's are running one on a Kolb, but I'm
looking for some other honest evaluation from those actually running
the engine. My application isn't for a Kolb, it is for a
ThunderGull. So if you running one or know of or have directly
observed one in operation, I would like to hear what your experience
is with the engine.
Thanks,
jerb
At 07:06 AM 2/18/2010, you wrote:
| Quote: |
elleryweld(at)aol.com wrote:
> I put over 900 Hours on a 447 Rotax single ignition in my old
firestar without a problem nice little engine in my book easy on
fuel plenty of power for a heavy firestar I thought,and I could out
climb any thing at any airport and I could stay with a bunch of
friends GA planes and go bye a few of them with it.
> the 503 another good engine plenty of power some people
really think they need it because it has dual ignition compared to
the 447 I have flown with the 503 a lot less hours but plenty of
friends have them that I fly with and I can only say they have had
ignition problems more than I have on much newer engines
> just my experience
>
The only engine-out I've ever had flying a 2-stroke was with the 447
and it was an ignition "problem". I put quotes around that because
the fault wasn't with the engine, it was a wiring problem of mine
that I introduced when I installed it on the plane.
But you do indeed have one and only one ignition system on the engine.
I did and do feel a little more comfortable with the 503 as a
result, but I'll still happily fly a 447 too just keeping the lack
of redundancy in the ignition in mind.
The 447 is the longest-lasting engine in the 2-stroke line followed
closely by the 503. The only other drag about the 447 is it tends to
run hotter especially at higher power settings. It's basically a
suped-up 377 with a much better provision 8 crankcase and bottom
end, so the cooling isn't quite as good as on the 503.
I think Steve Beatty has something approaching 1400 hours on a 447
and it's still going. In the field, there's lots of guys with over
500 hours and getting near 1000 with the 447.
IMO, the 447 and 503 are aviation's best kept secrets in the 40 and
50hp range. Lots of folks are out paying 10 grand for 4-strokes
because they're afraid of the 2-strokes for some reason. But us guys
who've spent a lot of time in front of/underneath the air-cooled
rotaxen enjoy the higher bang/buck ratio they offer  .
LS
--------
LS
Titan II SS
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ulflyer(at)verizon.net
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| Posted: Fri Feb 19, 2010 7:47 am Post subject: Valley Engineering Big-Twin - Any one flying with one? |
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At 11:03 AM 2/18/2010, you wrote:
| Quote: | Herb,
I think the biggest application of the Generac is as a generator. But, that aside, you're probably correct regarding their use in aircraft.
You know what would be nice???? A spreadsheet that list ALL engines in a certain power range....say 40-55 HP. Rotaxes, Generacs, half VW, Victor, Cuyuna, Victor, etc., etc. etc. All of 'em!!
Then, try to list their atributes, like TBO, cost per hour, maintenence interval, GPH, rebuild costs, number of hours of proven use, etc.
This would be a big list, but it would make for interesting reading. You could also cover different engines in the 60-80 HP range, and finally, the 80-100 HP range.
Mike Welch
Reply to above: |
Interesting but the problem as I see it is I don't feel there is enough quantifiable information on a population of each type of engine out side of the Rotax's to produce a creditable rating. In effect, you're just reproducing Kit Planes engine directory.
jerb
[quote][b]
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ulflyer(at)verizon.net
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| Posted: Fri Feb 19, 2010 7:47 am Post subject: Valley Engineering Big-Twin - Any one flying with one? |
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Excellent feedback and appears excellent folks there at Valley
Engineering. Always liked those folks. Think of this as early days
of the Rotax - adapting the snow mobile engine to aircraft use. Teething.....
Jimmy, do you think you may have been over propping the engine not
allowing it to generate the RPM it needed to produce the HP - best to
prop to be in the highest torque area.
jerryb
At 11:51 AM 2/18/2010, you wrote:
| Quote: |
List,
I did a few in-detail posts of my experience with the Valley-Generac
Twin V, they should all be in the archives.
To clarify a few comments made today,
1) Valley Engineering does not cut down the flywheel in any way on
their version.
2) They (Valley Eng.) do suggest to mount the engine direct to the
airframe. My opinion is, not a good idea. Even though it's a fairly
smooth engine, it's not smooth enough to do that, at least it wasn't for me.
3) I tried 4 different props. A 3-blade 72" IVO, 2 blade Culver 76"
39 degree pitch, a 2-blade 76" Culver 41 degree, and a 2-blade 78"
Culver, either 41 or 39 degree, can't remember. There were subtle
differences between each, nothing substantial. I got a little better
cruise speed with the 76" 39 degree over all the others, but cruise
speed was not the problem I was trying to overcome, it was lack of
adequate climb rate, and none of them solved that.
4) Yes, today I am broke, own an HKS, and am very happy with it.
I also had a bit of a rum-rum harmonic issue going on as well with
the Twin V, and Larry Smith at Valley told me they had that problem
solved with a different redrive ratio. Also, the last time I spoke
with Larry they were trying out a different cam grind to get more
power out of the Twin V, and at that time they had given up on the turbo ideas.
They are very good folks at Valley Eng., even took my engine back at
a fair discount. They worked hard with me to try and make the engine
perform to my satisfaction. Bottom line was, the Twin-V was not
enough power for my application.
--------
Jimmy Young
Missouri City, TX
Kolb FS II/HKS 700
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Jimmy Young
Joined: 24 Nov 2007
Posts: 182
Location: Missouri City, TX
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| Posted: Sat Feb 20, 2010 6:58 am Post subject: Re: Valley Engineering Big-Twin - Any one flying with one? |
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| Quote: | Jimmy, do you think you may have been over propping the engine not
allowing it to generate the RPM it needed to produce the HP - best to
prop to be in the highest torque area.
jerryb
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Jerry,
I do not remember the specific max rpms with each individual prop, but all of them turned between 3550 & 3700 at WOT. The max rpm is (at) 3600. The 40 HP (at) 3600 rpm claim comes from Valley Engineering. I do not know if that # comes from a dyno test session or not, you would have to ask them. Generac rates it at 33 HP continuous, I think that was at 3200 rpm.
Regardless of all the power claims, the engine did not have the necessary power required to fly my plane safely.
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_________________
Jimmy Young
Missouri City, TX
Kolb FS II/HKS 700 |
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