Hirth or 2Si experience?
Justin and Daphne Travis
The Hirth 2702 and the new 2Si 460L-46 seem the be the best alternatives so
far to me. If anyone has any experience with either of these brands I'd
appreciate some input.
Thanks,
Justin Travis
Batesville, MS. USA
jus...@panola.com
mike vaughn
popular. I like the idea of a US made engine, but there must be some
history or the 2si would be more popular. What's up with this? Anybody
wnat to let us in on the story?
David Ohnsager
now without any problems. It's a good, solid, reliable engine that so far
has lived up to the hype. Will let you know if it goes 1000 hrs without a
rebuild, but at 250 hrs it still looks brand new both inside and out.
The 2704 is 50HP with a 5000RPM redline. Fuel economy is 2.4GPH in a
single seat FAR 103 legal UL, and 2.7GPH in a two-place UL trainer. Both
figures have been verified by at least four people.
Service is good, and parts availability is not a problem now that the
Canadians are out of the picture. Earlier Hirth horror stories that I
heard were traceable to them. It's a shame that an apparently good engine
got off to a bad start in the USA because those guys in the Great White
North had some problems.
A word of caution: The manual recommends a 10 HOUR GROUND RUN BREAK-IN.
DO IT! Do NOT fly off the hours; do NOT shortcut the break-in. Out of
ignorance (not knowing it all beforehand) I read the manual (horrors!)
and followed the procedure (my gawd! I must be sick!!). My engine has
been flawless. Another guy where I fly was very knowledgeable and just
KNEW that an hour or two was all the break-in he needed. He blew up his
2706 TWICE! First time was a relatively minor blow-up requiring new
pistons and cylinders. After replacing them he did another hour or two
break-in then flew off the remainder again. The second failure grenaded a
piston sending shards of connecting rod and piston skirt clean through
the bottom of the case. Totaled the engine. If you select the Hirth I
recommend that you assume a posture of ignorance no matter how infallible
your knowledge or great your experience and trust that the engineers at
Hirth know what they're talking about.
I should note that there are now over a dozen Hirths flying out of the
airfield I use and all of them decided to follow the recommended break-in
after the guy blew up his 2706. None of them have had any engine seizures
or failures. Striped bolts have been a problem with one engine, but the
rest have had no problems that I'm aware of.
What happened to the guy with the 2706? He bought another one and broke
it in right. Hasn't had any problems since, and loves his engine. I guess
the third time's the charm. Or maybe you CAN teach an old dog new tricks!
Hope this helps.
Regards,
DAO
In article <6uk9fe$83f$1...@supernews.com>, jus...@panola.com says...
ra...@my-dejanews.com
"Justin and Daphne Travis" <jus...@panola.com> wrote:
> I've been researching some alternatives to the Rotax 447 engine.
> The Hirth 2702 and the new 2Si 460L-46 seem the be the best alternatives so
> far to me. If anyone has any experience with either of these brands I'd
> appreciate some input.
> Thanks,
> Justin Travis
> Batesville, MS. USA
> jus...@panola.com
>
>
Flitplane builders log is interesting.
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Steve Lyons
Thanks for the info. that you have provided for everyone here. I am
seriously considering purchasing the 2704 engine to put on my single
place trike. A friend of mine has the 65HP 2706. These 2 engines
appear to be identical in all respects except for the torque/hp rating.
The 2704 is rated 50hp @ 5000 RPM and has 52ft.lbs of torque @ 4500 RPM.
The 2706 has 65hp@6200 RPM and has 56ft.lbs of torque @ 5700 RPM. Both
engines are 625cc, both have the same bore and stroke, both have the
same compression ratio, and both have the same size dual 38mm carbs. Do
you happen to know what specifically is different about these 2 engines?
How would this different torque/hp rating between the 2 engines
translate to real world performance dfferences on an aircraft? Thanks
in advance.
Steve Lyons
Is your group of Hirth engine fliers having good luck with their Hirth
gearboxes? Do you think that the Hirth gearbox is better than the Rotax
C-box?
Why did the Hirth engines initially receive such bad press here in the
USA? You mentioned something about the experience of the Canadians.
Thanks again.
Greg Johnson
listed as 3GPH at 3000 rpms. Are you doing better then this?
http://www.recpower.com/2704.htm
> > I've been researching some alternatives to the Rotax 447 engine.
> > The Hirth 2702 and the new 2Si 460L-46 seem the be the best alternatives so
> > far to me. If anyone has any experience with either of these brands I'd
> > appreciate some input.
> > Thanks,
> > Justin Travis
> > Batesville, MS. USA
> > jus...@panola.com
--
Greg Johnson
Mount Vernon, IL
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David Ohnsager
> At what rpm are you getting 2.4GPH? I went to RPE site they got it
> listed as 3GPH at 3000 rpms. Are you doing better then this?
>
> http://www.recpower.com/2704.htm
>
Greg,
In the true Ultralight I was running about 3700RPM if memory serves me. I
sold the bird nearly two years ago, and only had the Hirth on it for
break-in, anyway (AFTER the ground-run break-in, that is! :-)). It
seriously overpowered the aircraft, but delivered a truly spectacular
rate of climb. It was fun, but almost scarey to fly.
In the two-place trainer I run at about 4100RPM, give or take, depending
on the weight of the student.
As I said, the fuel economy figures have been independantly verified by
at least four people and they are repeatable. I repeat them every time I
fly. :-)
I was surprised by the fuel economy myself. My first UL had a Rotax 377
which never got better than 3.4 GPH, even after an overhaul. When I
replaced it with an engine with 15 more HP I had a hard time believing
that my fuel consumption DROPPED by 1 gallon per hour! But I checked it
again and again, and the economy figures were (and are) real.
I run a three-blade 72 inch Powerfin prop, and that may or may not have
something to do with it. The legal UL was a Spectrum Beaver RX28; the
trainer is an RX550. I also fly near sea level, rarely climbing much
above 1500ft. That's true sea level, too; I fly near Puget Sound a lot.
That might have something to do with it, as might the fact that
temperature is rarely extreme in the Pacific Northwest.
For whatever reason, the fuel economy figures are real. The other Hirths
that fly where I do report similar figures, and none report fuel
consumption above 3 gallons per hour unless something is wrong with the
carbs. We have examples of most of the Hirth lineup flying now, so I can
say with fair certitude that Hirths are relative fuel misers as far as
two-strokes are concerned.
The latest Hirth to appear at Arlington is an 80HP flat four that's being
fitted to a RANS S12-XL. It runs smooth and quiet, looks great, and
sounds like a big outboard motor. It hasn't flown yet, but was scheduled
to do so today. I don't think it happened because the test pilot went
home early. If THAT puppy turns in a 2.7GPH fuel burn I'll have to
believe that either the engines manufacture fuel, or the pilot was
smoking something illegal.
I have no idea why Rec Power claims a higher fuel burn unless Matt is
being conservative. I wouldn't blame him for being cautious; he took a
lot of flak during his association with the Canadians. Still... 3GPH at
3000RPM? Not in MY experience!
Hope this answers your questions.
Regards,
DAO
David Ohnsager
jet...@webtv.net says...
The engines ARE identical in many respects, including the ones you
listed, but they are not identical in every respect.
I'm not a mechanic, but I think Clare Snyder got it right when he (she?)
said compression ratio and porting are different. Timing is also
different if my recollection of what a real Hirth mechanic said is
accurate.
I have been told that you can convert a 2704 into a 2706 by changing
cylinders, heads, and timing. Everything else stays the same. The
mechanic where I fly keeps offering to do the mod, but I keep declining.
Why mess with a good thing and risk screwing it up?
I like the idea of an engine that's capable of working lots harder than
it does because that implies some reserves in the construction and
oprating parameters. A 50HP 2706? Sounds good to me! Maybe it will last
longer and be more reliable!
The trike guys around here run 2706's when they run Hirths. I don't know
what that says about power unless they're into wretched excess. I know I
am, so maybe we're kindred spirits. Other than that, I don't know what to
tell you about the relative merits of the two engines on trikes.
David Ohnsager
jet...@webtv.net says...
> David:
>
> Is your group of Hirth engine fliers having good luck with their Hirth
> gearboxes? Do you think that the Hirth gearbox is better than the Rotax
> C-box?
At Arlington, yes, but I have seen two demolished gearboxes. One came off
an airboat; the County Sherriff search and rescue team slammed it into a
tree, or something, at high speed and brought it back in a bag. The other
came apart on an airplane in California, or someplace. These were the old
style gearboxes.
The new boxes seem to be better all-round. They seem to be more robust,
and they have a shock absorbing donut instead of the star-shaped shock
absorber in the old boxes. Most of us have switched to the new boxes at
the urging of the Hirth dealer at Arlington. I never had any trouble with
my old gearbox, but I switched anyway. Rather be safe than sorry, I
always say!
I've been told that the new Hirth gearbox is a clone of the Rotax C box.
If this is true, it implies that both boxes are similar in performance
and reliability. Beyond that, I don't know, and even that much is
hearsay.
>
> Why did the Hirth engines initially receive such bad press here in the
> USA? You mentioned something about the experience of the Canadians.
> Thanks again.
>
From what I've been told, the problems were related to 1) lack of parts,
2) lack of service, 3) failure to provide warrantee service, and
4) incomplete engineering development of the engines. According to my
sources, the first three were caused mostly by the original distributors
for North America and, to some extent, by the factory in Germany. But I
wasn't around back then, so I can't say for sure.
The fourth problem is uncharacteristic of German engineering, but DOES
appear to be true. Several major upgrades have been made to Hirth engines
since I acquired mine, and most (but not all) of them have been
retrofitable to my engine. It's nice to know that the factory has an on-
going development program, but it's not so nice to know that my engine
was an interim configuration. If it didn't run so well I might even be
upset.
New Hirths have some sort of magical electronic ignition that's supposed
to be just marvelous. I've seen it, but don't have it because I can't
retrofit it to my engine without a lot of expensive parts. Like the
crankshaft and the entire ignition system.
I've been told that next year will see computer controlled fuel injection
(as an extra co$t option) on top of the superhero ignition. If it
happens, and it works well, and it's reliable, I'll buy a new engine with
all the bells and whistles. Until then I'll just float along with what
I've got.
Regards,
DAO
Clare Snyder
Lyons) wrote:
>Hello David:
>
>Thanks for the info. that you have provided for everyone here. I am
>seriously considering purchasing the 2704 engine to put on my single
>place trike. A friend of mine has the 65HP 2706. These 2 engines
>appear to be identical in all respects except for the torque/hp rating.
>The 2704 is rated 50hp @ 5000 RPM and has 52ft.lbs of torque @ 4500 RPM.
>The 2706 has 65hp@6200 RPM and has 56ft.lbs of torque @ 5700 RPM. Both
>engines are 625cc, both have the same bore and stroke, both have the
>same compression ratio, and both have the same size dual 38mm carbs. Do
>you happen to know what specifically is different about these 2 engines?
>How would this different torque/hp rating between the 2 engines
>translate to real world performance dfferences on an aircraft? Thanks
>in advance.
>
I believe the difference is in compression ratio and porting. A 30%
difference in power would definitely be noticeable.
As for the Hirth problems, it was the Canadiene problem, not the
Canadian problem, back when I had dealings with Hirth in the
snowmobile days (eatly 70s) If you didn't speak French, you had a
problem communicating.
In those same years the Cayuna and Chapparal engines (now 2SI) were
not as reliable as the Hirth, Rockwell JLO, CCW, Rotax, Sachs, etc.
Some of them were nightmares as well.
Snyder Enterprises
Appropriate Technology for the Information Age
Waterloo Ontario.
To reply please drop the r, and send to :
cls...@ibm.net
Too many misdirected replies plugging my mail box!!!
Justin and Daphne Travis
I also noticed that Hirth has a direct drive option. I suppose one would
need a gearbox or belt frive for a UL though...correct?
Justin Travis
BAtesville, MS. USA
jus...@panola.com
Steve Lyons
ratios of these 2 engines, the 2704 (50hp) and the 2706 (65HP) are
identical. 9.5 to 1.
William Gleason
He cancelled the order last month and the dealer made it right with him. At
least the dealer had integrity!
ra...@my-dejanews.com wrote:
> In article <6uk9fe$83f$1...@supernews.com>,
> "Justin and Daphne Travis" <jus...@panola.com> wrote:
> > I've been researching some alternatives to the Rotax 447 engine.
> > The Hirth 2702 and the new 2Si 460L-46 seem the be the best alternatives so
> > far to me. If anyone has any experience with either of these brands I'd
> > appreciate some input.
> > Thanks,
> > Justin Travis
> > Batesville, MS. USA
> > jus...@panola.com
> >
> >
David Ohnsager
Sorry to say I don't know the numbers. G27? G50? All I know them by is
"old" and "new".
My old box had a 2.11:1 reduction ratio. My new box has a 2.65:1, I
think. I'm not sure because I relied on the mechanic and prop builder to
select the right gear ratio for the prop. Sometimes it's handy to have
the prop manufacturer and the engine distributor at the same field. When
they collaborate you can be fairly sure you'll get what you need, and so
far everything is working great.
Regards,
DAO
donsu...@mindspring.com
experience. I have a Cuyuna 430 that has been around since 82. I just
overhauled it and still fly it. Most of the guys who have been around will
tell you that the Cuyunas were pretty good engines. In fact they were the
engine of choice before the "Rotorooters" took over the market. The reason
that they fell out of favor is because Cuyuna refuse to sell engine for
ultralights after a while because of the liability and focused on government
contracts instead. The new 2Si engines appear to be basically the same as
the old Cuyunas, especially the 430. Hope this helps.
William Gleason wrote in message <360FF673...@kodak.com>...
mike vaughn
SHOULD be a decent choice based on it's experience and the made in the USA
doen't hurt a damn bit either. (I didn't agree with NAFDA). Anyway, more
choices mean lower prices and better products. I hear the new liquids from
2si have great numbers., weight and HP. I like the fact that liquid cooling
reduces expansion co-efficient problems, and the damn things weigh less, and
as I understand, cost less to produce than fan cooled. Go figure.
nospam
>
>..... (I didn't agree with NAFDA [sic] ). Anyway, more
>choices mean lower prices and better products.
>.....Go figure.
>
??!!
Eugene Gill - please remove (nospam)
eugene@(nospam)americamail.com
http://www.mindspring.com/~egill
ultralivi...@gmail.com
> The Hirth 2702 and the new 2Si 460L-46 seem the be the best alternatives so
> far to me. If anyone has any experience with either of these brands I'd
> appreciate some input.
> Thanks,
> Justin Travis
> Batesville, MS. USA
> jus...@panola.com