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brentbidus(at)juno.com
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 Posted: Fri Nov 10, 2006 9:30 am Post subject: Rotax 912 or 912S decision |
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List,
Looking for opinions on the suitability of a 912 on a Classic 4 at higher
elevations. I live at 6200 feet in Colorado Springs and need to make a
decision to go with a 912 or 912S. I already have the FWF kit, so my
choice is between these two options. If I have to buy new, a 912S is my
hands down choice. I have a lead on an older but never run 912 that may
save me a few thousand dollars. The money situation is tight, so if I'll
still get good performance at gross weight, I may go that route. If
those of you who have flown with a 912 at 10-12000 MSL think it is
underpowered, I'd rather know that upfront and continue to save for a
912S. Also, anybody have any experience with costs to have an older 912
checked out and all service bulletins complied with? Thanks,
Brent Bidus
Classic 4
Colorado Springs
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darinh
Joined: 20 Apr 2006
Posts: 327
Location: Utah
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| Posted: Fri Nov 10, 2006 10:33 am Post subject: Re: Rotax 912 or 912S decision |
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Brent,
I owned a model III with the 912 (80 hp). It had the model IV wing and a bunch of the other upgrades and mods that are standard on the IV. I considered it to be comparable to the IV and it had the 1200 lb. gross. I flew it out of Salt Lake City, Utah (4300' msl) and much of my flying was done in the Idaho backcountry with a number of landings at Fish Lake strip (around 6200' as I recall). I would routinely cruise at 9000' to 11000' msl when enroute. When I went into Fish lake we had me and my brother and around 1/2 fuel which was around around 1100 lb. total weight. I didn't have a problem getting in or out and the approach and departure is over a lake with notoriously strong downdrafts. On that departure, I could definately feel the effects of the downdrafts but the Kitfox gets off so quickly that I was alread 200'-300' agl over the lake...my climb rate was 400 fpm. All this being said, I sold the Model III because I wanted better performance at the elevations I fly from. Although the 912 will fly the IV and do it just fine, I would say it will not have the performance you will want in the highlands of Colorado. I would go with the 912S without a question. Spend the extra couple of grand and go with the 912S otherwise you will be unhappy.
Just for the record...as I said, I sold the Model III so I could have better performance at high elevations in the mountains...well, I am currently building a Series 7 that will get the 914 turbo and an Airmaster electric CS prop...nothing like producing full rated power regardless of conditions and the field elevation  She should climb like a homesick angel!
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lcfitt(at)sbcglobal.net
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| Posted: Fri Nov 10, 2006 10:44 am Post subject: Rotax 912 or 912S decision |
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Brent,
Our flying group has been in and out of Smiley Creek in Idaho elev - 7160 a
number of times. Once one of the guys was in a IV powered by a 582. We did
fine, but always departed in the AM for obvious reasons. Only one of us had
the 912S and he was in a Rans S-6. Most of the morning flying
recommendations in the mountains has to do with turbulence, but density
altitude is certainly a factor.
I remember the days when I flew a C-170 and I would put it in Max climb
heading east from CCR and would have the altitude to get over the Sierras
just as I needed it - from sea level to about 11,000 ft. in about a hundred
miles in just over an hour. I can do the same from Cameron park easily in a
more moderate climb - from 1300 ft the same 11,000 ft. in 30 minutes. The
Model IV with either of the Rotax 912 series engines is a real performer.
Money no object - go with the 912S, otherwise the UL is what I have and have
felt no need for change.
Incidentally, on our air camping trips we are all close to max gross - camp
chair, tent, clothes for a week, you know the drill.
Lowell
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runwayrex(at)juno.com
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| Posted: Fri Nov 10, 2006 12:26 pm Post subject: Rotax 912 or 912S decision |
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Just to hear the other side, I have a model 3 with the 912UL. I love it and never wish for more power. I cruise between 100 and 105 (GPS). The main advantage to me with the 80 horsepower over the 100 is the ability to use unleaded regular fuel. The 100 horsepower definately needs premium or 100 LL. I plan to buy a model 7 in a year or two and am facing a tough decision on engine choices. One of the mechanics for a leading Rotax distributor told me this summer that if he were to build a Kitfox, he would definately go with the 80 horse because of less issues with them. The 100 horse (S) has more concerns with abrupt start up and shut down plus less smoothness. It's a tough decision, but I think you'll be happy either way.
Rex in Michigan
-- "Lowell Fitt" <lcfitt(at)sbcglobal.net> wrote:
--> Kitfox-List message posted by: "Lowell Fitt" <lcfitt(at)sbcglobal.net>
Brent,
Our flying group has been in and out of Smiley Creek in Idaho elev - 7160 a
number of times. Once one of the guys was in a IV powered by a 582. We did
fine, but always departed in the AM for obvious reasons. Only one of us had
the 912S and he was in a Rans S-6. Most of the morning flying
recommendations in the mountains has to do with turbulence, but density
altitude is certainly a factor.
I remember the days when I flew a C-170 and I would put it in Max climb
heading east from CCR and would have the altitude to get over the Sierras
just as I needed it - from sea level to about 11,000 ft. in about a hundred
miles in just over an hour. I can do the same from Cameron park easily in a
more moderate climb - from 1300 ft the same 11,000 ft. in 30 minutes. The
Model IV with either of the Rotax 912 series engines is a real performer.
Money no object - go with the 912S, otherwise the UL is what I have and have
felt no need for change.
Incidentally, on our air camping trips we are all close to max gross - camp
chair, tent, clothes for a week, you know the drill.
Lowell
---
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propellerdesign(at)tele2.
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| Posted: Fri Nov 10, 2006 12:33 pm Post subject: Rotax 912 or 912S decision |
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Brent,
At 6200´ you have about 79 % power left, so an 912S will be 79 hp and the 912 will be 63 hp. many have 65hp!
but more at about same weight is never wrong.
Jan
[quote] ---
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starlaker
Joined: 24 Jun 2006
Posts: 16
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| Posted: Fri Nov 10, 2006 12:46 pm Post subject: Rotax 912 or 912S decision |
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Brent,
Regarding performance of the 912 UL on a Classic 4 at altitude. My C4
has an empty weight of 640 lb.
Flying solo with about 2/3 fuel load I have recorded 500FPM climb at
12,000 Ft MSL.
Regarding buying a used engine, I bought a used engine with 250 hrs on
it and somewhat incomplete records for half the price of a new engine.
It has performed well, but there are times when I would like the peace
of mind that a new engine would have given. Another factor is that the
912 has gone through a continuous process of improvement. If you buy a
new engine you will have the advantage of having an engine with all the
latest improvements.
Dick
Brent E Bidus wrote:
| Quote: |
List,
Looking for opinions on the suitability of a 912 on a Classic 4 at higher
elevations. I live at 6200 feet in Colorado Springs and need to make a
decision to go with a 912 or 912S. I already have the FWF kit, so my
choice is between these two options. If I have to buy new, a 912S is my
hands down choice. I have a lead on an older but never run 912 that may
save me a few thousand dollars. The money situation is tight, so if I'll
still get good performance at gross weight, I may go that route. If
those of you who have flown with a 912 at 10-12000 MSL think it is
underpowered, I'd rather know that upfront and continue to save for a
912S. Also, anybody have any experience with costs to have an older 912
checked out and all service bulletins complied with? Thanks,
Brent Bidus
Classic 4
Colorado Springs
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_________________
Dick D'Archangel
Classic 4 6061D |
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kerrjohna(at)comcast.net
Guest
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| Posted: Fri Nov 10, 2006 1:43 pm Post subject: Rotax 912 or 912S decision |
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Have had great success with my 80 hp rotax on Classic IV. My home field, Logan UT is 4450 but do a lot of high and hot flying, including Idaho back country with no concerns. Sure the 100 would be great but I would probably opt for the $$$$ and 80 hp.
John Kerr
[quote]-------------- Original message --------------
From: Brent E Bidus <brentbidus(at)juno.com>
[quote] --> Kitfox-List message posted by: Brent E Bidus
List,
Looking for opinions on the suitability of a 912 on a Classic 4 at higher
elevations. I live at 6200 feet in Colorado Springs and need to make a
decision to go with a 912 or 912S. I already have the FWF kit, so my
choice is between these two options. If I have to buy new, a 912S is my
hands down choice. I have a lead on an older but never run 912 that may
save me a few thousand dollars. The money situation is tight, so if I'll
still get good performance at gross weight, I may go that route. If
those of you who have flown with a 912 at 10-12000 MSL think it is
underpowered, I'd rather know that up front .com/c [quote][b]
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darinh
Joined: 20 Apr 2006
Posts: 327
Location: Utah
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| Posted: Fri Nov 10, 2006 5:24 pm Post subject: Re: Rotax 912 or 912S decision |
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I guess I am the only one who likes power. I look at it this way, with the 912S, or the 914 for that matter, you can always throttle back and use the 80 horses, but when you need it, it is very nice to have that little extra push. Sure, you can make do with the 80 horse and your performance will not be bad, mine wasn't in the Model III, but that is all you have and for me it wasn't enough.
As for the lister earlier in the thread with the model III, I never saw anything over 100 mph ground speed unless I had a 20 mph tailwind. Granted my Model III was about 50 - 100 lbs heavier than most model III's and that may be the difference but with the Vne of 100 mph I wouldn't feel too comfortable with a 105 mph groundspeed, unless that is due to a tailwind. My typical cruise was around 75 - 80 mph IAS at 5000 rpm and I had almost every speed mod made.
I am not badmouthing the 80 hp 912, it is an awesome engine and I had no problems with mine...I am simply saying it is easier to pull out power than to add ponies and there were times I would have loved to have the extra power.
Darin Hawkes
Series 7 (getting a 914)
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brentbidus(at)juno.com
Guest
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| Posted: Mon Nov 13, 2006 5:31 am Post subject: Rotax 912 or 912S decision |
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Thanks to all who wrote to offer their perspectives. It's not an easy
decision, but it's nice to know that either one should be fine. More
power at essentially the same weight is a very compelling argument for
the 912S. Still not sure what I'll do but the advice is very helpful.
Thanks,
Brent
On Fri, 10 Nov 2006 17:24:26 -0800 "darinh" <gerns25(at)netscape.net>
writes:
| Quote: |
I guess I am the only one who likes power. I look at it this way,
with the 912S, or the 914 for that matter, you can always throttle
back and use the 80 horses, but when you need it, it is very nice to
have that little extra push. Sure, you can make do with the 80
horse and your performance will not be bad, mine wasn't in the Model
III, but that is all you have and for me it wasn't enough.
As for the lister earlier in the thread with the model III, I never
saw anything over 100 mph ground speed unless I had a 20 mph
tailwind. Granted my Model III was about 50 - 100 lbs heavier than
most model III's and that may be the difference but with the Vne of
100 mph I wouldn't feel too comfortable with a 105 mph groundspeed,
unless that is due to a tailwind. My typical cruise was around 75 -
80 mph IAS at 5000 rpm and I had almost every speed mod made.
I am not badmouthing the 80 hp 912, it is an awesome engine and I
had no problems with mine...I am simply saying it is easier to pull
out power than to add ponies and there were times I would have loved
to have the extra power.
Darin Hawkes
Series 7 (getting a 914)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=73617#73617
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