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Subaru vs. Jabiru 5100
- Thread starter brister
- Start date
cjensen
Well Known Member
brister,
This is an engine that I've been watching from the beginning. I just emailed Jabiru today for current info. I got a response right away, but the sales people and higher ups are on their way to OSH. They have several flying, and they do have a company RV-6 that has over 130 hours on it with no problems. It provides 180hp at 3,000 rpm for takeoff (5 minutes), then 170hp at 2750rpm. They are using a wood two blade fixed pitch for testing, and are getting 150-155kts in the RV-6. It's a great looking engine. One of my concerns is the cowl that they have on that -6. It just isn't that pretty. It's not bad, but not as nice as Vans or Sam James. They say it's "turbine smooth" because it's eight cylinders. It burns 9.4gph at 75%, and will burn 100LL or 91 octane with the 8.5:1 compression.
Here's a link to the .pdf brochure-
Jabiru 5100
Here's the site info page-
5100 site info
It looks very promising, and it's one of my first stops at OSH next week.
There is one for sale in the classified section that I'd love to have, but I need to answer some questions first. That's what OSH is for! The one for sale is a GREAT deal...I'd buy it if I were a little more decided, and ready for an engine.
This is an engine that I've been watching from the beginning. I just emailed Jabiru today for current info. I got a response right away, but the sales people and higher ups are on their way to OSH. They have several flying, and they do have a company RV-6 that has over 130 hours on it with no problems. It provides 180hp at 3,000 rpm for takeoff (5 minutes), then 170hp at 2750rpm. They are using a wood two blade fixed pitch for testing, and are getting 150-155kts in the RV-6. It's a great looking engine. One of my concerns is the cowl that they have on that -6. It just isn't that pretty. It's not bad, but not as nice as Vans or Sam James. They say it's "turbine smooth" because it's eight cylinders. It burns 9.4gph at 75%, and will burn 100LL or 91 octane with the 8.5:1 compression.
Here's a link to the .pdf brochure-
Jabiru 5100
Here's the site info page-
5100 site info
It looks very promising, and it's one of my first stops at OSH next week.
There is one for sale in the classified section that I'd love to have, but I need to answer some questions first. That's what OSH is for! The one for sale is a GREAT deal...I'd buy it if I were a little more decided, and ready for an engine.
RudiGreyling
Well Known Member
Hi CJ,
yes I like the Jabiru and their efforts, I have been following them with their smaller engines in the micro light category. The smaller engines is starting to make inroads now, and are starting to be accepted as a replacements for some of the 2 stroke rotaxes...What I like is the Jabiru engine is designed from the begining as an Aero Engine.
This big one J5100 still needs a lot of flying time, before I would consider it, but that is me personally, conservative. I think the biggest problem is that the engine is +/- 5" longer than a typical Lycoming/clone which means another cowl. That is such a pitty. If they could have met the form factor (dimensions) of a Lyco then for the first time we 'could' have a 'potensial' real on par competition for Lyco i.e. Aircooled Aero engine.
I will be following them with interest...and hope they make a success out of it. Just not yet for me.
Kind Regards
Rudi
yes I like the Jabiru and their efforts, I have been following them with their smaller engines in the micro light category. The smaller engines is starting to make inroads now, and are starting to be accepted as a replacements for some of the 2 stroke rotaxes...What I like is the Jabiru engine is designed from the begining as an Aero Engine.
This big one J5100 still needs a lot of flying time, before I would consider it, but that is me personally, conservative. I think the biggest problem is that the engine is +/- 5" longer than a typical Lycoming/clone which means another cowl. That is such a pitty. If they could have met the form factor (dimensions) of a Lyco then for the first time we 'could' have a 'potensial' real on par competition for Lyco i.e. Aircooled Aero engine.
I will be following them with interest...and hope they make a success out of it. Just not yet for me.
Kind Regards
Rudi
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gmcjetpilot
Well Known Member
Weight
I suspect with the HOG out method of construction (block of aluminum machined out) will be heavier than and equivalent Lyc with precision castings, just my opinion. The power to weight ratio is pretty fixed and don't see anything they did to produce more power per weight. Because it is air-cooled I suspect it will be much lighter than the water cooled Subaru.
They do look pretty. The length thing is a bit of a bummer, but I think a long cowl replica experimental would be cool. I noticed they use dual carbs sticking out the back? That looks like it would take more room and not sure how you get air back there (easily).
I read their site and they measure parts down to "2 microns". Cool
A micron is about .000 03937 inch, wow. I get CNC is accurate but a Lyc is CNC where needed and has very tight tolerances. When you get into 10 thou (0.0001) it gets expensive.
I suspect with the HOG out method of construction (block of aluminum machined out) will be heavier than and equivalent Lyc with precision castings, just my opinion. The power to weight ratio is pretty fixed and don't see anything they did to produce more power per weight. Because it is air-cooled I suspect it will be much lighter than the water cooled Subaru.
They do look pretty. The length thing is a bit of a bummer, but I think a long cowl replica experimental would be cool. I noticed they use dual carbs sticking out the back? That looks like it would take more room and not sure how you get air back there (easily).
I read their site and they measure parts down to "2 microns". Cool
A micron is about .000 03937 inch, wow. I get CNC is accurate but a Lyc is CNC where needed and has very tight tolerances. When you get into 10 thou (0.0001) it gets expensive.
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cjensen
Well Known Member
Jabiru RV-6 cowl pics
Here are a couple of pics from the OZ Jabiru website of the modified cowl they use in their -6. It's not terrible, but could be prettier...
They do say it's 257 pounds dry, and 264 pound ramp weight. I'm sure a few of the airframe install components do add some more weight, but this is certainly on par, if not lighter than the 320/360. I think that the carbs off the rear end is the reason it is longer. They are both pressure compensating carbs. The 130 hours of flight time was as of July 2003 (according to the OZ site), so I'm sure there is more time on it now. That's one question that will definitely be asked at OSH next week.
Here are a couple of pics from the OZ Jabiru website of the modified cowl they use in their -6. It's not terrible, but could be prettier...
They do say it's 257 pounds dry, and 264 pound ramp weight. I'm sure a few of the airframe install components do add some more weight, but this is certainly on par, if not lighter than the 320/360. I think that the carbs off the rear end is the reason it is longer. They are both pressure compensating carbs. The 130 hours of flight time was as of July 2003 (according to the OZ site), so I'm sure there is more time on it now. That's one question that will definitely be asked at OSH next week.
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Harvey
Well Known Member
Jab 5100
I think there is still a few issues concerning the big Jab - cooling, crankshaft, billet heads to name just a few.
The engine was destined for the scale all-metal Spitfire but engine problems meant that the kit manufacturer developed his own conversion using a V6 Isuzi engine with over 200 hp. Real nice conversion.
The smaller Jabs have a history of oil cooling and cylinder head problems, some of which is caused by using billet instead of castings for the heads, as well as crank and rod dramas.
I would like Jab to succeed so as to give the big boys some competition, but what was thought acceptable reliability in an ultralight is not acceptable in a GA-type sport 'plane.
My $0.02 worth
Harvey
I think there is still a few issues concerning the big Jab - cooling, crankshaft, billet heads to name just a few.
The engine was destined for the scale all-metal Spitfire but engine problems meant that the kit manufacturer developed his own conversion using a V6 Isuzi engine with over 200 hp. Real nice conversion.
The smaller Jabs have a history of oil cooling and cylinder head problems, some of which is caused by using billet instead of castings for the heads, as well as crank and rod dramas.
I would like Jab to succeed so as to give the big boys some competition, but what was thought acceptable reliability in an ultralight is not acceptable in a GA-type sport 'plane.
My $0.02 worth
Harvey
garnt.piper
Well Known Member
5100
I've flown the RV-6/Jabiru 5100 combo, and was imprerssed by it. I've posted on it before if you want to do a search. I have a 180hp Lyc RV-4, and jumped out of that and into the RV-6/5100 for a fly. I didn't get precise numbers but the performance wasn't shabby and it felt similar to my -4, but a lot smoother. The engine was very easy to operate, no mixture, solid state ignition, very smooth and quiet. Ther cowl is a bit rough but could be cleaned up a lot with more elbow grease. Temps weren't a problem, and we were two-up with 2/3 fuel at low level, high humidity.
I understand the Spitfire replica kit builders found most people wanted more power and the water-cooled look, thus the change. I would certainly consider the Jabiru if I was building an RV again.
I've flown the RV-6/Jabiru 5100 combo, and was imprerssed by it. I've posted on it before if you want to do a search. I have a 180hp Lyc RV-4, and jumped out of that and into the RV-6/5100 for a fly. I didn't get precise numbers but the performance wasn't shabby and it felt similar to my -4, but a lot smoother. The engine was very easy to operate, no mixture, solid state ignition, very smooth and quiet. Ther cowl is a bit rough but could be cleaned up a lot with more elbow grease. Temps weren't a problem, and we were two-up with 2/3 fuel at low level, high humidity.
I understand the Spitfire replica kit builders found most people wanted more power and the water-cooled look, thus the change. I would certainly consider the Jabiru if I was building an RV again.
cjensen
Well Known Member
The guys from Jabiru (Tennessee) stopped in today on their way to OSH, and I talked to one of the guys about the 5100 in RV's. He told me that a -7 had just flown in TN about two weeks ago (at their home airport), and may be at OSH. He was very pleased with the installation, and also said that Jabiru has changed the cowl design to be "more RVish" and the difference is almost unoticable. The cowl inlets were redesigned to match those from Vans, and the only visual difference is the lower cowl air inlet for the oil cooler (and it is "slightly" longer).
There is also a -6A in Janesville, WI that apparently has a 5100 in it, but has yet to fly. Maybe we'll get some numbers before too long...
There is also a -6A in Janesville, WI that apparently has a 5100 in it, but has yet to fly. Maybe we'll get some numbers before too long...
Subaru
I have been hoping to hear about the subaru i am really interested but all i have been hearing is the cons on the matter ( weight and temperatures) was really hoping to hear some pro eggenfellner responses but maybe I just need to face the fact that it has more cons than pros.
I have been hoping to hear about the subaru i am really interested but all i have been hearing is the cons on the matter ( weight and temperatures) was really hoping to hear some pro eggenfellner responses but maybe I just need to face the fact that it has more cons than pros.
Eggenfellner Subaru
Also, you can read some information on http://groups.yahoo.com/group/subaruaircraft/
The weight is higher, that's for sure, but the cooling issues are no more difficult to solve than with a lycoming.
If you do a search for eggenfellner in the search box, you'll get links to lots of threads discussing the Eggenfellner package.brister said:
Also, you can read some information on http://groups.yahoo.com/group/subaruaircraft/
The weight is higher, that's for sure, but the cooling issues are no more difficult to solve than with a lycoming.
Subaru Cooling
If you live in a hot climate you will have cooling problems with the Subaru. I live in Phoenix, Arizona, and I understand that both H4's that operate here have problems in the summer time. Several of the h6's have summer difficulties also. The third radiator might be the cure, but I don't know for sure. More weight, more forward cg though.
I am now a Lycoming guy, but have researched the Subaru heavily as it was my first choice when I started my project. It is very difficult to get information on these engines. You sort of have to read between the lines to get the full picture. Search the Eggenfellner Yahoo group for David Domierer's posts. He has owned bot the 4 and the 6 and is very candid about both engines.
Good Luck,
John
brister said:
If you live in a hot climate you will have cooling problems with the Subaru. I live in Phoenix, Arizona, and I understand that both H4's that operate here have problems in the summer time. Several of the h6's have summer difficulties also. The third radiator might be the cure, but I don't know for sure. More weight, more forward cg though.
I am now a Lycoming guy, but have researched the Subaru heavily as it was my first choice when I started my project. It is very difficult to get information on these engines. You sort of have to read between the lines to get the full picture. Search the Eggenfellner Yahoo group for David Domierer's posts. He has owned bot the 4 and the 6 and is very candid about both engines.
Good Luck,
John
Done!.............
gmcjetpilot said:I read their site and they measure parts down to "2 microns". Cool
Where does it say this on their site? I couldn't find it...
bumblebee
Active Member
I must respectfully disagree. Assuming one does not wish to sacrifice more than a knot or two in TAS, or overcompensate with more HP (weight, heat, fuelburn), a tractor liquid cooled installation is very difficult to cool properly without adding significant drag and weight.rv8ch said:
Pusher liquid engines are much easier to cool without drag penalties.
In tractors, you can have one or the other (drag OR cooling) without excessive engineering, but "both" is extremely elusive, especially if holding to original cowl form factor.
It's all related to the deceptively-complex effective diffuser lengths, heat exchanger areas and their respective mathemetical ratios.
Buyers of Subies (and other liquid-cooled alternatives) should be realistic about these types of installations. While not impossible, the reality is that "matching" the performace of the Lyco RV's will require extensive modification, testing and engineering beyond what we've seen to date.
bumblebee said:
As someone who has actually done this and know of others who also have, I'd have to disagree with you on the basic point above. As we incorporate proven concepts from WWII liquid cooled aircraft and combine this with modern aluminum heat exchanger design, it is clear that the cooling drag penalty compared to air cooled engines approaches parity when done properly.
You are correct in saying that proper diffuser/ duct shape and length is critical to achieving this and that cowling mounted radiator designs are unlikely to offer effective low drag performance due to packaging and short lengths.
Belly or wing mounted rads with exit airflow control on tractor aircraft offer the best solutions and we are fitting these now to new aircraft under construction. Reg Clarke has been flying these setups for years now with excellent results.
cooling a subaru
The weight of the Subaru is higher than a Lycoming, to the best of my knowledge, so that much is a given. I've never seen any scientific data that shows that cooling drag must be higher with a liquid cooled engine, but it could be possible that that is the case. I'll be very interested to see the results of Ross' developments on his RV-10.
I was not really making any of these assumptions. I was assuming that brister's question was about potential overheating problems with the Eggenfellner Subaru package. These problems are easy to solve, and have been solved on most of the flying engines. A bit of work on the cowl is all that is needed. No more complex than playing with engine baffles on a Lycoming.bumblebee said:
The weight of the Subaru is higher than a Lycoming, to the best of my knowledge, so that much is a given. I've never seen any scientific data that shows that cooling drag must be higher with a liquid cooled engine, but it could be possible that that is the case. I'll be very interested to see the results of Ross' developments on his RV-10.
bumblebee
Active Member
rv6ejguy said:
Actually, I think we're on the same page...
As you state on your website:
"....I believe that even with a properly designed diverging, converging duct containing the heat exchangers, that the liquid cooled engine probably cannot achieve cooling drag numbers similar or superior to an air cooled installation. Others may not agree, but I don't see any of the liquid cooled RVs exceeding the Lycoming powered RV speeds at lower altitudes with similar installed hp."
I'm not clear where you disagree with my comments in responding to Mickey Coggin's suggestion that "cooling issues are no more difficult to solve than with a lycoming". I was referring to the level of effort involved, especially in reaching parity with air-cooled re cooling/speed/hp. Your excellent efforts to properly cool your RV6A seem to concur.
The complexity, weight, engineering investment, etc etc all contribute to the basis of my comments re difficulty in matching air-cooled numbers. CAN it be done? Probably. Will it be easy? No.
Most of my efforts have been with turbo intercooled liquid pusher installations for military UAV platforms, but there's a tractor setup being tested in the RV performance envelope, namely 200hp/200mph. As expected, the belly rad has demonstrated best cooling/drag/weight combination so far.
As you say, belly scoops/rad is the best solution per P51, WWII, etc. To the best of my knowledge, no one has yet incorporated a belly rad solution in an RV. I'd love to see it done b/c I think this is the best answer for Subie cooling/drag problems.
Ironically, I fly a Lyclone-a-saur. No time for building my own wet pylon racer (yet!).
The earlier comments were based on knowledge at the time. In the last 2 years, additional study on the flow bench with models and different rad designs to test drag have yielded potentially better numbers. Only flight testing will prove or disprove these new designs.
Our new EG33 twin turbo powered RV10 will have a belly rad with proper controllable exit door. This part is already built. The rad will be fully instrumented with pitot and pressure probes plus temperature probes. We are exploring the Meridith Effect as it relates to 200 knot aircraft and liquid cooled engines.
We are treating the entire scoop/rad as an internal aerodynamic structure. There are smooth contours from inlet lip to rad face, not exceeding 7 degrees. We use oval tubes on the rad. Exposed coolant tubes are faired into streamlined shapes. Rad tanks are faried into the duct walls for low wake drag. Flow gently converges to the aft duct exit lip and we are using a cockpit actuated exit door to control mass flow and squeeze the air down in cruise for optimal exit velocity.
Other thermodynamic tests have validated the rad design as being much more efficient than some other common designs used per unit area.
The big question is how much drag from the scoop be offset by efficient internal design and heating/ converging the airflow in cruise.
Other studies into intercooler airflow are also underway to reduce drag in this area to a minimum are also underway.
You are absolutely correct in stating that much thought/ work and validation goes into this problem. I've learned a lot from old technical notes on these problems from the 1940s and tried to apply these ideas where possible. Applying liquid cooling to an RV involves many compromises due to existing layout and structure compared to clean sheet designs with liquid cooling integrated from the start.
Always an interesting, time consuming and sometimes frustrating area to work in.
Our new EG33 twin turbo powered RV10 will have a belly rad with proper controllable exit door. This part is already built. The rad will be fully instrumented with pitot and pressure probes plus temperature probes. We are exploring the Meridith Effect as it relates to 200 knot aircraft and liquid cooled engines.
We are treating the entire scoop/rad as an internal aerodynamic structure. There are smooth contours from inlet lip to rad face, not exceeding 7 degrees. We use oval tubes on the rad. Exposed coolant tubes are faired into streamlined shapes. Rad tanks are faried into the duct walls for low wake drag. Flow gently converges to the aft duct exit lip and we are using a cockpit actuated exit door to control mass flow and squeeze the air down in cruise for optimal exit velocity.
Other thermodynamic tests have validated the rad design as being much more efficient than some other common designs used per unit area.
The big question is how much drag from the scoop be offset by efficient internal design and heating/ converging the airflow in cruise.
Other studies into intercooler airflow are also underway to reduce drag in this area to a minimum are also underway.
You are absolutely correct in stating that much thought/ work and validation goes into this problem. I've learned a lot from old technical notes on these problems from the 1940s and tried to apply these ideas where possible. Applying liquid cooling to an RV involves many compromises due to existing layout and structure compared to clean sheet designs with liquid cooling integrated from the start.
Always an interesting, time consuming and sometimes frustrating area to work in.
