View Full Version : JABIRU engines
04-09-2004, 01:03 AM
I am considering buying a plane with Jabiru engine.
They are not very popular here in Europe,
so I decided to look for help in US.
Can you say anything (good or bad) about these engines ?
Rather few gyros use them, as far as I can see.
Is there any reason for that ? Any flaws ?
Thanks in advance for any help.
04-09-2004, 08:26 AM
They are designed for direct drive, but make their rated power at about 3300 RPM. That is a little too fast to spin a prop for good efficiency, yet a little too slow to justify a reduction drive.
As for reliability or durability, let's see if someone here has actually flown one.
04-09-2004, 04:10 PM
Steven you probably got it nailed there.
This engine was designed for the Jabiru airplane and does OK in that application, mainly because for cruise the pilot can shave the power off after climb out, just like any other fixed wing craft. On a gyro, we don't usually have that luxury!
And as PW P says, the speed they are designed to run at is 'bigger than a snack but less than a meal' and not suitable for autogyro flight. I know they were tried on gyros a few years ago but there are none that I know of right now...wonder why that is?
If there are any of these engines on gyro's (and going well) lets hear from the owners?
Thanks, Goordon Gibson.
04-12-2004, 04:29 PM
I had one in a Sonex sportplane. I had a early version of the 3300 six cylinder Jabiru.
they are good engines and they have a great Yahoo chat group to discuss Jabiru issues. They have to turn shorter props than a Rotax 912 would and they as a result don't climb out as well, but will give a higher cruise speed for a given percentage of power compared to the 912. They are simple and very well built engines. I think they would do okay in a tractor gyro but they would have to work too hard and probably not get enough air to keep them cool in a pusher gyro.
05-01-2004, 04:55 AM
Jabaru is sold as a simple engine, but how simple when you have to add two extra cylinders just to match the output of a four cylinder Subaru engine?
05-01-2004, 05:59 AM
Neil the 6 cylinder engine is direct drive 3.3 liters. it is rated at 120 horsepower at 3300 Rpm. How much horsepower will a Sub give at 3300 rpm??? not 120 I am pretty sure of. Also the Jabiru is detuned like most real aircraft engines, it is not hopped up to make as much power as could be made. It has a 1500 or 2000 hour Tbo - can't remember for sure -
Also Jabiru has several dealers in the USA that are class acts. The Guys in Naples Florida were great when I had questions or problems, and the guys up near Oshkosh go WAY out of their way to help anyone with questions or concerns. I would say customer support or service is abot as good as you could get when it comes to Jabiru aero engines.
05-01-2004, 03:09 PM
120 HP @ 2500 rpm. (At the prop flange, continuous)
120 x 6500
BMEP = -----------
3.3 x ( 3000 :- 2 )
= 157 psi
120 x 6500
BMEP = -------------
1.8 x ( 5600 :- 2 )
= 154 psi
It would seem the SUB is in a slightly lower state of tune!
Is it rpm's that kill engines? 5600 is hardly high crank speed. With the short stroke these SUB's run they are WELL down on max piston speed.
Which engine was it that was detuned?
05-01-2004, 06:38 PM
Neil do your math again... The 3300 six cylinder Jabiru is rated for it's 120 horsepower at 3300 RPMs. The smaller jabiru - the 4 cylinder - is rated for 80 horsepower at 3300 RPMs and the newest Jabiru - a 4400 8 cylinder - is rated for 160 horsepower at 3300 rpm.
2.2 liter Jabiru puts out 80 horsepower ---- 2.2 liter Subaru EJ-22 puts out 130 horsepower..... a 50 horsepower difference.
Steve, I never had a reason to call overseas. The dealers here know as much or more than the factory does about these engines. I bought the plane used so there was no warrenty coverage by the time I got it. But I did have to talk to the dealers concerning he engine while I had it and they were very helpful, and sent parts when I ordered them right out.
The jabiru engines are not bad at all. Bigger engines turning slower to make their power. Everything is build from the best materials and the machine work is beautiful. They are also very simple engines anyone ought to be able to work on without special tools and special training - the owners manual details a complete teardown and rebuild in easy to understand english. I wouldn't say they are the best engines on the market, the Rotax 912 is a nice little engine and the Subarus are very very nice for their cost, But the Jabiru is a engine very much worth looking into if you got something that needs a new four stroke engine....
05-01-2004, 07:30 PM
I looked at the Jabiru when I started my plane and decided against it for the following reasons.
It's 40+ year old technology with carb, they don't offer FI. I asked them why not, they said you couldn't find anyone to work on FI in the outback. I told them that FI is the way to go, because you very rarly have to work on them among all the other benifits. No reply.
It's air cooled, I like liquid.
Cost about 16k when you add the install package.
You can buy 3 sub 2.5s with drives for that price. And with cam work, you can get 195 hp at 6600 rpm. Jabiru is 120 hp, but the reports I read said it's more like 105.
The only plus I saw was the weight.
Just my opinion.
Just thought I'd butt in so you guys didn't think I was dead. Just steady working on my 701 and selling a stab or two now and then.
05-01-2004, 07:42 PM
Hi Larry, My brother just ordered his rudder for a 701 to start. He wants one bad. Hope to have the rest by June. He wants to use 912s. I suggested the Sub but he said factory support comes with 912 install. Hows yours coming?
05-01-2004, 11:13 PM
I probably didn't set my last post out that well. But I've checked the maths and found it to be right.
The SUB delivers 120hp @ 2500 prop rpm. ( continuous )
I did in my haste to reply use 3000 rpm instead of 3300 ( what efficiency / dia prop can soak up 120 hp at this rpm? ), this will change the calculation a little and put the Jabaru figure slightly under the SUB, not much though.
When you consider a standard SUB is about 90 psi and a F1 is about 240 ish it's clear that both the SUB and Jabaru are in about the same safety slot, state of tune. Apart from old style aviation engines, what else uses direct drive now? Where are all the Jabaru gyro installations, can you push the throttle through to full for half an hour? Trade revs for torque, turbine engines do it very well! I would say the SUB is certainly no more complicated and more efficent in terms of thrust per weight per cost. Your move.
05-02-2004, 07:45 AM
Neil I would rather buy a Subaru since their cheaper. But my only point is the Jabiru is a good engine. Who cares if it is a 40 year old design??? that only means it is proven. Why did RAF take a fuel injected, electronic ignition engine and convert it to a Carby and distributor??? Must be a reason....
The Jabiru is very light weight as well. Less parts = less weight. The all up weight of the 120 hp version is under 170 pounds.
the jabiru has to turn a shorter diameter higher pitch prop. I don't think at the speeds a gyro flys at it would make a good engine, but on a fast plane like a Sonex or a Zenith 601 or a Titan Tornado or the Vans RV line - which is what the 8 cylinder was designed for - the Jabiru is a great engine.
Look you guys can have your opinions as you already have them. I had a jabiru and flew behind it for a summer and it was a good engine. Very simple and trustworthy.
05-02-2004, 10:01 AM
Thanks for the inputs.
The reason Jabiru and Rotax use carbs is simple.
The rule for the aircraft engine is, it should run with total electric power out.
The modern EFI injection just quits when alternator and battery quit !
The same with the double ignition. Jabiru and Rotax use completely separate magneto
systems runnig at power out without problems.
I was recently considering also the BMW motorcycle engine from R1100S.
Very reliable engine, but 2 cylinders, you need redrive (110 hp at 7500 rpm)
but also slip clutch and torque vibration dampener. By this size of cyliders
without this trick you just kill your engine on low revs with a big prop.
(The clutch catches at 2500 rpm).
Against this combination (redrive, clutch, dampener, BTW used also on 912s Rotax)
Jabiru 6 cylinder is just as simple and smooth as a baby toy.
The only thing I was worried about was, how popular they are and how good is the
service an reliability.
But what Ron says is encouraging.
BTW1: the BMW is twice as fuel efficient as Rotax, uses a Lambda sensor and Motronic
engine control, but what happens when the sensor is out in mid air or there is a bug
in the Motornic software. (Happend to some of my bike friends.!!!)
BTW2: The BMW R11000S eengines are factory fitted with 2 spark plugs per cylinder, double ignition,
but controlled from the same Motronic....
I stay with your opinion Ron !
05-02-2004, 01:22 PM
In the case of RAF fitting a carb, I don't think it has a lot to do with power out situation as the elctronic ignition would stop the engine anyway. More likely they didn't have a suitable after market system ( that they understood ). Carburators are crude in their metering duties at best, with altitude always an issue. It could be said of course that the geared drive is an older design than the direct drive if you like with the Wright Brothers using a chain reduction drive to the two props. I've been to the Jabaru factory and found it to be a VERY well run, well organized facility with a very nicely manufacterd engine. I just think it's a pitty Jabaru didn't take advantage of the last fifty years of engine development, latest tec machinery out dated engine design. Next you will be telling me that side valves should be used again, would be simpler!
HP for HP ( forget capacity ) there are more parts in a Jabaru than a SUB, two extra pistons, rods, inlet pipes,exhaust pipes, four extra valves, pushrods, rockers, in fact half an engine again. The SUB has extra,two gears four bearings and a rubber damper and a little more alloy case. Besides what sort of engine is said to be underated ( for long life ) when you can't hold full throttle continuous for fear of engine damage. Water cooled engines can, which one is safer.
05-02-2004, 01:51 PM
Up until a few years ago, I'd have chosen the older air-cooled, magneto-fired carburated engines, but given recent advances in the reliability of electronics, not any more.
Electronic ignitions are now less likely to fail than magnetos, last much longer, and are adjusted by the ECU for optimum timing to match RPM, load and other conditions. EFI delivers more power and better fuel efficiency than a carb, does away with intake icing concerns, and does a better job than any pilot of keeping the mixture right.
I guess the one circumstance in which a carb may have the edge is if you catch some dirty fuel, and don't find out till you're airborne. Injectors are unforgiving.
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