Jabiru mixture

[pmccarthy]

The latest EAA mag has an interesting tech article at the back about vibration in engines and the wear it can induce. Case study is a 912 with unbalanced carbs leading to linkage wear and further vibration etc. very interesting

 

 

[facthunter]

The Rotax is the only engine I know of where crankcase pressure returns the oil to the remote tank. How endless is the discussion on burping it? None of that is an issue with any other motor.

 

A very new engine is hard to burp as the rings seal very well within a few hours and the "idea" requires blow by. A wet sump needs no return pump. The oil just falls to there but the conventional gear or trochoid pump has very long life. both in the delivery (pressure) and scavenge function if you have one.. and one is usually built on the other as a single unit. They are NOT expensive items and the return needs no pressure regulation and operates with no back pressue=reThe scavenge often having twice the flow rate as the pressure pump for obvious reasons.. You try to have no residual pressure in an engine as it relies too much on sealing then, and puts pressure on all the seals and gaskets to a greater extent than a "normal" system. Many engines attempt to have a "suction" in the crankcase to reduce oil leaks. Generally any external oil, coolant or fuel lines are not an asset but a liability. ALL oil passages internal and NO external oil cooler if you can get away with it are desired and achieved in many aircooled and liquid cooled motors . Any hole or seal failure makes the return system fail on a Rotax. Also the return pipe has to be kept to a small diameter or the idea doesn't work at all. If a larger dia pipe is used the air will just slide around the oil especially when it's hot. In turbulence or inverted flight the vent in the remote tank will allow a high rate of oil to be forced out of it's vent at times by the pressure returning the oil. but all of it venting fully through the oil tank as well..( All the engine's blow by goes out through the oil tank). This is not a desirable feature either. More contamination by condensates getting into the oil than otherwise..

 

The siting of the carburetters is less than ideal. They are better under the motor and not above hot parts. Two carburetters on this motor is a necessity not a design advantage as the way the firing order is on a flat four they don't sequence well (even Pulsing) and have a poor mixture distribution outcome similar to a jabiru but for different reasons.. That's why the Balance adjustment has to be so correct for smooth running. The crucifix vertical intake on the C 200 is simple and effective by comparison and is one of the best I've seen. It's probably got a close to optimum fuel mixture and volume distribution.

 

I don't see the Rotax as anything like the perfect motor and I think the points I've brought up are valid and not bias.. As I've always said no engine is perfect and I'm not holding any up in that light.. but don't just write off the older designs as just being a con by some conspiratorial process.. They are still basic and sound engines for this section of the Market. There's very high standards required on materials and quality control needed on any of them or they fail. as well as appropriate installation and servicing in use.. Nev

 

 

[skippydiesel]

Nev Nev - the response to your oft repeated argument (tirade ?) is:

 

You can not change the fact that Rotax 912 range has been around for so long it is now a TIME proven concept, no matter what engineering shortfalls you believe it has. (they passed the 50,000 912 units produced in 2014)

 

Many of your observations/concerns are conceptual/theoretical, in that they are not born out in real life operation - in other words, from an engineering purists point of view, you make good points - they just dont seem to be an issue in the real world.

 

For example

 

Carburetor "the Balance adjustment has to be so correct for smooth running" - Yeh! so? - what twin/multi carb system is designed to run out of balance?

 

Oil return "If a larger dia pipe is used the air will just slide around the oil especially when it's hot. " - Again So? Rotax engineers have specified the diameter of the pipe so the oil (even hot) will reliable be pushed through to the remote tank - system works!

 

Your arguments are quite possibly correct, taken in isolation and without the benefit of experience (operational success). No engine is perfect, they represent a host of compromises. Everyone's best engine, is the one that works for them/their mission.

 

Seems to me an engineering team come up with a concept - this will be adjusted to meet a whole range of factors/compromises will be made - a prototype is developed producing more changes to concept - production commences/real life operation produces more changes to concept - engine either survives or dies in the market place - if survives probably continues to evolve until superseded by new concept/product, which renders the original obsolete.

 

Rotax have, with the 912 taken a bold step forward in the evolution of the boxer aircraft engine. They have taking concepts & systems from the automotive world,to produce an alternative to the traditional old air cooled direct drive engine. For me, I think they have produced a fantastic product that, with the exception of initial acquisition cost, is better in almost all respects (in this hp range) to the alternatives.

 

What will you say about electric aero engines, when they come on line?

 

 

[facthunter]

I've ALWAYS been a promoter of electric engines almost from day one? Not everyone has the know how to look after internal combustion engines. and they are noisy smelly and dangerous (They CAN have character though.). Nev

 

 

[jetjr]

the 912 is an exceptionally good engine, far from infallible though, despite what some believe.

 

Not all Rotax are at this same level of reliability or performance

 

They happen to be very expensive

 

Not everyone can afford or want one and in plenty of situations like larger Jabirus there isn't a cost competitive Rotax offering

 

Why do threads on Jabiru operations often end up with someone seeking reinforcement that Rotax 912 is a better engine?

 

 

[kgwilson]

The 912 is a good engine, it just sounds like crap. I think my Jab 3300A is a good engine too and it sounds good as well. A Rolls Royce Merlin is also a good engine but it sounds fantastic.

 

 

[skippydiesel]

the 912 is an exceptionally good engine, far from infallible though, despite what some believe. - Lets stop using words like "infallible" its just emotive BS that can not apply to any complex mechanical device. If you mean " reliability" relative (to other engines (in a similar hp range) then the Rotax is comparable to the Lycoming.

 

Not all Rotax are at this same level of reliability or performance - What does this mean????

 

They happen to be very expensive - This needs to be qualified - YES, the purchase price is substantially higher than a similar Jab, less than a LyCon - HOWEVER the running costs (say over 2000 hrs) are probably considerably less - so this is the swings and roundabout argument.

 

Not everyone can afford or want one and in plenty of situations like larger Jabirus there isn't a cost competitive Rotax offering - See above and dont forget the Rotax 915 @141 hp

 

Why do threads on Jabiru operations often end up with someone seeking reinforcement that Rotax 912 is a better engine? - No reinforcement required - Jab owners are happy with their engine - Rotax owners are ecstatic about theirs.

 

 

The 912 is a good engine, it just sounds like crap. I think my Jab 3300A is a good engine too and it sounds good as well. A Rolls Royce Merlin is also a good engine but it sounds fantastic.

Hi Kgwislson - Rotax design their engines to operate under European noise pollution regulations - hence their nice quiet (relative) operation.

 

For my part, I like the fact that my aircraft is so quiet, my neighbours ride on mowers make far more noise and I dont get any fly over complaints. Animals dont scatter in panic and I have to phone down to anyone I want to take notice that I am flying over, just to get them to look up.

 

It is about time aircraft owners started to address the noise footprint of their aircraft - it may be ecstasy for them but it just annoys the people down below and it is their vote which will close your air field.

 

 

[kgwilson]

The Jabs are also quiet but don't sound like some gnome trying to escape from a tin can.

 

 

[facthunter]

Military aero engines particularly have no exhaust noise suppression at all but often the props are equally responsible for the noise problem. A C-180 can make as much noise as most. Engine brakes on trucks are a bigger problem as the road may be just outside your front door on a hot summer's night. Nev

 

 

[Yenn]

I am told that my un silenced Jab 2200 is quieter than a Rotax 912 and coupled with that it isn't there for as long a time.

 

 

[skippydiesel]

I am told that my un silenced Jab 2200 is quieter than a Rotax 912 and coupled with that it isn't there for as long a time.

Odd statement - care to elaborate?

 

 

[turboplanner]

The Rotax is the only engine I know of where crankcase pressure returns the oil to the remote tank. How endless is the discussion on burping it? None of that is an issue with any other motor.

 

A very new engine is hard to burp as the rings seal very well within a few hours and the "idea" requires blow by. A wet sump needs no return pump. The oil just falls to there but the conventional gear or trochoid pump has very long life. both in the delivery (pressure) and scavenge function if you have one.. and one is usually built on the other as a single unit. They are NOT expensive items and the return needs no pressure regulation and operates with no back pressue=reThe scavenge often having twice the flow rate as the pressure pump for obvious reasons.. You try to have no residual pressure in an engine as it relies too much on sealing then, and puts pressure on all the seals and gaskets to a greater extent than a "normal" system. Many engines attempt to have a "suction" in the crankcase to reduce oil leaks. Generally any external oil, coolant or fuel lines are not an asset but a liability. ALL oil passages internal and NO external oil cooler if you can get away with it are desired and achieved in many aircooled and liquid cooled motors . Any hole or seal failure makes the return system fail on a Rotax. Also the return pipe has to be kept to a small diameter or the idea doesn't work at all. If a larger dia pipe is used the air will just slide around the oil especially when it's hot. In turbulence or inverted flight the vent in the remote tank will allow a high rate of oil to be forced out of it's vent at times by the pressure returning the oil. but all of it venting fully through the oil tank as well..( All the engine's blow by goes out through the oil tank). This is not a desirable feature either. More contamination by condensates getting into the oil than otherwise..

 

The siting of the carburetters is less than ideal. They are better under the motor and not above hot parts. Two carburetters on this motor is a necessity not a design advantage as the way the firing order is on a flat four they don't sequence well (even Pulsing) and have a poor mixture distribution outcome similar to a jabiru but for different reasons.. That's why the Balance adjustment has to be so correct for smooth running. The crucifix vertical intake on the C 200 is simple and effective by comparison and is one of the best I've seen. It's probably got a close to optimum fuel mixture and volume distribution.

 

I don't see the Rotax as anything like the perfect motor and I think the points I've brought up are valid and not bias.. As I've always said no engine is perfect and I'm not holding any up in that light.. but don't just write off the older designs as just being a con by some conspiratorial process.. They are still basic and sound engines for this section of the Market. There's very high standards required on materials and quality control needed on any of them or they fail. as well as appropriate installation and servicing in use.. Nev

This is very much the argument that if your aunt had balls she'd be your uncle and grow whiskers so she can never be beautiful.

 

The thread is about Jabiru mixture, and you aren't going to solve that by bagging another product with this sort of claptrap.

 

 

[skippydiesel]

This is very much the argument that if your aunt had balls she'd be your uncle and grow whiskers so she can never be beautiful.

 

The thread is about Jabiru mixture, and you aren't going to solve that by bagging another product with this sort of claptrap.

Steady Turbo - Nev may be a little one sided but then so am I.

 

I confess to absolutely despising front wheel drive in cars/light commercials. I have a multitude of arguments to support my case (like Nev's vendetta against 912"s) BUT with great reluctance, must accept that the system has been around so long now, that my position is very much a lost cause (just like Nev's)

 

 

[turboplanner]

the 912 is an exceptionally good engine, far from infallible though, despite what some believe.

 

Not all Rotax are at this same level of reliability or performance

My advice is for people to take a look at the monthly RAA figures, and the for sale ads which show frame hours and engine hours. If the engine hours are half the frame hours on a number of similar engines, that's a better guide than listening to someone damning an engine with faint praise.

 

These figures don't relate to real life, they're just to show how correct costing pays off.

 

[TABLE]

 

[TR]

 

[TD][/TD]

 

[TD]Engine A[/TD]

 

[TD]Engine B[/TD]

 

[TD]Notes[/TD]

 

[/TR]

 

[TR]

 

[TD]Initial price[/TD]

 

[TD]$50000[/TD]

 

[TD]$25000[/TD]

 

[TD]"A" is "expensive", most people would buy "B"[/TD]

 

[/TR]

 

[TR]

 

[TD]500 hours replacement required[/TD]

 

[TD]$0[/TD]

 

[TD]$25000[/TD]

 

[TD]Total cost of life is at breakeven[/TD]

 

[/TR]

 

[TR]

 

[TD]1000 hours replacement required[/TD]

 

[TD]$0[/TD]

 

[TD]$25000[/TD]

 

[TD]B is now $25000 behind + downtime[/TD]

 

[/TR]

 

[TR]

 

[TD]1500 hours replacement required[/TD]

 

[TD]$0[/TD]

 

[TD]$25000[/TD]

 

[TD]B is now $50000 behind[/TD]

 

[/TR]

 

[TR]

 

[TD]2000 hours replacement required[/TD]

 

[TD]$50000[/TD]

 

[TD]$25000[/TD]

 

[TD]B is now $25000 behind[/TD]

 

[/TR]

 

[/TABLE]

 

In looking at the used RA aircraft ads, a lot of people bail out of the industry and sell at the 500 - 1000 hour mark because they don't have the spare cash to lay out for a new engine, but this shows why, in industries/sports, analysing the total cost of life can save you huge amounts of money. In flying schools this multiplies across all the aircraft, so up front price doesn't matter if it has a life cycle saving over the cheaper engine.

[turboplanner]

Steady Turbo - Nev may be a little one sided but then so am I.

 

I confess to absolutely despising front wheel drive in cars/light commercials. I have a multitude of arguments to support my case (like Nev's vendetta against 912"s) BUT with great reluctance, must accept that the system has been around so long now, that my position is very much a lost cause (just like Nev's)

Yes, but I'd hope you wouldn't try to sink them by saying something like: "front wheel drive is a terrible system. If you leave the torsion bar off, derate the shockers and use a high roll centre they'll give you massive understeer, wheelspin and a harsh ride."

 

There are people here just entering the sport with no practical knowledge and we have an obligation to steer them on to the most economic path.

 

 

[Bruce Tuncks]

Your poorly-disguised anti Jabiru figures are quite different from what I am experiencing in real life turbs. I reckon my Jab engine ( 700 hours now with no problems) is running at less than half the cost of a Rotax. I will be able to replace it at 1000 hours with a new engine and still have savings over a 912. That's if I choose to do this, what if it continues to run just fine?

 

And I agree with Nev about burping the Rotax in the morning. It takes quite a long time. Sure, it's not a big thing, but its another thing to remember. Rotax mandatory replacements ( rubber goods ) are a big thing, and quite expensive, and it is painful for cheapskates like me to throw away good condition things because of orders from the other side of the world.

 

Rotax are also hostile at the idea of owner-maintenance. Try comparing their written stuff with Jabiru's. It's not even in the same ball-park.

 

I don't think that I am anti-Rotax, I just flew one across half the country and it was good. But they are expensive and complex things.

 

 

[turboplanner]

Your poorly-disguised anti Jabiru figures are quite different from what I am experiencing in real life turbs. I reckon my Jab engine ( 700 hours now with no problems) is running at less than half the cost of a Rotax. I will be able to replace it at 1000 hours with a new engine and still have savings over a 912. That's if I choose to do this, what if it continues to run just fine?

 

And I agree with Nev about burping the Rotax in the morning. It takes quite a long time. Sure, it's not a big thing, but its another thing to remember. Rotax mandatory replacements ( rubber goods ) are a big thing, and quite expensive, and it is painful for cheapskates like me to throw away good condition things because of orders from the other side of the world.

 

Rotax are also hostile at the idea of owner-maintenance. Try comparing their written stuff with Jabiru's. It's not even in the same ball-park.

 

I don't think that I am anti-Rotax, I just flew one across half the country and it was good. But they are expensive and complex things.

I specifically said my figures didn't relate to real life.

 

The point I was making is that Prime Cost is just one of the costs in total cost of life.

 

Many people are put off by the product with the highest cost and buy a cheaper alternative, but often pay dearly for it in the long run.

 

So just bagging an engine because it is "dear" is misleading.

 

Is this "700 hour" engine the one which overheated?

 

 

[facthunter]

I definitely am NOT indulging in a vendetta against the Rotax. Anything I've brought up is factual and all I'm saying is it like other engines does have it's own problems. Jabiru's good deal of "rebuilding" the whole engine and updating it in the process at a good price is used against THEM when in actual fact they were helping people who had their product.. What better way than to return an aero engine to the factory rather than do a part job in the field if the economics make sense which they certainly did... I don't take sides.. Just point out reality. Nev

 

 

[jetjr]

Not sure what the numbers are about if just made up?

 

New jabiru is well under $20k and around $10 for a rebuild, many done for less

 

Plenty of RA aircraft take many years to reach 500 hrs

 

 

[skippydiesel]

Your poorly-disguised anti Jabiru figures are quite different from what I am experiencing in real life turbs. I reckon my Jab engine ( 700 hours now with no problems) is running at less than half the cost of a Rotax. I will be able to replace it at 1000 hours with a new engine and still have savings over a 912. That's if I choose to do this, what if it continues to run just fine?

 

And I agree with Nev about burping the Rotax in the morning. It takes quite a long time. Sure, it's not a big thing, but its another thing to remember. Rotax mandatory replacements ( rubber goods ) are a big thing, and quite expensive, and it is painful for cheapskates like me to throw away good condition things because of orders from the other side of the world.

 

Rotax are also hostile at the idea of owner-maintenance. Try comparing their written stuff with Jabiru's. It's not even in the same ball-park.

 

I don't think that I am anti-Rotax, I just flew one across half the country and it was good. But they are expensive and complex things.

 

Brucy boy - read my earlier response on this (item by item), with costs and number of turns (which even Jab owners should be doing) to get a burp - you are just wrong (I deleted my earlier expression on this). Every one of your comments is so far off the truth as to be laughable.

 

 

[skippydiesel]

I definitely am NOT indulging in a vendetta against the Rotax. Anything I've brought up is factual and all I'm saying is it like other engines does have it's own problems. Jabiru's good deal of "rebuilding" the whole engine and updating it in the process at a good price is used against THEM when in actual fact they were helping people who had their product.. What better way than to return an aero engine to the factory rather than do a part job in the field if the economics make sense which they certainly did... I don't take sides.. Just point out reality. Nev

 

Factual ?? may be (if I squint hard enough) but out of context on not balanced.

 

At least I admit my bias.

 

 

[skippydiesel]

Not sure what the numbers are about if just made up?

 

New jabiru is well under $20k and around $10 for a rebuild, many done for less

 

Plenty of RA aircraft take many years to reach 500 hrs

Forgive my poor maths, but are you comparing an engine that costs under $30k , that with good maintenance, is likely to last at least to 2,000 hrs + with considerably lower fuel and oil usage, with an engine that you say costs under $20 k PLUS another $10k at 500 hrs (=$30k) and in that time guzzle prodigious quantities of fuel & oil (not to mention valves & variose through bolts) and then you have to send it to the factory for a rebuild ??????? and you thinks that's a cost effective purchase ????? wow!!!!!!

 

This debate seems to be descending into farce!

 

 

[facthunter]

You are good at taking things out of context yourself SD. No one HAS to send their motor to Jabiru for a rebuild It can be done any way you like. but it's a GOOD DEAL the factory OFFER. which I have just explained.. IMMEDIATELY above your last post. and you are quite happy to disregard.. (probably because I wrote it). The Jabiru motor is lighter which mitigates against using another motor in a Jabiru aircraft as you need weight in the tail to convert.

 

People are free to make their own choice in a market. You like your choice (that's nice) but some will go the other way and many are happy with their choice. The amount of Jabiru bashing going on here over the years hasn't been very informed or productive. I suppose you would like the CASA to ground them? Well they sort of did that in a very controversial way that didn't enhance their reputation and damaged people financially who had not committed any crime. Now good people are bankrupt. There are plenty of engines flying that have a much worse likelihood of engine failure than a Jabiru and how you look after any of them has a big effect over the longer term, rather than just who the maker was . As far as I'm concerned the more motors available the better . The "perfect" one hasn't been made yet. Nev

 

 

[jetjr]

Reckon Skip you might be commenting on something you know little about

 

Without Jabirus low upfront cost many would own their own aircraft and as Nev and I have both said in many airframes there isnt a direct option to compare.

 

Also not sure about the 500 hr engine exchange youre and others are talking about? Plenty go to tbo with some repairs along the way. Reckn interest on the $25 k could pay for much of repairs and top end work if required

 

Jabiru offer attractive exchange programs and plenty are self maintained

 

Lots of FTO’s run Jabiru aircraft as they have certified and lsa versions and cost effective to own and run. Highly popular airframe and tough. More than just engine to consider

 

 

[turboplanner]

I think we can take it that the collective brain of the Illuminati has not been able to understand this new mixture controller, based on the reversion to stories of fantasy and excitement.