Are Jabiru engines really that bad?

[bexrbetter]

I'll send you mine, if you promise to return it one day ! ! ! ! Phil

 

 

[dazza 38]

Dazz. . . . have a look around for a book called "Behind the cockpit door" by Arthur Whitlock. If you enjoyed Ernie's book ( as much as I did. . .) you'll like that one too.If you can't find it, PM me a snail-mail address and I'll send you mine, if you promise to return it one day ! ! ! ! Phil

Cheers Phil, I will search for it.

 

 

[lark]

I will say this, some operators have had a great run. Some operators have had a not very good run. BOTH operators have maintained them by the book. I still after all these years have no idea why this is so. Reminds me of my favourite book by Ernest K Gann. Fate is the Hunter.

Hey, your right about Fate is the Hunter! Great book havent read it in years, well worth a re-read. He had a few other books that were quite good as well. Names of these elude me at moment.

 

 

[Ultralights]

i have just finished reading the latest edition of Kitplanes magazine out of the USA. a good 6 page story on keeping a Jabiru engine running reliably... they identified 2 main culprits for their failures. lack of oil cooling, and lack of airflow around the engine and heads.

 

their first recommendation.. throw away the oil cooler! its useless apparently, on a Cub they found the best was the oil cooler from a 180Hp lycombing. and then you have to make sure it gets enough airflow, requiring a separate ducting system, that didn't increase the air pressure under the cowl and reduce head cooling. so the cooler was in a duct, with inlet at front of the cowl, and exit below the engine at the outlet at the bottom, no air allowed to flow into the engine bay area. good cooling over the heads was next, but also be aware of excess cooling on the fwd cylinders, fixed by a small air dam over the front cylinder fins. and third and final tip, run them hard.

 

the last point i agree with, i have only had experience with the 2200 in a school environment, and the boss told us to run them hard, and they did go the distance. cruise at 2800 to 2900 rpm. but this was almost 6 yrs ago.

 

so maybe temps are the issue over here, just we have been looking in the wrong area..

 

 

[fly_tornado]

Run the engine hard 2800/2900 and the through bolts will fail?

 

 

[Yenn]

If cooling is the problem, what sort of temps. are users getting? Are they seeing too high a temp and still powering on with a high nose and low airspeed? What sort of oil temps are they getting? I never have a problem with temps and the only problem I have ever had was due to shonky fuel causing detonation. On e thing in my favour is that I don't have to work the motor flat out, but I find it does go better if the revs are 2800 or more. Lower revs seems to equate to more oil use.

 

 

[jetjr]

3300, Cht are all 100 to 120, egt 650 to 700 cruise, oil temp max 90 cruise 75 ( bit low), cruise 2850-2900, 26 lph.

 

Many dont have any idea what spread is accross engine and could very easily be running well outside spec

 

Its taken alot of fiddling to get it to run like this and i think they are a long way from this out of the factory, older heads ran out to 180 deg, oil to limit in summer, egt 500 to 760, cht only fitted on coolest head.

 

A problem with lower rpm is bing leans right off at around 2700 eapecially when running without much load

 

 

[facthunter]

Your mixtures can be altered by modifying the taper on the needle. This may be a bit beyond the average person but the principle is simple. At higher altitudes your slide will end up well down anyhow and of course it will lean out as that is what is required. 26 Litres /hour is a bit but probably needed to be on the safe side. The oil may blacken a bit more. Has anyone noticed this? Nev

 

 

[jakej]

3300, Cht are all 100 to 120, egt 650 to 700 cruise, oil temp max 90 cruise 75 ( bit low), cruise 2850-2900, 26 lph.............cht only fitted on coolest head. ...............

Why ??

 

 

[facthunter]

Pilots should have cool heads. Nev

 

 

[jetjr]

Why ??

They fit the single cht to no 6, in my case this was coolest head

Nev is right much of the "tailoring" is beyond average owner, sorting out cowl air flow is even harder, and thats a key issue I think, owners are led to believe they are all sorted out right from factory and it isnt the case.

 

 

[alf jessup]

Pilots should have cool heads. Nev

They usually do Nev right up until the fan that keeps them cool at the front stops.

 

Alf

 

 

[kgwilson]

i have just finished reading the latest edition of Kitplanes magazine out of the USA. a good 6 page story on keeping a Jabiru engine running reliably... they identified 2 main culprits for their failures. lack of oil cooling, and lack of airflow around the engine and heads.their first recommendation.. throw away the oil cooler! its useless apparently, on a Cub they found the best was the oil cooler from a 180Hp lycombing. and then you have to make sure it gets enough airflow, requiring a separate ducting system, that didn't increase the air pressure under the cowl and reduce head cooling. so the cooler was in a duct, with inlet at front of the cowl, and exit below the engine at the outlet at the bottom, no air allowed to flow into the engine bay area. good cooling over the heads was next, but also be aware of excess cooling on the fwd cylinders, fixed by a small air dam over the front cylinder fins. and third and final tip, run them hard.

 

the last point i agree with, i have only had experience with the 2200 in a school environment, and the boss told us to run them hard, and they did go the distance. cruise at 2800 to 2900 rpm. but this was almost 6 yrs ago.

 

so maybe temps are the issue over here, just we have been looking in the wrong area..

Agree. I have a big mutha oil cooler with its own large air intake & a better full flow cylinder head cowl. I know of a 3300 with good oil cooling & cylinder head air flow now at 4200 hours with normal maintenance.

 

Run the engine hard 2800/2900 and the through bolts will fail?

Rubbish, thats the best RPM to run them.

[Guest davehw]

My 3300 Jab engine has to date been excellent. I installed a separate naca inlet and large duct to the latest issue jab oil cooler. Just forward or cooler is a controllable butterfly valve and manifold. (same effect as cowl flaps) Oil temp is fully controllable, and kept at the 80 to 90 degrees range.

 

It is a great option with jab engines, and is usually fully closed in cold weather cruise, to fully open during a hot day, to anywhere in-between as required.

 

Lower engine cowl has a ram air opening directly on to sump fins also.

 

Dave.

 

 

[lorraine powell]

I can think of several. How about the two gentlemen from WA who picked up a new one at Bundy, and didn't make it pass the ranges before coming to grief ???...............Maj...

what was the weather conditions like and was it engine related or pilot error??

 

 

[Bruce Tuncks]

My engine went just fine for 14 years until I ran it too hot and lost an exhaust-valve seat. I was running it at cruise rpm on the ground, concentrating on a propellor-balance device.

 

So kgwilson and Dave are right. Cooling is the critical thing. You need to do better than the factory seems to say, and then the engine will go for years and years.

 

 

[Keenaviator]

what was the weather conditions like and was it engine related or pilot error??

I believe it was weather related; scud running and controlled flight into terrain.

 

 

[Keenaviator]

My 3300 Jab engine has to date been excellent. I installed a separate naca inlet and large duct to the latest issue jab oil cooler. Just forward or cooler is a controllable butterfly valve and manifold. (same effect as cowl flaps) Oil temp is fully controllable, and kept at the 80 to 90 degrees range.It is a great option with jab engines, and is usually fully closed in cold weather cruise, to fully open during a hot day, to anywhere in-between as required.

Lower engine cowl has a ram air opening directly on to sump fins also.

 

Dave.

I am running the same set up, separate naca duct to oil cooler with air flow to cooler controlled by butterfly valve. Same observations too, closed most of the time and opened as required to maintain 80 - 90 degrees C.

 

 

[lorraine powell]

My engine went just fine for 14 years until I ran it too hot and lost an exhaust-valve seat. I was running it at cruise rpm on the ground, concentrating on a propellor-balance device.So kgwilson and Dave are right. Cooling is the critical thing. You need to do better than the factory seems to say, and then the engine will go for years and years.

I agree with you we have had no trouble with our engine it is also around 13 years

 

 

[coljones]

I have been reading these forums for a while now and there seems to be a lot of Jab bashing going on. Now I have noticed myself in the RAA Members Market you see a lot of airframe 400 hrs new motor type listings. I have done a couple of hours in a jab and didn't mind flying it at all and there seems to be quite a few around that are affordable. So1. Are they really that bad ?

 

2. If they are as bad as people make out what do you all think causes the issues they have and are the problems manageable?

 

3. Do they have any other big problems

 

All opinions welcome I would love to here from Jab drivers seeing they trust these things with there life.

 

Thanks

 

Marc

There are lots of Jabs NOT on the market that have very high hours doing sterling service. If it works, why sell it? The preponderance of Jabirus in the marketplace is mainly because of the preponderance of Jabirus in Australia. They are popular little buggers and do a great job for the price.

 

 

[facthunter]

Many of them are used for long(er) trips. Merlins used to overheat on the ground if you stayed there too long. I see people running engines with the cowl off for extended periods. That is one way to ruin an engine. If it's a heat treated part, once you cook it, it's not on spec. It will be softer and less strength. You can't fix it. It was heat treated as a raw casting or forging, prior to being machined. Nev

 

 

[Icarus]

Overheating heads can cause post ignition detonation.

 

Post ignition detonation creates a multitude of problems:

 

Heating of valves and pistons to very high temperatures, particularly at sharp edges like valve head corners and piston tops at the perimeter.

 

These high temps can then cause pre ignition detonation.

 

Both types of detonation put high heat and massive strain on all engine parts.

 

This includes:

 

high impact type pressure on piston top through to bottom end and into crankshaft..

 

this is then transferred to main bearings which are in the crank case,

 

trying to break it apart.

 

The head is also now being forced in the opposite direction at much higher force than normal.

 

Are your through bolts strong enough? Bolt heads Flat on the clamped surfaces?

 

Hot Head?

 

The exhaust valve can overheat and swell in the guide, or break the head off or stick in the guide then the piston finishes the ex head off.

 

Also the seat can warp and or chip and allow hot gasses to flow past the valve head burning the stem and then fracturing

 

the ex valve seat can drop out if the head is overheated and expands and the interference fit is not tight enough.

 

tops of pistons especially at the top edge can be destroyed etc etc

 

Too lean a fuel mixture can create too much heat ,followed by pre ignition detonation

 

The point of all this is that poor fuel or fuel with too low octane rating can cause detonation as well.

 

Creating all the same problems as above and any others I missed.

 

So

 

Jabiru often claims poor fuel, some owners claim poor quality control , while others claim overheating heads as the cause. Some say poor fuel distribution causes lean condition.

 

My opinion is that the issues are probably a mix of one or any combination of these factors.

 

Interestingly Jabiru now appear to provide full exhaust and cylinder head temperature monitoring on all cylinders as standard. Possibly urged by CASA

 

A school jab I was in recently, had dropped an exhaust valve and I believe it was only run on avgas.

 

My actual experience with jabiru engines is exactly 0. and my opinions are based on hours and hours of reading on the subject .

 

http://www.experimentalaircraft.info/articles/aircraft-engines-detonation.php

 

http://www.contactmagazine.com/Issue54/EngineBasics.html

 

 

[facthunter]

You didn't mention the piston crown's temperature. You aren't monitoring that. The design of the Jabiru piston is not optimal for getting the heat out of the crown. "W" slot and skirt relieved pistons are designed for a Holden car or cars generally. IF you spray a lot of oil on the bottom of it you will improve the situation. This is done on turbo charged air cooled aero engines. Nev

 

 

[jetjr]

Oil cooling underneath also done in CAE engines.

 

 

[Icarus]

You didn't mention the piston crown's temperature

Me :

 

Heating of valves and pistons to very high temperatures

I guess a hot crown could start detonation , but why did it get too hot?

 

. Cant dissipate enough heat? is that a design/ engineering issue? or a symptom of an overheating top end?

 

Too lean? hot plugs? detonation from hot heads or too low octane ?

 

An engine running normally, as you know ,should not melt or heat damage the piston crown.

 

A detonating engine can heat the piston to melting point. hot carbon deposits on a crown can cause pre ignition.

 

Monitoring EGT and CHT can give warning that detonation is happening and time to reduce load. hopefully in time to save the engine from near total destruction.

 

http://www.acl.com.au/web/acl00056.nsf/a7d23b8ace0d7e31ca2560d3001fb663/014b681fc66eeab44a2563c6002578c5?OpenDocument