Another Jab bites the dust.

[rick-p]

I really can't follow all the comments in this post as all these temps etc you keep referring to on my Jab 2200 don't get anywhere near them and I haven't adjusted or added anything and this is also the case for all the Jab motors I know that the guys are running in the Philippines. No real problems so what is really going on. I know personally abouyt 25 people running Jab motors who have had nothing more than very minor problems not even worth mentioing. I would dearly like to know the true spec's for Jab motor failures and major problems both in engine model and serial numbers and dates of the incidents etc. There probably is a problem but what is the cause of the problem maybe it's operator related, who knows, but until someone really does come up with the correct answer I wish people would put up or shut up. If you don't like the product don't knock it, just don't buy it and let us who really don't care whether it kills us or not use it in peace until it either wears out or breaks and then we who paid for it can then bag it. It would be really interesting to see the specs on what aircraft the Jab motors have failed in maybe it is an induction cooling problem as was the case for all the 912 failures when they were first installed in Jabiru aircraft, maybe I'm wrong but just about all of them got cooked.

 

Rick-p

 

 

[facthunter]

It would have to help the temps and consumption. I think the power increase of that order might be a bit much, and I wouldn't go for it although in theory if you improve things you could push the comp ratio. ( Don't even think of it or supercharging it either)

 

A mixer downstream of the carb might even things out somewhat. Carbs usually spray an uneven mixture depending on what side of the carb bore you take it from. Nev

 

 

[damkia]

Relating to EGT and CHT's

 

As much as I don't believe the reason given by Jab for the failure (ie not living in Bubndaberg etc) they may well be on to something.

 

Could high humidity (northern climes) play a part in keeping the engines cooler than they would be in low humidity? Would it be worth tracking where these failures actually occurred in Australia (or at least where the engines have spent most of their time)? (related to the experiences in the Phillipines per rick-p's post)

 

Anyone that has used water injection in car engines would be familiar with the principle.

 

 

[Steve Donald]

In terms of the thru-bolt failure, is there any evidence that the new longer bolts and nuts are failing? In my mind this is the real acid test, everything before this upgrade is past events and falls into the history bucket and already known. There was an AD out to upgrade the bolts and/or nuts which had timed out for mandatory completion on the 14th April 2012... this AD also included crankcase dowels in some prescribed circumstances.We know Jab have added 0.5mm to lengthen the barrels or have fitted 0.5mm of spacers on earlier barrels to lower the compression to help manage the detonation .... to the best of my knowledge this has not been mandated to owners but has been a standard process during factory rebuilds since 2010 inclusive of new production engines.

 

On the current production engine they have increased the thru-bolt dia as well as the longer 12 point nuts, along with a higher interference fit on the crankcase dowels ..... this is a significant improvement but it can't be preformed on old engines easily.

 

In terms of retrospective upgrades today ... is there any evidence of the new longer thru-bolts with 12 point nuts failing????

 

Cheers

 

Vev

Yes there has been failure, the new nuts fit the thread better than the 12 point nuts which have a better rolled thread, unfortunately the 12 point nut thread is given for the AD nut fix is a poor fit on the old machined threads on the through bolts, guess what a worker from the engine factory said they often had bolts fail during assembly, bigger bolts are not needed just better stronger material grade 8 through bolts as shown on the bolt forum with rolled thread and the 12 point nuts, these handle 2x the set tension of 30 ft ib 32 would be better, and safe but the old system of bolting had you on the failure point or so close its not funny, the quicker we get approved to use these WA grade 8 rolled thread bolts with double the strength the better, hell only $120 or dollars, we need to make some noise and make it happen it is a joke and hard to believe the resistant attitude of the powerheads, put lives at risk unnecessarily.

 

 

[Gnarly Gnu]

As much as I don't believe the reason given by Jab for the failure (ie not living in Bubndaberg etc) they may well be on to something. Could high humidity (northern climes) play a part in keeping the engines cooler than they would be in low humidity?

Except that Durban (mentioned by Vev #269) has a fairly tropical type climate also.

 

 

[eightyknots]

Relating to EGT and CHT'sAs much as I don't believe the reason given by Jab for the failure (ie not living in Bubndaberg etc) they may well be on to something.

 

Could high humidity (northern climes) play a part in keeping the engines cooler than they would be in low humidity? Would it be worth tracking where these failures actually occurred in Australia (or at least where the engines have spent most of their time)? (related to the experiences in the Phillipines per rick-p's post)

 

Anyone that has used water injection in car engines would be familiar with the principle.

Water injection was used as early as World War II, both in Spitfires and Messerschmitt 109s. The main reason was to reduce detonation.

 

This begs the question, why aren't water injection systems used in smaller recreational aircraft engines today?

 

 

[facthunter]

Steve, That all sounds pretty grim. Nev

 

 

[planesmaker]

I don't really think the Jab engine is detonating, I have attached a photo of a piston that has experienced detonation,(on take off) as you can see it is destructive, any Jab pistons out there with similar damage?

 

 

[Guest Howard Hughes]

Back to while you were lined up on the runway. We should ALL be giving ourselves a pre takeoff safety brief. Not a robotic speech, but a real briefing on what your actions will be in the event of an engine failure. Say it out loud, I will immediately lower the nose to maintain flying speed. Point to the airspeed indicator at about best glide speed. Hopefully doing this will remind your brain where the needle needs to be. What options are available to you?..On THIS strip, in this direction. Where are the best paddocks, roads, paths of least resistance. Where is the wind coming from. Is the best paddock straight ahead?..left or right of the centerline.? Are there any options at all??.. sometimes there aren't.

Great post Motz!

In the Kingair we have 'departure procedures' for airports with high terrain. While it is a completely different situation to the single engine EFATO, the premise is the same.

 

You not only need to have a plan, but you need to stick to it!

 

 

[planesmaker]

here it is, sorry a little finger trouble uploading

[David Isaac]

Unfortunately I don't have pictures of my pistons of some years ago, but your picture shows relatively mild damage compared to what can happen with severe detonation. For those who don't know detonation begins long before you actually hear it and can be causing long term damage behind the scenes. Usually the ring lands are broken and the rings broken (your picture shows that was close) and departed out the exhaust valve. It does largely depend on what material the piston is made of and how it is formed, the worst are the silicon hyperatectic types (if I have spelt that correctly), the strongest being the forged types.

 

In my case, a 6 litre boat racing engine fitted to a Jet Sprint boat, the piston melted and departed via the exhaust valve and port and we found molten aluminium in the exhaust manifold. In my case, we heard it, felt the immediate reduction in power and then a continuous rattle in the engine. I had the misfortune of destroying two engines like this (caused by bad Shell fuel ... well perhaps a poor choice on our part). One memorable occasion was at full noise on the Broad water on the Gold Coast, and that was just test running ... an expensive day.

 

 

[jetjr]

Long topic, lots of interest.

 

So far I read

 

Through bolts need upgrading maybe beyond current longer/ARP nuts spec

 

Fuel distribution could be a key contributor

 

Poor torque of through bolts and re-tensioning also linked.

 

BUT - why is this not an issue on solid lifter engines?

 

Ill keep watching my EGT and trying to even them out.

 

The RSA injection looks good but cant understand the 30% power increase - fuel efficiency yes.

 

Nor do I want 30% more power, this will surely test some components including airframe.

 

 

[planesmaker]

Unfortunately I don't have pictures of my pistons of some years ago, but your picture shows relatively mild damage compared to what can happen with severe detonation. For those who don't know detonation begins long before you actually hear it and can be causing long term damage behind the scenes. Usually the ring lands are broken and the rings broken (your picture shows that was close) and departed out the exhaust valve. It does largely depend on what material the piston is made of and how it is formed, the worst are the silicon hyperatectic types (if I have spelt that correctly), the strongest being the forged types.In my case, a 6 litre boat racing engine fitted to a Jet Sprint boat, the piston melted and departed via the exhaust valve and port and we found molten aluminium in the exhaust manifold. In my case, we heard it, felt the immediate reduction in power and then a continuous rattle in the engine. I had the misfortune of destroying two engines like this (caused by bad Shell fuel ... well perhaps a poor choice on our part). One memorable occasion was at full noise on the Broad water on the Gold Coast, and that was just test running ... an expensive day.

David, yes you are correct in that the photo I posted shows very mild detonation, just wanted to put it up so that others can see the result of detonation.Yes the ring lands were close to broken and the rings were jammed in. If the Jabirus are detonating then there should be evidence of it. I am not saying they are not but there should be telltale signs. Tom

 

 

[Yenn]

I had detonation in a 2.2 Jab, caused by mogas. Broken rings and land between 1 and 2 rings. I flew it from Old Station to Rodds bay in that condition. It still had full power, but was misfiring on 1 mag at low RPM. I blame Caltex fuel.

 

 

[motzartmerv]

What octane fuel yen?

 

 

[renbo]

i have enjoyed this discusion on the jabiru engines. although some confusion on detonation , preignition ect

 

i am not an engineer, but engines are a hobby , from what i have read there seems to be a problem with mixture distrubution,

 

and from this detonation , but know one has mentioned doing a plug check which would tell you what is going on.

 

having a certain octane rating the easiest fix would be retard the timing a couple of degrees , water methinol injection set to

 

work at wot is a good if a bit over the top,but easy to rig up, valve failure is a sign of overheating,faliure to dissipate the heat to the seat/

 

head.the silicone cylinder base seal shouldnt bother it its still metal to metal with silicone filling the gaps ,its all held together

 

by the bolts stretched in tension,of course this is just my two bobs worth,but i know that detonation destroys engines

 

through heat and mechanical shock the black or silver balls on the plug centre electrode porceline is a giveaway

 

though knowone has mentioned it, i am only going on what is being said, i havent looked at a failed jab engine

 

but would like to as its a tricky problem they seem to have, i think the plugs would show whats going on ,

 

at least thats how i did it when i had a harley drag bike, something is set to close to the edge on these engines and some at least

 

thats over the edge , they need more head cooling , higher octane , less timing, richer mixture, better distribution, especially

 

if its only certain cylinders

 

 

[turboplanner]

i have enjoyed this discusion on the jabiru engines. although some confusion on detonation , preignition ecti am not an engineer, but engines are a hobby , from what i have read there seems to be a problem with mixture distrubution,

and from this detonation , but know one has mentioned doing a plug check which would tell you what is going on.

 

having a certain octane rating the easiest fix would be retard the timing a couple of degrees , water methinol injection set to

 

work at wot is a good if a bit over the top,but easy to rig up, valve failure is a sign of overheating,faliure to dissipate the heat to the seat/

 

head.the silicone cylinder base seal shouldnt bother it its still metal to metal with silicone filling the gaps ,its all held together

 

by the bolts stretched in tension,of course this is just my two bobs worth,but i know that detonation destroys engines

 

through heat and mechanical shock the black or silver balls on the plug centre electrode porceline is a giveaway

 

though knowone has mentioned it, i am only going on what is being said, i havent looked at a failed jab engine

 

but would like to as its a tricky problem they seem to have, i think the plugs would show whats going on ,

 

at least thats how i did it when i had a harley drag bike, something is set to close to the edge on these engines and some at least

 

thats over the edge , they need more head cooling , higher octane , less timing, richer mixture, better distribution, especially

 

if its only certain cylinders

The hard part Renbo is for us commentators to get quality information.

 

eg is is only exhaust valves?

 

is it only the the valve head coming off?

 

is it always the same cylinder(s)?

 

what fuel was being used?

 

as you say, what was on the plugs?

 

and about 30 other questions, but mostly the information is vague and generalised

 

 

[renbo]

yes that is the problem

 

 

[Kyle Communications]

In the jab engine I saw 2 days ago it failed just doing test running the valve seat ( I think inlet valve) had popped out of the head and turned a little jamming the valve in the open position also denting the piston...... this happened about 2 weeks ago doing test runs for pre delivery to a guy who bought the aircraft second hand I think the engine TT is about 150 or so hours

 

 

[facthunter]

Inserts (valve seats), will dislodge if the interference fit with the surrounding aluminium head is not adequate. You would need to know the history of the head. In any case you can measure the recess diameter and compare it with what it should have been.

 

A valve head often breakes off ( Usually the exhaust) because of play in the valve guide. This can be checked in situ. (I've said this many times). You can't run engines without checking and.maintaining them..

 

Jabiru's may have problems, but they do not control the standard of work done in the field not the way the engine is operated. I don't want to open up the Rotax vs Jabiru thing, nor have I ever taken sides in this. I merely believe there is a better way to examine the problem than people offering opinions of the problem and completely ruling out others. There are many factors. To start by doing all the things Jabiru suggest would be adviseable, but don't limit yourself to that if you have the ability. I'd be putting the best studs and nuts in any motor I had anything to do with. I might do a lot of other things too, but I will not be elaborating on them here, now.

 

Everyone is entitled to their opinion, but there are clearly some suggestions where the terminology used and knowledge of motors is lacking. You can only get so far on this forum.

 

The certified engines are a separate issue, and problem. The manufacturer is a victim of the system there.

 

If you JUST want to bag the brand. you're not constructive. If you are anti something you develop a selsctive perception of the issues, usually exaggerate the bad and ignore the good. It's called bias. Nev

 

 

[Guest Maj Millard]

Facthunter, I would certainly and promptly put up my hand as being biased, as you suggest !...Well biased towards quality engineering with excellent service history Vs piss poor engineering with a very poor service record. I'm guilty as hell !!.............................................................Maj...

 

 

[facthunter]

I'm not having a go at anyone . Just suggesting that there comes a point where saying the product is no good doesn't get us anywhere. Nev

 

 

[Guest Maj Millard]

I would agree that just 'knocking' a product is totally non-productive. That has not been the case in this instance.

 

Many forumites, including self have put forth good, to excellent suggestion on solutions to problems over the past years, with both the 2200 and 3300 Jab engines. These constructive suggestions in most cases have been in response to continued inherent failures of certain engine components within the engines, which continue.

 

Personally I don't feel these regular failures do a thing for the safety image of our sport, and for this reason should be a focus of all RAA flyers, and indeed the Safety regulator also.

 

A lot of critism has also been directed at the manufacturers for A. Not taking some of the suggestions on board and turning them into real engine improvements, and B. generally continuing with the attitude that there is no reliability problem, and continuing to offer, what is in many eyes now, a faulty product.

 

There are several users in the field who have instigated successfull aftermarket products, or improvements, into the engines, with great success in improving reliability, and general running overall.

 

Additionally many owners or users of jab engines also don't want to admit to their own personal dramas with reliability, and instead side with the factory view that there is no problem !...This site in fact had been a leader in both highlighting failures, discussing solutions, and generally allowing the free discussion (biased or not) on the problems. May this continue until a suitable solution is found.........................................................................Maj...

 

 

[facthunter]

I have been very careful how I worded my post Maj, and I can't see why you think it was aimed at you. Never suggest I would stifle debate and discussion, because that is NOT me. Nev

 

 

[Guest Maj Millard]

I know that Nev and I always enjoy your posts, and will continue to...In the big picture all we want ultimatly is the engine maker to improve his damn product for the safety of all. I don't mind being referred to as 'biased' or a Jab-knocker' by anyone, in fact I'm quit used to it by now!....it's the old story really isn't it...'The squeaky wheel gets the grease !.............................Maj...