How to improve the reliability of the 6 Cylinder Jab

[facthunter]

Yes, but having any kind of flywheel at the opposite end of the crank to the Prop isn't desirable. Nev

 

 

[jetjr]

They have taken a lot of weight out of it now

 

 

[facthunter]

Most aero engines don't have a flywheel , but at the other end of the scale some have dynamic counterweights each end of the crank to damp out torsional vibrations. Radials likewise (the BIG ones) Having to balance 7 or 9 rods and piston assemblies, with counterweights means there's a lot of weight just doing that, and it's all got flywheel effect. The way that flywheel is mounted on the Jabiru isn't the best. Flywheels coming loose has been a problem with many other types of engines since they first made them. The associated noise is considerable with damage as well, when they do. Nev

 

 

[reggie]

Does anyone else not run them between 2100 and 2700 rpm? Just curious.

 

 

[frank marriott]

Does anyone else not run them between 2100 and 2700 rpm? Just curious.

I only come back below 2700 once in the circuit on landing, use a descent profile > 2800.

 

 

[Aldo]

Does anyone else not run them between 2100 and 2700 rpm? Just curious.

Reggie

I run mine full noise from take off run to top of climb (mostly somewhere above 5000) then 2900-2950 during cruise (lower than that sees an increase in CHT's), 2850-2900 on descent back to 1800 at the end of downwind or at 3 miles if on a straight in approach maintain 1800 through until pulling back to idle in the flare or just prior.

 

I have 1100 hrs and counting on mine (doesn't mean it won't stop tomorrow though).

 

I can't imagine why you would want to run in the 2100-2700 rev range.

 

Aldo

 

 

[reggie]

Hi Aldo,

 

I don't run mine between 2100 and 2700 at all. I was wondering if others were given the same info.

 

 

[Aldo]

Hi Aldo,I don't run mine between 2100 and 2700 at all. I was wondering if others were given the same info.

Reggie

 

Sorry I didn't mean to insinuate that you did, and no I have never been given that information.

 

Aldo

 

 

[Jabiru Phil]

Twin carbies on two I saw last week.

 

 

[facthunter]

What does that do?. Nev

 

 

[Jabiru Phil]

What does that do?. Nev

Guess that it would give a better fuel distribution and hence cooling.

 

PHIL.

 

 

[facthunter]

It MAY do that but it's more complex, non standard and not guaranteed. On the six it's a proposition, with some validity, to feed each side separately, certainly not on the four where you should "Pair" the front and rear cylinders and there's no room because of the sump. This is one situation where the Rotax 912 hasn't got it right. Nev

 

 

[Jabiru Phil]

Both 6 cyl J230's

 

Looked a good setup and very neatly done.

 

Phil

 

 

[Peter008]

Were these mods done by Jabiru Phil? I saw an engine at the factory some time ago where they were experimenting with twin carbs.

 

 

[Jabiru Phil]

Yes.

 

If I remember correctly, I was told that it would be ongoing addition.

 

Phil

 

 

[onetrack]

Why do they still stuff around with carbs in this day and age? They're essentially just crude jugs pouring fuel down the neck of the engine.

 

Car engines have nearly all been EFI for over 30 years. It's proven technology, it's reliable, it delivers fuel virtually right to the combustion chamber at the right time, and with great precision.

 

I don't understand why a little more complexity is shied away from. Aeroplanes are already complex machines, big jets reflect that to the nth degree - yet, today, it's a newsworthy event, when something goes even slightly wrong with a big jet.

 

Increased complexity doesn't necessarily translate to unreliability - particularly when you can add redundancy, and even multiple redundancy. Nothing to stop EFI from having a backup ECU, it's not like electronics are a huge weight penalty.

 

 

[facthunter]

Simple float equipped carbs are not much of an idea on an aeroplane, from many angles. They ice, they can flood, suffer from vibration, wear and they are finicky. A mechanical injection (dribble system) manual leaning and used with a flow meter is my idea of the best for the least. This will be too old fashioned for some who are hooked on the sort of stuff cars use, which I haven't found that reliable. What cars need is not what planes need and I like it to keep working when the lights go out, and not rely on sensors. Nev

 

 

[onetrack]

Nev, you rely on a myriad of sensors to keep working when you drive your car down the highway in heavy traffic. The stats say the most dangerous part of piloting is the drive to the airport.

 

Soon, you'll be relying on sensors to drive you down that highway, when automated cars are lobbed on us, and you're just along for the ride.

 

Electric-power-assist steering, common on most vehicles today, relies on sensors. The vehicle designers have designed the system to have redundancy.

 

Go to a minesite and watch the multiple 300-400 tonne dump trucks and 800 tonne excavators all operating around the minesite in massive synchronicity - without an operator to be seen. All done by ECU's and sensors.

 

You'd better believe the sensors are coming, to rule our lives on a daily basis.

 

 

[Old Koreelah]

...Electric-power-assist steering, common on most vehicles today...

All good, Onetrack, until something goes wrong. Sure it rarely happens, but how many drivers have experienced a power steering failure? I have and I bet many drivers would have lost control in the same situation.

 

 

[onetrack]

Old K - Yep, been there, done that (lost power steering). It sure got my attention pretty rapidly. Suffered a brake boost failure, too, on a Holden ute (inside of manifold vacuum hose peeled off and blocked the vacuum line).

 

That got my attention, pretty quickly, too! - particularly as I'd just roared up over a dam bank in a paddock, to check the water level!

 

I can't see where a moderately competent driver would be fazed by either a power-steering boost failure, or even a brake-boost failure.

 

However, just looking at the salvage yards tells me there there's an awful lot of car drivers out there, who can't even keep a fully-operational vehicle upright, and steering straight, on perfectly good roads.

 

This is why all the current vehicles are being fitted with so much automation - anti-swerve controls, hill-descent controls, anti-lock braking, collision-avoidance controls, even lane-drifting controls.

 

It's all heading towards full automation of driving, because there's so many idiots who just can't drive, or respond appropriately to any out-of-the-ordinary event.

 

Slow reflexes, inadequate training, just plain carelessness or lack of attention behind the wheel - the reasons are multitudinous - but the designers say their sensors and control systems have a higher level of reliability than humans.

 

They are very likely to be right. Personally, I'm pretty much old school, like most on here, I'd guess - I learnt to drive in the early '60's by broadsiding Holden utes around sharp bends on gravel roads, just to find the limits of Holden ute handling, and my own skill levels. After a few excursions into the bush, you learn what your limits are.

 

I still much prefer my vehicle control skills to those of the manufacturers - but I don't think I'm going to be able to, for much longer - the drive is on to take all our hard-won driving skills from us, because we obviously can't be trusted with them!

 

 

[facthunter]

Well let's keep SPORT/Recreational flying simple and hands on for as long as possible. Managing your engine wouldn't require a flight engineer, if you've set it up properly. Nev

 

 

[Jaba-who]

Why do they still stuff around with carbs in this day and age? They're essentially just crude jugs pouring fuel down the neck of the engine.Car engines have nearly all been EFI for over 30 years. It's proven technology, it's reliable, it delivers fuel virtually right to the combustion chamber at the right time, and with great precision.

I don't understand why a little more complexity is shied away from. Aeroplanes are already complex machines, big jets reflect that to the nth degree - yet, today, it's a newsworthy event, when something goes even slightly wrong with a big jet.

 

Increased complexity doesn't necessarily translate to unreliability - particularly when you can add redundancy, and even multiple redundancy. Nothing to stop EFI from having a backup ECU, it's not like electronics are a huge weight penalty.

The issues that Jabiru are having to deal with are both real practical and bureaucratic.

 

The issues of practicality are first cost.

 

Secondly that there has to be a redundancy for if the electrical system fails.

 

So in itself it may not be that heavy or that costly but you have to have some backup system which does add more cost and more weight.

 

The bureaucratic issue is that to change the engine does not simply mean bolt a new EFI on and go for it. ( Jab have been putting fuel injectors in jab engines for nearly a decade and selling them to other countries for use in military drones. ) But to do that with a people carrying engine in Oz means huge more certification testing and costs. They have made a business decision that it's not worth the effort and cost.

 

 

[Bruce Tuncks]

Wow that is interesting news Jaba-who.

 

What would it take to get one of these things and install it on your 19 reg plane?

 

 

[Jaba-who]

Wow that is interesting news Jaba-who.What would it take to get one of these things and install it on your 19 reg plane?

As far as I know they are not selling them, have never sold them in Australia.

I must admit I have no idea if they are still selling them or if the sales have ceased.

 

 

[jetjr]

i pretty sure they sell normal engines there and customer fits EFI - not really much to do with Jabiru.

 

The issue with jabiru and EFI is the faith that they have the best compromise of cost and complexity. I reckon EFI might solve some pretty core problems if they get the right setup. Someone in RSA working with Autronics and Jab engines I heard