Rotax 912uls versus Jabiru 80hp

[skippydiesel]

It's been said before: Fuel is the cheapest thing you'll put in your aeroplane.

 

True o king - but this nugget of wisdom, doesnt stop any of us from looking for the cheapest price/litre of our chosen brew. Most of us have been guilty of driving past a servo that is only a cent or two more expensive than the one 10 k down the track.

[Old Koreelah]

True o king - but this nugget of wisdom, doesnt stop any of us from looking for the cheapest price/litre of our chosen brew. Most of us have been guilty of driving past a servo that is only a cent or two more expensive than the one 10 k down the track.

I don't recall ever being influenced by the price of fuel; I've recorded pretty well every tankful I've bought over the last fifty years and also worked out my fuel consumption. Saving a few bob on a tankful is small beer compared to the savings from riding/driving/flying economically.

 

The original reason for the comment was that using cheaper fuel and saving a few shillings could end up costing you big mobs if you get vapour lock, detonation, etc.

[skippydiesel]

I don't recall ever being influenced by the price of fuel;

 

 

You are veritable paragon of virtue - I, at the other extreme, love the illusion of a deal.

[marshallarts]

I, at the other extreme, love the illusion of a deal.

 

I reckon it's a bit more than an illusion. With this ridiculous fuel "price cycle" that we have here (for car fuels anyway), the price can change overnight by anything up to 30%. Personally, I think that IS worth saving, so we make constant use of the Fuelwatch website here in WA, and adjust our purchasing accordingly. We have a Prado with large tanks which can take 180 litres of diesel - 30% saved on a fillup is worth at least a lunch, maybe even two!

[facthunter]

It is acknowledged the service station margins are higher than we are used to but those% changes in a short period seem unjustifiable and not related to crude prices and currency fluctuations. You just know you are being ripped off.. Nev

[onetrack]

We are being ripped off mercilessly by both the servos and the oil companies. The historical average profit level for servos was 2 to 3 cents per litre. In recent times it has been 14-18 cents per litre - and up to 30 c.p.l.

 

I have never seen so many new servos being installed as I have seen in the last 12-18 mths. Even old sites where a servo was ripped out and the site left vacant - they are now building new servos back there again.

 

The global money is pouring into fuel retailing, because it is vastly more profitable than any other retail operation. Personally, I love the fact that Costco has moved in to Australia, and is into fuel retailing.

 

At the Perth Airport Costco, the queues for fuel are always huge, and the fuel savings are enormous. The savings are often around 15 to 20 c.p.l.

[danny_galaga]

Retail fuel profit itself is quite low compared to other products. When I worked at a servo, the margin was maybe 5% over wholesale. That's ludicrously low. To compare, a lot of things you sell on shop shelves would have 50-100 % mark up over wholesale. Which of course is where the servo makes its money. But it is incorrect to say fuel itself is a good earner

[marshallarts]

But it is incorrect to say fuel itself is a good earner

 

Not for the retailer running the servo, I think it's the fuel companies further up the food chain that are doing the ripping off. I certainly wouldn't be investing in a servo now, but people are - there's a new one being built near me, despite the fact that there are at least 3 others within a couple of km. Very hard to see the viability there.

[onetrack]

The API publish the Terminal Gate prices for ULP and diesel, for every major city, weekly. This is the price that virtually all fuel retailers pay. Compare the TGP to what your local servo is selling at, and that's their margin.

There are exceptions to the TGP of course, heavy fuel users get far better prices, and the likes of Costco buy direct from refiners, thus they don't pay TGP prices.

If you want to build or lease your own terminal storage, you too can buy whole shiploads of fuel from refiners, at very attractive prices.

 

https://www.aip.com.au/pricing/terminal-gate-prices

[John M]

I was wondering about people’s ideas on both the above engines.

Thinking about a new aircraft but it has the Rotax 912uls in it. I’ve currently got a Jabiru 2200 80hp. The Jab engine has been extremely reliable and easy to work on. Theres plenty of room around it and most things are easy to get at for the minor servicing. It only uses 13 litres per hour, but I’ve always used avgas. You can use unleaded but fuel types can’t be mixed. Cruises at 90kts. The Rotax is heavier on fuel, around 17 litres per hour, but I’ve been told they run better on unleaded, and the fuel can be mixed if necessary. The engine seems considerably more complicated, and takes ap much more room, which I’m guessing makes it more difficult to do routine servicing. From what I’ve a heard parts also seem more expensive, so I guess annuals would be too. Also heard they are hard to start in colder weather? Does anyone know if the power is as good as the Jab (80hp v 100hp)? The Rotax cruises at around 80kts. Are they as reliable?

Just interested to know others thoughts ...

Jenny

Jenny

 

I have over 5,000 hours behind Jabiru 2200 engines.

 

This most recent Jab is the Generation 4. On this version Jab improved the top end which allows closer tolerances so that I don't have to add any oil between oil changes at 30 hours.

 

The engine is much simpler design that fits easily into my Avid MK4.

The earlier engines had issues with valves, valve guides and separated valve heads.

As mentioned the top end has been completely redesigned including better lubrication of the rocker box.

That said, the Rotax engines do have some advantages which can also be a disadvantage.

The gear box allows longer props, but the gear box is one of the problem parts. The engine sound is different since it typically is running at twice the room of the Jabs.

The engine is about 20 pounds heavier which eats up some of that extra hp.

Yes, parts are much more expensive.

Two carbs have to be synced properly.

I mix gas types with no issues and run my 2200 on ARCO premium 91 AKI. The higher compression of the Rotax may not allow this octane level. Although I have noticed that some do run mogas.

The Rotax engine is well built and runs a long time between overhauls. It's the gear box and Sprauge clutch that need more frequent servicing.

I fly a lot and already have 160 hours on my new Jab gen 4 engine.

The only issues I have had is Starter Bendix unit. Jabiru changed from the reliable Honda Bendix to a brand the only lasts for 50 hours in my experience.

I am in contact with Jab in encouraging a change back to the Honda brand.

My engine burns 2.8 gph at above 7500 MSL when I lean it out.

I am counting on this engine to take me to the day when due to age I'll have to hang up my headset for good. I'm 83 so I still have a few years to enjoy flight.

[skippydiesel]

Jenny

 

I have over 5,000 hours behind Jabiru 2200 engines.

 

.......................................................................

That said, the Rotax engines do have some advantages which can also be a disadvantage.

The gear box allows longer props, Marginal but the gear box is one of the problem parts. This is news to me - please give evidence. The engine sound is different since it typically is running at twice the room of the Jabs. That's why Rotax 912/814 run a gearbox, to bring propeller speed down to an efficient range (The Jab @ around 3000 rpm is at the upper limits of efficiency)

The engine is about 20 pounds heavier which eats up some of that extra hp. Please state comparative installed figure (and I for one would prefer KG)

Yes, parts are much more expensive. Expense can also be related to frequency of replacement - most Rotax 912's go to their 2000 hr TBO (and above) without significant repair/overall costs

Two carbs have to be synced properly. True - but potentially you have better air/fuel distribution (better economy/smoother running/ more even combustion chamber temps) and in truth its not hard to do - I do a check every 100 hrs and rarely have a need to "tweak"

I mix gas types with no issues and run my 2200 on ARCO premium 91 AKI. The higher compression of the Rotax may not allow this octane level. Although I have noticed that some do run mogas. Most Rotax 912's run on MOGas (95-98 RON) but can also run on AvGas (with changes to servicing regime)

The Rotax engine is well built and runs a long time between overhauls. Very true It's the gear box and Sprauge clutch that need more frequent servicing. Really ?? - in general the Sprag Clutch gives problems when people persist in using a low energy battery (avoidable) and now 912's are fitted with "Soft Start" which reduces the shock loading on components further making it unlikely that clutch problems will occur. As for the gearbox - there is an inspection scheduled for mid life engines but this does no necessarily mean replacement/rebuild.

.....................................................................................

My engine burns 2.8 gph at above 7500 MSL when I lean it out. Very good. I flight plan my 912 ULS (100 hp) at a conservative 14 L/h, routinely get under 13 L/h and have seen under 10 L/h for slow flights "around the patch" (these are whole of flight figures not cruise)

I am counting on this engine to take me to the day when due to age I'll have to hang up my headset for good. I'm 83 so I still have a few years to enjoy flight. Long may you fly

[shajen]

Jenny

 

I have over 5,000 hours behind Jabiru 2200 engines.

 

This most recent Jab is the Generation 4. On this version Jab improved the top end which allows closer tolerances so that I don't have to add any oil between oil changes at 30 hours.

 

The engine is much simpler design that fits easily into my Avid MK4.

The earlier engines had issues with valves, valve guides and separated valve heads.

As mentioned the top end has been completely redesigned including better lubrication of the rocker box.

That said, the Rotax engines do have some advantages which can also be a disadvantage.

The gear box allows longer props, but the gear box is one of the problem parts. The engine sound is different since it typically is running at twice the room of the Jabs.

The engine is about 20 pounds heavier which eats up some of that extra hp.

Yes, parts are much more expensive.

Two carbs have to be synced properly.

I mix gas types with no issues and run my 2200 on ARCO premium 91 AKI. The higher compression of the Rotax may not allow this octane level. Although I have noticed that some do run mogas.

The Rotax engine is well built and runs a long time between overhauls. It's the gear box and Sprauge clutch that need more frequent servicing.

I fly a lot and already have 160 hours on my new Jab gen 4 engine.

The only issues I have had is Starter Bendix unit. Jabiru changed from the reliable Honda Bendix to a brand the only lasts for 50 hours in my experience.

I am in contact with Jab in encouraging a change back to the Honda brand.

My engine burns 2.8 gph at above 7500 MSL when I lean it out.

I am counting on this engine to take me to the day when due to age I'll have to hang up my headset for good. I'm 83 so I still have a few years to enjoy flight.

Thank you, John.

theres a lot more to choosing a new plane than I ever thought!

[shajen]

 

Thanks Skippydiesel,

it’s really been great hearing everyone’s ideas, comments and replies. I appreciate the time you have spent to share your knowledge. What a great forum this is!

[shajen]

Now to choose what instruments to put in.