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Need info re Rotax

E

Ex Bonanza Bucko

Well Known Member
I have a new S-LSA on order from Van's. I have a couple of questions about the Rotax:
1.)I assume the the lead from 100LL gets into the reduction gear box because it uses engine oil and that gets the lead from the gas. Is that so?
2.)Where are the coolant and oil cooking radiators in the engine. I can't see them in pictures.
3.)I heard that high power settings reduce the lead fowling from 100LL. How high is High?
Thanks for your input and anything else you wanna say about this.

EX Bonanza Bucko....my Bonanaza that was my best buddy for 29 years flew away last week to a new home in Northern Wisconsin where it's in a heated hangar.....because the place is above the permafrost line:)
 
Preface: I'm no ROTAX expert, but I learned enough in the 2 day service and maintenance courses to answer some of this.

1. You are correct in your assumption that the common oil system brings lead into the reduction gearbox.

2. The oil cooler is in the air scoop on the front. The air flow splits there. Some goes straight through the oil cooler and the rest goes down a fiber glass duct on the pilot side to the radiator mounted near the firewall. A door behind the radiator directs the hot air either to the engine compartment or the cabin heater.

3. I don't know about high power settings and lead. I recommend using a scavenger like Decalin if you have to use 100 LL. I routinely buy premium 91 UL in 5 Gal cans and bring it to the airport. I only use 100 LL on the road. If you use 100 LL less than 30% of the time ROTAX maintenance doesn't change.
 
Hi Bruce,

Lead is evil! :eek: LOL

Rich is right.
"3. I don't know about high power settings and lead. I recommend using a scavenger like Decalin if you have to use 100 LL. I routinely buy premium 91 UL in 5 Gal cans and bring it to the airport. I only use 100 LL on the road. If you use 100 LL less than 30% of the time ROTAX maintenance doesn't change."


There is nothing good in any plane using 100LL. High concentrations of lead causes issues in all planes.
Your engine will be better off if you use 91 oct. and I doubt ethanol will be an issue for your average flying. Your engine was designed to run over 5000 rpm and continuous up to 5500 rpm. I would guess most people cruise around 5000-5400 rpm. (5100-5300 is a pretty good spot to be) Some cruise at 5500 rpm for the life of the engine. If using 100LL you're better off running 5300-5500 rpm with Decalin and both of these will help keep lead down, but it isn't a cure all. Your engine and gearbox will lead lead up. People that use 100LL and run <5000 rpm ranges are really building extra lead deposits. If you use 100LL you will need to do a gearbox tear down at 600 hrs and if you use 91 Oct. that number is 1000 hrs. The main reason for that is the lead gums up the overload clutch in the gearbox around 800 hrs and it won't be functional any longer. It will need to be sent in to a distributor for the clutch dis-assembly. You will have 2-3 times more oil changes and can even lead up valve guides, valve seats and rings.

The more you stay away from leaded fuel the more money you will save all the way around for the life of the engine. Your pocketbook will thank you. Besides 100LL cost $1.80 - $2.25 more per gal. That will bite into your flying time.
 
Roger,

Here's some heresy! Even if you have to use 100 LL >30% of the time why worry about the gearbox if the only issue is the overload clutch? My understanding is that the overload clutch is only there to protect the crankshaft on a prop strike. Have I got it wrong --as usual?! :)

Rich
 
The entire engine - -

gets gummed up using 100LL. Have you seen pictures of 2 - 912's torn down, one using 91, and the other using 100LL. 100LL makes the same mess inside any engine. Rotax is no different. If possible, I'd avoid 100LL. If you have no choice, change the oil often.
 
Hi Rich,

As far as the overload clutch part in the gearbox you are right. It is mainly the clutch, but once gummed up what if you do have a prop strike. With a fully functional clutch you may get off with only an inspection and with no clutch and a crank twist which would be highly likely it would cost around $12K to get it fixed. lead still deposits on other parts inside, but it isn't as critical as the overload clutch. The other issues as stated above is just general leading through the entire engine. You may need at some point later in the engine's life to do a top end to get the lead out of the valve guides, seats and rings. If you use leaded fuel then you really need to do the 200 hr. oil tank removal and cleaning. This procedure wouldn't be as big a deal with only a steady diet of 91 oct. I have seen a number of engines dismantled that had a steady diet of 100LL. I avoid it like the plaque. I do get stuck using it when I travel, but that is only a small percentage of the time and I always us Decalin and keep my rpms up a little higher and after running 100LL on a trip I don't skimp and nickle and dime an oil change.
 
Intervals between oil changes?

Roger, speaking of which. What is the current interval between oil changes when running 91 octane unleaded? With all the new manuals being issued its hard to keep up.
Thks.:confused:
 
Thanks, Roger. Like I said, I am a definite devotee of 91 UL. I just like to know the actual downside effects of 100 LL.

RICH
 
Alex Edwards said:
Be careful. The way octane is specified between Australia and the USA is different....
Click to expand...

Thanks. I was aware of different rating systems, but hadn't yet looked into the details of what we have compared to what Rotax specifies. Just wondered if using mogas with a higher rating would have any advantages for engine performance.
 
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