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G2 on operating a Rotax in RV-12

E

Ex Bonanza Bucko

Well Known Member
Hi:
I'm a newbie and I'm all full of questions. Thanks to a bunch of guys here for starting my education.

My next wonderment is about the Rotax engine and A.)ethanol and B.)Lead in 100LL.

Naturally I will try to operate on 91 octane auto gas but sometimes that won't be available. So how big a problem is it and how is it best managed when I have to use 100LL. I have heard that 25 hour oil change is recommended (I do that anyhow on a Bonanza) and that at the oil change the lead has to purged from the oil tank. Your comments would be valued about this.

Then I note that Van says they have been running 10% ethanol auto gas for four years with no problems. But what are the best steps to manage that? It's been said somewhere here that you shouldn't allow a tank of auto gas with ethanol in it to sit over 30 days and, if you do, to drain it out and start over. Is that so and why?

It also would seem that any water that got into the tank would combine with the ethanol and, thus, disappear.....in other words, not cause engine stoppage as it would in a Continental or Lycoming. Is that so?

I've also seen the uTube that says you have to "burp" the oil tank before starting the Rotax engine and that not doing that will potentially cause you to burn up the cylinders. Is that so? Do you always do that?

Thanks for your input. I will go to any web pages you suggest and read your comments with great interest.

EBB
 
I recommend that you take the two day ROTAX service course offered through Lockwood or California Power Systems. It helped me a lot. I don't claim to be an expert, but I can share my operating experience over the last 18 mos. The burping is done to get an accurate oil level. You are pressurizing the crankcase with cylinder leakage to force oil back to the tank.

I use 10% ethanol almost exclusively and add Decalin (sp?) when I have to use 100LL. The ROTAX instructor told us that the engines that run on car gas look like new when he disassembles them for overhaul as opposed to heavy lead deposits on those using 100 LL. He recommended full synthetic oil if you have to use 100 LL on a steady basis since it holds the lead in suspension better and decreases deposits.
 
Do What Rotax Says

I had no trouble at all with my engine in 2 years. I did exactly what the Rotax documentation suggested. It takes some getting used to as information is relayed in a different manner than other manuals, some patience is required. A membership to Rotax Owner (www.rotaxowner.com) is highly recommended. They have the manuals, videos and other training aids to learn how to tame the Rotax beast.

As far as gas is concerned the Rotax is far more tolerant to ethanol than it is to lead. The certified version of the engine is certified for up to E10 and Lockwood (Lockwood Aviation, a good resource) has used up to 20 or 25% ethanol with no problems.

The best way to handle the stale gas issue is to fly more often. If that is not feasible the best thing to do would be to not top off the tank when you expect to not fly for an extended period of time and top off with fresh gas the next time you do.

The idea of "burping" the engine to check the oil is simply to get as much of the oil as possible out of the engine and into the tank to get an accurate reading. Failure to do so will give an artificailly low reading wich could lead to overfilling the tank which will effectivly lubricate the belly. I didn't do this before every flight. After a while you get a feel for where the oil level is and when you need to add.

The part about damage to the engine is if you fail to perform the purging processs prior to first engine start and / or any time air could get into the oil circuit. Yes, this must be done, it is not worth the chance. It is not really that hard to do.

One other place you should look into is California Power Systems, they have a lot of Rotax parts and provide information. For parts ordering, though, I prefer Leading Edge Airfoils, their online catalog and internet ordering process in first class (better than Aircraft Spruce).

There are also places that offer Rotax Maintenance classes. The first level is basically all about routine servicing. I think it is a weekend class and would be time very well spent.

Good luck
 
Ex Bonanza Bucko said:
Hi:
I'm a newbie and I'm all full of questions. Thanks to a bunch of guys here for starting my education.

My next wonderment is about the Rotax engine and A.)ethanol and B.)Lead in 100LL.

Naturally I will try to operate on 91 octane auto gas but sometimes that won't be available. So how big a problem is it and how is it best managed when I have to use 100LL. I have heard that 25 hour oil change is recommended (I do that anyhow on a Bonanza) and that at the oil change the lead has to purged from the oil tank. Your comments would be valued about this.

100LL only effects operating and maint procedures if you run it more than 30% of the time. For most owners, the amount of time the do long cross country flights that require use of LL is far less than 30%. Also, there are some airports that sell Mogas (though not lots) that can help save $ and reduce LL use

Then I note that Van says they have been running 10% ethanol auto gas for four years with no problems. But what are the best steps to manage that? It's been said somewhere here that you shouldn't allow a tank of auto gas with ethanol in it to sit over 30 days and, if you do, to drain it out and start over. Is that so and why?

Auto fuel has never been stabile to store for very long compared to avgas. That is why so many companies sell fuel stabilizer additives to protect fuel systems like your lawn mower etc, while it is not used. Ethanol just amplifies the problem, but is not the entire cause of the problem.

It also would seem that any water that got into the tank would combine with the ethanol and, thus, disappear.....in other words, not cause engine stoppage as it would in a Continental or Lycoming. Is that so?

Read up on Phase separation

I've also seen the uTube that says you have to "burp" the oil tank before starting the Rotax engine and that not doing that will potentially cause you to burn up the cylinders. Is that so? Do you always do that?

False. The only reason for burping the oil system is to get an accurate measurement of the oil level. If you don't burp it, some of the oil you need to measure may be laying in the bottom of the crank case. If you add oil based on the reading you get at that point, you might be over filling the oil system.

Thanks for your input. I will go to any web pages you suggest and read your comments with great interest.

EBB
Click to expand...
An old news letter article you may find helpful can be found HERE
 
i had always heard that synthetic oil was less able to keep lead deposits in suspension than conventional oil. now i am reading the opposite.
bob noffs
 
bobnoffs said:
i had always heard that synthetic oil was less able to keep lead deposits in suspension than conventional oil. now i am reading the opposite.
bob noffs
Click to expand...

Where are you reading that?

It is a generally accepted fact.
In SI-912-016, Rotax is specific about recommending that you use ony regular or semisynthetic approved oils if burning 100LL. Fully synthetic oil is specifically not recomended with any 100LL use.
 
My mistake. Scott is correct that SEMIsynthetic, not synthetic is best for leaded gas. I've been using the California Power Systems AV-9 and MOGAS so it was not a critical issue for me and the details slipped into the abyss of my aging brain! :). Another good reason to take the ROTAX course so you get the info first hand.
 
And I can confirm that from experience. Even only a couple of tanks of 100LL from cross country flights will show significant lead fallout when using fully synthetic oil at the next oil change. Use semi-synthetic when you anticipate ANY use of 100LL.
 
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