Rotax 912

[blakemorem]

I"ve got 62 hrs on a Rotax 912 and I"ve noticed me exhaust has a lot of carbon. I was told me carby"s had been tuned/ balanced but I think it"s running a little rich. I"m solo flying and it doesn"t work real hard cause i"m not a fat *******. A CFI said do climb / descends put it to work still no change in exhaust. Is this a typical rich fuel setting for run in period and when do you consider a Rotax to be run in. I have compared it to another rotax with 500 plus hours and it"s almost white tip on the exhaust. My endurance is about 15/16 L per hour which is about right. I"m gunna make a mental note to check my flight RPM at cruise I"ve seen 5000 rpm suggested but I think that will be too fast. generally I"m at about 65 to 75 and no faster than 80 Knots. I"m not convinced low RPM will cause a sooty exhaust, and It"s not burning oil. What do ya recon carby Tune/balance? I did notice the choke lever move with throttle but fixed it with some lube.And it wasn"t pulling on the choke leaver on the carb anyway. Can be a problem but you will notice this on landing as engine will run a high idle. So back to carby tune possibly. Or not worry about it yet wait till 100 plus hours. Any suggestions?

[birdy]

Tail pipes tell Lise.Sumthn as suttle as ambient temps will change tail pipe culu.Only really way to know is shut it off at cruise speed, float down n land, then wen it cools, check the plugs.But just check

[Colinm-m22]

I had the same issue on my 914UL, and i was told to change my fuel from using a Caltex 98 to a BP91. I have the same power and cannot notice a any performance chance, however I dont have any soot on my tail, exhaust or on my main rotor blades anymore! i am happy with the suggestion as it is cheaper, cleaner and its delivering the same performance.

[Adrian S]

Guys,CAUTIONThe Rotax 912ULS and 914 Turbo needs a min of 95octane otherwise detonation will occur under load and engine life will suffer!. The 912ULS engine has a comp ratio of 11:1 and the 914 Turbo exceeds this under full boost on take off. Please check the Rotax owners manual.A lot of 98 octane fuels in Australia achieve this octane rating through the use of additives to the 95 octane stock and not additional factory refining. The burning of these additives sometimes leads to more soot in the exhaust.Another contributor to soot is not achieving the correct oil temp during operations. If the oil doesnt achieve 90-100 deg C during its operation then there will be a lot of water vapour in the oil. Dirty aircleaners also impact on the mixture leading to a rich mixture. As usual just my 10c worth,Cheers,Adrian S

[birdy]

As usual just my 10c worth,And as usual, worth ten times my two bob.

[RickE]

My information is probably only worth five cents but I have always been told to not use any less than 95 in my 914, Avgas however will give you a white to light grey colour to the exhaust.

[Brian]

Talking fuel, the rotax fuel pump has a fine screen to catch any impurities....shouldnt be a issue unless you are not running a proper fuel filter.In regard to oil temps, a oil thermostat is worth its weight in gold & should be standard equipment.From all I have read, Avgas should be avoided like the plague. Not at all good !

[t-bird]

[RickE]

I use 98 whenever I can 95 when I have to and Avgas when traveling as it is generally all you can get at airfields, I have been advised to change the oil every 20 hours when using Avgas.I also put all my fuel through a Mr Funnel as I know of an engine out due to the clogged filter that Chopper is talking about in the Rotax fuel pump.Some people may be unaware of this filter and it is worth checking!

[blakemorem]

Thank"s Gyro Gurus I have a lot more to think about. I"m running BP ultimate and stopped running Fucchs upper cylinder lubricant sometime last year as I thought this was adding to the carbon problem. Must say it makes them purr and starts real easy.No change. Carbon still there.I was told a fella run this in his choppers and got the (engines) thru 2500 hr maintenance interval. Don"t know how accurate this info is. I was worried that i was probably killing me Rotax with love, as I"m Very precious with it, I know I won"t be getting another one for a while, got to pay for this one first. I probably wasn"t listening when the bank told me i had to pay em back. I was also told about differences in oil and some not being suitable with AV Gas. the differences in mineral oil and synthetic. I was running Shell Advance oil but now running Aero 2000 oil which is more suitable with Av Gas. Never run Av Gas always been BP Ultimate anyway, which has been suggested to add to carbon problem burning off additives. I have an oil thermostat and is running in optimal range on gauge.I think a needle above 90 from memory have to make a mental note of that too. Some fellas rap a strip of gaffa tape around the oil cooler, never done that myself as I think the oil thermostat takes care of it. Just make sure me gauges are good before blast off. Sometimes ya gotta sit there and be patient especially on a cold day. I"ll be doing a oil change service soon and will check and may replace plugs, have to look at service scheduled.

[Colinm-m22]

We dont have 95 in Mackay so i will mix 98 and 91 50:50 yes?

[MilesW]

We dont have 95 in Mackay so i will mix 98 and 91 50:50 yes? I know you were trying to be funny, but I have actually done that quite often to stretch the available fuel a bit further. Works a treat. Nothing different to what the refinery or tank farm does anyway.In this country 98 is little more than 95 with an additive. Mostly Toluene. Probably familiar to most as a low cost degreaser and paint thinner. Can play havoc with seals, hoses, tanks and the like.Most times you will also run hotter with 98. Overall, you are far better off running fresh 95 all the time.And, regardless of special oils, reduced oil change times and what the book says, running avgas in one of these is nothing short of abuse and should be a crime.

[MilesW]

I"v always pitched my props to keep the WOT rpm to bout 5300, this gives a cruise of bout 4200-4400, and a margin for high DA.Just curious as to why you would strangle a donk that makes its maximum horses at 5800rpm down to 5300rpm. Is"nt max available HP to the prop kinda handy when you want to climb?Also a bit confused as to the margin for DA since WOT actually drops as DA increases.

[birdy]

Firstly, I"m only a pissant, so don"t need full soot. But the main reason is to stretch the tank as far as possible. If I cruise at 4400 I can stretch it past 5 hours.I"v seen WOT variations of over 300 rpm on the same day, and sum times you can be in a situation where your on WOT continuously for more n 20 mins, so, to play it safe, I choke it a bit.

[tonydenton]

HEY WEBBY, can you change the title of this post . it sounds like the 4 banger rotax owners are having trouble with their 4 banger rotax"s.