912 ULS Carburetters

[skippydiesel]

THIS[/url] from BP "EXAMPLE OF HOW PETROL CHANGES WHEN STORED IN FUEL TANK"Kiwi

Thanks Kiwi - great article! Certainly cleared up some of my miss understandings, particularly just how fast All (petrol) fuels, open to atmosphere, deteriorate. From the article, it would seem the main problem with old fuel is engine starting - this was emphasised at least twice if not more. So presumably once running the fuel may actually have better performance characteristics.

 

 

[facthunter]

IF you log hours against fuel loaded you will pick up any significant change in fuel usage /Hr.  Another point  about the Bing. The needle will only open fully near sea level at Wide Open Throttle with the correct prop fitted to let you get the right revs. As you go to higher levels it moves open to a lesser degree as your power drops off with altitude gain and  the mass airflow reducing . This gives you your automatic mixture adjustment with increasing altitude feature. Nev

 

 

[skippydiesel]

IF you log hours against fuel loaded you will pick up any significant change in fuel usage /Hr.  Another point  about the Bing. The needle will only open fully near sea level at Wide Open Throttle with the correct prop fitted to let you get the right revs. As you go to higher levels it moves open to a lesser degree as your power drops off with altitude gain and  the mass airflow reducing . This gives you your automatic mixture adjustment with increasing altitude feature. Nev

Thanks Facthunter - I do indeed log my fuel consumption/hrs, so will go back and see if there has been any change.

 

 

[skippydiesel]

Have drained tank & refilled with BP. Also cleaned and re oiled air filters and cleaned off underside of aircraft. Not a good idea to introduce two variables when trying to track down a symptom but there you go.

 

Will let you know (after a few hours of flight) what if any difference to residue deposit.

 

 

[Blueadventures]

I only use 95, as I have had problems with 98 and it has left contamination in the float bowl of a stationary engine I used it in !  I would inspect in float bowls for any contamination, it is like a varnish appearance ! I definitely would not use 98 Ron !  I'm told that 95 does not have additives but 98 does have additives to boost octane rating so correct me if I'm wrong on this ! 

I also only ever use 95.  Twice I have topped up and filled with Avgas.   I know of a guy who tests his oil every change and it took two oil changes for the oil analysis to come back to normal after running  Avgas.  I believe its worth trying a few tanks of 95 and see what you think.  Cheers

 

 

[skippydiesel]

I also only ever use 95.  Twice I have topped up and filled with Avgas.   I know of a guy who tests his oil every change and it took two oil changes for the oil analysis to come back to normal after running  Avgas.  I believe its worth trying a few tanks of 95 and see what you think.  Cheers

Hi Blue - I do not believe there is any debate regarding the use of AvGas in the Rotax 912/914 range. With regard to AVgas usage, Rotax goes to some lengths to advise increased oil changes and reduced time to "tear-down" for inspection/cleaning of lead residue. The occasional , no other option, use of AvGas is not a problem (I believe there is actually a recommendation from Rotax on this).

 

I dont think the use of 98 RON confers any particular benefit, other than the users feeling that in doing so, they are meeting/exceeding the Rotax recommendation for a minimum of 95 RON.  When away from home. I have often resorted to 95 RON , and very very occasionally topped up with AVGas  and noticed no change in engine performance.

 

To the best of my knowledge ALL fuels are a blend ie there is no such thing as a straight or pure fuel. The blend varies over the year to address seasonal changes and over time  to conform to legislative changes. The blend may vary from brand to brand  and I am interested in this because the exhaust "staining" I have experienced seemed to coincide with first my use of a "Budget" premium (95) fuel from Evans Head AND the change of my local servo from BP to Caltex.

 

Concerns about "ageing" fuel  is only a factor with  infrequent use of the aircraft  and may apply equally to both 98 & 95 RON (read Kiwi's post)

 

 

[1Phils]

Hi, I found during a carb synchronization that adjusting the idle mixture screws to the factory specs made my engine run a bit cooler. If you fly high maybe checking the idle mixture screws will sort it out. How to do this is shown on the rotax site under carb synchronization.

 

Phil.

 

 

[skippydiesel]

Hi, I found during a carb synchronization that adjusting the idle mixture screws to the factory specs made my engine run a bit cooler. If you fly high maybe checking the idle mixture screws will sort it out. How to do this is shown on the rotax site under carb synchronization.Phil.

Thanks Phil - I have fairly  recently done a full carb synchronisation (both static & vacuum balance) as part of my 5 year/100 hr service (which included a partial strip, clean & inspection of the carb's). I believe my engine to be running normally, at both full throttle & idle settings. That's not to say I may have made an error somewhere and a revisit could be worth while - I will check it out.