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Guest Stkin0

fuel type used  

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  1. 1. fuel type used



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Be careful...avgas is heavily leaded...isn't it? Bruce

-Yes Bruce, if anyone is using Avgas in a Rotax make sure you change the oil every 25hrs
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  • 1 year later...

Avgas in 912.

 

A few people I know have observed that continuous use of 100 LL avgas seems to cause compression loss, wheras occasional use does not cause this to occur. The reason is considered to be a build-up of lead deposits on the exhaust seat, part of which detaches and leaves a poorly sealing surface remaining. Compression seems to recover when unleaded is again used over a period of time. There would have to be a chance that the seat could be damaged in the meantime. Some engines employ very strong valve springs and narrow seats to ensure the high seat pressures to prevent the lead build -up in the first place. I am not sure of the spring pressures in the rotax The manufacturer's octane requirements would indicate that normal unleaded is marginal and that premium unleaded would be more suited.. Nev

 

 

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HIRTH ENGINES

 

Slightly off topic.

 

The Hirth two strokes should also use premium unleaded as they have a 9 to 1 compression ratio. In the USA they have been modified to 8 to 1 and run OK on Standard. There is a character out here who shall remain nameless who has managed to demise a Hirth by running it on Standard because he thought he was going to save money.

 

 

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Guest disperse

a couple of questions: what are the benifits of useing avgas either full time or part time and howmuch per litre at the moment

 

 

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Avgas

 

If you are using Avgas in a 912S anyway, you need to change the oil at 25 hours instead of 50 and it costs more. The price of premium unleaded depends a bit on the day of the week and sometimes the time of the day. Perhaps the only advantage of Avgas is that you can get it at all the airports so if you are flying cross country it is probably your only alternative unless you have a ground crew.

 

David

 

 

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Guest disperse

so whats involved in swapping over from one to the other ie: can you put avgas straight in on top of unleaded left in the tank or do you need to completly empty the tank and lines. and is a carby tune required

 

Thanks Troy

 

 

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Mixing & swapping avgas..

 

The avgas will keep better , but evaporates readily, so keep the lids on drums sealed. I have used it for years for racing,though it's not used now, and I am unaware of any difficulties with mixing with other fuels,(petrol) in any ratio. With motorcycle engines, ( even 2-strokes) there has been no need for major tuning adjustments. The most noticeable effect of using avgas is that you don't have to use as much choke when starting. DO NOT PUT ANY OF IT IN YOUR CAR AS IT WILL KILL THE CATALYTIC CONVERTER. Nev...

 

 

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  • 5 months later...
  • 6 months later...

Avgas in car.

 

IF you want to KILL your cat. converter put avgas in your car tank. (repeating it for emphasis) There's not much of a problem with high octane. Years ago I thought that the slower rate of burning might be a disadvantage with exhaust valve life' , particularly with low compression motors. The difference in rate of burning is in milliseconds (of no consequence). Other factors like poor vapourisation have a bigger effect The oil company BP and the chief fuel technologist (Alan Gissing in particular) was most helpful in sorting out the difficulty, and I am happy to acknowledge that publicly. Just another instance of popular belief being misleading . Of course, if you run a higher octane than your engine needs you are wasting money, as you get no benefit whatever, from it's antiknock properties, the possible exception being where the engine recognises the fuel and retunes itself to cope with it..Nev..

 

 

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Guest Elk McPherson

I used to have a VK Commode, I have to say it ran like a bag of the proverbial on AVGAS.

 

...but then it ran like a bag of the proverbial on anything 049_sad.gif.af5e5c0993af131d9c5bfe880fbbc2a0.gif

 

In the Guzzle we quickly found that running AVGAS we had hell's own time trying to start the bugger and we needed to reset the plug gap every 15-20 hours.

 

Running a shandy of AVGAS and ULP on cross-country exercises worked just fine.

 

 

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  • 3 months later...

I had this discussion with my instructor last week. His answer was to use premium unleaded where ever possible and only shandy with unleaded when premium is not available. This is on the 80 hp model.

 

 

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