AVGAS/UNLEADED?

[Flooi]

Hi Guys!

Can the Jabiru engine flyers please advise:

Some say Avgas only.
Some say Unleaded 95

What do you use?

Thank you

[RV4ker (RIP)]

From the website...

Fuel AVGAS 100/130

Never heard of anyone driving with unleaded?

[Flooi]

UK Website states Unleaded 95 OK, but wondering about SA Unleaded....

Heard some Bantam owners flying unleaded 95........

[Rudix]

My Jabiru 2200A manual says 100LL or RON 95 so I mostly use unleaded unless I have to fill up at a flying field.

Most reports on guys using unleaded says the engines run far cleaner with less maintenance !

Fly safe,
Rudi

[Flooi]

Thanks Rudi!

That's good news! Have u heard about the adding of a spot of 2- stroke oil to Unleaded 95?
Some believe that this is a good way to ensure upper cylinder lubrication when using Unleaded.

Regards!

[Rudix]

Thanks Rudi!

That's good news! Have u heard about the adding of a spot of 2- stroke oil to Unleaded 95?
Some believe that this is a good way to ensure upper cylinder lubrication when using Unleaded.

Regards!

Hi Flooi,

Yes, I have heard about the 2-stroke adding but I have not tried it, I am a bit worried that it will foul the plugs but I suppose if it is just a bit it won't harm.

I did quite a bit of research and many guys are using only unleaded in their Jabirus but some refuse and stick to Avgas. I recently took delivery of a new in the box 3300 and the manual also states that RON 95 or above is fine.

The main concern with Mogas is vapor lock so if you have long feed lines from the tank to the carb it is worth looking at keeping the fuel cool and "pumping" not "sucking" the fuel with a booster pump close to the tank.

Fly safe,
Rudi

[justin.schoeman]

My Jabiru 2200A manual says 100LL or RON 95 so I mostly use unleaded unless I have to fill up at a flying field.

Most reports on guys using unleaded says the engines run far cleaner with less maintenance !

Fly safe,
Rudi

Note that only 3300 and 2200a engines are approved for MOGAS. 2200 is avgas only.

[Old, Fat and Hairy]

Are there any problems with detonation on the engines? I'm planning on using a 1:8 compression ratio and a mix of avgas/unleaded 95 in about a 1:6 ratio on an Aerovee.

[justin.schoeman]

Are there any problems with detonation on the engines? I'm planning on using a 1:8 compression ratio and a mix of avgas/unleaded 95 in about a 1:6 ratio on an Aerovee.

Surprisingly enough, the only instances of detonation that I have heard about on the Jab motors, are when running Avgas! Apparently they build up some lead deposits that result in hot spots (I was told this was the cause of the engine failure I had). Been on the mailing lists for a while, and I have never read of anyone having detonation problems with Mogas.

On the Aerovee list, one builder complained of detonation with 10% ethanol fuel with an 8.5:1 ratio. Was solved by dropping down to 8.0:1.

[Miskiet]

How come car engines can run 10.:1 compression ratio's without detonation on Mogas? Alcohol is not the problem as alcohol is more resistant to detonation than petrol (E85 engines in European cars actually produce more power than when they run on petrol because the spark can be advanced more - E85 is 85% alcohol and 15% petrol).

If you've run leaded avgas for a while and switch to mogas the dirty lead deposits inside your combustion chamber might lead to detonation of the now lower octane fuel. If your engine is new I see no reason why mogas should be a problem.

[justin.schoeman]

How come car engines can run 10.:1 compression ratio's without detonation on Mogas? Alcohol is not the problem as alcohol is more resistant to detonation than petrol (E85 engines in European cars actually produce more power than when they run on petrol because the spark can be advanced more - E85 is 85% alcohol and 15% petrol).

Air cooled engines have much higher CHTs, which means the fuel will ignite earlier, and you need a much lower compression ratio to guarantee that detonation does not occur.

No idea why alcahol makes a difference - I was just dumping info from the aerovee mailing list...

[Dish]

My Bantam has been running on unleaded (during its time with the previous owner) and while he had it he would occasionaly top up with avgas when at an airfield or fly in. I have subsequently been running it on avgas only and working like a charm. Also did some research and to be honest it seems that there isnt too much difference. I think we should chat to Andrew and sort this out for once and for all..

[Flooi]

Where are all the rocket scientists and other clever people?
What about using 95 Unleaded with a touch of Lead Additive?
I've also heard about adding a touch of 2-stroke to improve lubrication.

Is there anyone out there flying a Jab 3300 with Unleaded?

[grostek]

[quote="Old, Fat and Hairy"]Are there any problems with detonation on the engines? I'm planning on using a 1:8 compression ratio and a mix of avgas/unleaded 95 in about a 1:6 ratio on an Aerovee.[/quote]

Hi Old Fat and Hairy,

The cylinder heads on the VW motors remove the majority of the head from the motor.

These heads were used on the 1300cc motor then when the motor was bored out to 1600cc the heads remained the same.

Now these self same heads, as far as external dimensions and cooling area goes, are used in 2180cc engines.

More cc means more mixure which means more fuel which means more heat to be got rid off.

Now remember in the beetle these motors had full shrouding around the cylinders and a dedicated fan to push the cool air through the shroud system.

In aero applications we rely on airflow from our foreward speed to do the cooling.

The Americans have found out that to get a reasonable life out of the motor the max CR ratio should be 7:1 maximum with 6.5:1 being better.

You want to raise the CR to 8:1 well more CR means more heat and ulimately less reliability and less time between TBO.

On the fuel mixture I have no experience, so can't pass comment.

Try phoning the technical departments at Shell or BP or Engen, they will have much more information available on the fuel mxture.


Hope this helps you

Kind regards,

Gunter Rostek.