:headvswal

Could anyone tell me if it's OK to use Aviation fuel rather than Optimax on a TT. The cats have been removed so no problems there.

Normal Aviation fuel is 100 Octane low lead, but I remember some years ago a guy filling up jerry cans to be used on a racing powerboat with a Chevy engine blown to 15 psi.....

Biggest problem I can see is that the nozzle won't fit in the filler cap!

Been trying to find out in a couple of books that I have but its very 'chemistry'. Basically it talks about straight aviation fuel having different composition and having very low throttle response as aircraft only alter it for take off and landing. The high knock resistance that it has is due to its tight molecular structure but this can be a disadvantage at low revs (low temp and boost) because it doesnt combust fully giving poor throttle response and possibly a drop in power.

Quote:'fondness for the dual fuel approach where normal petrol is used for start up, (good throttle response and minimal cylinder wash and oil dilution). Then with either toluol, toluol/avgas mix or straight avgas in the secondary tank' - which has the greater knock resistance and because of the higher temp and boost they get complete combustion (which doesn't happen at lower temp and boost due to tightly bonded molecular structure (which is what gives it its resistance to det)).

Dr Dave (Not!)

Just found what he means by oil dilution from tightly bonded fuels. When engine was cold some fuel would remain unburned, washing oil off the cylinder walls and diluting oil in the sump. On the other hand very volatile fuels have little knock resistance. Therefore differences in composition depending on use.

Perhaps I'll try a blend then! At 89p litre it's got to be right, (just paid £1.03 for Optimax!!!)

 

Not totally sure of it's legality as it still contains plenty of Tetra ethyl lead, will let you know if it has any adverse effect, did used to use it on an old Porsche 3.2 and seemed to suit that.

Would def like to know results mate, know some RAF people! Is it the old 'green barrel' stuff or the new low lead stuff? I can take a picture of the chapter of the book if you want, gives stacks of info on the subject, wont be able to do it till later though.

Dear doctor,

Should be able to grab some this week, will let you know the results, currently running standard boost so will also try turning up the wick a bit - My next post will probably be in the items wanted - looking for a new lump!