facthunter Posted July 3, 2013 Share Posted July 3, 2013 You guys are lucky to get this good gen. ( From Vev ) There's a lot of unreliable myth out there. We have a potentially large problem with fuel lines and tanks, even without worrying about ethanol.Nev Link to comment Share on other sites More sharing options...
Guest Andys@coffs Posted July 3, 2013 Share Posted July 3, 2013 Vev I realise that the content of any particular fuel at any time can change but ATM you made the point that some premium 98 fuels are higher in aromatics and some lower. You also made the point to Avocet that in regional SA BP is lower. Is that the case Australia wide or does it vary by state, or weather zones or.????.....in other words how can an aviator make an informed decision, or is it simply impossible because of the vagaries of supply chain and 3rd party/n parties involved? Andy Link to comment Share on other sites More sharing options...
BoxFat Posted July 4, 2013 Share Posted July 4, 2013 Thinking, thinking (it's a curse !). It should be pretty simple to set up a test for total aromatic content of gasoline using a diode UV or colorimetric method that each pilot concerned about this could have in their hangar. I published something 30 years ago about such an analytical method as applied to environmental samples (aromatics are the most toxic part of pollutant hydrocarbons in sediments and shellfish etc). It's not ATSM and would be semi-quantitative but good enough to track variability. Reckon that'd be useful to ppl ? Link to comment Share on other sites More sharing options...
Russ Posted July 4, 2013 Share Posted July 4, 2013 running a cocktail avgas / premium..........would that be good practice ??? Link to comment Share on other sites More sharing options...
facthunter Posted July 4, 2013 Share Posted July 4, 2013 I doubt there are any great risks but you are denying yourself the advantage of the avgas. To put it another way whatever you consider undesirable , is still there. ( though in a lesser concentration). Nev Link to comment Share on other sites More sharing options...
Yenn Posted July 4, 2013 Share Posted July 4, 2013 A lot of people use a cocktail, or more often Avgas in one tank and mogas in another. Take off and climb on Avgas. Personally I wouildn't trust mogas, having had detonation destroy a piston, while using it. the cost saving is far less than the risk for me. Link to comment Share on other sites More sharing options...
facthunter Posted July 4, 2013 Share Posted July 4, 2013 The comparison of the octane figures shows how far worse off you are with mogas. The DC-6 used to use avgas 130/145. That would be a hot drop. Nev Link to comment Share on other sites More sharing options...
Vev Posted July 4, 2013 Share Posted July 4, 2013 VevIs that the case Australia wide or does it vary by state, or weather zones or.????.....in other words how can an aviator make an informed decision, or is it simply impossible because of the vagaries of supply chain and 3rd party/n parties involved? Andy G'day Andy, Hard to answer this as it depends on the supply chain... the spec can be wide on allowable aromatic content which can move things around a bit, although the oil industry is very mindful of this and try to manage aromatics % carefully and not create big step changes... often engine components need to acclimate to the formulation and big changes can cause problems with seals etc. Having said that, some brands have a lower caps on aromatics than others, BP 98 Ultimate is one of those. Cheers Vev Link to comment Share on other sites More sharing options...
BoxFat Posted July 4, 2013 Share Posted July 4, 2013 Ahhh this is gonna sound dumb...probably because it is. Does higher octane fuel translate into more power in the same engine ? I can see how it will allow a higher compression ratio without detonation occuring but if the compression ratio doesn't change...is it burning more efficiently or something ? Link to comment Share on other sites More sharing options...
Vev Posted July 4, 2013 Share Posted July 4, 2013 running a cocktail avgas / premium..........would that be good practice ??? Russ, Notwithstanding some engines (I believe Rotax) prefer >95 RON Mogas, cocktails usually don't cause a problem ... however you do need to observe the min octane requirement for your engine, being mindful of the different ways of measuring octane values. Apart from octane, you also need to take into account the higher propensity of vapour lock, carb ice and faster octane drops during storage as well as the potential for damage to synthetic and rubber materials if it's not designed for aromatics. On the positive side ... the lead in avgas has a synergistic effect when it reacts with mogas in terms of octane, that is, the sum of the two parts are greater ... this is small but it is a positive outcome. Mogas additives do help keep the engine cleaner and in a cocktail will help reduce lead deposits and lead fouling as it acts as a diluent. Personally, I am happy to have a 50/50 cocktails in my Jab but only use 100% Avgas in my Continental engine... There's a lot to consider before you jump into using Mogas ... always best to consult with the engine manufacture and sick with their recommendations. Cheers Vev Link to comment Share on other sites More sharing options...
Russ Posted July 4, 2013 Share Posted July 4, 2013 thankyou.........great read Link to comment Share on other sites More sharing options...
AVOCET Posted July 4, 2013 Share Posted July 4, 2013 Just noticed ( the smell ) of the offending 98 calx vortex i drained out of the wing tanks ,I drained it into a 60 liter drum that had had asitone in and it's started to seep out the bottom rim , I'm guessing the drum had a sealant to seal the asitone that doesn't like the pulp ! Cheers mike 1 Link to comment Share on other sites More sharing options...
BoxFat Posted July 4, 2013 Share Posted July 4, 2013 Acetone dissolves more stuff than hydrocarbons so maybe not. But...acetone tends to contain acids and absorbs water so possibly some corrosion if the drum has been empty for while. 1 Link to comment Share on other sites More sharing options...
AVOCET Posted July 4, 2013 Share Posted July 4, 2013 Thats Acetone dissolves more stuff than hydrocarbons so maybe not. But...acetone tends to contain acids and absorbs water so possibly some corrosion if the drum has been empty for while.[/quThat's Probly it then ,been emty for a while. That fuels only going in the the old landrover & stuff that doesn't fly Thanks Mike Link to comment Share on other sites More sharing options...
Vev Posted July 4, 2013 Share Posted July 4, 2013 Ahhh this is gonna sound dumb...probably because it is. Does higher octane fuel translate into more power in the same engine ? I can see how it will allow a higher compression ratio without detonation occuring but if the compression ratio doesn't change...is it burning more efficiently or something ? Hi BF Very simply no ... higher octane wont give you more power on its own ... it does allow you to optimise engine performance improvements ie higher compressions etc just as you mentioned. I'm sure Nev can reply to this in detail with his hands on experience of performance engines. Cheers Vev Link to comment Share on other sites More sharing options...
facthunter Posted July 4, 2013 Share Posted July 4, 2013 I'm off for a week after tonight, but I can't see that the engine would suffer in practical terms until detonation occurs . Then it all comes unstuck. Detonation is like taking to the engine with a sledgehammer. It should not be confused with pre ignition which is like lighting the fire by another means before it should happen with the firing of a spark plug. pre ignition can cause detonation. This could result from a bit of incandescent carbon build up or a wrong heat range spark plug. or a red hot exhaust valve. Nev Link to comment Share on other sites More sharing options...
geoffreywh Posted July 8, 2013 Share Posted July 8, 2013 Brings back memories "pinking" and "knocking" old friends from long ago before fadec and knock sensors.... I used to live on a steep hill and you would hear Morris's and Hilman's pinging their way up the hill with the old drivers tring to stay in third.... Link to comment Share on other sites More sharing options...
Vev Posted July 8, 2013 Share Posted July 8, 2013 Brings back memories "pinking" and "knocking" old friends from long ago before fadec and knock sensors.... I used to live on a steep hill and you would hear Morris's and Hilman's pinging their way up the hill with the old drivers tring to stay in third.... You're not that old Geoff or are you? Cheers Vev Link to comment Share on other sites More sharing options...
geoffreywh Posted July 9, 2013 Share Posted July 9, 2013 To my regret, yes, I used to sit on a street corner in London "collecting" Car rego numbers. A "coloured" car (ie: not black) was written in blue ink ! ( you had time to change writing instrument between cars) ..... also remember quite clearly the first car in our street. It was a new Rover 75 Cyclops, black of course. I lived near North Weald where they had NF Meteor's stationed, Plus the occasional Dragon Rapide over our rooftop...How nice that was........ Link to comment Share on other sites More sharing options...
nomadpete Posted July 9, 2013 Share Posted July 9, 2013 There seems to be a shortage of research into the problems caused by various fuel additives ( or other petroleum component chemicals). After my GRP fuel tanks in my Lightwing developed pinhole leaks I did some web crawling and found this informative link: http://www.boatus.com/seaworthy/fueltest.asp I had been using 98 RON but I suspect that I my have settled for a brand of 95 that has Ethanol in it. Although the article is from a boat magazine, it seems that they have actually done some research. It is important to read right through the article because it starts with a talk about polyester resins (which are not generally used a lot in aircraft). Further down the article refers to a test done with "Ethanol resistant" Epoxy. The test showed that it lost a significant amount of its strength after only a short period of immersion in E10 petrol. Even if you avoid Ethanol contaminated petrol, there are almost certainly other potential problems lurking in the fuels also. Worth a read just to become aware of some problems. Peter T Link to comment Share on other sites More sharing options...
biggles5128 Posted July 15, 2013 Author Share Posted July 15, 2013 Received information back from my local Caltex dealer today. The 95 and 98 both have 1% Benzene and between 17-45% aromatics. Much higher than I would have thought. This might just sway me to travel the distance and go back to avgas. 1 Link to comment Share on other sites More sharing options...
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