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582 Fuel requirements

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Posted

! run mainly 98 unleaded pump gas but use avgas when on a xcountry for convenience,the egt's generally are slightly lower on avgas,

yes the timing can be advanced(I did)but the performance gain was not noticable

Where are you buying 98 pump gas?

I don't think you will be flying the Avid to where the 98 gas is sold - Dusty is a few miles South East of the Bahamas - Like New Zealand!

EDMO

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Posted

You had my hopes up with the Bahamas, till I read New Zealand!  Bahamas is ~60 miles from the last uncontrolled airport on my way to the beach.

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Posted (edited)

You had my hopes up with the Bahamas, till I read New Zealand!  Bahamas is ~60 miles from the last uncontrolled airport on my way to the beach.

I think NZ is a couple miles farther...a container ship might get your bird over to his airport...I would love to go there - My Uncle was there and in Australia with Gen. McArthur during WW2.

EDMO

Edited by EDMO

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Posted (edited)

! run mainly 98 unleaded pump gas but use avgas when on a xcountry for convenience,the egt's generally are slightly lower on avgas,

yes the timing can be advanced(I did)but the performance gain was not noticable

Where are you buying 98 pump gas?

In New Zealand our pumps sell 96 and 98 lead free as "super grade" we have a lot of jap and euro cars which like high octane 

what do you guys run?is the rating system the same?

Edited by Dusty

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Posted

In the US, "premium" fuel is 92, sometimes 93 octane.  That is the highest unleaded auto fuel we can get. "Regular" is 87 octane. 

I don't know the math or chemistry of it, but this is an average octane rating. Yours may be a peak rating, so it may or may not be the same thing. 

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Posted

Different systems are used for posting pump octane.  US and Canada generally use AKI (Anti-Knock Index) which is a calculated average of (RON + MON)/2.  New Zealand, Australia and Europe use RON only.  RON and MON are both determined on test engines with variable compression ratios, but each test is at a different RPM and the fuel is supplied under different conditions.

Wikipedia link: Octane Rating

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Posted

When I  was in Alaska 10 yrs ago I  made friends with a petroleum engineer who designed the Matco refinery in North Pole, Alaska. I also maintained a PA-20 for one of the

employees at that refinery who was a fuel blender.  WHen oil  is heated and runup thro a cracking tower, fuel distillates come off at different temperatures. OUt ofa 43 gallon barrel of crude oil you only about about 15 gallons of high quality gasoline. Avgas base stocks are made from this. It is very stable and last for a few years in tight storage.

Car gas is a whole can of worms. The refinery takes the lower grades of gasolines and blends them.WHy? Because you will never get your engine started on like70 octane gas, so they blend in aeromatic at a fairly high volumn like40%.Now the engine will run but you still have the problem of starting the engine. So at the refinery they force butane and propane into the gasoline under high pressure. I dont know exactly how they do it but that is the stuff that allows your engine to start because your effective cranking compression ratio is very low and that cheap 70 octane gas will not light off any more than diesel would. sorta like watering down whiskey. IT is a tightly guarded secret and the petro companies will not release any  of this info. I have seen planes sit out  in hot sun with car gas in the tanks for 30 days and while they would crank over, they would not start.Drain that fuel and put infresh fuel and it would run. 

The other issue is octane. pure iso octane has an anti knock index of 100 and you would know this if you were awake in chemistry class in college. I helped several people in Alaska with issues trying to run car gas in their planes. Straight run avgas has an octane rating of about 70 so the easiest way to raise that is add Tetraethyl Lead to the gas. It only takes a small amount. Of course your kids will be born with 4 eyes and extra fingers so the EPA had laws passed in congress to outlaw its use. Problem in ,no one considered aircraft engines. So for the last 30 someodd years the EPA had not enforced avgas with lead in it , however a couple of years ago "friends of the earth" sued the EPA and said hey you EPA have had 30 yrs, you have to  quit allowing the use  of avgas in aircraft engines. So far no one has comeup with a suitable chemical to add to the fuel that will take the heat and pressure that a TSIO540J2BD Piper Najaho TUrgo Supercharged engine produces 45" MAP on takeoff.

The blender did help me determine that we only needed to add 10% 100 LL to unleaded car gas to get the antiknock index up to 100. Any more 100ll and you start having problems with lead buildup.

80/87  91/96  100/130/ were all avgases made from the same base stocks. The only difference was the amount of T.E.T.added.

80/87 had an average of .5 ML per gallon ofTET, 91/96 had 3 ml, 100/130 add 3.5 to4 ml per gallon. The petroleum companies and refueling sites had to have seperate handling facilitied for each grade of  fuel and since they were sellling less and less they settled on avgas 100 or 100LL. OK what does that mean? Well 100LL has 2.5 Ml ofTET lead and 10% tolulene(paint thinner) added a an octance booster. Thats why they call it low lead...It has a little less lead.

The biggest problem with the car  gas is the light distilates that are infused into teh gas under pressue evaporate easily and aircraft tanks are vented to atmosphere unlike your sealed car gas cap. So however you store you avgas, keep a tight lid on it.

I know lots of guys  in Alaska that run car gas + 25% avgas in 160 and 180- hp cubs without any  problem... is it legal?????probably not but it works.

 

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Posted

My source at the local refinery told me the same exact thing.  If I want my 2 stroke to not burn down, don't use car gas more an a week or two old.

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