Fuel and AV Gas

[kim]

Last weekend I forgot my fuel drum and had to borrow some gas of my mate.
As he uses AV Gas I wasn’t sure how it would go.
The first tank was about 50% AV Gas and ordinary pump gas.

Bike started and idled much better than normal.

Second tank was straight AV Gas and was running very rich, but idled and started excellent.

However I could really only use the first 1/8 of the throttle as it would start to splutter badly. Still had a good day riding, just had keep hooking up in higher gears.

WFO seemed OK, but it took some effort to get if up there.

Since I got home I have changed the pilot down from 45 to 42 and its now 40.
It starts and idles much better than it used to.
Air screw seems to have much less effect than it uses to.

Here is the question:
When running AV Gas would you expect to change your jetting significantly ?
And would you expect to go leaner all the way ?

As I have just found out I can get AV gas for the same price as super thru work and the airport is only 2km away, which have a 24-hrs fuel bousser.

With the idleing and starting alone it seems very worth it to change to AV Gas

Also I run 2% mix.

Any comments most welcome on AV Gas.

K

[iajim]

You might want to be very, very careful about running aircraft fuel in anything else. The octane numbers/ rating are different because a refinery lab uses a completely different engine for testing the fuels. Aircraft fuel also uses de- icers that automobile fuels don't, although with the use of ethanol and E 85, that isn't the big problem it used to be. Av gas will have a much different vapor pressure than gasoline. Conventional gas runs anywhere from 8.2 up to 9.5 (ballpark figures) . Av gas will be much lower at sea level, then in the higher altitudes and lower air pressures it would become more comparable to gasoline. It becomes easier for the fuel to turn to a vapor.
By way of comparison , water will boil at about 185 degrees F at 10,000 ft. Altitude has just as great an impact on fuel as water, lower pressure equals lower temperatures.
Av gas will give you more consistent jetting largely because gasoline has summer and winter , and here in Minnesota, intermediate blends. Winter gas has a higher vapor press. Summer will be at the low end and intermediate ,obviously in the middle. In very cold climates, butane is sometimes added to bump up the vapor pressure since cold weather tries to condense the pressure. If you have more butane then an adjustment needs to be made with the blending , usually cutting the hi octane platformate, reformate, full range "crack" (this is the liquid coming from the catalitic cracker unit of the refinery). I know you think I giving you a "snow job " with the tech . terms, but these are common to almost all refineries. All these variables are what drive people crazy when re jetting, however you' re re- jetting with something that's made your bike not something made for a Cessna.
When lead was phased out of gasoline many years ago, some refiners switched to using Manganese, I don't know if this has continued until now,but the point is, av gas and auto gas are two COMPLETELY DIFFERENT products.
Av gas does have higher octane ratings , so it probably feels as though your bike has a little more crispness in the response, and Av gas can be made to work , it will just take more trial and error tuning. For all the potential problems, you might be just as well off to run 50/50 blend of race fuel. You'd have a slightly higher octane rating, correct vapor press.and the summer /winter/ intermediate variables would be cut in half.
And now that everyone thinks I've been sniffing too much of that gas for my own good; I started working in the oil industry in 1979, Houston, Tx. propane/butane gas plant, tank farm & pipeline. 3 years laboratory, testing samples, 10 years operating units, Hydrogen reformer, desulfurizer,gas/oil reactor, amine contactors, etc. I've been out of the petroleum industry for almost a year now (and no, I don't miss it at all) but I learned enough in 27 plus years to speak with some conviction and truthfullness about these matters. If you want to run Av gas , you can , just be aware of all the potential problems.

[kim]

iajim

Awesome write up. Thanks a lot.

I have spoken to a number of local people and most of them say they are using a mix of BP racegas (octane 100) and normal gas (Octane 93). They don't know why thou ?, but I guess somebody told them to.

The biggest issue is that everybody seems knows a little bit, but nobody knows enough.....

Man, the bike was just so easy to start. First kick after taking the bike of the truck, after lunch etc. I want that back....

Kim

[Brian VT]

They always seem to run best just before they grenade. (LOLJK)

[skid jackson]

Originally Posted by kim

iajim


I have spoken to a number of local people and most of them say they are using a mix of BP racegas (octane 100) and normal gas (Octane 93). They don't know why thou ?,
Kim

lot of guys do that in my area ....2 reasons

1. it makes the bike run better

2. Economics, it's simply a way to stretch out the expensive race gas.

I have to run 50/50 in my trials bike to get it to run right. So I run 50/50 in the gasser, because well ... I got it!!

[iajim]

To Kim and other Gas Gassers, I hope I didn't run on too much with the techno- babble on gasoline. I just don't want to see anyone ruin a piston/ cylinder for the sake of half an octane number. I'm sure that somewhere, some one has a 1979 Yamaha, Kawasaki or Moto Guzzi that runs like a million on Av gas. Most fuel today isn't that great and just about any dirt bike is hi-performance enough to benefit from higher octane. My apologies if " I stepped on anyones toes". I try to limit my opinions and stick to the known qualities of petroleum. I noticed you're from New Zealand, I've never been in that area of the world, but I do pickup Trail bike Adventure Magazine. It looks like you've got some of the most spectacular riding "down there", and a lot of it appears to be exactly what Gas Gas riders' like. Have a good ride for me.

[kim]

To me its refreshing when somebody who has great knowledge actually takes the time and puts the facts on "paper".
If I can't understand the stuff, then I have an issue and needs to educate myself.

Hanging around this forum for a little while, one actually finds that there is very little the "group" doesn't know collectively and people are just sooo friendly here.

Riding is pretty good here with heaps of variety and not very far to drive for it.
Also the trail riding scene is quite large with lots of rural school using a trail ride as a fund raiser.
Often they can raise $6-8000 in a day. ie 3-400 riders at $20 per head and for that you often get the best country lunch and a 100km loop on private station land. Pretty good day out.

[SpeedyManiac]

I used to run 100LL AV gas in my EC200. The bike was jetted for it and ran perfectly. I've since switched back to 94 octane pump gas because it was a pain to get the 100LL, but I must say the bike ran a little better on 100LL. It wasn't necessarily making any more power, but it started easily, idled more consistently and ran a little cooler on AV gas. Just my thoughts.

[RBD]

Originally Posted by SpeedyManiac

I used to run 100LL AV gas in my EC200. The bike was jetted for it and ran perfectly. I've since switched back to 94 octane pump gas because it was a pain to get the 100LL, but I must say the bike ran a little better on 100LL. It wasn't necessarily making any more power, but it started easily, idled more consistently and ran a little cooler on AV gas. Just my thoughts.

Yep! Two Strokes sure do like their lead

And here is a great brew to try;

4Gal AV gas (100LL)
1 Gal Toluene
28 cc K1 Kerosene
And your Pre Mix at the ratio you usually use.

Ron

[skid jackson]

Originally Posted by RBD

Yep! Two Strokes sure do like their lead

And here is a great brew to try;

4Gal AV gas (100LL)
1 Gal Toluene
28 cc K1 Kerosene
And your Pre Mix at the ratio you usually use.

Ron

Home Brew Gas!!!