GAMI’s search for an avgas alternative

GAMI's Tim Roehl (in back) and George Braly in the company's test cell.

Recently, my wife and I decided to take a road trip to Texas to visit friends and fill up on good Cajun and Tex-Mex food. On our return, I stopped to visit GAMI — General Aviation Modifications, Inc. — in Ada, Oklahoma.

GAMI builds and sells a line of parts designed to improve performance for a variety of aviation applications. It is best known for GAMI injectors. The concept of the GAMI injectors is to even out the variation in air/fuel ratios for all the cylinders of an engine. This, combined with proper instrumentation, will allow the pilot to operate on the lean side to peak. I know many people think that operating on the lean side is operating on the dark side and can harm the engine. However, if done properly, it can be done with little or no problem. There are several advantages to operating on the lean side, but the biggest is that you can decrease your fuel consumption by a very significant amount.

GAMI’s latest project is to design an unleaded fuel that will satisfy the same engines that presently require 100LL. There are presently three approaches to finding a replacement for 100LL.

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The effect of lower octane fuel on your airplane


Last week I was watching TV when I heard a loud clap of thunder and saw a flash. This was followed by the lights going out and the very sickening sound of electronics going bye-bye from the computer desk.

The next morning the lights were back on, but the computer had sacrificed its life to protect a $4 surge protector — and with it all of my files of questions I have received for this column. I am going on my memory as to questions, and we all know that our memories are the second thing to go when we get older. I do not remember the first.

I do remember that several weeks ago I received a question from a couple who operate an FBO. They had a source of 93 R+M/2 premium motor gas that they were selling to LSA and STC’d aircraft. Then their supplier informed them that the octane quality was being reduced to 92, and then some months later, it was reduced to 91. They were wondering what they should do.

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Avgas Economics 101

After I wrote about my visit to Swift Fuels, I received several notes asking why it would be so difficult to determine a price for the finished product. I have a good friend who runs an auction company and when I ask him what something is worth, he usually replies, “Whatever someone is willing to pay for it.”

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The staggering chicken test

In response to a previous column in which I expounded on the problem of exhaust valve recession with unleaded fuels, I received a note from Ron Newberg, which reminded me of work done by the oil companies back in the early 1970s. I actually ran some of these tests, in which we demonstrated that Tri-Cresyl Phosphorous (TCP) added to an unleaded fuel reduces the amount of exhaust valve recession. It worked well. Since TCP is approved for almost all aircraft piston engines, it is an immediate approved solution for the exhaust valve recession problem. But, alas, nothing is that simple. TCP will work, but it has some health concerns.

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Ethanol: It will get you coming and going

Recently, reader Frank Klein asked if he should be concerned about filling up containers of auto gas for his plane if the previous customer pumped 10% ethanol fuel from a pump island that uses a common dispensing hose for several grades of auto gas.

When I do some rough calculations, I figure that the amount of fuel contained in the hose and meter would give you close to a gallon of fuel, so if you are using a five-gallon container, you would have close to 20% ethanol-containing fuel.

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Oil giant pulls out of 100LL business

UPDATE: Calls from AOPA and EAA Tuesday morning inform us Ben’s column is incorrect. Exxon-Mobil will continue the manufacture of unbranded 100LL fuel. Exxon-Mobil will discontinue branded fuel sales under the Exxon Avitat flag. We are awaiting confirmation from Exxon’s public relations people.

I recently read that Exxon-Mobil stopped manufacturing and selling 100LL. (I tried to contact them but did not receive a confirmation by press time.) What does this mean for you and your plane?

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What part of ‘no’ don’t they understand?

One of the joys of being retired is that I get to read more of the newspaper each evening. Now the front page has all of the big stories that are of worldwide importance, like the Kim Kardashian marriage that lasted only 72 days. But if you read the inside pages, you can find some very interesting information. On page 5 of our local daily paper here in the agriculture heartland was an article that caught my eye. The headline read: “Study: E15 damages boat engines.”

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Why lead reduces knock

In the Sept. 23, issue of General Aviation News, there was a letter to the editor from Jack Thompson, who wrote: “Re: Visser’s Voice: Knock free, Aug 26 issue: It is a sad commentary given that the IC engine is such an integral part of aviation that the user community is so ignorant of its operation and engineering issues. What percentage of the users understand the impact of fuel detonation resistance and the if-then relationships of fuel suitability for a given service?”

The actual truth is that no one really completely understands the interaction, especially how lead additives work in a fuel to reduce knock.

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Winterizing your plane

A couple of days ago when I went out for my morning walk I noticed something had changed. Instead of warm and sunny, there was a chill in the air. I then realized that fall is approaching and I needed a jacket.

The same kind of thing happens to many pilots each year. They are enjoying the nice flying weather when all of a sudden, winter is upon them, so they put their plane away and figure they will just change the oil in the spring before they do any more flying. There is a big problem with this plan.

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Knock free

In one of my recent columns I stated that if an engine runs knock free on an 87 octane fuel, using a higher octane fuel will not benefit you in any way. I received several inquiries about whether this was for automobiles or airplanes. Basically it applies to both.

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