2024 the year of GAMI - finally?

[AV8R_87]

Surprised to hear that. Turbines can usually handle multiple grades of jet fuel, and you never see mentions in the TCDS about fuel quantity inaccuracies when using different fuels.
I wonder if the problem might be caused by some anti-static additives that might be included in the avgas. I could see those messing with the fuel conductivity in ways that might get unpredictable.

EDIT:
Anything is better than most resistive-based fuel probes we have in GA today. With today's technology I think there could be better ways to measure fuel levels in the tanks (even better than capacitive probes), but that sounds to me more like stuff to write in a patent application and not in a public forum.

 

[Pinecone]

Anything is better than most resistive-based fuel probes we have in GA today. With today's technology I think there could be better ways to measure fuel levels in the tanks (even better than capacitive probes), but that sounds to me more like stuff to write in a patent application and not in a public forum.

Cies has them

 

[Tusayan]

And all those blends run just fine in my air-cooled, 8:1 compression ratio, fixed ignition timing cheap generator, that can generate 7 hp from 13 cubic inches (at 3600 rpm). That's comparable to the output of the typical air-cooled airplane engine.

But not comparable in terms of the required octane. That is a function of cylinder bore, as well as CR, RPM and ignition/cam timing. Large displacement cylinders need more octane, with everything else held constant.

 

[AV8R_87]

Not really. The 7:1 O-320 was certified to run on 80/87 Avgas and has auto fuel STCs approving it to run on regular (AKI 87, MON 82) gasoline. The 8.5:1 O-320 requires 91/96 Avgas and the auto fuel STC approves it to run premium (AKI 91, MON 88). Similar situation for the O-540, but I haven't looked at all the different variants there.
I'd say that's pretty comparable.

I think (please correct me, my knowledge is definitely limited here) 100LL is needed mainly for the turbocharged models. A lot of the engines "requiring" 100LL only do that because at the time the airframe/powerplant combination was certified, 100LL was the only fuel available. Nobody will issue a TCDS for fuels that haven't existed in decades.

 

[Racerx]

Not really. The 7:1 O-320 was certified to run on 80/87 Avgas and has auto fuel STCs approving it to run on regular (AKI 87, MON 82) gasoline. The 8.5:1 O-320 requires 91/96 Avgas and the auto fuel STC approves it to run premium (AKI 91, MON 88). Similar situation for the O-540, but I haven't looked at all the different variants there.
I'd say that's pretty comparable.

I think (please correct me, my knowledge is definitely limited here) 100LL is needed mainly for the turbocharged models. A lot of the engines "requiring" 100LL only do that because at the time the airframe/powerplant combination was certified, 100LL was the only fuel available. Nobody will issue a TCDS for fuels that haven't existed in decades.

1967 NA Cherokee six requires aviation grade 100/130 for the io-540-k1a5.

 

[Jim K]

I think (please correct me, my knowledge is definitely limited here) 100LL is needed mainly for the turbocharged models. A lot of the engines "requiring" 100LL only do that because at the time the airframe/powerplant combination was certified, 100LL was the only fuel available.

My io540 requires 100ll and has since 1976. 8.7:1. The only 540 that has a mogas stc is the 235hp version.

It's much more complicated than compression ratio, it really has to do with peak pressures in the cylinder (which have a lot to do with airflow). An IO-540-C4B5 vs. an IO-540-K are great examples. 8.5 and 8.7:1 compression (respectively), however the -C4B5 will use MoGas just fine, and the -K will not. Difference? The parallel valve cylinders on the -C4B5 flow much less air than the angle valve cylinders on the -K.

Ignition timing comes into play as well and there are all sorts of things that can be changed to impact things. You need to look at the engine as a complete system, not just one part of it.

Basically any angle valve lycoming requires 100ll. That's the io360 & io540. The big continentals that power the bonanza and cirrus fleet also require 100ll. Eliminating 100 octane fuel grounds pretty much anything other than the c172/pa28 fleet.

 

[Ted]

Basically any angle valve lycoming requires 100ll. That's the io360 & io540. The big continentals that power the bonanza and cirrus fleet also require 100ll. Eliminating 100 octane fuel grounds pretty much anything other than the c172/pa28 fleet.

Correction: angle valve 360/540s. There are plenty of IO-350/540s that are parallel valve, and those don’t require 100LL.

The valve arrangement only matters because angle valves flow more and make more horsepower.

 

[tspear]

In terms of lead, there is a source for a lot of the benefits which could be seen. From my limited knowledge, it mostly applies to new or overhauled engines.
Look at Rotax. They provide the information when running mogas vs avgas.

Tim