Dynamometer, Sportster. Octane, Performance.
Someone should do back to back runs using a small (Replacable) one liter tank.
Non-Ethanol fuel
First run would be 87 octane (Recommend using an 883 for all of the tests).
Next try 92 octane to see if there is a measurable difference.
Then find out the mid octane levels (89 and 91) to see which one produces the most HP and torque,

Afterwards there would be no guessing.
I do realize that elevation and temperature also play a part in the performance numbers game, but it would provide a baseline.
If several shops would contribute to the effort, we would gain further knowledge and something to base our opinions upon.

87 Octane would probably win out, but it would be interesting to find out if the 92 octane crowd has always been right,

Would it be a waste of time?
Probably not.
Would it be expensive for the average Joe to purchase some Dyno time?
Yes..

Perhaps a compromise could be worked out and someone would step up to volunteer their ride, their time and their efforts to do a public service.
Imagine how many forums would reference your shop findings?
Great way to market your services..

 

 

The specs of my ecoboost 2.0 turbo are 231 hp with 87 octane, 240 hp with 91.

And for your info, it does no add power to an engine. You cant take a shitty engine and make it better with premium fuel. But some engines are designed to use that fuel and giving it the cheap stuff will make them run weaker.

Now your question should not be " if the 92 octane crowd has always been right", that would imply people are stupid and buying snake oil. But if the manufacturers are lying to us.

ALWAYS FOLLOW THE RECOMMENDATION OF YOUR MANUFACTURER!

 

Basically you state: The ECM will retard your spark (fire later) so your lower octane fuel will not ping.
Retarding the spark allows your vehicle to run on fuel without pinging.
If you retard the spark far enough you would be able to run your engine on ethanol (or Vodka) if need be,
You could retard your spark AFTER top dead center and your engine would still run.
Your engine would lack power, but if your fuel would explode instead of doing a slow burn, your emissions would still show a complete burn.
Your ECM can adjust over time to advance the timing (Increasing power) if the fuel has a higher flash point, thus burning slower and more evenly throughout the entire/longer stroke of a Harley engine, you MIGHT even have more power. A lot of effort has been made to reduce emissions by the manufacturer and this is why you hear the term Screaming Eagle.

You can MAKE your engine burn 85 octane or even 74 octane.. You can even make your engine run on pure ethanol or a mixture/blend of ethanol or even propane.
This does not mean it will make more power.
BMW requires you to use Premium in your M5.
The truth is, after 50 starts the ECM in your M5 will have built a table to burn your 87 octane efficiently, but you will lose power.
Every driver is different.
If you drive hard, your ECM will adjust to your driving style.
Do you KNOW that the manufacturer is meeting YOUR needs? or are they satisfying the EPA and providing a few vehicles that they sell at a premium to use premium?

The simple answer is to use what the manufacturer recommends.
Simply Watch CNN, NBC, CBS, ABC and FOX if you want to know what is happening around you.
All news broadcasts are fair and honest. You can trust their efforts and their reports

Or you could actually watch Congress in action and judge for yourself,
I realize a true and comprehensive test would be difficult without building a table of 50 starts, but not all is truth. Some things are Myths.
Just saying, a test would give us numbers we could base opinions upon.
Or you can just accept the "Common Knowledge" you have been fed.

I believe your Owners manual is correct. and that your engine was set up from the factory with a table built to take advantage of less expensive low octane fuel.
I also believe everyone is different enough and believe strongly enough to even mod their rides to increase HP.
Are we still meeting that need when we change the perimeters?

You are NOT wrong. but you also may not be totally right.
Some engines will not be able to adjust to 85 octane unless the government mandated the policy and the ECM was re-flashed or some mods were done to the engine.
Just trying to open up the other side of the debate.
Without testing, either side could be totally wrong in their assumptions.
Perhaps there will be some middle ground for discussions..

 

My 2014 Sportster does not have a working knock sensor like the big twins do. They have ion sensing. The spark does not get retarded on my bike. My ecm does not adjust for different fuels. Not sure on the 2017, 2018 Sportsters

 

That is what I was thinking. ( I know, I should have mentioned that or at least confirmed one way or the other)
The timing is "hard set" by a cam sensor.,
Most owners mess with the carbs once they do some other mods
Still would be interesting to see how the different fuels would perform on the Carb'd 883's
Re-jetting the carbs after adding your exhaust and intake mods would more than likely change the perimeters.
It is more than just the compression ratio that determines the Octane requirements.

 

Measuring the Air Fuel ratio of the older Sportsters on a dyno would be of more interest to me.
Just how rich did they run with stock jetting? Both at cruising range and full throttle.

 

I was under the assumption Harley simply recommends premium since it is more resistant to burning because of the heat generated by the engine in an attempt to stop/reduce pinging/spark knock. I don't know the exact numbers but, the compression ratio isn't that high in a Harley v-twin to justify premium fuel is it?

I do know that a Honda Rebel I had would run fine on regular 87 octane fuel UNTIL it got HOT out, then it would ping/spark knock like crazy. I ran premium in it during the hot summer months, and had no pinging/spark knock. Come fall, I would revert back to 87 octane fuel.

 

Amazing.. Just read about the ion sensing technology and it is impressive.
Thank you for sharing..

 

This is a dumb test. Whatever octane your motor was designed for will perform best. All others will perform lower.

Pro tip, this is all done during powertrain development to a level much much much much higher than you could ever test with out a multi-million dollar R&D facility. Might as well test whether you ride faster after drinking Dasani or Poland Springs. Has about as much relevance.