A question for fuel experts

I appreciate this is a long post, so I'll start with the questions. Answers appreciated.

Then... if you want to understand why I'm asking them, and want to follow the thought process... there's the rest of the post to amuse you.

QUESTIONS

*** What fuel octane rating do you think the Panigale V4/V4S bike is tuned for as stock?
What is optimal, recognizing the minimum is spec'd at 90 (R+M)/2

*** Is there going to be a predictable loss in performance or potential damage to the engine (buildup etc.) in using a higher octane than what may be optimum?
Can the octane be too high?

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WHAT I THINK I KNOW

What took me a long time to grasp is:
Higher octane does not provide better fuel mileage, does not increase engine horsepower, and does not make the engine start quicker.
Higher octane only reduces the likelihood of engine knock or ping.

There is essentially the same energy available in low octane fuel as there is in higher octane fuel.
The difference is that with a higher octane rating, there is a higher ignition temperature and slower burn rate.

So... if we expect massive power out of our high compression engines, we better be feeding it fuel that burns at the correct time (in the cycle) and the optimal rate (length of burn in the available time). Using a higher octane fuel (higher than optimum) may result in less perceived power output and will certainly result in unburnt fuel.
At the very least, the whole combustion cycle may not be as efficient as expected with higher/lower octane compared to the "correct" octane.

BACKGROUND

Here in Canada, 94 octane with no ethanol is an "always available" premium grade gas - Chevron with Techron.
In this case, the "94" is calculated as (RON+MON)/2. As a calculated value, it appears to be essentially the same as AKI.

I was given "wise advice" years and years ago that using 94 was the best thing I could do for my motorcycle engine.
I've been diligently using Chevron 94 ever since, in four very different bikes over the years. KZ1300, 907ie, R1200S, and now the V4.
An extra couple of bucks per tank has never been an issue... because I thought I was doing each bike a favour.

Now I'm not so sure.

My V4 manual (2020, page 338) says to use a minimum 90 (R+M)/2.

So, if you're still reading... at most of the local name-brand stations (Shell, Chevron, Esso, etc.) you can get 89 and 91.
At Chevron, as I mentioned, you can get 94.
So, 91 and 94 are the two local options available for road riding, if you accept that 90 is the minimum.

As a side note, my BMW R1200S asks for 91 AKI as a minimum. AKI is more or less identical to (R+M)/2 as far as I know.
I have fed it 94 for over 13 years, feeling pretty pleased with myself. But on a few recent road trips where I've had to feed it 91, I could swear it actually runs better.
Perhaps foolishly, on those specific occasions I have attributed that to cooler/denser air, etc. but I'm now thinking that is simply prefers 91.
Until now, nothing has shaken my "belief" that 94 is better ... even if the evidence suggests it. Yep, that defines foolish. And that's why I'm asking.

ISSUE

I was surprised to see the "minimum 90" in the Panigale V4 manual expressed as (R+M)/2. Very North-American-friendly.
With my other Euro-manufactured bikes, I've been so used to converting Euro-spec RON to North American spec (R+M)/2 octane (and cross-referencing AKI equivalencies) to get a workable number.

I've been diligently putting 94 in the Panigale V4. I'm starting to doubt my choice as I get more comfortable with the bike.
I've noticed the response seems a little constrained in Street and Sport mode... so I spend a lot of time in Race mode.
Maybe it's the stock tune and the response to the fuel I've been feeding it. Maybe the octane is too high.

To further confuse me, some pundits have suggested that using an octane rating that is too high (for a given configuration) can cause detonation issues, carbon buildup etc., and other issues associated with unburnt fuel. In other words, performance degradation may be accompanied by more serious longer-term issues with the engine.

Also, the 94 at Chevron is sold locally as a fuel choice for "high compression" engines.
I have a sports car with 12:1 compression (considered fairly high) and my V4 is 14:1 so I'm guessing we can safely call the Ducati a high-compression engine.
But I do not know if matching 94 octane to a 14:1 compression ratio is the right answer all the time.

IN CLOSING...

Unless I hear otherwise, I'm going to try a tank of 91 and see if I can detect a difference.

I read that some folks suggest starting with a lower octane and if there is no pinging you're OK. If there is pinging, move up to a higher octane.
But that's much like saying "... start hitting your forehead with a 5-pound hammer and if it hurts, move to a lighter hammer..."
Better to determine the route to the least damage and start there.

The additional of ethanol is a bit of a novelty where I live, so I'm not too concerned with adding that into the discussion.
But if it's relevant in providing a more meaningful answer that will address issues for a larger reader group, please go ahead.

Also, I have tried to avoid dropping down the rabbit hole of aftermarket tunes, and exhausts, etc.
And, while there may be transferrable knowledge gained, I'm not asking about racing fuel... because as I understand it, that is best matched to a higher performance, track specific configuration.
And, I know of one Arbuckle who thinks it's fun to run 100-120 octane avgas in his bike. But that's leaded fuel... and crosses the line into crazy town, in my opinion.

I understand that (R+M)/2 is an averaging function. And I have learned that "Research Octane Number" = RON and "Motor Octane Number" = MON.
But I have no idea what is really means in a practical application so I just use the calculated number and go from there.

Thanks for your input.

This post was aimed to address what a lot of riders may face with a stock bike, riding on the road. Looking forward to a response.

Thanks again. Be well.

Interesting you can get ethanol free gas in Canada. I guess there aren't a lot of corn farmers that the government had to subsidize. In the US, at least where I'm at, everything is at least 10% ethanol with one gas station near me selling 110+ octane ethanol free race fuel. There, you can only fill a gas can, you can't pump it into a vehicle unless its on a trailer and the price is obscene. I don't know if its leaded or not.

On ethanol...when you get into air fuel mixtures, you can get away with more boost (turbo and supercharger) and even a higher compression ratio with ethanol fuel. The reason being is that its generally richer than non-ethanol fuel. It being more rich gives a slight cooling effect to the compression stage and prevent detonation.

The big questions is; what was Ducati using when they came up with the air/fuel map?

With a full custom tune E85 can make a lot of power. The shelf life is hot trash with any ethanol gas though. The power washer in my garage with 10% ethanol will need to have the carb jets de-gunked after sitting for a few months.

Back to the topic though, compression equals heat. Heat can cause detonation. Higher octane fuels resist detonation at higher temps than their lower octane friends. I think Ducati plans for the worst possible situation. Hot day on a track with the engine running at full tilt will likely have temps well above a weekend grocery store run. The bike has a knock sensor though and I wonder if it will adjust fuel level if it detects knock or change timing etc.

I think the race mode has a better throttle feeling because its not trying to smooth out or dumb down the throttle response at lower RPMs.

If you want to go down a rabbit hole, google "stoichiometric air fuel, " slightly off topic but very interesting.

I don't think in the life span of a motorcycle that longevity is really a concern. That X oil or gas is significantly better than Y cause of blah blah reason. Its like how like 99% of men over 85 have prostate cancer. At some point its not going to be around long enough to matter.

I think you answered your own question, but it does help to write things down to help your thought process. You're on the right track as far as running the lowest safest octane, just have to see it through. Ducati makes their bikes to handle American 91 octane or equivalent for the countries that might not have access to anything higher. You are ahead of most people with the understanding that octane is only a measure of resistance to detonation, not how much power it will have. RON is an octane test using an ideal laboratory engine to get the octane number. MON is the test using an engine closer to what you would find on the street. Hope this helps a little and I do appreciate the post.

UPDATE -

87, 89, and 91 (R+M/2 ~= AKI) all share the same hose at most/all local gas stations.
Paying for 91 risks half a tank of 89 as the hose clears from the prior purchase.
I may have experienced that because I tried a couple of tanks of "91" and performance suffered.

94 has its own hose.
For that reason alone, I'm back on 94 and the bike seems happy.

YMMV

a few points higher rating of octane is not going to hurt anything.

Our fuel in the United states almost all has up to 10% ethenol. As was mentioned earlier a biproduct of our government subsidizing corn growers for years. Switching from up to 10% ethenol fuel to non ethenol fuel will make the bike richer. I have tested this and it was approx 6% richer with my local ethenol free then when testing with fuel with up to 10% ethenol.

No gas stations in USA sell 94 octane and zero ethanol gas? Not even Shell?

I cant speak for outside the US, but in the US you are not getting a half tank of lower octane fuel at a single pump gas station; you may be getting a few ounces at most. The fuel is drawn back in from the hose to the tank as a safety protocol and this is required, not optional. Significant amounts of fuel is not just sitting around in a gas pump hose, period. It's an internet myth.

in the old days when Sunoco sold that sweet Venezuelan juice, you turned a lever to dial in your octane on the side of the pump. there was no dollar digit.

I get 93 non-ethanol at the farmers co-op for all my cars from the same pump then fill up a 5 gallon jug for the bike. i get 10% better fuel economy but i do burn a gallon go there and back. a false economy dollar wise but some cars are only driven once a month. corn is bs, imho.

wanting to make it home, i've added a splash of shell 93 and the bike does run like a scalded dog until the fuel trims adjust.

an interesting video....fuel stabilizer from fortnine

thomasmryan said:

in the old days when Sunoco sold that sweet Venezuelan juice, you turned a lever to dial in your octane on the side of the pump. there was no dollar digit.

I get 93 non-ethanol at the farmers co-op for all my cars from the same pump then fill up a 5 gallon jug for the bike. i get 10% better fuel economy but i do burn a gallon go there and back. a false economy dollar wise but some cars are only driven once a month. corn is bs, imho.

wanting to make it home, i've added a splash of shell 93 and the bike does run like a scalded dog until the fuel trims adjust.

an interesting video....fuel stabilizer from fortnine

Click to expand...

your fuel injection on your bike does not have fuel trims. There is nothing providing feedback except narrow band o2 sensors and that are only active at light throttle and lower rpm.

being behind the tourist, that is a bulk of my driving. it does run different with some corn mixed in.

I’m not only looking at different octane when looking at gasoline

Specific gravity affects burn rate WAY MORE than octane does

Short stroke high rpm engines need a very fast burning fuel to make power (low specific gravity)

Just cuz the internet says yer bike has 13:1 compression doesn’t mean ..... That’s static compression. That number has nothing to do with fuel requirements. Effective compression ratio (difference in volume between when the intake valve closes and tdc) does tho

You gotta look at ALL the numbers when choosing gasoline for an application. If you’re pumping it outta the ground do you really know what’s going in yer tank anyways?

Ethyl alcohol is a whole different story

Octane relates well to ignition advance, with many people thinking that more advance is better, but it doesn't mean anything unless your engine is running high rpm or you have more fuel in the cylinder. The burn rate is constant so either case will require more advance to burn all the fuel in time to create the max pressure for the downward stroke. Too much advance and the peak possible pressure is reached to early (reduced power) or insufficient fuel is burnt again missing the opportunity to get peak pressure.

I would suggest that a manufacturer would be conservative in their fuel requirement as a little unburned fuel after TDC is unlikely to cause anything more than a very slight decrease in efficiency, while too low will cause detonation resulting in a dead engine. Detonation though has a number of additional factors; the squish zone at the edge of the cylinder and fouling may retain heat causing premature ignition.

In Oz, anything over 95 tends to have additional additives. I was told by the previous owner to use 98, however that fouled the plugs quickly and the rough ride almost made me regret getting the bike. At 95 and a tune, it runs brilliantly. It just so happens that here, Ducati's recommended fuel is 95.

My recommendation would be to stick as close to their recommendation without going below. If that means 93 or 95 is available in the US, then go 93. Going higher will just mean peak pressure is t met and power may suffer