proven benefits of higher octane

It's not a question to be skeptics or not.
The heating value of 91 or 98 ron fuel doesn't change, so the power gain in a N/A engine due to advanced timing si negligible, in a F/I engine you have actually a light increase at rpm peak because air/Fuel ratio could be adjusted by ECU.
Here an old article of Quattroruote (sorry in italian) about Shell V-Power (100 RON) but you can check as well the numbers.

http://put.edidomus.it/auto/mondoauto/attualita/pdf/QRTLAB1_062006.pdf

You have a F20C Honda engine in the test.

You can see that during topgear pickup you have better results

 

totally clueless.

 

This gentleman has it correct.

No disrespect meant but octane by itself does not improve power output. All octane is a number that predicts pinging that can cause engine damage. It is the result of an equation posted on the fuel pump that compares a gas to a base explosive chemical. Some modern cars have electronic tricks that help save the engine like change the timing automatically on an engine. The higher the compression of your engine the more you need the higher octane gas. If you use the higher and more expensive high octane gas on a low compression engine you are not hurting anything just wasting your money.

Best

Lee

 

I did watch the video.

1. Cars designed to run on lower octane produces the same hp with low and high octane
2. Cars designed to run on high octane produces low hp with lower octane and higher hp with high octane.

Conclusion: Cars produce the highest power running at with the octane it was designed for and produces no more hp running higher octane.

 

I apologize for my harsh reply above. The answer to your question should be on the fuel filler door. The video at the 5:15 mark pretty much sums up all octane arguments.

 

The Impreza is a turbocharged car, and turbo cars have an impressive ability to respond to octane. Both boost and timing increases are possible with increased octane. A turbo car is not a good comparison to the normally aspirated 458. Plus the test was of lower octane vs. octane the car was designed for, and not surprisingly, the car made more power with the intended octane fuel.

I am sure the US 458 is designed to run on 93 octane fuel and would make less power on 87.

ECU tuning is very complex, and I am not sure how the 458 engine management works, but I am confident it controls spark timing from both a map (that has baseline timing as a function of engine rpm and load) and feedback from knock sensors (and other sensors). The knock sensors are suffciently sensitive to allow the car to detect incipient detonation and therefore advance or retard timing to compensate. I am sure all of the cars tested and the 458 have the ability to retard timing if the fuel octane is lower than the design octane. I do not know if they can advance timing for octane beyond the design octane. I'd be skeptical of that because (1) for engine longevity a conservative timing map is best; and (2) it is expensive to map an engine and I don't know that the factory would bother to have the necessary algorithms for higher-than-design octane when most owners can't get high octane fuel anyway.

Now if the 458 has a sufficiently agressive ECU algorithm, it might try to advance timing beyond the baseline, so adding say 98 octane fuel might allow the engine to make more power. That said, since the engine is normally aspirated, the power increase is likey to be modest, maybe 2% or so at most I'd expect, so from 570 hp to maybe 580-ish.

Now all this said, there can be benefits to hight octane fuel in a street car. On track, I Have found that an engine can run cooler in hot weather with higher octane fuel, which can be the difference between overheating and being able to run all day.

Finally, the reality is that you will use maximum power in the 458 very lilttle and I defy you to even be able to feel a 2% gain. When racing I can tell power differences, but only if in traffic to see relative acceleration rates or when studying data to see speed vs. distance and time.

For the street, 93 is just fine and unless I saw dyno results to prove it I'd be very skeptical of any measurable power increase with higher octane fuel in a 458.

I do think it would be fun for you to do a dyno test, though. It's a lot of work, as you'd need to drain and flush the fuel system with the different fuel(s) and do back-to-back tests to eliminate variables intrinsic to testing on different days or locales.

 

In Europe the car was designed to run on 95 ron. IMHO if you increase octane, what you'll see is nothing more that some warning lights on.

 

Not absolutely sure, but I think it's the 91.

 

If you say so, I believe.

But I was told by Ferrari to not do it. IMHO they know what’s better to their cars, so I tend to respect those advices.

Anyway:
IAD = (MON+RON)/2
Usually MON is about 10 octanes lower than RON.

 

EU 95 ron = US 91 octane

Octane is not a measure of the "power" or "energy" in the gasoline; all gasoline releases essentially the same amount of energy when it burns. Octane is a measure of the speed at which gasoline burns; the slower the better because it means that the gasoline is more resistant to detonation (otherwise known as knocking or pinging). You want the gasoline/air mixture to burn fully through the combustion cycle, and not to detonate (which produces less power and can cause damage to the engine). The higher the pressure on the gasoline/air mixture -- the pressure is typically expressed in terms of compression ratio -- the more likely the mixture is to detonate, which is why high compression engines need higher octane gasoline. The compression ratio is affected by the engine design (length of stroke and cylinder dimensions), and can be boosted by pumping the air into the cylinder under pressure through supercharging or turbocharging. Some engines (including the 458's engine, I believe) have anti-knock sensors that can change the spark timing to resist knocking (essentially, they cause the mixture to burn at a time when the mixture will be at somewhat less than peak compression).

Therefore, using gas with an octane rating of higher than 93 for an engine truly maximized for 93 octane will not create any major benefits. It has at least two possible benefits:

1. It is possible that the software controlling an engine which is claimed to be maximized for 93 octane might be able to take advantage of slightly higher octane. I don't know whether this is true for a 458. Also, it would not shock me if some of the gasoline that comes out of pumps marked as 93 octane is actually 91 or 92 octane. I know there are regulators who are supposed to check these things, but I am dubious. At least with racing gas, you probably have a better chance of getting no less than 93 octane.

2. When you do hard down shifts or otherwise get off the throttle quickly, some unburned gas often goes out the exhaust. If the gas burns more slowly (i.e. higher octane gas), somewhat more of it is likely to exit the exhaust and create burbles, backfires, etc. (which can sound pretty good) and may even produce some flaming (which can look pretty good).

I've been perfectly happy using 93 octane gas from a trusted service station in my Italia.

 

Luca di Montezemolo.

 

Very unlikely. Marketing aside, the 458 Italia (and ZR1/911T/GTR/SLS etc for that matter) are street cars, NOT race cars, with a factory warranty, designed for long term durability. I would be shocked if the ignition timing is aggressive enough to take advantage of anything over 93 octane. As I told you in your previous thread, the benefit you are seeing with 100 octane is no different than you would have with a good 93 octane fuel, which is what we have as our run of the mill "premium" in Texas. It's a shame you guys only have 91 oct.