Octane and Horsepower

[68X426]

Attention all scientists. Can we talk about octane and power?

Does running higher octane actually produce more power/torque -or- is it a case of better efficiency and consistency throughout the rpm range? Just more or simply better?

Phrased another way, if all else is equal, will a motor running 100 octane deliver more (real) horsepower (peak or otherwise) on a dyno than the same one running on 91 octane?

[Troy]

From what I understand, octane just decreases detonation (makes the fuel harder to burn). This allows advanced timing which will affect horsepower. However, the fuel alone doesn't increase power.

Troy

[Silver R/T]

you can have higher compression  with higher octane

[Ghoste]

But again, the fuel alone doesn't add the horsepower in that case.  It allows the use of higher compression which creates more power.
I can tell you that my car starts easier and runs smoother on high octane fuel but I can't provide any dyno results.  (not being oxygenated likely has as much or all to do with my experience as stated)

[wrench]

  higher octane fuel is actually harder to ignite than regular fuel which is actually what you you need in a high compression engine to prevent pinging or detonation.using higher octane fuel ALLOWS you to bump the timing,or compression for more power,that' all.Don't worry your high energy ignition has no problem igniting that fuel.50,000 volts can easily do it. make sure you have good ignition wires so the spark reaches the plugs.

[Ghoste]

So why would my car be easier to start on the stuff?

[wrench]

what engine and mods?

[Ghoste]

383 and some, nothing radical though.

[Cooter]

Agreed, Higher octane fuel will NOT make more power, but allows for things like Timing, Nitrous, Supercharging, that DO...

[CB]

we have 95 or 98 octane fuel overhere, I only drove the car in Vegas (on regular '85' gas)
I wonder if I need to adjust my timing now


Read this on wikipedia:

Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.

[Troy]

we have 95 or 98 octane fuel overhere, I only drove the car in Vegas (on regular '85' gas)
I wonder if I need to adjust my timing now


Read this on wikipedia:

Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.

You guys calculate octane using a different formula. The equivalents are listed somewhere on the site.

Troy

[aussiemuscle]

i see it written all the time that it doesn't increase horsepower, so maybe it's a psychological thing, but i'm certain that my old hyundai got better performance when using high octane fuel (maybe it was also higher quality fuel?) giving that edge it needed when going up hills. when i upgraded to a six cylinder ford, the difference wasn't as noticable, more of a 'smoothing out' of the engine. i can't detect any difference with my new V8 ute.

[68X426]

However, the fuel alone doesn't increase power.

Thanks everyone for the observations.

So then I'll ask this question: with no horsepower gain (all else being equal), why run 100 octane fuel in a street car at the race track?

It appeared to me at my last visit that very few were adjusting/tuning their car for the races but I understand that everyone fills up with 100 before they get there. Would this just be wasted money (if no adjustment is made for the octane boost?).

Dedicated (real race cars) were adjusting, but the street guys sure were not.

[Cooter]

However, the fuel alone doesn't increase power.

Thanks everyone for the observations.

So then I'll ask this question: with no horsepower gain (all else being equal), why run 100 octane fuel in a street car at the race track?

It appeared to me at my last visit that very few were adjusting/tuning their car for the races but I understand that everyone fills up with 100 before they get there. Would this just be wasted money (if no adjustment is made for the octane boost?).

Dedicated (real race cars) were adjusting, but the street guys sure were not.

True....IF NO adjustments were made, but most, Like myself, run N20 (Nitrous) or Turbo's/superchargers and turn the boost up when racing...

Most "Street" guys you seem to be refering to are mostly uneducated "Posers" that THINK their cars produce more power with "Race fuel"...
Most if not ALL "True street" cars today are Fuel injected and things like Timing CANNOT be screwed with so, they resort to the last hope of making more power and that's running Race fuel...We have 'em here as well that SWEAR their cars produce more power on Cam 2 than on regular pump gas premium...Sometimes, you just can't talk horse sense to a jackass, so I quit trying....

[elacruze]

There are two important components to fuel which must not be confused or conflated.
1. Octane.
2. Energy Content.

Octane is a measurement of gasoline's resistance to self-ignition. This means only that you can have more compression before detonation.

Energy Content is just what it says, how much energy per unit the gasoline contains. Honda and Shell Oil got together in 1993(?) and won the F1 World Championship with a fuel of only 75 Octane or so, because the energy content was very high and the specific gravity (weight) was very low.

Energy Content and Octane are not necessarily correlated.

Energy Content and Fuel Quality are what you notice when you notice difference in starting etc. 93 Octane fuel is reasonably high quality, where 87 Octane No-Brand fuel is likely to be fermented lizard skin and goose fat, or whatever else they can mix in that might or might not burn.

[Troy]

For people with "stock" cars they are just throwing money away by running higher octane fuel than required. However, certain "Premium" fuels have better detergents or other additives which may be beneficial. Also, fuel injected cars *might* run better at the track with higher octane gas since the knock sensors won't be retarding the timing under acceleration. You can't really "tune" the car manually but it can figure out what to do with the fuel it has.

Troy

[Cooter]

BUT! Most Newer cars Cannot Run High octane LEADED race fuel because of the cat. converters..Lead stops them up by sticking to the catalyst...

[Ghoste]

And when talking about our old cars of course, lead adds another useful beneift in addition to it's detonation cure, the valve seat "cushion".