octane/HP rumors?
 

ok i must have came across 10 different websites by now stating that what people beleave about higher octane giving you more power is actually flase. is that true? cuz i know when i run 93 octane as oposed to 87, it seems to have more power and i definatelly get more MPG. so how can that be?

There's no rumor, it's a fact. I'm glad I saved this when I typed it the first time:

Here you go:


Unfortunately, many people assume that higher octane fuel is better for all engines, no matter what. This, as I'm sure you know, is absolutely false. Ultimately, the best octane for any vehicle is the lowest one you can run without detonation (pinging) occuring.

Running too high of an octane will ultimately make it necessary to continue using that octane.

Just to clarify, it's not the fuel that increases the performance, it's the fact that the timing has been advanced. The higher octane permits this to happen. Basically, the way it works is something like this:

Octane represents a fuel's stability. When you compress an air fuel mixture, it becomes quite unstable, and explosive. In fact, this is why diesel engines don't require spark plugs. They commonly have compression ratios of 22:1 (as opposed to a stock Mustang with 9:1), which makes the air/fuel mixture so explosively unstable that it ignites itself when the piston reaches TDC.

Octane, for all intents and purposes, is used to slow down, or control the burn rate. Modifications that increase performance, such as increased compression, or advanced ignition timing, will cause the mixture to become too unstable, and pre-ignition (aka: detonation, pinging) will occur. This is when the mixture fires on it's own, at the wrong time. Severe damage will occur if left untreated. Anyway, the only way to perform the mods that increase the power is to further slow down and control the burn rate of the air/fuel mixture, and the method used to do this is increased octane.

People often think of high octane fuel as being more flammable, and easier to explode, whereas that is actually the opposite of the truth. 110 octane race gas is much tougher to light than low grade 87 octane. BUT, because of that fact, it is the use of 110 octane fuel that permits the compression to be increased to 12:1 without melting the pistons.

On a side note, nitrous oxide works on a very similar principal. With nitrous, the power comes from the added oxygen. The problem has always been trying to find a way to add oxygen safely. As I'm sure you know, oxygen is EXTREMELY flammable, and if you were to try and add it straight to your engine, you would likely die, and not even be able to explain to people why it was you died. It was discovered that the nitrogen in the nitrous oxide was just enough to keep the oxygen from burning uncontrollably, thus permitting it to be used in a gasoline engine. In other words, the nitrogen is to nitrous oxide what the octane is to gasoline, except for the fact that octane is a calculation, and nitrogen is an actual element, but you get the idea.

Okay, back to the story...

Use of a fuel that has a higher octane than is required by the engine and the way it has been tuned will result in unburned deposits being created and left behind in the combustion chamber, and on top of the piston. Often referred to as carbon deposits, these cause the combustion chamber to become very unstable, for several reasons, all of which will ultimately require you to use a higher octane fuel to restore stability. Among the reasons, are increased compression (the deposits take up space, and actually increase the compression enough to make it unstable), retained heat (deposits retain heat at times when those surfaces shouldn't, increasing the likelyhood of pre-ignition), and the development of sharp edges (like sand under the waves, carbon deposits can be "shaped" by their environment, and can develop sharp edges, which act to the compressing mixture like a hat pin would to a balloon.


Take care,
~Chris

I just realized that you're the same person that I already answered this to today.

look guy, I do have better things to do than to answer you again and again just because you didn't like the answer. You don't have to believe me, but if you ask a question, accept the answers you get and move on, don't keep posting it. You waste server space and my time.

i didn't ask this specific questions earlier, i asked another question, your answer just remained the same. because it answered both questions, i just wanted other peoples opinions on THIS exact question too.

also with the facts... that higher octane does not incress power, only reduces detonation. well that would be half true... because my car (with 9.5:1 compression) DOES have more power with 93 as oposed to 87. this is because (im my best guess) with 93 reducing detonation, my timing stays advanced as where with 87 my timing gets retarded alittle. there for in any vehicle where the timing is being retard by even the smalled amont of detonation, higher octane fuel will incress power. up to the point where all detonation is eliminated. if all detonation is eliminated with 93 octane, then 100 octane isn't going to up any performance.

But again it's not the higher octane that is increasing power, it is the timing. The octane just allows the timing advance.

thats true. but in the same sense, without the higher octane the timing can't be advanced. yes the timing is actually uping the power, but the octane is allowing it to do so. the octane itself cannot make power, yet the timing cannot (safely) make more power without the octane. so techniclly the octane does not boast power. but in reality, it does boast power by allowing the timing to stay advanced.

Octane does not create power, period. It simply allows power making changes to take place. If you took an engine, and placed it on a dyno w/ 87 octane fuel, and rung it as hard as it would go, and it didn't have any mechanical failures, and then ran the same engine, the same way, but with 93 octane fuel, the results would be the same, OR LOWER with the 93 octane.

You have a better chance of slowing down with higher octane than you do of going faster. Understand this: higher octane essentially means less flammable, slower burning fuel.

Do not believe for a minute that simply using a higher octane fuel will make a stock n/a vehicle faster, because it ,won't.

I would like to see time slips from your experience.

Take care,
~Chris

You are starting to use circular logic to get the answer you are looking for. Note, not actual figures for any car I konw of.

Consider this:

At tdc, 87 and 93 octane make 200bhp.

At 5 degrees btdc both make 210bhp.

At 10 degrees btdc both make 215bhp.

At 15 degrees btdc, 87 predetonates and 93 makes 220bhp.

One could say look, I get more bhp (220 v 215) running 93. However you only get such by running in an area not accessable by 87 octane.

Now go with stock intake v. CAI.

At tdc stock 200bhp, CAI 210bhp

At 5 degrees btdc: stock 210bhp, CAI 220bhp.

To determine the actual power benefit of a variable, you can only change one at a time. It's obvious in the example above that a CAI gives you more power than stock, period. It also shows that 93 will give you more flexibility in setting the timing, and thus allowing more power in certain applications. But in and of itself, higher octane does not boost power. It only allows you to do other things that actually make more power. So if the car runs fine on 87, any 'increase' from 93 will be purely placebo effect. You should theoretically notice a decrease in power, all other things being held equal.

Set your timing, and then run the lowest octane gas possible. It will save you money and headaches.

i completely understand that octane itself does not incress power. im simply saying in most cars (with knock sensors) it can incress power by eliminating any detonation the knock sensor is picking up there by stopping the timing for being retaded. even just unpluging the knock sensor can inprove performance, because knock sensors offen pickup sounds thats not neven detonation.

And you would simply be misstating the fact. It is because the knock sensor does not retrard timing that the power is there. There are other ways to 'fool' the sensor, like unplugging it. So then does unplugging the knock sensor increase power?

To get a solid yes answer to your question it would have to be shown in a controlled environment. So unplug the sensor and run both types of gas. You won't see any difference, unless the knock sensor was actually doing its job with the 87. I don't recommend it, but I hope you get the point.

yes, unpluging the knock sensor does incress power(at least with my engine it did), its only a very small amount we're talkin' about here, not 50 HP or anything... and it does so because knock sensors almost always retard the timing, even when there is no detonation. because they're so sensitive.

He also asked about MPG's. When the knock sensor detects knocking wont the computer also add fuel if it needs to? If so adding a higher octane would stop pinging stop the addition of extra fuel and "Increase MPG's" is this correct or does it only take away timing?

The knock sensor justs tells the ECM to reduce thue amount of advance that it has implemented.

Gizmo, you areone stubborn little schit. That's pretty cool, usually, but you're getting to me.

High Octane does not increase power by itself, PERIOD.

You can draw circles and squares, and twist this and bend that, and even add a bottle of compressed air, but it won't change that fact.

let me try putting it another way.

Some fancy restaurants have a tie policy. All men must wear a tie, or they aren't permitted to dine there. Many are by invitation only.

Now, does that mean that the tie itself got you dinner in a fancy place? No. It just made it possible for you, if you decided to, to get past the front reception, provided you met every other standard they had.

You need a different hobby. Lego maybe.

;)

Take care,
~Chris

Octane myths and facts
 

gizmo83:

As PKRWUD stated, simply adding 93 octane gas to your tank will not increase HP or performance over using 87 or 89 octane gas. Advancing your timing will give you some more power and the higher octane allows you to do that, as you stated. I think that's obvious.

I've run 15 degrees of initial advance on my near-stock 5.0 since I bought it, new, in 1990. I've also run Sunoco Ultra 94 octane in the tank for all 118,000 miles on the engine.

My injectors are clean, my valves are intact, my 5.0 runs strong and sweet and I've never regretted the extra cost of the gas.

As a side note: I run 12 degrees advance on my wife's '95 Mazda 626 2.0 (stock is 10) with 87 octane gas and never a problem in seven years.

If you want to run 93 octane gas (and advance the timing) do so and enjoy the benefits but don't run the 93 octane with stock timing and expect better performance...it won't happen. The seat-of-the-pants dyno is highy inaccurate.

PKRWUD, like i've said in my last few posts... i completely understand octane does not incress power on its own... on its own it does nothing but reduce the likelyhood of detonation... but it does allows timing to stay advanced, there for with the "help" of octane, the timing incresses the power which is could not do without the help of octane. yes octane by itself does not increse power. period.

for some reason we are all talking about the same thing and getting nowhere. so whats the problem?

as for higher octane being better for engines, that is partially true from what i have read. let me explain. the higher octane 93 has more detergents in them than the 87 does (this is advertised and i cannot truthfully prove it). so it will clean the injectors a little bit as stated by the companies themselves. like i said, "they" say the put more detergents in the higher octane to make your car run "cleaner". as for it being BS, i wouldnt know. just thought i would mention that.

HAHAHAHA!:D

i sort of understand what hes trying to ask but here another one for you standard helicoter fuel jp 40 is 40 octane. its a kerosene chemical mix

I wouldnt get in if you filed it with 93 to give it more power.

when my dad was young they would put avgas in there cars to run faster avgas about 60 octane. no computers or knock sensors in his flat head