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852 Posts
Running higher octane (slower burning) gas can lead to unburned fuel fouling plugs.
Once the air/fuel mixture ignites, it explodes. Tell me more about these 'slow' explosions.

Running leaded gasoline, as it was stated his race gas is, is also not recommended in a stock LT1.
...race gas...could harm your motor.
I know lead is bad for catalytic converters (which he claims he is not running) and oxygen sensors, but what would it harm in his motor?

As has been asked several times before, why does he need 93 or 94 octane fuel? Or race gas? I get no spark retard at the track with my 11:1 383 using 93 octane unleaded.

· Premium Member
852 Posts
It's not about the 'explosion' as you incorrectly phrased it.KW
ex-plode (verb) 1. to expand with force and noise because of rapid chemical change or decomposition.

I guess you're aware of the expansion and force, but it's that bit about noise that really gives it away, don't you think? Or do you not have mufflers?

Granted, burn rates change with some higher octane fuels. My point about 'slow' burn rates is whether or not the difference between varieties of unleaded pump gas (and even the lower octane race fuels) is enough to make a difference in performance. Given the relatively low RPM potential of the common pushrod V8, I seriously doubt it. If you have info from real science guys, I'd be very interested in seeing it. Thanks.

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852 Posts
just to clear it up for some

pre-ignition is just that, the fuel igniting BEFORE ignition ever occurs.

detonation aka ping aka knock is when the fuel does not burn nicely in a cascading fashion with the oncoming flame front, but instead it starts spontaneously combusting as the flame front moves (i.e; lets say fuel at the end of the line starts to burn before it's turn). But this all happens AFTER the spark plug shoots spark.
Yes. Non-controlled ignition before or after the spark plug fires is unwanted. Good clarification.

preignition=very bad

I think the bottom line of this thread is,

2)high octane WONT give you an increase in performance IF your car is tuned for a lower octane UNLESS you are seeing knock retard from an overly aggressive tune

that pretty much states it. It's pretty simple really. If you have an aggressive tune and a high compression motor, hook it up to a scanner when you run and see if you are getting any knock retard. Run the car with some high octane UNLEADED if you wish and see if knock count goes down and knock retard goes away. If so, using race gas is a benefit for you. For most of the guys on this forum I would gather, using higher octane fuel than what they are tuned for would be useless as most guys here aren't pushing the limits of pump-gasable dynamic compression or super aggressive timing curves.

If you aren't geting knock retard but you think you can get more out of your car by using race gas, put some in and have it tuned. If you can get more power before she pings with the race gas, then you've found a reason for it. But as many already know (but yet some MECHANICS I have met STILL don't get) putting high octane fuel in your bolt ons, stock motored car is going to do NOTHING.
I'm with you on this. However, some race fuels will burn more completely, giving a power increase even without the benefit of more aggressive tuning.

· Premium Member
852 Posts
I really don't think that's least not without extreme expense.
If your definition of extreme includes the difference between pump and race fuel, sure.

Burning fuel = expansion of gases = the need to blow off (through exhaust ports). don't need 'explosions' to do what you discribe.

Explosions in your engine would be an enormously bad thing; to the extent that your engine wouldn't all. The only 'explosions' I know of is the improper consumption of fuel; as in, pre-ignition.

Properly ignited fuel in an engine's combustion chamber will NOT 'explode'; it will burn. That's why it's called a "combustion chamber".
You're going to argue that an event that meets the requirements of being defined as an explosion is not an explosion? Well, uh...don't let insignificant little things like facts cloud your opinion.


Do I detect a whiff of sarcasm here? The following was taken from this article. Yes, things in Hot Rod are often dubious, but this seemed to be legit.

… we discovered that our presumption that higher-octane fuels burn slower than lower-octane fuels (and therefore require more ignition lead) is largely incorrect. There are too many other fuel-formulation issues at work to assign a general rule about octane. Race fuel tends to have a more powerful formulation than pump gas, regardless of octane rating, because it is denser and can release more power and heat.

Thanks for the debate, Kev. It's been interesting to say the least.

· Premium Member
852 Posts
No......I'm saying......a lot more difference than that......I'm thinking something with a much higher degree of 'formualtion' than race fuel.
Like what?

In this case........yes. Because the proper state of fuel consumption in an engine's combustion chamber is not by way of 'explosions', it's by way of 'burn'. Which, BTW, also meets the 'requirements' of your 'explosion' definition.
Except for the noise. Get it? It goes boom. Rapid burn (aka 'combustion') plus noise makes it an explosion by definition. It looks like a duck, it walks like a duck and it quacks like a duck, but it's not a duck?

No......skepticism......HRM not withstanding.
No? You replied with a sarcastic remark. To convey skepticism, you'd have to say something such as, "I'm skeptical," or "I doubt that." Do you have your own personal dictionary that the rest of us don't have access to? Geez, I'm getting a headache...

· Premium Member
852 Posts
I never really got the idea that race fuel 'burns slower'. Higher octane resists detonation better than lower octane, that is what octane is essentially a measure of. But how does that have any affect on burn speed? I always figured perhaps this is flatout untrue, as octane rating itself, as defined, has nothing to do with burn speed, but maybe lead vs unleaded affects the burn speed?
No, not necessarily. Could it be possible that a given fuel can resist spontaneous combustion at a specific compression level, thus being able to be used in a high compression motor; but have the same rate of 'burn' from start to finish as a lower octane fuel (when both are tested at the same compression, one that is within the lesser octanes fuels ability to resist detonation).

Being that 'octane rating' does not actually mean the amount of octane in a fuel, it only means how that fuel compares to a percent of iso-octane and heptane mixture in regards to how much pressure it can resist before spontaneous combustion, it seems that you can have a variety of different ways of making a say '105 octane' mix and because of this there could be varying characteristics in the rate of burn.

I don't really know that for sure, im just sayin. I would really like a chemists explanation. I might try to seek one out. :)

I'd wager the folks that make Rockett Brand fuels have some chemists working for them. They, as one would assume all other fuel makers, claim to adjust their formulations for maximum power given the customer's requirements. KW would probably argue this was written by their sales department and has no basis in fact or science (or that the sun sets in the east), but I'll take their word over his.


· Premium Member
852 Posts
Like what ain't readily available on the market.......and no, I'm still not talking about race fuel.
So...It's a SECRET!

When you burn large quantities of fuel in a confined space (combustion chamber) and then only allow the exhuast to escape that confined space for a short period of time (opened/closed exhaust valve) and futher allow the exhaust to escape through contructing tubes (headers & pipes), then're gonna have noise!! But I've never heard my car go BOOM.
You're saying the noise emitting from and engine is simply the sound of exhaust gasses passing through various chambers, orifices and tubes? I am skeptical. I doubt that. That is BS!

You'd be hard pressed to find an engine builder who will concede that several thousand 'explosions' are occurring safely in a properly running engine every minute of its operation, because that's not what happens :rolleyes: .
Engine builders? I'd guess the majority would concede the point. Scientist, chemists, engineers? No problem. Can you find a prominent engine builder who'll back your supposition?

OK......let me put it this way with no sarcasm.......and no mere skepticism. As I see it, that hot rod magazine article is bullsh1t. Feel better, now?
I found that article to be more believable than most magazine fodder because they're not hyping some product. Same engine, same dyno, different fuels, different outcomes. Can you show me something that contradicts their test results? Also, I'm feeling fine. Thanks for asking! <This is sarcasm.

Bob.....two quick points and a comment about this article;
It's not an article. It's a sales flyer, but it addressed SSandman's questions.

1. You'll note that everything they wrote pertaining to fuel consumption spoke to fuel 'burn' or 'combustion'. Ask yourself why your so very trusted source speaks NOTHING to 'explosions' (I think your duck just died cwm3).
Er...because it's not necessary? (What duck? I thought you said it wasn't a duck).

2. In stating that race fuel has a more complete 'burn' (damn that word :p ), they never/or superficially mentioned the primary factors involved.......increased compression and ignition timing. Put that fuel in a car tuned for 87 octane fuel and has 8.5:1 compression ratio and we'll see how 'complete' the fuel gets burned cwm2.
Which fuel? They're talking about race fuels in general. Are you saying race fuel won't 'burn' in a low performance engine? Nice use of smilies, by the way. <More sarcasm? Could be.

What's your hard-on for the word burn? Fuels burn. Be it gunpowder, wood, gasoline, lighter fluid, C-4 or whatever, it burns. It's where the flames come from in fires and explosions. It's not exclusive to or separate from explosion, it's a part of the process.

From Wikipedia

"An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive" . Subsonic shockwaves are created by low explosives through the slower burning process known as deflagration."

Also from Wikipedia

In engineering applications, deflagrations are easier to control than detonations. Consequently, they are better suited when the goal is to move an object (a bullet in a gun, or a piston in an internal combustion engine) with the force of the expanding gas. Typical examples of deflagrations are combustion of a gas-air mixture in a gas stove or a fuel-air mixture in an internal combustion engine, a rapid burning of a gunpowder in a firearm or pyrotechnic mixtures in fireworks."

In summary, fuel burns in an internal combustion engine via deflagration. Deflagration, along with detonation, is one of the two types of explosions.

3. Yeah......a sales pitch is the best evidence ever conceived in bosltering an arguement.......the best evidence ever ;) .
That flyer was intended to answer some of SSandman's questions and I'm not arguing with him. It seems I'm arguing with you, and your denial of the obvious is quite stunning.

Here are a few more items you can dispute. definition 5. Bottom of page 51, top of page 52

· Premium Member
852 Posts
As far as your wiki regarding deflagrations, every definition I’ve seen on the word pertains to burning fast or burning violently. None have stated burning uncontrollably or ‘exploding’.

First two articles support your position.....4th articles say combustions "is like an explosion'......3rd article wouldn't open. I can post as many article where the word 'exploding' or 'explosion' never appears in the course of explaining the working of an internal combustion engine. So.....what? You have a point of view and I have a point of view.

For the record, and from my point of view, I do not agree that ignition and burn = explosion......regardless as to what you or the few articles you post may state.
The point is deflagration, which is what takes place in a combustion chamber, is a more controllable and containable type of explosion. I also do not agree that ignition and burn = explosion and have never stated so. That is simple combustion.

Here's another mention of explosion. Also from Wikipedia on combustion. ..."Rapid combustion is a form of combustion in which large amounts of heat and light energy are released, which often results in a fire. This is used in a form of machinery such as internal combustion engines and in thermobaric weapons. Sometimes, a large volume of gas is liberated in combustion besides the production of heat and light. The sudden evolution of large quantities of gas creates excessive pressure that produces a loud noise. Such a combustion is known as an explosion."

You agree that gasoline in a combustion chamber burns rapidly. That it creates a large volume of gas, heat and light. Oh, here's the tipping deny that a loud noise is produced and apparently are unswayable on this point. Well there you go!

While you certainly have a right to your opinion, I remain completely flabbergasted by your stubborn adherence to it.

Take care my friend.
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