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      03-03-2010, 03:09 AM   #1
Bob MG
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Octane Boosters and Race Fuels

I have asked questions regarding the benefit of using race fuels and octane boosters and how much the RON rating will increase when a good octane booster is used.

I did some research on this and thought i would share the results:
Whether boosters work or not isn't the question. If you've used a booster, you already know it works based on the not-so-accurate accelerometer called your behind. The question is which booster offers the highest octane gain. At $3 to $10 per treatment, a bottle of octane booster can almost equal a third of the cost for an average tank of premium gas. At that price we all want the best bang for the buck. To find the answer, we tested three octane boosters, each with different active ingredients, to see how much of a kick in the pants they supply.
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CFR engines; MON on the left,...

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CFR engines; MON on the left, Ron on the right

So what is octane? Without getting into chemistry, molecular bonding and hydrocarbon chains, octane is simply a measure of fuel-detonation resistance. The higher the number, the less prone the fuel is to detonation.

Detonation is the un-uniform ignition of the air/fuel charge in the combustion chamber. Normally, the combustion flame front originates from the spark center. When detonation occurs, the charge is lit at not only the spark center, but also from hot spots caused by build up from carbon deposits within the combustion chamber. This causes an uneven flame front, resulting in a sudden rise in combustion pressures, which can damage a piston on the power stroke.
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Infrared Octane testing performed...

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Infrared Octane testing performed at Rockett Brand Racing Fuel

A more catastrophic scenario, called pre-ignition, occurs when the charge unintentionally lights off without a spark. This usually means the event occurs toward the end of the compression stroke when charge temperatures and pressures are still rising. With pre-ignition, the sudden change in charger pressure from premature ignition as the piston is still moving up is equivalent to taking a hammer and beating it on top of your pistons. The sound is very similar, just like a ping.

Higher octane fuels are especially helpful to boosted or high-compression performance engines, along with older engines. With boost or a high-compression ratio, the air-fuel charge is compressed to higher pressures, which makes it more susceptible to detonation. Older engines with carbon deposits built up in the combustion chamber also benefit from high-octane fuels as the added space occupied by the deposits also effectively increases the compression ratio.
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Sample mixtures

To avoid detonation, engines with knock sensors retard the spark timing at the onset of knock. Retarding spark timing or richening the air/fuel mixture to reduce knock ultimately robs power. This is why an increase in octane increases horsepower. Since the engine's knock threshold is effectively raised with higher octane fuels, spark timing is not retarded. This allows combustion and charge expansion to occur so that more force is put into the power stroke. Bottom line: Higher octane fuel only helps you make more power if your engine is at the verge of detonation (whether you know it or not).

Most likely, anything you've read in enthusiast magazines involves roundabout methods of measuring the effects of changes in octane. Most methods incorporate a chassis dyno, a 1/4-mile run or, at best, an engine dyno. Each method is flawed because each uses horsepower changes to correlate to octane changes.
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RON CFR engine: Note the heated...

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RON CFR engine: Note the heated intake and black variable compression head assembly.

The problem with measuring horsepower is its a function of the combustion process, which varies with ambient conditions, spark timing and air/fuel ratio--all of which are continuously varying and often computer controlled. The measurement method also isn't precise enough to establish an accurate estimation of octane gains. Most chassis dynos will have a range of variability of up to 5 whp. This is enough to cover many octane boosters' gains. Though differences are measured, the amount of variability and lack of experimental controls prevent a reliable margin of repeatability.

Instead of trying to evaluate gains in octane through horsepower, it's more appropriate to evaluate actual octane gains. Having to account for how each engine reacts and adapts to more octane adds more pieces to the puzzle.There are two primary ways of measuring actual octane values: 1) The combustion fuel research (CFR) engine and; 2) a newer infrared method. Currently the American Society for Testing and Materials (ASTM) uses the CFR engine method, developed in the 1920s to obtain official octane measurements. The CFR engine measures octane by combusting the fuel and physically measuring the knock that occurs.Infrared technology offers a faster method of non-official octane measurement by spectral analysis of all the different chemical contents in a fuel. It guesses the octane of a sample based on the percentage of various hydrocarbons present and references these contents against a known library of data. Unfortunately, this library of hydrocarbon data doesn't include the active ingredients found in commercial octane boosters. This is why our test was performed on a CFR engine, which also made it certified.
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Variable compression head...

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Variable compression head.

Octane boosters can be broken into three types based on their active ingredients. Methyl cyclopentadienyl manganese tricarbonyl (MMT) and ferosene are used in limited amounts in off-the-shelf boosters. The majority of commercial boosters use MMT. Another type of booster uses alcohols or aromatics as the active ingredient. Many tuners use toluene as a home-style octane booster. Toluene, an aromatic circular hydrocarbon chain, is a regular component of pump gas and is available in various grades at chemical supply stores. Premium street gasoline carries roughly 3- to 5% toluene, which partially helps octane characteristics. Unocal's 100-octane race gas has almost 25% toluene.

The drawback to any of these additive ingredients is the diminishing effect they have on higher-octane fuels. Adding the same booster to 87-octane pump gas will yield a lot more octane gain than adding a bottle to 91-octane premium gas. Excessive concentrations of these additives also damage emissions-control hardware, such as spark plugs, injectors, oxygen sensors and catalytic converters. This is why most off-the-shelf boosters have an emissions-legal street formulation and an off-road formulation that exceeds the government-regulated concentration of MMT or ferosene.For the power-hungry, there really is no point in testing 87-octane gas and street-legal octane boosters. That's why we performed our tests with a base sample of 91-octane premium gasoline taken from a local SoCal station. By law this gasoline must have an octane rating of at least 91 octane. Octane boosters were obtained at local auto parts stores while 99%-pure gasoline-grade toluene was sourced from the laboratory of Rockett Brand Racing Fuel.
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Knock intensity meter.

We chose Nitrous Oxide Systems' (NOS) Racing Formula octane booster, which uses MMT as its active ingredient, and Outlaw's Super Concentrated Octane Booster, which uses ferosene. Outlaw originally had off-road and street formulations, but just recently combined the two into just one street-legal formulation. The toluene mixture we tested was based on an Internet-sourced home brew.Saybolt LP, a division of Core Laboratories, performed a certified, independent octane test on samples of three different types of octane boosters we prepared. Each sample, along with the base fuel, was tested for research octane number (RON) and motor octane number (MON), as prescribed by ASTM Method D-2699 and D-2700, respectively.

The resulting pump octane number--also referred to as antiknock index (AKI)--was calculated using the (R+M)/2 method, which takes the average of RON and MON. These tests have a repeatability (same operator/same lab) of 0.2 octane for both RON and MON, and a reproducibility (different operators in different labs) of 0.7 for RON and 0.9 for MON. In addition to octane testing, each sample's specific gravity, or density, was tested according to ASTM method D-4052.
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Overhead valve rockers and...

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Overhead valve rockers and knock sensor (center).

The CFR engine is basically a carbureted, single-cylinder, variable-compression engine. The head can be raised and lowered to change the compression ratio and thus increase knock intensity. By reading the knock intensity at a given compression ratio, the operator can determine the octane rating of a sample fuel. Each engine, (one dedicated to RON testing and the other to MON testing) has to be warmed up to maintain a 100- to 130*F oil temperature and a 2- to 3-Hg manifold vacuum. Air/fuel ratio is held at an elevation-corrected constant. Prior to every test, both a toluene and an iso-octane mixture of known octane are run through the engine for reference and calibration checks.

The less-severe RON test is performed at 600 rpm with intake and air/fuel charge temperatures regulated at 125*F. Ignition timing is held at 13-degrees BTDC. The higher load MON test is performed at 900 rpm. Intake air temperature is held at 100*F; air/fuel charge temperatures must be 300*F. Spark timing varies between 19- to 22-degrees BTDC based on the compression ratio. The results of these two tests are averaged for the AKI number that you see at the pump.
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Calibration fuels

Each of our samples were mixed in a ratio equivalent to having added the entire contents of an octane booster bottle to a 15- gal. tank of 91-octane fuel. Each 1-gal. sample was stored in sealed metal containers at room temperature to prevent evaporation or degradation of the fuel or the octane booster. The toluene mix was composed of 12.5 oz of toluene and 3.125 oz of mineral spirits, treating the same 15-gal. fuel tank. As there was too little to make a difference in our 1-gal. test samples, 0.375 oz of transmission fluid (claimed to act as a lubricant) was left out. According to Tim Wusz, the mineral spirits and motor oil would only lower the octane rating if added in sufficient amounts. The results are shown in the tables below.

Since we wanted to determine the efficacy of the home-brew octane booster recipe, we re-verified the toluene results, using an infrared measurement system. Tim Wusz of Rockett Brand Racing Fuel performed the same tests using different equipment. The AKI results of the MMT and ferosene boosters were ignored as they were invalid on this equipment. We re-measured the RON and MON on the base gas and the home-brew mix. Any change was negligible.
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Intake manifold; the canisters...

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Intake manifold; the canisters on the left are for calibration fuels and the bank on the right is for test fuels.

To see how much toluene had to be added to 1 gal. of base fuel to make a significant difference in the AKI, Rockett Brand concocted three different mixtures ranging from volumetric 10- to 30% toluene.

As described by Wusz, there is an optimal window of effectiveness for toluene additives. Beyond that, the increased fuel density begins to have detrimental affects on proper fuel carburetion and also retards combustion.

Toluene-laden fuels burn slower and make less power on high-revving engines. So much in fact that much of the air/fuel mixture is still burning as the charge exits through the exhaust valve. This is a sure way to destroy your emissions-control equipment and not pass smog. For these reasons, true race fuels don't just use toluene or other active ingredients to boost the octane. Instead they use better-refined hydrocarbon chains that raise octane while retaining optimal combustion characteristics.

So there it is, octane boosters tested and explained in a nutshell.
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      03-03-2010, 10:27 AM   #2
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Maybe what I should have asked is do you think octane boosters actually raise the RON as this test suggests?
The one I would like feedback on is Liqui Moly as oer attached picture:

Octane Plus is designed to improve gasoline engine operation in areas where the octane rating (RON) is too low and causes engine knock, pinging, overheating and other problems associated with lowoctane gasoline. Raises the octane rating by up to 4 points. Contains no lead or other metallic-compounds that could harm catalytic converters.
Intended use
As additive treatment for all gasoline powered cars to increase performance and reduce problems of low-octane fuels. One can treats up to 50 l of fuel.

They also have a product called Speed Tec which claims the follwing:
Increases combustion intensity
Cleans entire injection system
Promotes optimum power & performance
Instant acceleration boost
Engine starts easier and runs smoother
Reduces non-combusted residual fuel
Liqui-Moly Speed Tec is a high performance fuel additive that significantly improves acceleration and throttle response by increasing combustion intensity. It’s far more than an octane booster, think of it as an energy drink for your engine – extra boost when you need it.
Ideal for track days and during conditions of high engine loads.


Its made in Germany and is TUV approved etc, so it cant be shit?
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Last edited by Bob MG; 03-03-2010 at 10:32 AM.
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      03-03-2010, 11:00 AM   #3
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Quote:
Originally Posted by TrackRat View Post
Increased octane only improves power if the engine management system is programmed to use the increased octane AND the engine actually needs the increased octane.

In regards to race fuels, octane is not the only consideration. Some race fuels achieve higher octane by using retardents. This does increase the octane but slows the burn rate. This type of fuel requires more ignition timing just to come close to a fast burn fuel of the proper octane.

There is a lot more to fuel and octane than what you typically find online. It's also worth noting that if the BUTT dyno was accurate we wouldn't use engine dynos, we'd just pull numbers out of our arse.
Information I have been given told me increased octane will actually add some power even if the engine management system and timing stay the same. This is because of the slower burn, allowing for the burn to continue for a longer period of the power stroke. Of course the difference is only minor and to take advantage you need an engine management system programmed for the higher octane. But typically the burn of fuel is long over before the power stroke has reached the bottom of it's travel, so the slower burning fuel helps to add some power. Any thoughts on this?
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      03-04-2010, 03:55 AM   #4
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I have actually tried to put Toluene in my old car GTI

my car made a lot of HP for the little 2.0T engine

and I must say you can feel a difference.

I added about 10% but our fuel is 98Ron from the pump.

I always had a question on is this safe? or am I adding too little?
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      03-04-2010, 04:34 AM   #5
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I like where this discussion is headed
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      03-04-2010, 04:40 AM   #6
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Quote:
Originally Posted by PedM5 View Post
I like where this discussion is headed
its a very useful information
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      03-04-2010, 09:01 AM   #7
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      03-04-2010, 10:23 AM   #8
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Quote:
Originally Posted by PedM5 View Post
I like where this discussion is headed
+1

Great info
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      03-04-2010, 04:47 PM   #9
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responded in red
Quote:
Originally Posted by TrackRat View Post
Octane is a rating of the fuel's resistance to detonation. It is not an indicator of power at all. More octane does not produce more power.
This I knew.

The information you were given is incorrect. Slow burn produces less power every time. The peak cylinder pressure needs to occur at a very specific point in the crank rotation. To get that peak cylinder pressure (bmep) at the correct point the ignition timing must be advanced on slow burning fuels. When you advance the timing to get the peak cylinder pressure at the correct point then the cylinder pressure before top dead center has to increase, causing negative work as the increased pressure tries to push the piston down before it reaches TDC which effectively tries to turn the engine backwards or stall the piston's upward motion. This is why slow burn fuels never produce as much power as fast burn fuels. In addition slow burn fuels can increase end gas burning which can increase spark knock or detonation depending on the chamber shape.
This is new info to me. I was under the impression that quicker burning fuels were spent long before the piston reached the bottome of its power stroke, therefore there is a period during the power stroke (while piston is traveling down) where no more power is being created. Hence the additional power that can be harnessed by slower burning fuels while keeping all other variables (i.e. timing) the same.


For all practical purposes at medium to high engine speeds, the useful power stroke is over as 90 degrees past TDC. Early cylinder blow down is used to reduce pumping losses because the change in cylinder volume vs. the expanding gas rate, means the push on the piston is minimal.

I have no idea what chemicals Liqui Moly is using. Read the label for contents. If you check many newer "octane boosters" they are primarily methanol or ethanol. They will increase octane some but so will E85 for a lot less though you can't use much if your fuel system wasn't designed to handle alcohol fuels.

FWIW, any college automotive engineering text such as Taylor and Taylor's "The Internal Combustion Engine in Theory and Practice", will help you understand the facts on engines, fuels and the combustion process.
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      03-05-2010, 12:21 PM   #10
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Quote:
Originally Posted by TrackRat View Post
The expansion stroke losses all practical push beyond 90 degrees after TDC because the change in cylinder volume by virtue of the downward piston motion increases faster than the pressure rise of the burning charge. The charge is still burning when the exhaust valve opens but the pressure rise has dropped long before that. Slow burn fuels can allow more energy to go out the exhaust valve compared to fast burn fuels.

In all situations a slow burning fuel of the same octane and energy content delivers less power than a fast burning fuel. In addition to the increased pressure build-up before TDC required with a slow burn fuel, the heat loss (rejection) to the cooling system increases also resulting in an additional tiny loss of power. If the engine could mechanically stand the forces, you'd want a really fast burn rate but if it's too high you get crank rumble as everything starts bending and vibrating from the extremely fast pressure rise. If the burn rate is excessive it's like hitting the piston with a sledge hammer at TDC.
Awesome info... Thanks
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