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steady73
Dodge Dakota
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5/29/2003
12:47:03
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 Subject: RE: What Octane is everyone running in 4.7?
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I rotate tanks with 87 and then 89. No ping, 60,000 miles
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Demon Dakota
DakotaEnthusiast
5/29/2003
19:15:51
|  RE: What Octane is everyone running in 4.7?
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87 with my 3923 plugs...no knock or visible preignition damage. Don't use anything higher than 89 unless you have a PCM flash or are runnign a stand alone FMU...something like that (or maybe you have higher CR pistons).
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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HotRodSRJ
Dodge Dakota
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5/30/2003
10:16:43
| RE: What Octane is everyone running in 4.7?
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There are many myths about fuel and octane. Here is an article that I have been updating for years because of the changes in fuels just in the last 10 years. This article has been published in national performance magazines and websites. You can also find in at http://www.inccn.net/jsoctane.htm
I run 87 in my 2001 quad. If you run anything else you are wasting money. Higher octane fuels do NOT contain any more additives or features than lower grades today. If you are experiencing "knock" or "ping" then either the fuel is poor quality or the mapping in the software is off.
Here is a shortened version of the article.
Let’s Not Be “Fuelish” About Octane
Many changes in fuel chemistry have taken place over the last 30 years including the removal of TEL (tetra-ethyl-lead) and an aromatic called benzene. Even though serving a specific purpose both of these were proven carcinogenic and problematic chemicals that needed to go. For the most part these octane-controlling substances were displaced by aromatics such as xylene and toluene (or toulene). Both of these chemicals are prolific in today’s fuels for everyday use.
It is kind of evident that a lot of the public is “octane inept” about the fuel products they are buying. This is not only a rodding issue, but a daily driver issue too. The selection and use of the proper octane rated fuel is paramount to the overall performance and health of your engine and moreover an application specific product.
Why do we need Octane Ratings?
First of all, octane rating is not fundamentally related to the energy content of fuel, and moreover the actual hydrocarbon and oxygenate components used in the gasoline will determine both the energy release and antiknock rating. In other words, more octane does not translate to more power per se. This was and still is a common myth.
To obtain the maximum energy from the gasoline, the compressed fuel-air charge inside the combustion chamber needs to burn evenly and propagating out from the spark plug until all the fuel is consumed appropriately. In real combustion chamber life, a series of pre-flame reactions will occur in the unburnt "end gases" in before the flame front arrives. If these reactions form certain molecules or byproducts that can auto-ignite before the flame front arrives, knocking or the pinging may and most likely will occur.
Simply put, the octane rating of the fuel reflects the ability of the unburnt/end gases to resist spontaneous auto-ignition under the engine test conditions set. If auto-ignition occurs the result is an extremely rapid pressure rise, as both the desired spark-initiated flame front, and the undesired auto-ignited/end gas flames are expanding. The combined pressure peak arrives slightly ahead of the normal operating pressure peak leading to a pressure that works against the oncoming piston and thus loss of power and eventual overheating and even catastrophic failures. The pressure waves are superimposed on the main pressure wave, leading to a pattern of pressure oscillations that create the "knocking/pinging" sound. As a side comment, knock/ping and pre-ignition are both enhanced by high temperatures so one may lead to the other.
Are brands really different?
Absolutely yes! While the base gasoline may be the same and even come from the same refineries, the additive is different, and hence the brand of gasoline you use is different because of the additive, not the base gasoline. The manufacturers spend a lot of R&D on this issue and add their own special ingredients to provide additional benefits to their products so as to differentiate them from their competitors. A quality gasoline additive package could include a variety of these additives:
- Octane-enhancing additives to improve octane ratings
- Anti-oxidants to inhibit gum formation and improve stability
- Metal deactivators to inhibit gum formation and improve stability
- Deposit modifiers to reduce deposits, spark-plug fouling
- Surfactants to prevent icing, improve vaporization, inhibit deposits
and reduce NOx emissions
- Freezing point depressants to prevent icing and improve stability
- Corrosion inhibitors to prevent gasoline corroding storage tanks
- Dyes for easy product identification
As an example of total additive fuel package, premium fuel suppliers have demonstrated that a well-formulated package could improve fuel economy, reduce NOx emissions, remove existing deposits and restore engine performance at the same time. On top of that, many differing brand labels will have the very same octane rating, but differing additive packages that can affect the performance of their fuel for your engine.
If you know your car is well tuned but the drivability is troublesome on a particular/required octane product from one vendor, just try another brand. Also remember that composition will change with the season and if you lose drivability in a seasonal change try switching to another brand for help as well.
In the future as various Clean Air Act changes are introduced and the technology of our new automobile engines change as well, gasoline will continue to morph with those issues.
Why are there two differing ratings for octane?
The correct name for the (RON+MON)/2 formula is the "antiknock index" and remains the most important quality criteria for motorists today. The combination of these two methods is the defacto, worldwide yardstick for measuring octane. RON is the research octane number and the MON is the motor octane number. The RON is a scientific calculated parameter that predicts the behavior of the fuel in kind. The parameters of the MON method represent severe, sustained high speed, high load driving for most hydrocarbon fuels. During the late 1940s - mid 1960s, the RON method became the important rating because it more closely represented the octane requirements of the motorist using the fuels then available. However, in the late 1960s European automakers discovered their engines were destroying themselves on long runs, even though the Research Octane was within the correct specification. They discovered that either the MON or the Sensitivity (the numerical difference between the RON and MON numbers) also had to be specified also. This became a marriage of measurements to last.
What happens if I use the wrong octane/fuel in my engine?
A selection of a fuel with a higher octane rating than required for your engine can be as damaging as selecting a too low octane fuel in the same way. If you are already using the proper octane fuel you will not obtain more power from higher-octane fuels. The engine will be already operating at optimum performance and a higher octane should have no effect on the overall performance and in fact may reduce the overall power of your engine due to proper flame front propagation. Your drivability and fuel economy will remain the same and the higher-octane fuel costs more, so you are just throwing money away.
If you are using a fuel with an octane rating slightly below the optimum requirement for your engine, then using a higher-octane fuel will cause the engine to most likely improve performance and possibly resulting in both increased power and improved fuel economy.
You also may be able to change octane between seasons (reduce octane in winter) to obtain the most cost-effective fuel without loss of drivability. Something that is commonly overlooked.
Once you have identified the fuel/octane that keeps the engine at optimum performance there is no advantage in moving to a higher-octane fuel. The manufacturer's recommendation is usually conservative, so you may be able to carefully reduce the fuel octane. Be careful not to go to low causing damage to your engine. In your everyday driver, follow the manufacturer’s recommendation. In your rod, careful experimentation can optimize your performance and perhaps even save you money. Every rodder has a tendency to run the highest-octane fuel available because he/she thinks that it is automatically required for high performance. This is not an absolute and compression ratios, head construction media (such as iron or aluminum) and timing will play a big part of your specific requirements for octane.
Do octane boosters really work?
The type of octane boosters that come in relatively small cans such as 10, 12 or even 16 oz and usually made up of small amounts of aromatics, light lubricants and engine cleaner do not appreciably affect the octane rating of your tank of gasoline! It’s a waste of money for significantly boosting your tanks overall octane.
A good home made brew of higher-octane gasoline can be made from pump gas and toluene/toluene or xylene! Racing gasoline has significantly higher proportions of these chemicals in content than regular pump gas. Both of these powerful aromatics can appreciably raise the octane rating of your tank of fuel and do so at a reasonable cost if mixed properly. We all know that racing gasoline is expensive and usually is an overkill for most street driven high performance engines. Aviation gasoline or AVGAS is NOT made for your application with extremely differing base formulas that will cause lean conditions for most street/performance engines and will not have the additive packages that you desire, regardless of it’s attractive cost and availability! I don’t recommend it at all for you octane junkies, whereas it can easily cause catastrophic failures. It also does not have the same BTU content as well!
Here is a good table of common chemicals that can help you our making your own high-octane concoction. I recommend researching this subject profusely before starting your own chemical mixing experiment. There are plenty of articles on the Internet on this very subject and caution is advised.
This table does not format correctly here......go to web site for viewing if interested.
NOTES:
1. Toulene: Common ingredient in Octane Boosters in a can. 12-16 ounces will only raise octane 2-3 *points*, i.e. from 92 to 92.3. It can be purchased for less than $3/gal at chemical supply houses or paint stores.
2. Xylene: Similar to Toulene. Usually mixed with Toulene and advertised as *race formula.
3. Methyl-tertiary-butyl-ether (MTBE): Oxygenate. Very common in octane booster products. Has lower BTU content than toluene or xylene, but oxygenate effect makes the gasoline burn better and produce more energy.
4. Methanol or Ethanol: Methanol is wood alcohol. Ethanol is grain alcohol and found in Gasohol in 10% ratios. Both alcohols are mildly corrosive and will eat gas tank linings, rubber and aluminum if used in excessive ratios. Main ingredient in "Gas Dryers", combine with water.
5. Isopropyl Alcohol and Tertiary Butyl Alcohol: Similar to Methanol/Ethanol. Isopropyl Alcohol is simply rubbing alcohol.
The legend of mothballs as an octane enhancer arose before WWII when naphthalene was used as the active ingredient. Be forewarned that some mothball recipes do not use naphthalene any longer. The amount of naphthalene usually required to appreciably increase the octane also may have adverse effects. The most obvious is due to the high melting point and when the fuel evaporated the naphthalene would precipitate out, blocking jets and filters. With modern gasoline, naphthalene is more likely to reduce the octane rating and the amount required for low octane fuels will also create drivability problems.
What effect does timing play?
The tendency to knock increases as timing is advanced. For an engine with recommended 6 degrees BTDC static timing and 93 octane fuel, retarding the spark 4 degrees lowers the octane requirement to 91 and advancing it 8 degrees requires 96 octane fuel. It should be noted this timing-octane issue depends on engine design moreover.
If you advance the spark, the flame front starts earlier and the end gases start forming earlier in the cycle providing more time for the auto-igniting phenomenon to form before the piston reaches the optimum position for power delivery, as determined by the normal flame front propagation. It becomes a race between the flame front and the decomposition of the increasingly compressed end gases. High-octane fuels produce end gases that take longer to auto-ignite, so the main productive flame front reaches and consumes them as a result.
What are other things that effect octane requirements?
Increasing the engine temperature, particularly the air-fuel charge temperature, increases the tendency to knock. Temperature improves the conditions for end gases to form and propagate. Increasing the water-jacket temperature from 160 degrees F to 180 degrees F increases the (R+M)/2 theoretical demand by two points. This is a relatively unknown trick to curtailing your pinging when pump gas is a smiggin short on octane. Try a decrease in engine operating temperature to reduce the octane requirement.
Faster engine speed means there is less time for the pre-flame reactions in the end gases to occur, thus reducing the tendency to knock. This is why your engine may knock at lower RPMs but not at higher RPMs. On modern engines with management systems, the ignition timing may be advanced with engine speed and load, to obtain optimum efficiency at incipient knock.
A new engine may only require a fuel of 6-9 octane numbers lower than the same engine after 30,000 miles. This increase is due to the formation of a mixture of organic and inorganic deposits resulting from the fuel and engine lubricants combining in the combustion process. When the engine starts to burn more oil the octane requirement can increase again. Deposits form and raise the peak dynamic compression ratios as an engine ages in general.
An increase in ambient air temperature of 40 degrees F increases the octane requirement of an engine by about a half point. When combining the effects of air temperature and humidity, it is often possible to use one octane grade in summer (higher) and use a lower octane rating in winter.
With all the changes in chemistry, is gasoline safe?
There is little doubt that gasoline is full of toxic chemicals, and should therefore be treated with respect. However the biggest danger remains the flammability, and the relative hazards should always be kept in perspective. The major toxic risk from gasoline comes from breathing the tailpipe, evaporative, and refueling emissions, rather than occasional skin contact from spills. Breathing vapors and especially prolonged skin contact should always be minimized.
I hope this helps educate a few of you good folks here and feel free to pass the article along to whomever and wherever you want.
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TexasTodd
Dodge Dakota
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5/30/2003
11:25:12
|  RE: What Octane is everyone running in 4.7?
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87
01 QC 5spd etc.
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00287RC
Dodge Dakota
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5/30/2003
13:24:34
| RE: What Octane is everyone running in 4.7?
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well if you are running a blower or turbo you sure as heck better run higher octane unless you want detonation.
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no kidding
Dodge Dakota
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5/30/2003
13:40:12
| RE: What Octane is everyone running in 4.7?
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duh
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jim
Dodge Dakota
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11/10/2004
10:21:53
| RE: What Octane is everyone running in 4.7?
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if you want to mess up your engine run premium fuel in a motor not set up for it...unless your engine has higher than a 10:1 compression using premium fuel will carbon it up...reason-premium fuels have a slower burn and with lower compression engines you are not going to burn all the fuel and may end up carbon up your engine and exhaust..
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eddy
Dodge Dakota
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11/10/2004
11:07:32
| RE: What Octane is everyone running in 4.7?
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MAnufacturer says 87, I run 87. 04 Quad 4x4.
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eddy
Dodge Dakota
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11/10/2004
11:34:32
| RE: What Octane is everyone running in 4.7?
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I figure if higher octane would consistently bring some kind of benefit, there would be no reason why the manufacturer wouldn't have recommended it in the first place.
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bnc
Dodge Dakota
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11/10/2004
11:50:41
| RE: What Octane is everyone running in 4.7?
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I run 100 proof Jack Danials in mine......lol just kidding......87 octane in mine with a can of SeaFoam once a month.
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