Mike,

I've been enjoying your informative posts about the various performance chips and what they do to the vehicle... I've been learning a lot. I did notice one slight mis-statement however, and that was something to the effect that "premium gas burns slower".

This is not quite accurate. Gasoline is composed of many different kinds of carbon chained hydrocarbons, from 2 and 3 carbon chains to six carbons (hexane), 7 carbons (heptane), and 8 carbons (octane). There are also a few longer chains but these are generally refined out. The most common molecule in gasoline is heptane, the 7 chain hydrocarbon. Attached to these carbon chains are atoms of oxygen and hydrogen, along with smaller quantities of sulfur, nitrogen, and other impurities.

When gasoline burns it is actually a multi-step process. The long chain molecules must first be broken down by heat into short (2 or 3 atom chains) before oxidation can take place. Then, the short chain molecules break down and actually burn... the carbon, hydrogen, and other atoms get oxygen attached to them to form carbon monoxide, carbon dioxide, water vapor, and pollutants like oxides of sufur and nitrogen.

As it turns out, the 5, 6, and 7 chain hydrocarbons break down at a rather low temperature. But, one isomer of the 8 chain molecules (octane) is much more resistant to breaking down until higher tempertures have been reached. This is why gasoline's anti-knock properties are measured in terms of an octane rating, and the reason that high octane gas resists pre detonation is that it takes a higher temperature to break down the molecules so that they will burn.

Simply refining gasoline with more octane in it is the simple way of getting high octane gas, but the process is very expensive. It was discovered that various additives could also enhance the perceived octane rating of a gasoline. For years gasoline came with tetra ethyl lead in it. 100 octane gas had between 2 and 3 grams of lead in it. Since tetra ethyl lead is very bad for us and has been banned, the alternative additive that has been used almost all over the country in unleaded fuel is MTBE... yes, exactly the same stuff as in oxygenated fuels, but only about 1 cup per gallon for premium gasoline, versus 2 or 3 cups for oxygenated fuels.

The additives work much like adding salt to ice works... it changes the temperature at which the long chain molecules begin to break down. Thus, heptane which normally breaks down at a lower temperature begins to act like octane and breaks down at a higher temperature. So, premium gasoline does not burn "slower" than regular gas, because in fact, it is exactly the same gasoline, with an additive in it. It is all about the temperature at which burn begins, not the speed of the burn.

Premium gas does have less energy per gallon than regular gas. The gasoline itself is identical in both cases, and therefore has exactly the same energy content per unit volume, but MTBE has less energy content per unit volume than gasoline, and thus, premium gas has less energy per gallon overall. Oxygenated fuels are even worse... with 2 or 3 cups per gallon of MTBE, their total energy content is lower still.

Hell, I've written half a book, and I still have scotch in my glass, so I'll write some more. Octane is measured two ways… research octane number (RON) and motor octane number (MON). Each of these are found by running gasoline in a specially designed single cylinder motor. Motor octane measures anti-knock properties under severe conditions… heavy loads, wide open throttle, high RPM's. Research octane measures anti-knock properties under more normal driving conditions… lower RPM's, cruising down the freeway at 55, partial throttle. Generally, any given gasoline will have a RON that is 8 to 10 points higher than its MON. The pump octane you see is (RON + MON) divided by 2.

Engine designers assign an octane number rating (ONR) to the engines they design and it is the octane number at which at engine will run without knocking. Many factors affect the ONR, including compression ratio, ignition timing, fuel/air ratios, cylinder head temperatures, and combustion chamber design. Compression ratio has the largest impact on both ONR and engine efficiency… higher compression results in a more efficient engine and a higher ONR.

Retarding the engine timing, running either rich or lean, reducing cylinder head temperatures, and using swirl type combustion chambers all reduce ONR. Other factors also affect ONR. Lower barometric pressure reduces ONR… this is why octane numbers for corresponding grades in the mountains are lower than at sea level. Increased humidity and lower temperatures decrease ONR. Deposits in the combustion chamber increase temperatures and pressures, and therefore, increase ONR.

Since the chips you sell are designed to improve engine efficiency and extract maximum power out of a hunk of metal, I'll close by talking about why using premium gas is essential with most of your products. Knocking alters the manner in which gasoline burns, and knocking will result in a power decrease. In the ideal engine, the gasoline is ignited somewhere well before top dead center. The flame front begins to spread evenly from the spark plug and reaches its maximum at about the time the engine is just past top dead center. The combustion process, now at its maximum, drives the piston down with maximum force.

If the gasoline ignites prematurely, several undesirable effects occur. First, rather than having a flame front that moves smoothly from the spark plug on out, there are pockets of flame that ignite in several places. This is not as efficient and the engine loses power. Second, if the pre ignition occurs too soon before top dead center, a tremendous strain is placed on the engine… the forces of burning happen too early and press against the piston while it is still traveling up. Third, hot spots develop in the engine. The cylinder head is designed to take maximum heat, and maximum flame duration. The pistons normally have the shortest period of contact with the flame front, but if the gasoline ignites close to the piston, say, due to a carbon deposit, then the piston is subject to temperatures for which it was not designed.

Keep up those posts. I'm real curious as to how the chips control oxides of nitrogen and stay within EPA guidelines when cranking out more power.

BeastRider

 

Very interesting and informative. Learned quite a bit - thanks
GDG

 

Beast Rider,

Very informative. Which leads to a question.......

Since higher octane fuels don't ignite until they reach a higher temp, is it correct to say that the ignition takes place later in the stroke when using higher octane?

 

I would think that the MAIN reason for using a higher octane gasoline would be due to higher compression ratios.
Higher compression places more pressure in the cylinder. When you've got a mixture of fuel and air under higher pressure, does not that mean you've raised the temperature at which the molecules will ignite?

I dont know for sure, but I would say this is a Thermodynamic property which holds true for all molecules and atoms... Pressure, or the lack there of, changes the way in which these things react with each other.

Similarly, your cooling system is under PRESSURE which RAISES the boiling point or the point at which the fluid starts to turn into a gas...

BTW: GREAT post! Its nice to have someone who REALLY know what they are talking about! Mike T talks about gasolines like he knows what HE'S talking about. When in fact, I've found MANY fallacies in his arguements.

I learned that Higher Octane gasoline does NOT burn slower. I did not know that!

Another BIG fallacy that Mike T tend to tell people about the MAJOR difference between brands.

BeastRider: Can you please tell us something about the difference between buying gas at Texaco, Amoco,etc... Versus buying it at Mom & Pop's Garage or Sheetz?

I've heard and read stories that suggest you are buying essentially the SAME gasolines at Pop's Garage, as you are at Texaco. The only difference being the additive package. Like Exxon's X12R49PD11 (being funny)... SO energy content should be the same. However, FRESHNESS of gasonline is another HUGE factor. They say to buy at places that do a lot of business...

 

I've been gone about three months, I come back and what do I find? Same ole' crap, Rand trying to get a "dig" in on Mike

 

The point at which detonation takes place is a function of ignition timing... the point at which the spark plug fires. What you have asked would be true of diesel engines where it is solely the compression of air that heats the cylinder to ignite the fuel. Note however, that diesel fuel has a 'cetane' rating which is a measure of how low a temperature is required to ignite the fuel.

Ignition _would_ occur later in the stroke with premium IF you were suffering from pre detonation problems, since the gasoline would be igniting before it is supposed to. But all other things being equal, in a gasoline engine, the gasoline is supposed to stay under ignition temperature until it is ignited by the spark plug.

FWIW, the reason that all modern engines have the timing retarded (at least 6 to 10 degrees more than models in the 60's and 70's) is to reduce a pollutant, oxides of nitrogen. When timing is advanced, cylinder head temps go up, and it is the higher temps that produce N02, N03. One way these 'superchips' give you more power is to advance the timing back to where it was on older motors, although the chips offer a great deal more flexibility than simply adjusting the distributor.

 

Compression ratio is the primary reason that one must run premium. Higher compression ratios lead to higher sylinder head temperatures, which require higher octane gasoline to avoid pre detonation.

However, the need for higher octane can be offset by retarding the timing so that the flame front and cylinder head temperatures do not get as hot. Most of the Ford motors out there today have a compression ratio of 9.0 or 9.2. My motorcycle had a compression ratio of 9.8 and I could run regular in it until I advanced the timing. The same holds true for the superchips. They advance the timing curve, which produces more power, and higher cylinder head temps... hence the requirement to run premium.

As to different brands of gasoline... this is a very complicated question. It is true that in some parts of the country, the same basic feedstock is used and different additive packages are used, but in other places (like Houston, where there are a ton of refineries), there will be many feedstocks. But, even the feedstocks change, and the exact composition of the gasoline is a function of the underlying crude oil used... could be high sulfur, could be low sulfur... crude is different all over the world, and unless the source for a refinery remains constant over time, the gasoline will change.

If you check with any seller of gasoline, you will also discover that the additive package changes with the season and the nature of the feedstock. Up north, in the winter, you'll get an additive package with more volatiles in it to make winter starting easier. In the summer, you get an additive package that works to prevent vapor lock. In Houston, the amont of MTBE is varied depending upon temperatures. I am not a petroleum engineer, but I have talked to several of them, and I can tell you that additives change all the time, all over the country. It is not a static thing.

I do agree about getting fresh gas... although gas would have to be in an undergrounfd tank for months to begin to varnish. But, I'd be worried about water contamination. This is also why I never buy gas at a station where the truck has just dropped off a load... filling the tank will stir up all the crud on the bottom of the storage tank.

 

Very interesting and informative.
I am curious Beastrider, is this something that you studied? If not were you able to retain all this information from the FAQ's site?
Reguardless I believe your knowlage can be an asset to the members.
I have a tendency to question credibilty, but so far you seem a-ok!
Hope you keep the info comming.
Tom

 

I spent several years working in the petroleum industry as a seismic programmer and I picked up a bunch of stuff there. My father was also a petroleum guru and I picked up a lot by osmosis.

But, I really got into this stuff over the use of correct octane in my motorcycle. It was based on the same thing as going on here... advancing the timing for increased power. We had many discussions and many web searches about gasoline. The FAQ I posted is amongst the best I found, but I have several other references as well.

I didn't do all of this from memory. About a year ago, I spent half a day on Saturday summarizing the FAQ for the VRCC motorcycle board, so I plagarized part of it, and remembered the rest. Stuff like this sticks for me, but I usually can't remember why the wife sent me to the store.

I have a philosophy about posting. If I don't know, I don't post. If there is uncertainty, I'll state it. If it is a guess or my opinion, you'll know it. If I am corrected, you may rest assured that I'll post the correction. I think the vast majority of incorrect posts are simply a case of the person having been presented with the wrong facts, but I love to call the b*llsh*tters on the carpet when they shoot from the hip.

So, if you ever find that I've made a mis statement, call me on it. Helps me learn. Truth and fact is the only way to view reality.

 

Hi BeastRider,

The fact of the matter is, premium gas of 92 or higher octane does in fact require a longer "time" (duration) to complete the burn in the combustion chamber compared to 87 octane fuels in this tuning. This is *precisely* why your owners manual tells you to use 87 octane, as that is what the fuel curves are calibrated for **from the factory**, and it clearly spells out in mnay of the owner;'s manuals for these trucks that using higher octane should not be done, becaues ofhte potential driveability problems, etc. in these Ford (and many other) trucks.

I can't tell you how many times we've taken calls from people panicked because they got a check engine light from running premium gas on the factory program. And of course, there are people who do that and don't get the lights. The point is simply that the fuel curves are in fact calibrated for teh use of 87 octane gasoline, and many of thes owners manuals warn you specifcally not to use premium gas, and that is why. We have had numerous Ford, GM & other powertrain engineers all say the very same thing, and they, along with other acclaimed tuners we work with all tell us the same basic thing.

To take it further, if you were to actually look at the programs right from the factory in Ford vehicles that are tuned specifically for premium gas from the factory, you'll find many of the very same kinds of differences to the fuel curves as has to be done in the Superchip for proper driveability. They have to deal with that just like all other tuners do.

Rather than bore everyone with claims of knowing this or that, this comes directly from some of the best powertrain engineers in this country, the people who actually tune these engines. We work, day in and day out, with many of the best powertrain engineers in this country, and to a man, they tell us that they do in fact have to compensate the fuel curves for sufficient burn time, I have personally seen those compensations, and I have tried running without them and I can tell you that the driveability will *never* be what it could be without those compensations.

This is also the reason why using 100+ octane racing gas, even when we program for it, as we have for many Lightning owners for example, cannot take full advantage of that much octane as the fuel delivery system simply isn't designed for it to begin with. If it were, we know we can get substantially more power gain from tuning from 100 octane instead of 92 octane that what we do. We get more power gain from re-tuning for 92 octane from 87, and we do from re-tuning for 100 octane from 92.

With regards to the other previous claim you made of how the Superchip was supposed to raise exhaust (NOx) emissions because it advances the timing, that is simply dead wrong. That has *never* been born out in any of the exhaustive (pun intended) emissions testing done not only in-house at Superchips, but also by the California Air Research Board as well as the independant labs used by Superchips for testing & verification, to say nothing of the numerous people who have posted their emissions test results right here, before & after the Superchip.

 

Needless to say, I want to respond but I've got to do some work today, and my response will take a while.

In the meanwhile, since I want to avoid semantics problems, please precisely define "fuel curve" as used in your post.

Thanks.

BeastRider

 

Thank you beastrider, It is refreshing to read some accurate infomation for a change. Keep it coming, like reading it.
Terry

 

MAN, My head HURTS!!!!

Some very interesting stuff, one side you have Mike T. who works with these engineers and engine programers.

And then you have BeastRider who has worked with the petroleum industry and has done some quite abit of studying.

Just waiting to see what BeastRider has to say about Mike's last post??

 

Mine too,PBALL. Mine too

 

Anyone remember the movie, "Mars Attacks"? Remember what happened to the Martians when Slim Whitman was played?..ROFLOL! Well, after this conversation and this kind of thinking, that's how my head is beginning to feel.