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austin
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Northern, CA Oct/07/02 2001 Type-R User ID: 9831
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Last Here
11/16/2009 |
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Since there have been a rash of questions concerning using higher octane gas in the car...I've decided to round up a few dyno plots that I have of when I tested out running a higher octane mixture without having the car tuned to run specifically on the higher octane.
Why run higher octane?
1. higher octane slows down the combustion process giving you a slower, more controlled burn.
....A. advantage to this is that it allows you to increase your timing, and/or compression as you're less likely to have detonation.
....B. advantage is that it helps to prevent pre-ignition, preventing detonation from hot spots in the combustion chamber.
....C. advantage is that you can run run more advance, and/or higher boost levels on forced induction vehicles, the slower burn helps to prevent the combustion process from blowing up, rather allowing it to burn(when it blows up you have bent rods, burnt valves, holes in pistons...)
....D. advantage is that you can run nitrous oxide with more ingnition timing, and a smaller chance of pre-ignition(read C above)
....E. disadvantage is that if you don't have the car tuned to run specifically on the higher octane gas, you'll end up with less power since the combustion process is still attempting to burn the fuel when the exhaust valves open, dumping still burning fuel into your exhaust.
....F. disadvantage is that it's going to make your wallet considerably lighter.
Information on the plots:
The difference in air temperatures was ~4 degrees, the barametric pressure were fairly similar, this is an SAE corrected graph. The only changes between the two graphs is that I added in a few gallons of 100 octane gas, the net octane was ~96.X that I computed at the time.
full size, cut and paste:
http://www.imagestation.com/picture/sraid69/pd754fc3092cc94beb04a7f1d3b5bf00e/fbb758d6.jpg
Have a good day...
Austin
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Recent assistance by...
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IPS Racing - The Import Performance Specialists
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MichaelDelaney 
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Late Apexing, YT Feb/23/02 User ID: 416
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Last Here
8/21/2009 |
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have a good day indeed...
nice stuff austin...once again you've left 'em speechless. LOL
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Who is Michael Delaney?
Type R Teg Baby |
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austin
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Northern, CA Oct/07/02 2001 Type-R User ID: 9831
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Last Here
11/16/2009 |
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Quote: Originally posted by MichaelDelaney on Jul/09/03
have a good day indeed...
nice stuff austin...once again you've left 'em speechless. LOL
~190 dyno runs and counting, I enjoy learning, just not learning the hard way...too many runs on the car, still runs great, which is why I toss it on the dyno every so often, about every 10,000-15,000 miles just to make sure everything is where it's supposed to be.
Austin - dynowhore, part tester
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scooby_dooby
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Edmonton, AB Jul/11/02 1990 GS User ID: 4522
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4/30/2005 |
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awesome man, that's the kinda thing i wish people would do more of, thx!
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JustinKlemgold |
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PA Mar/03/02 User ID: 673
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Last Here
2/7/2010 |
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WOOHOO! We love you Austin! Thanks a bunch for the info bro.
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95 Integra LS Fully built turbo...Sold. Wow. This is sad. =(
09 Toyota Corolla S - The lady's
09 Honda Fit Sport...the fit is GO! |
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DaBoyNBlu
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AL Apr/28/02 User ID: 1411
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Last Here
4/16/2009 |
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oh man, this is wonderful... if only i had this when i was in that 4-page-long debate about this exact subject a couple months ago
still angers me that people don't understand how octane works. 
thanks austin, i'm definitely bookmarking this thread.
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I'm deactivating my account. TI is becoming another HT. |
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LT6916
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Trenton, NJ Feb/21/02 User ID: 22882
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1/9/2010 |
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i think what confuses most people (including myself) who cannot afford a dyno tuning every 10-15K or at all (including myself) is WHAT octane to run.
I know for a fact that with my advanced timing on my mostly stock LS motor (i/h/c/e) with 153K miles, I'm still confused which octane to pump. 87, 89, 91, 93?? Which wont kill performance being too high or too low?
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93 MR2 turbo // 16psi : intake : downpipe : exhaust |
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Gvtec
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DNF in, GA Feb/21/02 1998 Type-R User ID: 4 Name: Garrett
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Last Here
7/11/2008 |
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Octane dictates the flash point and burn rate of gasoline, as stated. How hot and strong the spark needs to be and your static timing advance is important for running exotic fuel mixes.
The octane needed for your motor is all dependent on your setup and needs. It's a trial and error, from what I've been told, but I assume there's a formula to calculate the BSFC and VE, along with a few other variables that are near impossible to get real specific with. Like a long term heroin user; find out what will kill you, then back it off a notch.
If you've got a J&S or MSD knock indicator, you could adjust the timing advance to know what's "too much."
Some also get the impression that octane regulates fuel consumption, when it's more of an issue of how long it takes the mixture to burn. In some cases, you can add more fuel to resolve some preignition, but it's only part of the equation.
It's really similar to water injection. If you don't tune for it, you're only building a safety net that doesn't produce more power.
Next time you go to a 1/4 track, take note on the guys adding 103 octane fuel their tank. I'd say very few people have motors tuned for such and even some would say "to get more power, duh!"
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Hype-R #885
4 sale: J&S $afeguard
There is no expedient to which a man will not go to avoid the labor of thinking.
-Thomas A. Edison |
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scooby_dooby
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Edmonton, AB Jul/11/02 1990 GS User ID: 4522
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4/30/2005 |
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DaBoy, I hear that, How many people went on and on about how "OCtane DOesn't affect performance" blah blah blah...
so in general would using the lowest possible octane, wihout having any pre-ignition or detonation, result in the greatest performace?
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kelly
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Jul/19/02 1999 GSR User ID: 4948 Name: Kelly
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Last Here
1/13/2010 |
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Burn rate and octane are not directly related. You added some 100 octane gas and lost power, however do you know that the ONLY variable that was changed was the octane? No. In this case you are probably right in that the BURN RATE changed, but that is not what octane is a measure of. You would have to have different fuels tested with ONLY the OCTANE being different to make any valid statements concerning this. You only showed some evidence to suggest that a different fuel blend makes different power.
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Nam Myoho Renge Kyo
National Motorists Association |
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DaBoyNBlu
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AL Apr/28/02 User ID: 1411
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Last Here
4/16/2009 |
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not to be mean, but there's more to life then book definitions. the book definion of octane doesn't include burn rate. but in real life, they're related. this isn't the first time real-world applications have shown this. i'll leave it at that before i have another thread like the one before.
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kelly
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Jul/19/02 1999 GSR User ID: 4948 Name: Kelly
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Last Here
1/13/2010 |
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Different fuels perform differently. This is all these dyno graphs show. If this is all that is to be shown, then OK. However it keeps being stated that octane is a measure of burn rate and that it is strictly because the octane is different that the graphs differ which is ABSOLUTELY not true.
I posted on your other thread, and I understand your position and I know you understand the issues, but I believe you are causing confusion by refusing to make concrete distinctions. Some things have to be treated very scientifically, and this is one of them. If everyone has a different definition of octane, which you seem to believe is OK, we will never be able to agree. The reason the octane debate keeps going on is because there has never been a concrete foundation layed to build upon. Subtleties aren't a good foundation, but this is what is being attempted here.
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MichaelDelaney
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Late Apexing, YT Feb/23/02 User ID: 416
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8/21/2009 |
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it's an issue of understanding.
again, the internet which was supposed to have revolutionized information sharing has gravitated to the lowest common denominator: it's become the money making oriented wasteland that it is where commercial souless marketing sales drives the thinking rather than providing info that is meant to allow informed decision making.
What austin has done here is dispell the most common misconceptions of why one should buy a higher octane rated gas (whether it be based on the RON + MON averaging or the individual standards ratings). What he has done is undo a common internet misinfo you see floating on the beginner honda boards. That's all.
I don't think he set out to cause confusion.
If you have to follow the KISS principle and gravitate your communications on these boards to encompass beginners, then I think he has done a very effective job and has actually cleared up why one should not just blindly go and buy higher octane gas believing that it will automatically provide hp gains. Simple as that.
Now if you want to delve into the complexities and subtleties, I'm all for that. Actually I'd prefer it. But you would lose about 80% of your audience here, if you didn't start with undoing some of the bad info that has been passed around on the chatboards.
cheers
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austin
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Northern, CA Oct/07/02 2001 Type-R User ID: 9831
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Last Here
11/16/2009 |
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Quote: Originally posted by kelly on Jul/10/03
Burn rate and octane are not directly related. You added some 100 octane gas and lost power, however do you know that the ONLY variable that was changed was the octane? No. In this case you are probably right in that the BURN RATE changed, but that is not what octane is a measure of. You would have to have different fuels tested with ONLY the OCTANE being different to make any valid statements concerning this. You only showed some evidence to suggest that a different fuel blend makes different power.
I do know what octane actually it, but aside from using the technical jargon, I didn't want to lose the audience by using complex scientific language.
The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine.
Any motor fuel will spontaneously ignite under the right conditions - too much compression, hot spots from leftover carbon deposits, excessive boost, too much ignition advance, or a number of other causes can provide the source of ignition. When the flame front from this ignition event meets the one created by the spark plug, the result is sky-high cylinder pressures and a destructive shock wave that can shatter spark plug insulators, hammer rod bearings, break rings, or even put a hole in the piston. The octane number is a way to express the resistance of a fuel to this type of unwanted ignition.
Or to quote E.F. Obert, in "Internal Combustion Engines and Air Pollution" (1973, Harper & Row):
"During the compression stroke of a spark ignited engine, the pressure, temperature, and density of the mixture are increased and, depending on the fuel, chemical reactions ... may begin. The spark ignites the mixture, then the flame travels across the combustion chamber at a more or less orderly pace with the pressure rising uniformly throughout the chamber. Ahead of the flame front, the unburned mixture ... is compressed by the rising pressure, with an accompanying rise in temperature and density. ... If the ignition delay (chemical) of the end gas is consumed before the flame arrives, autoignition takes place. With autoignition, the orderly process becomes uncontrolled and a violent rise in pressure may occur. Energy may be liberated at such a rate such that the walls of the chamber ... vibrate, and knock is said to be present."
For all intents and purposes higher octane gives you a slower, more controlled burn, however if you would like me to I can get into RON, MON, iso-octane, and all of the other scientific jargon that will get over 90% of the people on this board lost.
Austin
p.s. the gasoline was purchased from the same station, so the brands were not changed, just the octane blend, and yes I used an octane blend conversion table that was availble from the station that I purchased the gasoling from, Unocal 76, so the octane level was computed correctly.
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