Reply With QuoteGood info...
If you run with the hondata reflash should you be running 91 octane?
Octane And You
After seeing some threads pop up about "My car runs better on premium gas" and the like I decided to post this up.
1. What is Octane Rating?
Octane rating is a gasoline's (or any fuel) resistance to detonation. It does not mean it makes more power, makes your car run cleaner/better, or cures cancer.
2. What should I run in the EP3?
Regular grade gasoline will run just fine as that's what it's tuned for.
3. When should I run higher octane gas?
Higher octane gas is to help prevent premature detonation, e.g. knock. When you are running the Hondata reflash/K-pro with a high octane map, forced induction (turbo, nitrous, blower, etc), or high compression to name a few mods, you will need 91+.
4. But my car gets better gas mileage and makes more power!
Since there are no valid reasons for stock/basic bolt-on (intake/header/exhaust/etc) EP3, it's all in your head. You can attribute the gas mileage increase to your driving habits, and you can attribute the additional power to your butt dyno needing a recalibration. The ONLY benefit of running high octane gas in an 87 octane tuned car will be from your new improved light weight wallet.
I hope this clears up some of the myths and confusion. Should also help to save you some cash as well. If you would like furthur information PM me, or check out the wonderful search feature of the interwebs.
Good info...
If you run with the hondata reflash should you be running 91 octane?
I'll have to agree to disagree with you on this. i've owned a fair number of cars/trucks as have my friends, and for the most part we have all had better starts and more power/mileage running 94 over 87. I'm the only one of us with an ep, lol, but i dont think that this is ep specific. I dunno if its different usa vs canada but up here 94 and 87 are quite different and their effects aren't just "butt dyno". Unfortunatly i cant prove it, but experience is always the best proof. Now that I'm turbo its a moot point as i have to have 93 or +Originally Posted by Stanz0r
Unless you specify for them to do a low octane reflash, yes you should run 91 octane.
A good discussion never hurt anyone
If your vehicle's computer retards ignition when it senses pinging/knocking you will lose power. Adding higher octane gas will help prevent the pinging/knocking and thus your car will not retard ignition. In that sense you will gain power, but only because your car is no longer knocking. It's possible that is what you were experiencing, however higher octane gas alone will not add power to your car. It produces no more energy than regular gas, the only difference is it's resistance to pre-detonation, e.g. knocking/pinging.
Going back to the retarding ignition scenario, it's possible that you could gain mileage as well. Again however, the higher octane gas isn't adding additional mileage if that is the case. If you're losing power due to knocking then you're going to compensate with the gas pedal and thus burn more fuel to make equivalent power. Take away the knocking with higher octane gas and suddenly you're not having to use as much fuel to make power and you will perceive an increase in gas mileage. Basically the higher octane gas isn't adding gas mileage, it's only giving you back what you should have been getting in the first place.
If the stock engine retards the ignition alot to deal with knock then the octane is insufficient.
The Kseries ECU advances the ignition till it hears knock and it retards the timing and then slowly advances it till knock is heard again, a higher octane fuel will allow more ignition advance before that knock occurs, thusly raising power. So a STOCK engine will most definetely see some improvements.
This is a common misconception left over from the NON-ELECTRONIC age and technologically deprived engine and engine management systems.
You cannot divorce the engine and engine management when talking about octane requirements.
Though the gains may not be much, there will be a measureable difference on a dyno.
ALL advice issued with this "Disclaimer"
Tim "the Toolman" Taylor is my HERO ! ! !
"Labor Unions are Domestic Terrorist orgainizations"
You're my hero Doug
There is some truth to this, with modern computer controlled motors. The computer does adjust some things with higher octane gas. I doubt seriously you can get the most out of 94 octane gas with a stock ep3. Maybe the 89 might be some small bit better with mileage, and hp. I doubt tho it be worth it as in a price per mile comparison...
What's the relationship between octane and compression? i.e. at what compression ratio is an increase in octane required?
yea, just remember that this (for me) is on a huge range of makes and years. from 1970-2004 but what the op and doug said both makes some sense. i'm not sayin it is gonna be a huge difference, but there is a difference......which could be explained proper by the op's reply and dougs post.
THANK YOU FOR THIS. ive always used 87 with minor boltons. im glad someone is sharing the full knowledge
Someone has a dyno chart/w 87 and 90 something it was a 5 hp difference. I forget who I read this from anyone know.
I'm going to throw this post up here too. I ganked it off another forum so heres the link too. The article is a little older, so don't pay much attention to specific prices it lists, but the general theory is still right. Doug has a point that modern engines can advance the ignition timing some, but I haven't seen any actual info regarding how much the stock ECU can advance the ignition timing to take advantage of higher octane fuel, and also there is only so far the ignition timing can be advanced. Its not like you can run 90 degrees of advance
Anyway, like I said. Just some added food for thought.
http://www.ford-trucks.com/forums/12...g-article.html
u b e r m e n s c h . o r g
Top > Cars > Technical Articles > Octane Ratings
Octane Ratings
by Matthew Kramer
Misconceptions
Do you have that friend with the Dodge Neon who claims he can beat 'Vettes down the straight when he fills up with 112 octane racing fuel? Or that buddy who works for the local airport that claims the AvGas he can get there makes his 15 year old Ranger pick-up into a virtual rocket ship? If so, maybe you should consult your friends to seek drug abuse treatment.
Despite what you may hear over and over to the contrary, a higher octane number does not mean a fuel will make more power. In fact, the two things have nothing to do with each other. Octane ratings are used as an anti-knock index, and mean little other than that.
Knock
"Anti-knock? Huh?" Well, anti-knock index refers to how well a fuel resists knocking. But what's knocking? Maybe you've heard of it referred to as detonation or pinging (and sometimes erroneously called pre-ignition). It's that dreadful "ping ping ping ping" noise your engine might make sometimes when it's struggling. Hopefully you've never heard this noise, but most of us have at some point.
What happens is this: In a 4-stroke internal combustion engine, air and fuel are sucked into the cylinders during the intake stroke. Then the valves are closed and this mixture is compressed as the piston rises in the compression stroke (appropriately named, no?). But in case you didn't already know, engines get hot. And on compression, the mixture in the cylinder gets even hotter. This might cause little bits of your fuel to ignite at the incorrect time (ie, some time other than when the spark plug fires). The uneven pressures from these little pockets of fuel igniting makes a pinging sound inside the cylinder. Hence the term "pinging" or "knock."
Knock is bad for more reasons that just the obnoxious noise it makes. The premature ignition of your fuel stresses components of the engine, leading to eventual failure. It increases temperature levels, which isn't good either. And for those people out there who care only for performance and couldn't give a damn about longevity (I envy you), it robs the engine of power.
Why Your Engine Knocks
So we know the underlying cause of knock, but what is the cause of the cause? Knowing that heat and high pressure inside the cylinder lead to knock, consider what can raise the temperature or pressure. Outside air temperature and barometic air pressure are givens. Making your engine work harder (hill-climbing or towing) have quite an affect. Other things are forced induction (turbo and supercharging), higher compression ratios, advanced ignition timing, and leaner fuel mixtures.
Looking at those "other things," notice that they all lead to performance increases. Ah, the bane of engine tuners. Turn up your turbocharger's boost, or shave a few mils off the cylinder head, and you get more power. That is, if you can keep the engine from knocking, which just got a hell of a lot more likely.
Fighting Knock
Obviously, if you're building a high-performance engine, much of what you do to the engine will increase its tendency to knock. Pretty counter-productive. So a way to prevent knock is greatly needed. If knock is caused ultimately by the fuel igniting too easily, a way to prevent it would seem to be by changing the nature of the fuel itself.
It was found that by mixing certain substances in with the gasoline, it became more resistant to knock. For the longest time, the common compound used was lead alkyl. This is where the term "leaded fuel" comes from. As you probably know, though, in the U.S. leaded fuel has been banned from the pumps by the EPA. European countries have begun banning its use now as well. Today's most common compounds are toulene, methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME). However, as seems to happen quite often these days, MTBE has been identified as a cancer-causing substance, and gasoline manfuacturers are under pressure to eliminate it from their fuels.
RON and MON
So that's great... We know that our engines are prone to knocking, and that by mixing in some substances with the fuel, the tendency to knock is reduced. But the older our engines get, or the more performance modifications we do to them, the higher that tendency becomes. How do we know that stuff we put in our tanks will resist knock in our particular engine. This is where the anti-knock index I mentioned earlier comes in.
The anti-knock index is how resistant a fuel is to knocking. This is also referred to as the octane rating. A higher octane fuel is less likely to knock than a lower one. Unfortunately, so many little things go into knock tendency, that there is no concrete way to determine knock resistance. The two most common measurement methods are the Reasearch Method and the Motor Octane Method.
It was found that a compound referred to as iso-octane had a high resistance to knocking, and that heptane was extremely prone to knocking. Studies were then performed to rate automotive fuels knock tendency against these compounds.
Subsequent tests of fuels in those days found that more reliable results were found with a slightly modified version of the Research Method's engine. The Motor Octane Method specified the same type of measurements using a faster engine and hotter mixtures. The results of these tests are specified as Motor Octane Number, or MON.
As fuels changed over time, it was found that neither RON nor MON accurately determined knock tendency over the full range of conditions. In the U.S., we adopted the use of their average as an anti-knock index. This is why when you read the labels on a fuel pump, you'll see soemthing like, "89 Octane (calculated using (R+M)/2)."
Your Car - From the Manufacturer
An automobile manufacturer designs a car's engine with certain parameters. They have to decide what the compression ratio will be, how high it will rev, whether or not it will have a turbo or supercharger, how they can keep it cool, and all sorts of goodies. There are trade-offs in every decision they make; considerations for longevity, cost-effectiveness, gas mileage, available fuels, environmental friendliness, etc.. In the end they give you an engine that will make X amount of power, and that you better always use Y octane fuel or higher.
Your Car - Using Lower Octane
As a fuel's octane number goes up, so does its cost. Why not just use the lowest octane number available to save money? By now, you should realize that by using an octane rating lower than what the factory determines is safe, you're risking damange and performance loss. Granted, they do specify these requirements with a bit of a buffer, as from refinery to refinery or even batch to batch, fuels may vary some. But while it is designed to run on a bad batch of 89 octane gas (that might as well be 87 octane), if you fill up with 87 octane, you might be getting a bad batch of it, and problems will ensue. You should always use the proper octane rating in your car, unless it's just plain not available where you're at (like Mexico).
Your Car - Using Higher Octane
I started this whole thing with the typical non-sense you hear from others who think higher octane fuel will turn their car into a land rocket. But face it, they're morons. In fact, using a higher-rated fuel than what your car requires will net you nothing in the power department. Your engine is made with certain parameters. Its compression ratio is fixed and its timing is set at its max setting (often it can be retarded by the engine control computer, but not advanced). As long as its not knocking, it's making as much power as it was designed to make. Increasing the octane of your fuel does not increase your compression ratio or advance your timing. Actually, if anything, the compounds mixed into the fuel to increase its octane rating will lower the stored energy of the fuel, decreasing power. However, this affect is negligible.
Your Car - Increasing Power
They make race fuel high-octane for a reason, though. It's not because the higher octane rating makes the engines more powerful. It's because the more powerful engines are more prone to knocking than a road car's engine, and a fuel with a higher anti-knock index must be used to prevent power loss and engine destruction.
So yes, your car can actually benefit from high octane fuel. But not when it's exactly as designed by the manufacturer. Only when you start making performance mods will the engine start getting hotter. Modifications like turbochargers (or increased boost if you've already got a turbo), shaved heads, advanced timing, or high-compression pistons are the real devils. When you make these, the tendency to knock will begin to increase. Then you too will need to follow the path of high-performance cars, and use a higher octane. But don't go straight for the 103 at your local 76 station, or the 112 at the race track. Increase by little bits. If you find your engine originally required 87 octane, see how it behaves on 89. If it still knocks at times, go up to 92.
Don't waste your money on $3.50/gal fuel that's not going to do a damn thing for you. Let your moronic friends do that. It depletes their budget for nice performance mods while you save the bucks.
Mike, this is false for the Kseries. The ignition advance is nowheres near MAX with 87 octane for the most part. It has been proven with the Kseries, on many dynos, that a higher octane will indeed allow for more ignition advance and the resulting whp gain.
And the cost per gallon difference is almost a wash between 87 and 91/93 as far as the mileage difference is concerened. Years ago the cost per gallon difference made the 87 octane a better deal. But with the base price raised so much and the cost difference between the grades staying the same, it is now a wash(pricewise).
ALL advice issued with this "Disclaimer"
Tim "the Toolman" Taylor is my HERO ! ! !
"Labor Unions are Domestic Terrorist orgainizations"
I understand, not everything on it is perfect, but it can help understand the reason why higher octane can make more power, and the limitations to it.
in my ep3 if i use regular the gas just goes quick as hell but when i use 91 octane it last a lot longer! when traveling 578 miles to colorado i only fill up twice on 90+ octane one way but if im using 86-89 octane i i filled up about 4 times one way! when i first bought my car i ran 86.....now i run 91+ my car goes from about 350ish miles on full to empty(the light) also shifting at low rpms! just my 2 cents about my experience...
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