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SilverDragon
yes, it's a dragon



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   Posted 4/5/2005 10:39 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
just did a post for one of the other boards i am on ... similar to the drilled pipe post ...

thought it might fit in here - if you want to make it sticky too (or not)


Post Edited (SilverDragon) : 4/5/2005 5:48:18 PM GMT

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SilverDragon
yes, it's a dragon



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   Posted 4/5/2005 10:40 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
GASOLINE OCTANE .... and Retarded ants ...

retardants that is ...

octanes are burn retardants

they slow it down and make it easier to manage (less bang for the buck - not more) .....

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http://www.surfmaine.com/rebelforum/viewtopic.php?t=2107

MillenniumRebel said...
70-75mph is in the normal area of WOT

it can get up past 80mph if conditions are right

some of the variables that affect how much throttle is left at 70mph are ...

headwind -vs- tail wind
70mph WOT against a headwind -vs- 70mpf with throttle left from a tail wind

air temperatures and relative humidy factors
cooler crisper air hold more oxygen than hot muggy air - affects carb mix

other vehicles
drafting does affect speed - wind tunnel effect helps (see wind above)

gas grade / brand
there is a differance between 87 and 93 octane (87 bangs harder/faster than 92)

as well as being slight differnces between various brands of gas

inclines
hills don't have to be obvious - what may 'look' flat to you can actually be a slight incline either up or down - and that affects the bike just like head or tail winds do

accordian thief said...

?? Am I reading right - a lower octane grade will produce more power? Howsawhatsa?

MillenniumRebel said...
octane = burn retardant
it slows the bang down for a more even cooler burn
thats how higher octane 'cures' pinging - by burning cooler and calmer

higher octane = tames the bang

lower octane = more raw BOOM BOOM - more violent explosion - more power - hotter

hercman said...
MR is absolutely corrrect. And get this the Top fuel drag cars use good ole' 87 octane to get the engines fired up. Race gas is high octane 100+ because they are running compression ratios of 12:1, 13:1 etc.

Chopdoc said...
Exactly. Aviation fuel is high octane too, but that is not th source of its greater energy. The higher octane is needed because they run high compression.

There was another screw-up on Mythbusters and it regarded this. It concerned the idea of mothballs in your fuel increasing the octane and hence the power of the motor. They are supposed to be busting myths yet the essential myth that increased octane will give you more power went right by them.


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http://www.surfmaine.com/rebelforum/viewtopic.php?t=218

RebelVixen said...
My Rebel tends to ping a bit with 87 octane. I use the mid-range stuff (ethanol here in Iowa) and I don't get the pinging. And here in Iowa, the ethanol is actually a couple cents cheaper than the 87 octane!

Jess

Chopdoc said...
Ping is ringing of the pistons like bells caused by preignition. Also heard as knocking or rattling. Also can present as run-on (continuing to fire with ignition off). It results from octane being too low and or hot spots in the firing chamber. This preignition occurs before the proper time and the piston is basically hit like with a hammer and it rings. It will damage your engine and is the only reason to run higher octane. People often associate higher octane with more power but this is a misnomer. The greater power (combustion energy) in some premium fuels and in things like AV gas is really due to other qualities of the fuel. If you hear ringing, rattling, or knocking, use higher octane.

Duke said...
Advanced timing creates the same condition; that is, it encourages the plugs to fire before the piston is in the proper postition. The fuel explosion hits the rising piston too soon and, to borrow Chopdocs expression, rings it like a hammer.

Chopdoc said...
Yes in fact there are many dynamics of tuning and/or engine condition that can cause it. The basic idea is that anything that causes the ignition of fuel too soon in the stroke can cause it and it is not good.

Advancing the ignition that far would probably be incompatable with an idle, but I guess you could do it. I sure would not want to try to kick start a bike that far advanced, it could kick back hard enough to break bones or blow knee joints. I in fact have hyperextended both knees on mechanical advance kickstart bikes as the result of a kickback. EXTREMELY painful, rolling on the ground screaming like a little girl. It can happen. Temporarily stuck advance maybe? All I know is you don't want it to happen.

Anyway, preignition will chip away at pistons and even break them so if you hear it get that octane up and/or check your tuning.


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http://www.surfmaine.com/rebelforum/viewtopic.php?t=3498

hercman said...
If an engine is designed to run on 87 octane and you are experiencing knock there are a few things that could be causing it. Over heating, carbon build up (increases compression ratio) or timing is off. Will 91,92,93 harm your motor no. But if you don't have knock with 87 don't waste your money on a higher octane. The higher the octane the hotter the fuel has to be before it burns. With that said race fuel will burn up your pistons.

Duke said...
For what it's worth,

a lot of big-bore deep-stroke air-cooled V-twins can suffer from overheating simply by running a low-octane fuel.

Most bikes, no big deal, but the big-bore long strokes tend to have both higher compression and less material to carry away the heat from the chamber.

Factor in the fact that on a V twin, only one cylinder really gets any appreciable air, and well----

we've junked a lot of S&S, RevTech, and even factory HD Big Twins because of heat damage to the rear cylinder. In over half the cases, the problem was initially caused by hot dogging the bike (a lot) with low-octane fuel.


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http://www.f6rider.com/Valk2/every_thing_you_ever_wanted_to_k.htm

website said...
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 settings, and a higher octane should have no effect on the management system of an engine. Your drive ability and fuel economy will remain the same. The higher octane fuel costs more, so you are just throwing your money away. If you are already using a fuel with an octane rating below the optimum, then using a higher octane fuel will cause the engine management system to move to the optimum settings, possibly resulting in both increased power and improved fuel economy." (this will only occur in engines managed, fuel and ignition, by computer taking into consideration air density, air temp, engine temp, exhaust gas temp, etc. None of this takes place in a typical Goldwing or Valkyrie engine.) "You may be able to change octane between seasons (REDUCE OCTANE IN WINTER) to obtain the most cost effective gasoline without loss of drive ability. Once you have identified the fuel that keeps the engine at the optimum settings, there is no advantage to moving to an even higher octane fuel. The manufacturers recommendation is conservative, so you may be able to carefully reduce the fuel octane." DO NOT REDUCE IT BELOW THE KNOCK THRESHOLD, OR SERIOUS ENGINE DAMAGE COULD RESULT !

This information tells me that there is no energy difference in different grades of gasoline, therefore no more power. The use of a gasoline with a higher octane than needed to prevent knock in my engine is a waste of money. If your engine knocks because of the conditions you encounter, use a higher octane fuel until it is no longer necessary. Use of higher octane gasoline in cold temperatures is counterproductive. Stick with the manufacturers recommendation for fuel requirements, unless knocking occurs. The engine in a Goldwing or Valkyrie is designed and managed with a specific octane requirement.

I hope this sheds some light on the gasoline threads, and save some people some money in the process. Remember, Oil companies who are in business to SELL PRODUCT say it is a waste of money to buy premium when regular will do.


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http://www.surfmaine.com/rebelforum/viewtopic.php?t=1754

Larry71 said...
My 2004 gets has gotten a steady 75 mpg in the past 5 weeks or so since I bought it new. It now has 1900+ miles on it and I've run everything from the cheap 86 octane to the Sunoco Ultra 94 and milage hasn't varied. The last few tanks I have been buying the cheapest grade it's either 86 or 87 octane.


Dj said...
2004 Rebel 250 @ 505.7 miles I've recorded a consistent 75mpg for each tank I've put in thus far.

In Dallas, at a "Name Brand" station, 87 = $1.98, 89 = $2.03, 92 = $2.08. Considering I've never had to put more than 2.25 gallons in the tank, I'm not going to bicker over a quarter difference in price using 87 octane and 92 octane. Sure that's an extra dollar for every 600 miles. ;)

I'd rather run higher octane and reduce my risk of pinging (especially with Texas July/August heat coming up) than run the cheaper stuff and possibly cause some damage.

I notice absolutely no performance difference between the two, but the subtle differences when all that gas and air get pounded into the head is enough to make me spend the extra.

On the flip-side, since people have been talking about their 4-wheeled counterparts, I spend about $70-100 filling my 1982 F-250 Pickup, and that's only good for 280-300 miles at 8mpg.

I love my Rebel, what can I say!


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SilverDragon
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   Posted 4/5/2005 10:43 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
hmmm.....

was too long ....

board software trunicated the thread and only allows a limited number of quotes per post

see part 2 below ...


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SilverDragon
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   Posted 4/5/2005 10:44 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
=====

Uneasy Rider said...
roll Buying ANY gas other then 87 octane for your Rebel is a waste of your money.

roachsix said...
I figure that for the amount of fuel a Rebel burns, I could put anything in the tank, **** the money. Same idea goes for stuff I drink.

Uneasy Rider said...
Your money your Rebel, have at it.
Higher octane fuels burn cooler and will cause carbon build up.
Like I said your money your Rebel.

Chopdoc said...
Uneasy Rider said...
Your money your Rebel, have at it.
Higher octane fuels burn cooler and will cause carbon build up.
Like I said your money your Rebel.


There is a great deal of truth in his statement. Premium fuels really should only be used if you need them to prevent pinging. The Rebel does not need them. Don't believe the TV commercials about gasolines.

Generally the best advice is to run clean fuel that does not ping, change your oil and filters, and if you want to run exotic fuels build a motor to run them.

Dj said...
First of all, the Ninja isn't a Honda, so no, it doesn't have the same engine.

Secondly, the Ninja is a water cooled plant, not air cooled like a rebel.

Lastly, the Ninja is a modern performance engine design, and the Rebel is more akin the 60's and 70's lineage of honda engines.

Furthermore, the ninja weighs different, is balanced different, has different sized tires, different clutch, different gear ratios, and different final drive ratios.

Regardless of what octane fuel you put into a Rebel, and regardless of how light you make it, trying to rev it past the redline and hold it there will _always_ have catastrophic results.

The rebel is not built to go 100. Its top rated speed is about 83 mph, judging by the shift point map on the speedo. I've had mine to 95, and was damn lucky I didn't swallow a valve.

I run 92 octane in the summer, even though this is a relatively cool summer. Before the end of August we will be seeing temps in the high 100's to 115 or so... As the engine is air cooled, and traffic stops are regular, the higher octane with the same flow rate acts to cool the engine.

As Uneasy said, it will cause some carbon deposits to form.

My Rebel, My Dollars. :) YMMV, etc!

cheers,
dj

hercman said...
As for higher octane running cooler causing carbon build up how can that be. 93 octane has a much higher flash point then does 87. That's how it prevents engine knock. As for running premium fuel in any thing designed for 87 is just a waste of money. 87 octane and 93 octane have the same additives and won't harm your motor. Premium fuel is for High performance engines only. We are constantly having to tell people in my car club that if the car says use X fuel use X fuel.

Dj said...
By the way, bikerboy... I still maintain that your "meltdown" was not a cause of octane, but rather a cause of speed. As I stated earlier in the thread, if you put any octane fuel into the thing, and even if you don't lighten it, if you run it for long enough in excess of redline, ANY engine will blow.

94mph = 1.566 times as fast as 60 mph.

802 Wheel RPM @ 60mph * 1.566 = 1256 Wheel RPM @ 94 mph.

1256 Wheel RPM * 2.357 Final drive = 2960 output shaft RPM * 0.913 5th Gear Overdrive * 3.632 Primary Reduction = 9816 Crankshaft RPM

If the Rebel redlines at 8500, it's no wonder your engine "melted".

Chopdoc said...
Although it could be discussed all day, it may or may not be pure RPM that killed the engine. Using a higher energy fuel (note I did not say higher octane) could have resulted in overheating and failure of a piston and caused catastrophic failure. Higher energy fuels can do amazing things. The extreme example would be nitromethane. But I agree, it was not by virtue of the octane alone.


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http://www.surfmaine.com/rebelforum/viewtopic.php?t=1308

taborjoshjlt said...
does any one know where to get a good used engine for a resonable price? i was trying different types of fuel on my rebel trying to see what the top speed would be. i was trying a high octane fuel with high octane boosters.(very dumb idea) i was doing ok but then i noticed my bike shakeing very badly on the road next thing i know my engine started knocking and just quit.
so now i need to find a used 250 engine. oh and another question has any one put a larger engine in a stock rebel 250 frame. i'd like to know how many cc's and what modifications were used to mount it.
thanks
tabor


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http://www.surfmaine.com/rebelforum/viewtopic.php?t=2454

superdesi said...
Ok. I tried to research this on my own, but got even more confused.
My owner's manual for my 2004 Rebel says to use "pump octane number of 86 or higher".

However, today I was removing the air box (to check the air filter) and saw a decal there that states to use "91 RON octane minimum" gasoline. I don't know if this decal is on other model years.

jeff schenkel said...
desi --

don't know what the RON refers to -- somebody will clear that up -- but there was a very long and very controversial thread not too long ago on grades of gasoline -- kinda like the argument between ford and chevy -- basically ranging from just use regular since that's all it calls for and you get more power to use premium since it burns cleaner and leaves fewer deposits in your engine but burns cooler to do that and gives a little less power.

your choice -- i use premium because i've seen car engines with deposits built up from regular.

Larry71 said...
From my brief search I came up with the 86 is what we in the USA will find on our gas pumps and the 91 is the same rating just using a different way of figuring it and giving a bigger number. I suppose you would find the latter rating on European gas pumps.

Just use the cheap stuff and change your spark plugs every 3 or 4 oil changes.

hercman said...
If the bike isn't pingin or knockin under acceleration what ever grade your using is fine. As for build up I wouldn't worry about it.


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SilverDragon
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   Posted 4/5/2005 10:46 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
sigh ....

still hit that trunication quote limit again ...

see part 3 below ...


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SilverDragon
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   Posted 4/5/2005 10:47 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
=====

http://www.surfmaine.com/rebelforum/viewtopic.php?t=1045

UTAH REBEL said...
Well I would have to say 91 is the best gas for a 250 rebel,
91 burns cleaner it also burns colderr and slower than 85 that is why it makes more power 85 just is a bang and its burned, 91 or higher is more of a baaaaang if you will, it just burns slower. and cooler, even though on alot of VW air cooled racing motors the difference in temp. between the 85 and 91 is 1-3 degrees. not much but it makes all the difference in air cooled motors, the reason it burns cleaner is just becuase it burns slower and has more complete combustion, where as 85 leaves traces of unburned fuel, it is ok to use 85 or 88 89 etc. in a small motor like the 233cc. on the rebel but for $.20 cents more a gallon and improved gas mileage when your bike at least mine gets 65-72 miles a gallon WHY NOT?
But a tip if you will if you like to use 91 get it one the rich/good side of town, becuase it will be fresh, poor/bad sides of town tend not to spend money on more expensive gas, so the 91 is usually stale, and I would rather have fresh 85 than stale 91 any day.
There is such a thing as to much octane but for the rebel 91 or 93 is fine, if you want to use race gas that is fine to WITH the right valve adjustments,
Now if you want to use diesel fuel instead of gas thats what we need big loud diesel bikes? I wonder if they have ever made one????

Hope this helps.
God Bless

Utah Rebel


Duke said...
And that--- the "baaaaaaang" (and the colder burn) is why it actually makes _less_ power int he Rebel than does the lower grade. The baaaaaaaaang only gives you more power if you have a long-stroke motor capable of taking advantage of it. With an extremely short stroke, your explosion is still expanding outward while your piston is trying to push up against it.

And the Rebel is already famously cold-blooded. And like most air-cooled engines, colder engine temps simply result in increased fuel consumption and a less-consistent explosion-- in short, shorter spark plug life.

But yes, if your engine was designed specifically for higher-octane, then it will be able to take advantage of it. V-twins in general do extremely well on high-test.

But the general findings are that you should run whatever you want; you aren't really damaging a street-machine by bumping the octane up. Just don't bump it down if it calls for higher-grade, as there may be cooling or pre-ignition or valve rattle problems.


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http://www.surfmaine.com/rebelforum/viewtopic.php?t=1279

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so ....

this is an extremely common MYTH ... due in part to what every red-blooded american *should* know -vs- what they *think* they know...

Hot Rods

there is a reason souping up an engine is called hot-rodding it

usually involves ...

an advance in the timing

higher compression mods (heads, cams, pistons, rods, etc...)
gee?? is that why it's called hot rodding ?

all of the mods that push the engine higher requires those engines to use higher octane to manage the higher compression and/or advanced timed explosion and (hopefully) prevent the engines from blowing up

these mods are also responsible for the faster speeds and more HP

the myth is due to a mis-understanding of cause and effect

because souped up cars require higher octane gas ...
many think it's the higher octane gas that increases the speed and HP

this is NOT the case ...

it's the faster wilder engine mods that require a tamer/slower (higher octane) gas to keep from blowing themselves apart

it's the higher performance tweaked engine mods that causes them to require higher octane gas

it's NOT the higher octane gas that causes higher performance engines


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ECeptor
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   Posted 4/5/2005 4:49 PM (GMT -7)    Quote This PostAlert An Admin About This Post.

Good info SD and a very spot-on conclusion. 

Here's a link for some further reading on the subject.  The article is about v-8's but the theories applie to any engine:  http://www.popularhotroddingweb.com/tech/0311_phr_power_squeeze/




ECeptor

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GeoffG
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   Posted 4/5/2005 10:06 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Although the advice given in SD's posts is valid, the reasoning is wrong. "Octanes" are not "burn retardants"--octane is simply the chemical name of a hydrocarbon with eight carbon atoms, just like methane has one C, ethane two, and propane three. Gasoline is mostly made up of octane, but it is "contaminated" with other hydrocarbons such as heptane (seven C's). The octane number of a gasoline refers to the percentage of octane in it--87 octane has 87%, 93 octane has 93% (or at least additives that make it ignite as if it were 93%).

Heptane ignites more easily than octane, therefore in an engine with very high compression it can be ignited by the heat of compression, or in an engine with carbon deposits it can be ignited by the heat of those deposits, prior to the sparkplug firing--this is pre-ignition, and in mild cases we hear it as a rattling sound and refer to it as "pinging." More highly refined fuel has had more of the heptane removed--it therefore has a higher percentage of octane, and a higher octane rating (and it costs more, since it requires more refining to produce).

I don't believe heptane burns any hotter than octane, it simply ignites more easily--in fact longer chain molecules (such as octane) usually release more heat of reaction (ie burn hotter).

Now, the additive packages in various gasoline blends are something else again...anyone for acetone? Hmmm...better living through chemistry, eh?
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Mac_Muz
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   Posted 4/6/2005 8:41 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
I made it 1/4 way in the forst posting and agree with that.. I intend to read the rest as I can.. it is likely this will be sticky.

I haven't read it all right!! So if there is a bit on pre and post ignition good... if not what we often call pre is really post.. and if you will SD, lok into that include it here as well please.. As you have time to do so..

Since Cadd is a co mod here I would like to allow him time to see this as well before it is sticktified LOL Mac


I'm out of my mind, but feel free to leave a message.

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CaddmannQ
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   Posted 4/6/2005 9:38 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
GeoffG said..."Octanes" are not "burn retardants"--octane is simply the chemical name of a hydrocarbon with eight carbon atoms, ...The octane number of a gasoline refers to the percentage of octane in it--87 octane has 87%, 93 octane has 93% (or at least additives that make it ignite as if it were 93%)...
This is a good point, since a lot of additives that affect the octane rating are not octane, and burn differently, release different amounts of energy, have different exhaust products, etc. 


Cadd
2004 Nomad 1500
VROC #11619  Rolling Blunder #128

 

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SilverDragon
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   Posted 8/2/2005 8:15 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
1Hawk said...
Do You Really Need Premium?
And Answers to Other Gasoline Questions
By Edmunds.com Editors
Date Posted 07-05-2005

Buying premium gas is like taking vitamins — you can't always feel the difference and yet you know it's the right thing to do. But as gas prices climb, paying the extra dime per gallon for premium is like adding insult to injury. Eventually, the thought is bound to jump into your head: do I really need to pop for premium?

Until about 15 years ago, if a car called for premium gas and you pumped in regular, the car began to knock and ping and even vibrate. But that was before they essentially put a laptop under the hood of the automobile, said Dr. Loren Beard, senior manager of Environmental and Energy Planning, for Daimler Chrysler. Now, sensors take readings and tune the engine as you drive by adjusting the timing for whatever fuel you put in the tank.

The result is that a car that calls for the midgrade gasoline will usually run on regular without knocking, Beard said. However, its performance will suffer slightly. How much? It will be perhaps a half-second slower going from zero to 60 mph.

Volvo cars call for "premium fuel [91 octane or better] for optimum performance and fuel economy," said Wayne Baldwin, product/segment manager S60/S80. "However, there is absolutely nothing wrong with using 87 octane as the knock sensors and engine management system 'protect' the engine from knocking."

Baldwin, a former rally driver who competed in SCCA Pro Rally events said that engines have changed a lot in the past 15 years. "Cars built before 1990 probably do not have knock sensors and many brands back then relied on high-compression ratios for the best performance. Today [performance comes from] electronically controlled spark curves, turbos, variable valve timing, supercharging and knock sensors."

Issues of performance aside, Baldwin said you should never use gasoline that causes your car to knock. "Constant knocking or detonation is a real bad thing for engines," he said.

When choosing what grade of gasoline to use, Steve Mazor, principle auto engineer for Auto Club of Southern California, said it is important to read the owner's manual carefully. The key is to figure out whether premium gasoline is "required" or "recommended." If it is recommended then a driver could opt to use a lower grade of gas, if they were willing to accept slightly reduced performance and fuel economy.

However, Mazor added, "We don't recommend that people switch down. Let's say you switch down to regular, and you have to accelerate to avoid an accident and it doesn't accelerate fast enough. The Auto Club can't be responsible for causing that situation."

Edmunds.com has a Volvo S40 in its fleet, so we consulted the owner's manual to see the exact phrasing in regard to fuel requirements. It said, "Volvo engines are designed for optimum performance on unleaded premium gasoline with an AKI (Anti Knock Index) of 91 or above. The minimum octane requirement is AKI 87." It appears that Volvo is making a recommendation for premium gas but is not requiring it.

In Edmunds.com's Forums debates abound over the pros and cons of using different fuel grades. One member even suggested there was only one type of gasoline, no difference — except for price — between regular and premium. Other members recommended using premium gas even if the manual called for regular. We put this question to Mazor and Beard.

Mazor: "All this does is do a very good job of draining your wallet. People used to put in a tank of premium to get 'the good stuff' to help their engines stay clean. But now they put detergents in all grades so it doesn't really get you anything."

Beard: "If you have car designed to run on 87 [octane], it doesn't help to run it on higher-octane-level gas. But there are several exceptions." He said that the 3.5-liter Chrysler engines are designed to run on midgrade gas (89 octane) and it allows them to advertise a certain peak horsepower. However, it will run well on regular gas. "The difference is very small," he said.

Interestingly, Mazor noted that at some gas stations, there are only two grades of gas. However, they blend the regular and premium at the pump to produce the midgrade gasoline. This allows them to have only two underground tanks for the gas storage.

In Edmunds' forums some drivers expressed concern about the quality of gas sold at independent gas stations and advised sticking to the so-called "name" brands of gasoline.

"Typically the only difference is the additive package they put in the gas," Beard said. The additive package is often put into the gas as the tanker is filled up at the refinery. A common additive is a detergent agent. "The law requires a certain level of detergents in gasoline. Shell for example is putting in more detergent — whether that has a measurable effect to the driver is debatable."

Detergents have a marked effect on engine deposits. "If you take apart a modern engine that has been running on a modern fuel, and compare this to an old engine that was running on old gas, you can see an obvious difference," Mazor said.

The biggest difference between today's gas and the gas sold 15 years ago is the removal of lead. Taking out the lead, and developing effective catalytic converters to more completely burn emissions, have radically cut pollution.

While oil companies like to advertise the magical powers of their gasoline, it appears that there is very little difference between brands. Most drivers fill up at the nearest gas station or the one for which they carry a credit card.

Does a gas expert like Beard have a preference when buying gas? "I just watch the light on the dash. After it has been on for a day I get nervous and go to the closest station available."


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SilverDragon
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   Posted 8/2/2005 8:16 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
guitardad said...
While it's true that the computer controls on a modern car engine can adjust the timing to operate safely with any octane gas, is the same true of modern motorcycle engines? I'm not even certain that many motorcycle engines have a knock sensor. My owner's manual recommends mid-grade (89 octane) gas, so that's what I use.


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1Hawk
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   Posted 8/2/2005 11:10 AM (GMT -7)    Quote This PostAlert An Admin About This Post.

The most important characteristic of gasoline is its octane rating, which is a measure of how resistant gasoline is to premature detonation (knocking). It is measured relative to a mixture of 2,2,4-trimethylpentane (an isomer of octane) and n-heptane. So an 87-octane gasoline has the same knock resistance as a mixture of 87% isooctane and 13% n-heptane. The octane rating system was developed by the chemist Russell Marker. 

 In each barrel of crude there are 42 gallons.  In the early 1900's we were getting roughly 13 gallons of gas from each barrel.  Today, we are getting roughly 25 gallons of gasoline from each barrel. 

Gasoline contains about 45 megajoules per kilogram (MJ/kg)
Volumetric energy density of some fuels compared to Gasoline:

fuel type     MJ/L     BTU/imp gal     BTU/US gal     RON
gasoline 29.01 125,000 104,000 87-98
LPG 22.16 95,475 79,500 110
diesel fuel oil 32.19 138,690 115,480 5-20
residential heating oil 34.74 149,690 124,640  
ethanol 19.59 84,400 70,300 129
methanol 14.57 62,800 52,300 150
gasohol (10% ethanol + 90% gasoline) 28.06 120,900 100,700  

A high octane fuel such as LPG has a lower energy content than lower octane gasoline, resulting in an overall lower power output. However, with an engine tuned to the use of LPG this lower power output can be overcome. This is because higher-octane fuels allow for more compression - this means less space in a cylinder on its combustion stroke, hence a higher cylinder temperature, less wasted hydrocarbons (therefore less pollution and more used energy), and therefore higher power levels coupled with less pollution overall.

Note that the main reason for the lower energy content of LPG is that is has a lower density. Energy content per kilogram is higher than for gasoline (higher hydrogen to carbon ratio). In lay terms, we burn mass, not volume!

Oxygenate blending adds oxygen to the fuel in oxygen-bearing compounds such as MTBE, ethanol and ETBE, and so reduces the amount of carbon monoxide and unburned fuel in the exhaust gas, thus reducing smog. In many areas throughout the US oxygenate blending is mandatory. For example, in Southern California, fuel must contain 2% oxygen by weight. The resulting fuel is often known as reformulated gasoline (RFG) or oxygenated gasoline.

MTBE use is being phased out due to issues with contamination of ground water. In some places it is already banned. Ethanol and to a lesser extent the ethanol derived ETBE are a common replacements. Especially ethanol derived from biomatter such as corn, sugar cane or grain is frequent, this will often be referred to as bio-ethanol. An ethanol-gasoline mix is called gasohol. The most extensive use of ethanol takes place in Brazil, where the ethanol is derived from sugarcane. The use of bioethanol, either directly or indirectly by conversion of such ethanol to bio-ETBE, is encouraged by the European Union Biofuels Directive.

 

Hawk



 

Post Edited (1Hawk) : 8/2/2005 6:29:50 PM GMT

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Fishman57
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   Posted 8/18/2005 6:44 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Hi
 Picked up my 05 Kawasaki Nomad 1600 yesterday . . It had 1 mile on it. It had a tank of *regular* gas in it supplied by the dealer in spite of the serious damage warning sticker stuck next to the filler cap if you don`t use 90+ octane. I was given a gas chemistry lesson from the service manager concluding with "regular gas was fine and used all the time by them." Today I called and asked for a written reccomendation for regular gas. They declined telling me to use higher octane and waste my money if I was concerned.  Should  I be concerned using this gas for my initial break-in miles? I put on 70 miles so far . Oil change tommorow. Can the FI system compensate ? It seems to run OK. Thanks for any comments.   
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cooler
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   Posted 10/30/2005 5:03 AM (GMT -7)    Quote This PostAlert An Admin About This Post.

If petrol were an explosive, then knocking would class as sympathetic detonation, as the fuel burns it pushes a pressure wave across the cylinder space, as the pressure wave compresses the remaining unburned mixture so rapidly an unwanted detonation can take place, the resulting shock wave of one pressure wave hitting another can seriously damage the piston head and in some cases bust a hole right through the piston head.

Increasing the compression in the cylinder can increase the chances of this happening and in very high compression engines a fuel with a higher Octane rating is required, the octane rating is obtained simply by increasing the pressure in a test cylinder to find out the limits of a certain octane to self detonate.

We used to 'dope' the fuel with lead tetroxide to increase its octane rating, this had the usefull side effect of coating the valve seats with metallic lead and increasing the valve/seat lifespan, today we increase the octane value by carefull mixing of the higher octane hydrocarbons with the lower and have had to fit hardened (stellite) valve seats to reduce the wear.

Pre-ignition is a different phenominum caused by a hot spot in the cylinder head and/or piston head.

Piston slap often mistaken for pinking is where the piston literally slaps against one side of the cylinder and is a sign of high cylinder wear.

Hope that clears up any questions.

Cooler.


Post Edited (cooler) : 10/30/2005 12:07:38 PM GMT

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Greywolf
Fuzzy Logic Inc.



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   Posted 11/7/2005 5:00 PM (GMT -7)    Quote This PostAlert An Admin About This Post.

I put my response here:

http://forum.motorcycle-usa.com/default.aspx?f=18&m=223233

 

It needs to be addressed in a rational and objective way.


This is no Kawasaki... It's a KAWALSKI!

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SilverDragon
yes, it's a dragon



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   Posted 11/7/2005 5:52 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
and i'm quoting that here ...
Greywolf said...
1) Octane is a measure of a fuel (petroleum based, gasoline specifically. For diesel the "CETANE" number is the big deal) to resist ignition due to temperature and compression.

2) The reason for this is that in higher compression engines pre-ignition (Ignition due to compression, heat, and also crap in the upper chamber that keeps glowing) is a real big deal.

If your hot stuff fires when it ain't supposed to, it can be way ahead of the timing marks - causing your engine to fight itself to run. A cylinder that fires too far ahead of time is still trying to compress mixture when the bomb goes off in it. If it was a one lunger, and it fired too far ahead - it would drive the crank BACKWARDS.

Prolly only once tho...

You want to see what low octane does? Go to Tiajuana Mexico (La FRONTERIA!!!) and fill up on low-test PEMEX.

'Be lucky if you get home...

I have had arguements about what OCTANE means before, and if it gets looking that way I'll hike my classroom and god knows how many road miles and shop experience right out of your way to believe what you want to.

High compression engines need higher octane factors. Octane has absolutely, totally ZERO to do with explosivety - it is the exact opposite. Greater gains are made by compressing the air/fuel mix to a higher degree before burning it than using something that blows up at the least notice. Nitromethanol is actually safer to have around than gas(AKA: Petrol).

In prior years, vehicles had compression ratios (rolling out of the factory...) as high as 12:1. Back then you could get 95 octane just about anywhere. You'd be lucky to find it at an airport now (reliably). 101 was cheap, and all the old Shell commercials that Bob Hope did were back in those days.

9:1 or even 8:1 is more like what is out there now, because the gas is crap.

Used to be able to get a "SPACER PLATE" to install in some cars to reduce the compression for travelling in Baja and other parts of south america. I think the low octane of the south is becoming the standard in "NORTE AMERIGO". The only difference between american and fronteria vehicles today is the sulphur content of further southern fuels.

The bottom line is - the higher compression ratio you have, the higher octane rating you need. The reverse is also true.

"Put a TIGER in your tank" only works if you have one under the hood...


Inputs requested


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Greywolf
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   Posted 11/8/2005 12:03 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
SilverDragon - 'pologies if I took your post wrong in the other thread. I was off my feed...

A problem I see coming up lately has to do with some of the discount gas stations and shoddy business practices. In Covington Tennessee there are two fuel pits that have been blatantly caught "ADDING" to their underground tanks with a garden hose from around the side of the stores!!!

The chain (whom I will not post the name of on the open board for MCUSA's sake. You can PM me if you need the info) was fined at least once for it, which I was told amounted to many thousands of dollars. I have also been told by my observant little rogues that they still water the tanks anyway.

A couple of brand new vehicles blew their mills over it from what I understand...

That's to the side of the main point though - the concern is that what we think we are getting might not necessarily be the octane we really ARE getting. And if most of us are running basic unleaded, it doesn't need to lose very many points before it gets into the grenade zone, know what I mean?

So - one thought here is to keep a stash of higher or at least decent octane around just in case you find that you have a tank of garbage on your hands. On a long ride or a trip though - a small bottle of some kind of octane boost could be valuable first aid for your bike. It would at least get it to someplace where the gas was "right".

That begs this question though: Are any of the supposed octane booster additives out there worth a dime in the first place? Do they really do what they claim in real empirically (laboratory) provable numbers?

Or are the all just so much "Snake Oil"...

"TRICK" racing fuels in San Diego California was for real, I know that. The price of their products was always kind of high though, and I don't know if they are even still in business.

Most of the JB line was good stuff, but I don't even remember the last time I saw a Justice Brothers display anywhere around.

I doubt anyone would want to keep a bottle of methanol on a bike. In fact HELL no...

So what's out there?

Also - how many of us are now watching for and keeping track of stations "TO AVOID"?


Murphy was right. 99% of everything is CRAP!

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tonyholbury
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   Posted 11/11/2005 7:32 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
As we are a bit late switching to unleaded fuel here in britain, off the shelve additives are still available to increase octane and include a lead free additive for the valves, are these commercial products not available in the USofA?
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Greywolf
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   Posted 11/14/2005 6:36 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
There are quite a few - the problem is that some are of greater or lesser quality than others, and some may also be totally worthless.

In theory, methanol in small amounts may remove water from fuel, thereby adjusting it's combustibility. But that is still not an octane booster. Not all products are what they could be, but "TECHNICALLY" they do what they claim - even if it isn't quite what is wanted.

In the USA, there are always the truth in advertising regulations to deal with, but a clever advertising campaign can get around just as much as a good legal council....

Sad but true.
 
 
OH and by the by, Tony:
 
If there are lead based additives available at this point, you can be assured that this will not always be so.
One can stock up on them of course, but in the end valve modifications may be required to four stroke machines in order to cope with the absense of lead in your fuels in the future. A modification that can be less expensive if one performs ones own repairs, but is still considerable.
 
Seats, for one, but guides as well. Bronze valve guides are often used to make up for the lack of lubricational properties in unleaded fuel over here.

I do not think that the powers that be over your way would wish for older, classic, and much appreciated machines to be without resources and rendered useless. But if the push is on to make the fuels themselves go away it cannot be long before the additives follow them. For the time being, I would expect an overlap period.

It won't last. That would be self-defeating.


"Give someone a fish, and they have dinner. Give them a fishing pole and they have sustenance..."

Post Edited (Greywolf) : 11/15/2005 1:49:59 AM GMT

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tonyholbury
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   Posted 11/22/2005 5:05 AM (GMT -7)    Quote This PostAlert An Admin About This Post.

Luckily Greywolf I live very near to the Beaulie Motor Museum and the garage in Beaulie is one of the very few who has an exemption to maintain a stock of leaded petrol, because some of his lordships cars need to run on Leaded only because of their age and the materials the valves and seats were made from.

There is a tax loophole for vehicles in this country licenced before 1970 (or was that 72) and many of these can ONLY run on leaded, many old Mini's can have a later Metro A plus last of the line head fitted, these are available for the 998cc and 1275cc models.

I have one of these heads in my back yard, the wifes Metro has only a year or so of tinworm munching left in it, so it isnt worth my while changing the heads over, I shall sell it instead!

Tony

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Greywolf
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   Posted 11/28/2005 10:19 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Pity - it's a shame to lose an original mini, but unless a museum got it, what choice have you?

I'd have liked to see more options on additives that really do what they claim and are available here. I'd also like to warn some of you: NEVER use additives intended for a petrol (gasoline) engine in a DIESEL. It will be junk before you know what happened...

One other note: Although there is another thread on "OCTANE" here, I'd like to see it reserved for the "THEORETICAL" point of view, while this one is completely "PRACTICAL". As in - day to day hands on stuff, as opposed to egg-head hypothesizing. :)


The only explanation for what my bike is doing is that it's hungry and likes 'fried lights'...
 
Current bikes:
1972 Kawi F7 (175) trail bike (in progress)
1973 Kawi F7 (175) Enduro
 

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Bonton
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   Posted 4/23/2008 3:52 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Very interesting stuff, should be read by all.


Treat every thing like a dog.   If you can't eat it or hump it, piss on it and walk away.

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Shade Tree Mech.
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   Posted 7/7/2008 3:17 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
=> Bonton <=

You are probably the one that came up with:

IF YOU LOVE IT, SET IT FREE, . . . IF IT DOESN'T COME BACK,
HUNT IT DOWN AND KILL IT.






Shade Tree Mech.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Always, a rubber-side-down rider

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