SuzukiSavage.com - Octane...

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Octane...
07/08/10 at 12:42:13

...a couple of interesting tidbits that may surprise some people...

"Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power."

"Most fuel stations have two storage tanks (even those offering 3 or 4 octane levels), and you are given a mixture of the higher and lower octane fuel. Purchasing premium simply means more fuel from the higher octane tank; the detergents in the fuel are often the same."

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james may

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Re: Octane...
Reply #1 - 07/08/10 at 21:31:16

yup only use higher octane fuel if your car/bike requires it or it is detonating or knocking. Octane rating is basically the anti knock rating. It is less likely to spontaniously combust from hotter engine temps or advanced timing or higher compression or forced induction. All of these modifications can also increase performance though so doing these performance mods can nessesitate the use of higher octane fuels, but higher octane fuel by itself will do nothing for your engine. Some saabs have a afc computer that can bring turbo boost up to maximum until knocking is detected. In the case of these computerized turbo systems the highest octane rating would actually have a performance advantage, but it's because the computer is modifying the engine characteristics.

Always thought it was silly when people use plus or intermediate octane ratings you either need regular or premium there usually isn't an inbetween unless your a sucker.

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Hashbrown Full Member Offline What can brown do for you! Posts: 235 Nashua, NH Gender:	Re: Octane... Reply #2 - 07/09/10 at 06:49:22 what about external factors like the outside temp affecting the temp of the engine. can a really hot summer day affect the temp of the engine enough to facilitate using a higher octane fuel?
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bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Octane... Reply #3 - 07/09/10 at 07:56:11 Motor will run a little cooler on higher octane gas.
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Re: Octane...
Reply #4 - 07/09/10 at 10:00:21

Hashbrown wrote on 07/09/10 at 06:49:22:

what about external factors like the outside temp affecting the temp of the engine. can a really hot summer day affect the temp of the engine enough to facilitate using a higher octane fuel?

If the heat is enough to cause predetonation and engine knock, it will help.... if not,.. it will do nothing...

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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Octane... Reply #5 - 07/09/10 at 11:08:57 Reelthing lives around Houston & runs down to Galveston. He runs premium in the heat of summer.
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weracerc Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 594 Greensboro, NC Gender:	Re: Octane... Reply #6 - 07/09/10 at 11:16:29 been running 93 octane the first 4 tanks since i got the bike - put 87 in it last night.....cant feel a performance drop - but oddly the decel rumbles and pops are a little quieter and the off poof is a little softer sounding...mid 90's high humidity here in central NC
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bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Octane... Reply #7 - 07/09/10 at 11:21:01 Higher octane gas burns slower,Its like retarding your spark It will run cooler and have less power than if you had a lower octane.
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Routy Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 2280 Winston Oregon Gender:	Re: Octane... Reply #8 - 07/09/10 at 13:19:09 Same as if you are going to horse it hard in hot weather w/ advanced timing, you may need a higher octane at sea level, but get it up in altitude a couple thousand feet, you probably won't need the higher octane. Or "water inject" that sucker, and you won't need it either. red = added on edit
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Charon

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Re: Octane...
Reply #9 - 07/09/10 at 16:00:43

Routy, I beg to differ. At high altitudes the absolute pressure in the cylinder is lower because of the lower atmospheric pressure. This lower pressure also lowers temperatures. Thus, the octane requirement drops. I offer in evidence that gas sold in Denver and Cheyenne is usually 85 octane instead of the 87 common at lower altitudes.

Bill, I would like to see some evidence of your claim that higher octane gas burns slower or cooler. Can you cite a source?

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Eschew obfuscation.

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justin_o_guy2

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Re: Octane...
Reply #10 - 07/09/10 at 16:08:43

Charon wrote on 07/09/10 at 16:00:43:

Routy, I beg to differ. At high altitudes the absolute pressure in the cylinder is lower because of the lower atmospheric pressure. This lower pressure also lowers temperatures. Thus, the octane requirement drops. I offer in evidence that gas sold in Denver and Cheyenne is usually 85 octane instead of the 87 common at lower altitudes.

Bill, I would like to see some evidence of your claim that higher octane gas burns slower or cooler. Can you cite a source?

Its on the back of the Klotz bottles, right under the "No Wear" statement.

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bill67

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Re: Octane...
Reply #11 - 07/09/10 at 17:32:23

Charon wrote on 07/09/10 at 16:00:43:

Routy, I beg to differ. At high altitudes the absolute pressure in the cylinder is lower because of the lower atmospheric pressure. This lower pressure also lowers temperatures. Thus, the octane requirement drops. I offer in evidence that gas sold in Denver and Cheyenne is usually 85 octane instead of the 87 common at lower altitudes.

Bill, I would like to see some evidence of your claim that higher octane gas burns slower or cooler. Can you cite a source?

Common knowledge my friend,Look it up.

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Routy

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Re: Octane...
Reply #12 - 07/09/10 at 21:51:34

Oh yeah, wanna bet ??? Angry

Just kiddin,.....the first 1/2 post kinda says I left out the word "won't".....as in "won't need hi octane Wink

But yep, hi octane gas burns slower,.....or always use to anyway.

Charon wrote on 07/09/10 at 16:00:43:

Routy, I beg to differ. At high altitudes the absolute pressure in the cylinder is lower because of the lower atmospheric pressure. This lower pressure also lowers temperatures. Thus, the octane requirement drops. I offer in evidence that gas sold in Denver and Cheyenne is usually 85 octane instead of the 87 common at lower altitudes.

Bill, I would like to see some evidence of your claim that higher octane gas burns slower or cooler. Can you cite a source?

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Rich
'07 S40 Blvd stocker, except drilled OEM exhaust and white spacer mod...1/2 (.055)

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Serowbot

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Re: Octane...
Reply #13 - 07/09/10 at 22:48:50

Routy wrote on 07/09/10 at 21:51:34:

Just kiddin,.....the first 1/2 post kinda says I left out the word "won't".....as in "won't need hi octane Wink

Yup,... I can see that..

Hell,... I've done that...
Plenty...
Foot comes out of your mouth a lot easier after a while... Embarrassed

...
Bill just nailed me for "adjusting the valves while running",... instead of "adjusting the valves while the engine was running"...
No way I can run that good.... Huh

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Routy Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 2280 Winston Oregon Gender:	Re: Octane... Reply #14 - 07/10/10 at 05:24:51 Was Bill always like that ?
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