[earossi]

[quote name='earossi' date='Mar 13 2005, 09:07 PM']968Z,



Sorry if I confused anyone about how octane is determined.  Gasoline octane is determined in the gasoline blending stage of manufacture.  Gasoline is actually a blend of 5 to 6 components which are the byproducts of crude oil.  Each of these "components" has its own octane.  Some octane numbers are relatively low, while some are much higher than you would every run in your engine.  During the blending phase of gasoline manufacture, a refiner blends a number of the components mentioned above to meet an ASTM specification.  Octane is also adjusted to meet the quality standards of the fuel....but this is not done to an ASTM standard......we actually have "knock engines" in a test lab that run on a manufactured blend.  With these engines, we can determine the knock rating of the blend, and from that data, we adjust the blend to meet the requirements of the market.



What I mentioned, that is confusing, in the first post was that ethanol produces a boost in octane.  So, for fuels that will not receive any oxygenate (ethanol), we blend to the pump octane (typically 87, 89, and 92 or 93 for regular, midgrade, and premium grades respectively).  If the fuel is to receive ethanol, we will blend the gasoline to a lower octane and ship the suboctane fuel to a terminal.  Then, when a tank truck is loaded, ethanol is added, by volume, to achieve the oxygenate level required, and coincidentally boosts the octane to the proper level.

[right][post="1824"]<{POST_SNAPBACK}>[/post][/right][/quote]

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[earossi]

There are many products out there to boost octane. I can't say that I have tried any, but others have. Increasing a fuels octane would allow you to run a higher compression ratio, with a gain in power. So, if you decided to put more aggressive cams in an engine, and did the modifications to increase compression ratio, you would then be required to run a higher octane fuel to prevent knocking. That is why racing gasoline is much higher octane. But, the key is that your engine has to be configured to take advantage of the octane.



In today's computer controlled engines, I doubt that you will notice any noticeable change in power by boosting octane. What has been the experience of others in the use of additives that increase octane?

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[Greimann]

Since the 968 has an 11:1 compression ratio and an adaptive knock control that is labeled "Electronic Octane" the more octane you feed it, the more ignition advance you get. More advance = more power. There is an upper limit at which more octane will not yeild any more advance, but I don't know what that is.



Here in CA you can only get 91 octane and that will work in a 968, but even the gas flap says minimum 93. Anything below 90 and I believe you get check engine lights. Adding 5 gallons of Unocal 100 in a tank gives a nice, seat of the pants boost, but that can get expensive every tank.



Why can't CA have 93 octane premium?

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[ds968]

[quote name='Greimann' date='Mar 13 2005, 07:36 PM']Why can't CA have 93 octane premium?

[right][post="1827"]<{POST_SNAPBACK}>[/post][/right][/quote]



Anwer: Committee for Octane Rating-Protection of State Emissions (CORPSE <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" /> )



no ? oh, well I'm sure it's some similar organization of bureaucratic boneheads who drive company Ford Fiestas and resent those with fun cars wanting to.. have even more fun with mo' power.

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[ds968]

p.s. 100 octane at a UNOCAL station close to where I live goes for about

$ 5 / gal. I presume, give or take 20%, that's the ballpark figure

troughout the State ?

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[rustech]

[quote name='ds968' date='Mar 14 2005, 10:44 AM']p.s.  100 octane at a  UNOCAL station close to where I live goes for about

        $ 5 / gal.  I presume, give or take 20%, that's the ballpark figure

        troughout the State ?

[right][post="1846"]<{POST_SNAPBACK}>[/post][/right][/quote]



Yeah, it's like $5.70 down here.

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[flash]

ranges a lot - 5.99 near me - 4.99 in newport

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[ds968]

let's see.. typically one adds 5 gal. of 100 oct. to the rest of the tank filled with 91 oct. So getting your gas in Newport would be $ 5 cheaper, but then from Palisades that's about a 55 mile drive, so averaging 22.5 mi / gal. on the higway you'd spend 2 gal. of 91 oct at about $ 2.50 e@, in which case you'll be at zero balance after the fill up.. but then the drive back is not only with a more expensive tank of gas, but you know you'll stomp on it to get that higher octane working as it should so I'm guessing your mileage will suffer to the tune of at least 25%, so you'll need 2.5 gallons to get back home at around $ 3.50 e@, so you arrive there

$ 7 in the hole. Aw, heck, bad idea - just buy the gas at the $ 5.99 / gal. station close to you <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/blink.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />



damn unemployment ! too much time on my hands.. <img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" />

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[ds968]

not to mention that my attention to details and ensuing math sucks !

that's 2.5 gallons, so more like $ 8.75 in the hole <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" />

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[flash]

lol - yeah - i was down there having dinner with ayn's parents who live in newport - filled up while i was there, so it worked out ok

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