well i was just wondering how all this works do u have to have so much compression to run certian octane? , for example would 120 octane hurt a stock motor far as 1/4 mile time or would it help it

i think i remember seeing a very descriptive post about this somewhere and i think if you would do a search you may find it. also there was a whole write up on octane in a car craft from the last few months or so (i cant remember what one)

nate

I won't go into a full explanation here, but you could run 118 in a stock engine and not hurt it (non smog vehicle), but it would definetly not help it, or make any more power. The more compression or cylinder pressure you have the higher octane you will need to prevent detonation. Higher octane does not burn any "hotter" (it does not burn holes in pistons or anything like that). It does not burn as fast/easy as lower octane fuel, this allows you to make more power by using higher compression, boost, NOS etc.. The higher the octane the more resistant it is to pre-ignition. This was an over simplified answer but that is the basics of how it works.

Royce

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70 Camaro 383ci
69 Camaro 385ci
91 Camaro RS V8 (305 TBI)
Link to my 70

http://profiles.yahoo.com/camaroman7d

I have been asked this so many times that I wrote an article on it, you can read it here:
www.grapeaperacing.com/GrapeApeRacing/tech/fueloctane.htm (http://www.grapeaperacing.com/GrapeApeRacing/tech/fueloctane.htm)

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www.grapeaperacing.com (http://www.grapeaperacing.com)

[This message has been edited by Grape Ape (edited 07-22-2001).]

You've got some great info on there! http://www.camaros.net/forum/smile.gif
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer

yeh that was some good info huh? thanks was just curios how all that worked

Nitromethane is an interesting sidelight to this subject - nitro has a very poor octane (resistance to detonation) number, and burns very slowly (relative to gasoline); it makes incredible power only because it carries its own oxygen, which allows you to use more fuel (heat energy), thus more power. However, because it has a low octane rating and burns slowly, it requires really radical timing; when I ran my fueler, way back in the early 60's, on 60-65% nitro with a Joe Hunt Vertex magneto (hottest spark you could get in those days), we had to set it up with 48-50 degrees initial, and even with that, you could just start to feel it laying down (detonating) through the lights. Any more advance than that and you couldn't even push-start it. That's why they run dual plugs with dual mags these days (at $8,000 each) with LOTS more fuel, at 90% (and the mags have to be recharged every ten runs, at $1,000 a pop). Lousy octane, slow-burning, but big power because of that oxygen molecule that lets you burn more fuel.

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JohnZ
'69 Z28 Fathom Green

That is so true, nitromethane is a very poor racing fuel, it is very prone to detonation and it burns so slow, which is why there is so much flame out of the headers. The one overwhelming virtue is that it is 53% oxygen, which is also why the burn 12-13 gallons of fuel in the burnout, staging and 1/4 mile. You can burn a whole lot of fuel when more that 1/2 of the fuel itself is oxygen.

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www.grapeaperacing.com (http://www.grapeaperacing.com)

[This message has been edited by Grape Ape (edited 07-25-2001).]

Going back to HS chemistry (which is a long way back) octane is a hydrocarbon C(8)H(18). Gasoline is generally a combo of hexane C(6)H(14), heptane C(7)H(16) & octane. Hexane and heptane are very poor when it comes to preventing knock while octane is very good. A gasoline that has a 90 octane rating is basically said to perform as though it was 90% pure octane. Therefore the octane rating is actually an index comparing the fuels relative ability to control knock compared to pure octane. Fuels that are over 100 octane therefore retard knock better than pure octane.
End of chemistry 101