Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site qubix.UUCP Path: utzoo!watmath!clyde!burl!hou3c!hocda!houxm!houxz!vax135!floyd!harpo!decvax!decwrl!sun!qubix!jeff From: jeff@qubix.UUCP (Jeff Buchanan) Newsgroups: net.auto Subject: Octane ratings, 1973 vs 1984 Message-ID: <1193@qubix.UUCP> Date: Tue, 12-Jun-84 15:36:22 EDT Article-I.D.: qubix.1193 Posted: Tue Jun 12 15:36:22 1984 Date-Received: Thu, 14-Jun-84 00:44:13 EDT Organization: Qubix Graphic Systems, Saratoga, CA Lines: 46 I need some information from some of you chemist/petroleum Engineer types. How does one compare the octane rating of todays gasoline to that of 1973? Around the time that gas started to lose it's octane, (1973-ish) the rating method was changed. Today the rating you see on the pumps is Research method + Motor method / 2 = octane number. I remember that the old rating was either research or motor but I can't remember which. I also remember the advertised octane then was "100+". That was the higher number of the two (research and motor). So typical premium gas like Texaco Skychief and Enco Extra was about 101. Sunoco was about 104, or so they claimed. If the typical 92 octane gas available today was rated the same as it was in 1973, (before the change in rating method) what would it's octane number be? I understand that the way gas is rated (motor or research) hasn't changed, only the way the final number is determined (above formula). Everyone knows that gas today has lower octane than it used to, but since the rating method has also changed, it is hard for me to see HOW MUCH it has been lowered. Also, I would like to get some opinions as to the effect on power output of engines with the low octane (92) gas. Obviously if you have a high compression engine (10.5-to 1 or higher) you must tune differently if you switch from high octane to low octane gas. But if you were to take a typical engine from the late sixties, say a 435 HP 427 Chevy and tune it for maximun HP on the old high octane gas, then tune it for max power on todays low octane (92) gas, what if any horsepower difference would you see on the dyno? The difference talked about between high and low octane gas is that high octane burns slower and more evenly. This means you can dial in more spark advance and a high compression ratio without power robbing knocking and pinging. I understand this, but that doesn't necessarily tell me that high octane gas has more potential energy per unit volume than low octane gas. I have more than academic interest in this issue. I have an L-88 engine in my '66 Vette that pings terribily with 92 octane. In 1973 it didn't, although I changed no components (except for rebuild items like rings and bearings). This is comparing the now and then engines immediately after rebuild. Same cam, carb, piston, gasgets, etc. So the only explanation is gas. Now, I know I can solve the problem of knock with octane booster, but my main question is will bringing up the octane rating of today's gas with booster necessarily mean it will have the power of 1973 !00+ gas? -- Jeff Buchanan @ QUBIX Graphic Systems, Inc., Saratoga, CA. ...{decvax,ucbvax,ihnp4}!decwrl! ...{ittvax,amd70}!qubix!jeff decwrl!qubix!jeff@Berkeley.ARPA