<VV> Octane Number

[Joel McGregor]

The numbers don't tell the truth compared to 20 years ago either.  I used to be able to run 50/50 93 unleaded/89 leaded pump gas in my motorcycle back then with no detonation.  Now I have to run 100LL.  It pings and clatters like crazy with today's "93".  It seems to have gotten worse when they took the lead out and even worse with the ethanol in.  I did richen the jetting to make up for the ethanol.  I can't remember when they started putting ethanol in gasoline but I remember having issues starting around 15 years ago.
Joel McGregor
________________________________________
From: virtualvairs-bounces at corvair.org [virtualvairs-bounces at corvair.org] On Behalf Of Dave Keillor [dkeillor at tconcepts.com]
Sent: Wednesday, April 25, 2012 12:17 PM
To: virtualvairs at corvair.org
Subject: <VV> Octane Number

The octane ratings posted on pumps today can't be directly compared with
the octane ratings back in the gud-ole-daze (pre-70s).  In those days, the
octane ratings used the RON method of measurement, today it's (RON +
MON)/2.  Since RON generally yields the higher octane number, today's
numbers are a few points lower than those of yesteryear.

(RON = Research Octane Number; MON = Motor Octane Number)

Dave Keillor