No knock sensors on a 1964 1/2 Mustang. Mark ----- Original Message ----- From: David Beierl <dbeierl@attglobal.net> Date: Monday, July 12, 2004 2:50 pm Subject: Re: Fuel Octane, Additives > At 17:22 7/12/2004, Mark Tuovinen wrote: > >My Audi calls for 91 octane fuel and I have observed over several > years > >and varying weather/driving conditions that it does indeed get > improved > >mileage and run better with 91 octane vs 87. Enough so to easily > justify > >the higher fuel cost, the mileage difference alone more then > covers the > >cost variance. > > > >with the higher octane fuel, and ran better too. In fact the 91 > octane > >fuel burned so much better that it increased the idle speed and > we had to > >readjust it. The differences were probably more noticable on the > car we > >used then most people would see as it called for a minimum of 99 > octane. > Or to put both of these things a different way, modern engine- > management > systems with knock sensors were able to retard the timing enough > that you > could get degraded performance instead of blowing holes in your > engine? I > don't want to be dismissive but in all honesty it's hard not to. > It's not > any sort of secret that engines designed for high octane (i.e. > high > resistance to detonation, using the properties of the substance > octane as > representing 100 on the scale (and then fudged around later > somewhat)) have > to have that quality to work properly and until recently, to > survive. Likewise it's not in any question that a) engines gain > nothing > from an octane number higher than they need under given > circumstances, > which one hopes will be covered under the mfr's specification; and > b) that > chemically speaking, gasoline with high octane properties has > measurably > less energy per unit than gasoline with lower octane qualities. > > But "premium" -- more to it (maybe) than octane. And there was > certainly a > time when EFI systems that had plenty of octane number from > regular gas, > didn't get enough detergent from it to keep injectors clean. Now > they do, > in US anyway, because it's Federally mandated. But only enough to > keep > them clean, not necessarily to clean them. So if there's a > question in > this area, it seems to me that it's best to specifically dismiss > octane and > look a bit closer. > > thanks, > david > > > > > -- > David Beierl - Providence RI USA -- > http://pws.prserv.net/synergy/Vanagon/'84 Westy "Dutiful Passage," > '85 GL "Poor Relation" > > |
Please note - During the past 17 years of operation, several gigabytes of
Vanagon mail messages have been archived. Searching the entire collection
will take up to five minutes to complete. Please be patient!
Return to the archives @ gerry.vanagon.com
The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.
Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.