Re: Usable BTUs

Ron Brown /
This single post is part of a larger thread. Start from the top or view this post in context.


If you consider the relationship between piston/crank position and speed of burning of different grades of gasoline, then ignition timing and engine rpm can have a sigificant effect on gas mileage.

As an example, if you have "knocking", you can usually cure it two ways.

You can retard the timing, this allows a greater volume of combustion chamber for the burning fuel to expand into, as the piston is a little further down the bore as combustion is complete.

You could, instead, switch to a higher octane gas. The slower burn rate would have a similar effect to retarding the ignition.

This is a very simplistic view as compression ratio, bore and stroke, engine rpm and temperature all have a significant effect.

Sometimes, running premium gas will allow the engine to run cooler by reducing pressures during the early part of the combustion cycle. Hopefully, this translates into more pressure applied to the piston near the center of its stroke where it can do the most good, possibly improving gas mileage.


This single post is part of a larger thread. Start from the top or view this post in context.
Subject Written By Posted
  Gas QuestionTopic by: KoLD KoLD 11/26/01 07:18PM
  Re: Gas QuestionRe: don-ohio don-ohio 11/26/01 07:24PM
  Re: Sorry, forgot...Re: miguel miguel 11/26/01 09:00PM
  Re: Sorry, forgot...Re: SteelToad SteelToad 11/28/01 01:18PM
  Re: Sorry, forgot...Re: don-ohio don-ohio 11/28/01 01:35PM
  Sorry, forgot...Re: KoLD KoLD 11/26/01 07:27PM
  Re: Sorry, forgot...Re: XBrandon EdgeX XBrandon EdgeX 11/26/01 08:35PM
  Re: Sorry, forgot...Re: Doug D Doug D 11/26/01 09:20PM
  Euro octane specsRe: Fred Fred 11/26/01 11:26PM
  Re: Gas QuestionRe: D Nyberg D Nyberg 11/27/01 12:13AM
  Re: Gas QuestionRe: Ron Brown Ron Brown 11/27/01 01:48PM
  Re: Octane 101Re: Jim C. Jim C. 11/27/01 11:53PM
  Usable BTUsRe: don-ohio don-ohio 11/28/01 10:43AM
  Re: Usable BTUsRe: Ron Brown Ron Brown 11/28/01 12:48PM
  Re: Usable BTUsRe: don-ohio don-ohio 11/28/01 01:13PM

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account