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Merritt Mullen <mmullen8014@mchsi.com> wrote:
[color=blue]
>In article <1144938466.694318.68220@i39g2000cwa.googlegroups.com>,
> [email]learnfpga@gmail.com[/email] wrote:
>[color=green]
>> However I do have doubts over quality of gas. My mechenic recommends I
>> use higher quality gas like 91 even though my camry can take 87. I dont
>> kow how much it really affects the peoformance of the car and life of
>> engine. May be someone can shed some light on it. Thanks....[/color]
>
>The octane rating of gasoline has nothing to do with "quality." It is
>simply a measure the gasoline's ability to resist detonation (where the
>fuel/air mixture burns explosively due to heat and pressure in the
>combustion chamber, rather than the normal combustion initiated by the
>spark plug). Engines are designed to run a certain combustion chamber
>temperatures and pressures and that is what determines the octane rating
>needed. Buying a higher octane gasoline than the owner's manual calls for
>provides no benefits and is simply a waste of money.
>
>Merritt[/color]

Exactly and precisely...while I have very little experience with
the technical aspects of automobile engines I have a great deal
of technial training and experience with large aircraft piston
engines and can vouch for Merritt's statements...I inadvertently
ruined a $150,000 aircraft engine in about 5 seconds once because
I missed noticing that the 'derichment valve' hadn't returned to
normal after takeoff when the 'water injection' was shut off and
the engine beat itself to death with heavy detonation.

I was interested and looked up the overhaul strip report on that
engine...almost all of the 18 pistons were holed, some of the
valves were 'headless' and some of the cylinder heads themselves
were split open...gives one a good idea just how destructive
heavy detonation can be...

I understand that modern automobile engines are protected with
'fancy pants' systems like 'knock sensors' etc now and these
engines in normal circumstances aren't stressed like aircraft and
race car engines anyway so detonation isn't nearly the concern
now but it certainly isn't something to toss off lightly either.
--

-Gord.
(use gordon in email)