Quote from Matt Kulka:
> BTW, urban myth rebuttal: Higher octane fuel does not give an engine more
> power. Octane is the ability of the fuel to resist pinging, or
> 'pre-detonation.' You can get more power from higher compression.
However
> this higher compression will increase the affinity for pinging. Thus,
the
> need for higher octane fuel in your big-hp motor.
Truth be told, I meant to delete this paragraph from my post. I thought to
myself "Oh, Mr. Know-It-All, who exactly are you showing off to?" Then I
got distracted, went back to the message, and punched the Send button a
little prematurely. So to the list I offer my apology, and ask forgiveness.
Now since I opened my fat mouth...
-----Original Message-----
>From: ccrobins [mailto:ccrobins@ktc.com]
> Where did you hear that business about the lead additive impregnating the
valve seats?
Not lead additive, real lead from old-fashioned leaded gas. And I'm afraid
I don't have a written source, I'm guilty of repeating hearsay from
hot-rodders and machinists I've spoken to. However, thanks to Paul Hunt and
David Lynes for coming to my rescue. (To save bandwidth I won't copy their
replies.)
Also...
-----Original Message-----
From: REwald9535@aol.com [mailto:REwald9535@aol.com]
> If an engine pre ignites (pings) the flame front in the cylinder is not
> happening at the correct time, or it is not happening smoothly. Both of
these
> conditions will not produce the same power as a properly firing engine.
I agree. In pre-ignition, you aren't directing the flame front from the top
of the cylinder down - in fact, you can get opposing flame fronts, from
bouncing off the chamber walls, or the compression flame front facing the
spark plug's flame front. Not the best for power, heat management or parts
longevity.
And...
-----Original Message-----
From: Simon Matthews [mailto:simon_matthews@avanticorp.com]
> Actually, a little knock does not neccessarily reduce power...
> Their engine specialists remarked that the reason they wanted to eliminate
> knock was because of owner complaints. I was told that a little low speed
> knock did not damage their engines and in fact they produced MORE power
> under light knock conditions.
I'd heard of this study, and that a modern engine would withstand a little
ping, but I didn't know the part about having MORE power under light
pinging. I'd believe an engine could have more power DESPITE some pinging,
but you're the guy who was in on the study, so I'll bow to your experience.
In any case though, I think this is where I'd put on my safety engineer hat.
If my engine is pinging a little, I don't know if I'm still on the power
side of the line, or over the overheat/uncontrolled_detonation line. Since
I'm no racer, I'd just as soon spend a few extra cents on premium gas or
retard the ignition a little and skip that last extra HP.
Matt Kulka
Huntersville, NC
'74 B
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