conversion question +

[Michael McBroom]

Fred Miranda wrote:
> 
> Hi Michael,
> I've come up with different figures than you for the conversion.
> All I have for specific gravity is for race fuels, two brands, this is
> interesting.
>            F&L                   76
> 100 UL    .72                   .777
> 108L      .72
> 110L      .722                  .728
> 114L                            .728
> 115L      .75
> 118L                            .704
> 
> The trends are opposite. What's with that?

It appears that F&L is adding more substance(s) of a higher specific
gravity to increase octane, whereas 76 is adding more substance(s) of a
lower specific gravity to acheive the same result.

> Looks like changing brands would require tuning changes also.

Sure does.  Looks like changing octane will, too.  I guess the bottom
line is, if you're into serious tuning at the race track, bring along
something to measure specific gravity on a batch-by-batch basis.  That
reminds me -- I've seen top fuel drag crews do exactly that (I took a
photo of Dan Pastorini taking a specific gravity measurement at Famoso
during the May Meets, oh must have been over ten years ago).  I'd
wondered at the time if it were really that critical to measure specific
gravity.  I guess, when the difference between winning and going home
early can be measured in hundredths of a second, every detail helps.
 
> Next for the conversion.
> You had a figure of "4546cm^3/gal"
> My calculator converts to 3785.4cc/gal

Woops!  You're absolutely right!  I've got a Casio SF-5780, one of those
fold-up business organizer jobs.  I checked it just now -- it says
4.546l/gal . . . but 3.785l/US gal.  What's up with THAT?  Seems to me,
it should read 4.546l/IMP gal, and 3.785l/gal (wondering if I bought a
"gray market" model now).  Oh well, glad you caught it, at least.  Now I
gotta redo my conversion factors.
 
-- 
Best,

Michael McBroom

'87 745T 123k w/APC (batoutahell!)
'88 765T 154k 
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Graduate Student, Linguistics                         Author of 
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California State University, Fullerton                        
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