How does the NASCAR guys read the sprak plug to determine the optimal heat
range and gapping of the tip?
--------------------------------------
Steven St.Laurent
C4i System Engineer
C4i Engineering Branch, PSD, MCTSSA
MARCORSYSCOM, U.S. Marine Corps
Office (760) 725-2506 (DSN Prefix: 365)
"Never be content with somebody else definition
of you. Instead, define yourself by your own beliefs,
your own truths, your own understanding of who
you are. Never be content until you are happy with
the unique person GOD has created you to be."
-----Original Message-----
From: Bob Tom [mailto:tigers@bserv.com]
Sent: Thursday, June 06, 2002 4:42 PM
To: dakota-truck@dakota-truck.net
Subject: RE: DML: Re: 76 Competition 100 Unleaded Racing Gasoline
At 12:02 PM 6/6/02 -0700, you wrote:
>Ugh, Jon. I think you have that in reverse. It is a proven fact
>the higher the fuel octane the more power. I wish I could
>run the SR-71 fuel (JP-7). Steven St.Laurent
No, Jon's right.
Octane is an arbitrary, calculated number which is only an indication
of a fuel's sensitivity to knock. High-octane race fuels burn slower
than most unleaded fuels and may reduce performance in stock or
lightly modified vehicles. Since a high octane rating, in itself, does
not necessarily mean that the fuel is slow burning, octane has no
direct bearing on the power characteristics of the fuel.
The real advantage of racing gasolines comes from the fact that they
will tolerate higher compression ratios (due to their higher octane rating)
and thus indirectly will produce more power since you can now build an
engine with a higher compression ratio. Also, alcohols burn cooler than
gasoline, meaning even higher compression ratios are possible with them,
for even more power.
The bottom line is that, in a given engine, a fuel that doesn't knock
will produce the same power as most expensive racing gasolines.
However, it sometimes happens that when you use another fuel,
the engine suddenly seems to run better. The reasons for this are
indirect. The new fuel may improve the volumetric efficiency (that is,
the "breathing") of the motor. This happens as follows. Basically a fuel
that quickly evaporates upon contact with the hot cylinder wall and piston
crown will create additional pressure inside the cylinder, which will reduce
the amount of fresh air/fuel mix taken in. This important, but often
overlooked
factor is described by the amount of heat required to vaporize the fuel.
For a measure how much power is contained in a fuel, one should look
at the amount of energy (heat) released in the burning of a particular fuel.
This is described by the specific energy of the fuel. This quantity
describes
the amount of power one can obtain from the fuel much more accurately.
The specific energy of the fuel is the product of the lower heating value
(LHV) of the fuel and molecular weight of air (MW) divided by the air-fuel
ratio
(AF).
By the way, pump gas has specific energies which are no better or worse than
most racing gasolines. The power obtained from pump gas is therefore often
identical to that of racing fuels, and the only reason to run racing fuels
would be
detonation problems, or, since racing fuels are often more consistent than
pump
gas (which racers call "chemical soup"), a consistent reading of the spark
plugs
and exhaust pipe.
Bob
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