29 fastlane
Naturally aspirated race motors with
large combustion chambers spinning
at high RPMs really like high-octane,
fast burning fuels. They need the
octane to prevent uncontrolled
combustion, and they need a fast-
burning fuel so that the flame
front can span the large bore of the
combustion chamber quickly.
If you’re not sure which fuel burns
faster than others, one indicator is
specific gravity. “Lighter” fuels – fuels
with a lower specific gravity – tend
to burn faster because fast burning
hydrocarbons are themselves light.
Look for a specific gravity close
to 0.70 and you’ll likely find a fast
burning fuel. Of course, consult
with the fuel producer to verify your
assumptions. You might be surprised
to learn that some of the highest
octane fuels may also be some of the
fastest burning fuels!
You might also be surprised to know
that fast burning fuels may not
need as much timing as their slower
burning counterparts. Many times
we get calls from individuals who
are dialling in new motors on a fast
burning fuel but they’re using timing
and jetting numbers from their old
motor and fuel combo. “Retard the
timing a couple degrees and see
what happens” is not the suggestion
they expect to hear! With high
octane, fast burning fuels, it is easy
to dial in too much timing. In such
cases, the engine is not detonating,
but it is past the point of optimum
spark advance, so it’s just heating
things up and making less power. A
little less timing may really wake up
the motor.
For more on Sunoco Racing Fuels,
visit www.SunocoRaceFuels.com
Proper storage can preserve octane
for years, but improper storage can
reduce octane and degrade fuel
within weeks. That is why we provide
proper storage information on our
website, www. SunocoRaceFuels.
com.