DI TECH
Piston domes on nitrous engines will be thicker
than their NA counterparts do to the increased heat
of nitrous.
Handling the Heat
Besides providing a compression seal, the top
rings also play a critical role in transferring heat
from the body of the piston to the cylinder wall,
and with the added energy in a nitrous applica-
tion, this becomes even more important. Both
ring material and the ring gap need to be specified
with s pray in mind.
“We have various ring materials that are popu-
lar,” DiBlasi says. “If we are using a 1/16 ring, we
configured for the specific application. The proper
have our hardened nitrous series of rings that
pin thickness and length are designed to handle
are available for any shelf or custom piston. We
the demands of the engine while making sure the
pin bosses have enough pin engagement material.” suggest a hardened nitrous series ring, carbon
The location of the top ring becomes a compro- steel nitride ring, or a stainless steel ring for best
longevity.”
mise; while modern factory engine designs tend
Another recent trend in piston
to place the primary compression ring
design has been to move the oil ring
as close to the crown as possible to re-
down to the point where the groove
duce crevice volume in order to help
actually intersects the pin bore. This
emissions, this is less than ideal in
allows for shorter overall piston
a nitrous engine. “The further the
height, more room to put the ring
top ring is moved down, the more it
package farther down from the crown,
is protected,” DiBlasi explains. But
or a combination of the two. But is
because a proper ring seal depends
it a good idea for a piston designed
on the gas pressure applied to it, he
for nitrous duty? DiBlasi says yes;
adds, “Moving it too far down will
“We have great success using oil rail
cause a reduction of power and seal-
supports to allow the pin to go into
ing ability.”
the oil ring. Providing the ring lands,
One added design feature com-
crown thickness, and ring material is
mon in high-performance naturally
designed for the application, there
aspirated pistons is also useful for
should be no difference to the perfor-
nitrous pistons. “In racing applica-
mance if using a rail support or not.”
tions, gas ports can do wonders for
Additional Support
sealing. It’s not much different from
The additional heat and higher cyl-
boosted or high performance N/A.
inder pressure generated by nitrous
The only thing to watch out for is the
applications also drive the shape of
Nitrous oxide has a
premature wearing of rings due to
reputation for eating
the piston in other ways, with DiBlasi
the increased pressure that the face
pistons, but with the
of the ring sees. Modern rings last
noting, “Crown thickness, pin length,
right tune and the
a very long time, so it’s less of a fac-
and pin thickness are all critical to
right parts, engines
tor with stainless and carbon steel
nitrous engines.” The design of the
can live long, healthy
lives on the bottle.
nitride rings.”
crown must take into account how
70 | D r a g
I l l u s t r a t e d | DragIllustrated.com
Short piston heights combined with a lowered ring
package can move the oil ring groove into the pin
bore area, but with a proper support ring, this isn’t
a serious drawback.
ing of the piston top, which eliminates a potential
source of detonation, regardless of what kind of
engine it’s being used in.
While nitrous has the reputation of being hun-
gry for pistons, we’ve learned that by specifying
the right parts that are designed for the unique
thermal and physical stresses spray imposes, it’s
not impossible to put together a durable, pow-
erful, nitrous combination. Just like any other
power adder (or even a high-strung naturally
aspirated engine), the secret lies in knowing
the limits of the components you’re using, and
upgrading where necessary to handle the extra
stress. - PAUL HUIZENGA
The right high-tech coating can help reject heat from
the piston crown and improve both performance and
longevity. Today’s coating processes like Wiseco’s
ArmorPlating and ArmorX are engineered specifically
for extreme environments.
Issue 134
Another characteristic of a nitrous piston design is
a thicker-than usual crown to act as a heat sink, as
well as special attention to the material thickness
around areas like valve relief pockets. Any thin or
sharp areas are potential hot spots that can become
sources of detonation.
heat will transfer, especially in regions like the
valve pockets where hard edges and thin spots can
create potential detonation sources. Overall, the
tradeoff between low piston weight and having
a sufficient ‘heat sink’ favors the latter factor in
a nitrous application.
“Additionally, we want to make sure that the
pin is supported as much as possible by widening
the pin boss towers,” DiBlasi adds. “This creates
the least amount of unsupported area from the
pin towers to the rod, limiting flexing.” Obviously,
keeping the piston as cylindrical as possible helps
the ring seal, as well as reducing friction and wear
and promoting heat transfer from the piston to
the cylinder wall.
A Choice of Coatings
Wiseco’s proprietary ArmorPlating process,
which protects the crown, ring grooves, and pin
bores, actually becomes harder when exposed to
heat. It’s a metal-based auto catalytic plating that
has the precision to accurately cover features as
small as gas ports without impeding their func-
tion, and it will actually help prevent carbon foul-