Race Design Is Production Design For LS7 Piston And Rod

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Nov 29, 2013 (3 years and 7 months ago)

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For Release:


June 23, 2006, 8 a.m. EDT


General Motors


GM Powertrain Communications

Pontiac, Mich., USA

media.gm.com







Race Design
Is Production Design For
LS7
Piston
And Rod

Corvette Z06 Piston Assembly Highlights Race
-
To
-
Production Engineering


PONTIAC, Mich.


The piston assembly for the 2006
Corvette
Z06 LS7
7.0
-
liter
V
-
8 engine is
one of
the
latest
examples

of
race

design
s

carrying over to
production

GM
engines
.
Almost every aspect of the
short
skirt, high strength piston
s

and titanium
connecting rods
used in the 505 horsepower power plant
is

developed through rac
e

design know
-
how
.


Thanks to racing experience GM
engineers have
brought
one of the
most advanced design piston and rod
assembl
ies
to

a production engine.

Besides
light
-
weight, t
he LS7 piston assembly has an abundance of
features built
-
in

through race experience
,
” said
Roger Duguay
, chief engineer for GM

small block engines.

Full floating pistons with valve reliefs and lightening pockets,
plasma moly rings,
tapered wall pins,
high
strength chromium nitrided titanium rods

just begin to highlight the racing DNA

of this assembly
.




The full
-
floating piston

is
made of

eutectic aluminum alloy and is
CNC
machined for balance and tolerance
consistency.

For durability the top land is anodized.
Between the first and
second ring land
s

i
s a pressure
balance groove, another racing carry
-
over, to control blow
-
by
and

oil consumption
at high speed.
Piston
tops are flat with symmetrical valve reliefs providing opportunities for a stroker crank or
higher lift. A
polymer coating
on the skirts to reduce scuffing creates an almost negative interference
fit in the bore
.



Th
e ring pack uses thin rings for
high speed sealing control.

A 1.2 mm top compression ring
is used
with a
plasma moly face
for superior sealing and durability
. The second compression ring is also 1.2 mm thick and
is made of ductile or high strength iron. Th
e
three
-
piece
oil control ring is 2.0 mm thi
c
k and i
s

made of
nitrided steel for
superior

wear control and spring force
longevity
. Nitriding also
enables

lower ring tension
resulting

in more power due to reduced friction.


Little was spared when it came to

developing the connecting rods. The rod is made of
a
titanium
aerospace

alloy
and uses

twelve
-
point doweled
cap screws. The rods
are heat treated and
have a chromium nitride
coating for
surface
durability.
The

coating is applied

to
the
thrust facing areas

via plasma vapor deposition
(PVD)


a process taking 1
2

hours to apply. Each rod has three weight pads for precise balance.
Blind holes
are used, to eliminate stress areas, in conju
n
ction with a
heat treated
style cap screw

with a neck down
shank
for con
sistent clamp
and controlled stretch
.
The LS7 rod weighs just 464 grams which is almost 30
percent lighter than the similar forged
powder metal

rod in the base engine Corvette.


Racing has always been on the fore
front

of reducing component weight. “
Racing
knowledge transfer
gave

us
the basic design eleme
nts for the LS7 piston assembly,
” said Tom Halka,
development engineer for GM
small block engines
.

Thanks to GM’s vast technical resources and racing background w
e now have a light,
high speed

assembly

that

balances reliability and durability

with performance
. What we learned
with this
assembly

we
will apply to other
GM engine
programs
.



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www.gm.com
.






SPECIFICATIONS

Engine


Type:

7.0
-
liter
(427.7
cu
.
I
n.)
OHV V8

LS7

for
the

2006 Corvette Z06

H
orsepower:

505
(377 kW)
@ 6300 rpm

(SAE
certified
)

Torque:

470 lb.
-
ft.
(637 Nm) @ 4800 rpm

(SAE certified)

Bore x
s
troke:

4.125 in. x 4.00 in. (
104.8

mm

x 101.6

mm)


Compression ratio:

11.0

:1

Fuel shutoff:

7100 rpm


Piston


Type:

Flat top, short sk
irt, with valve reliefs and lightening pockets
,
anodized top land, second land with pressure balance groove

Material:

High strength aluminum alloy
, T
-
7

heat treat,

polymer c
oated
skirts

Compression
h
eight:

30 mm

Weight:

482 grams

Piston
-
to
-
valve clea
rance
:

Intake: 8 mm Exhaust: 7 mm

Piston pin


Type:

Full floating,

taper wall

Material:

High strength
steel alloy,
nitrided

Length /
d
iameter

58 mm / 23.5 mm

Weight:

132 grams

Retainer:

Round wire

ring
, chrome silicon steel

Piston rings


Top com
pression:

1.2 mm
(.
0472

in.)
symmetrical barrel
face
and
twisted
,

plasma
moly coated


Second compression:

1.2 mm
(.0472 in.)
high strength
ductile iron
, taper face napier
style

Oil control:

2.0
(.0787 in.)
mm
stainless
nitrided steel
, three piece
, low
te
nsion

Connecting Rod


Type:

Forged
I beam, stepped down pin end, blind cap hole
,
alignment
sleeve


Material:

Titanium
aerospace

alloy


Center to center length:

154.1 mm

Bolts:

12 point c
ap screw
,

heat treated,
high strength steel alloy,
neck
ed

down
sh
ank



Weight:

464 grams

Rod Length
-
to
-
Stroke:

1.5:1


# # #


Contact:


Tom Read

GM Powertrain Communications