Automotive Engineering - April 2022 - 8

TECHNOLOGY REPORT
realized we had 650 [horsepower] in the bag, " said assistant
chief engineer Dustin Gardner. And Yoon Lee, design system
engineer, noted that the production engine makes more power
than the racing version of the LT6 (endurance-racing rules
require intake restrictions that limit power output). " I think it's
going to stand the test of time of being one of the true icons, "
Gardner added.
The LT6 is comprised of a two-piece aluminum block mated
at the crankshaft centerline and topped by aluminum cylinder
heads. The short stroke delivered a deck height some 23
mm (0.9 in) lower than the standard Corvette's LT2 V8. The
12.5:1 compression ratio is abetted by forged-aluminum pistons
that have startlingly short skirts and are supplied by CP
Carillo, a racing components manufacturer.
The new engine's intake system perhaps is the most visible
manifestation of the Gemini concept, its prominent dual-plenum
design encasing an approach to air-management that
enhances torque production. The system, extensively detailed
here (GM details new and mighty flat plane Corvette LT6 V8
(sae.org)), uses an arrangement of three valves to manipulate
air movement between the plenums. The result is a variable
volume of intake that optimizes induction resonance while
boosting torque output to its maximum 460 lb-ft (624 Nm)
and at the same time making it more consistent across the
Cutaway shows the direct-mounted oil tank for the dry-sump
lubrication system.
rpm range (see chart).
The complexities of the intake variables are one element
comprising some 41,000 adjustable calibration values for the
LT6, which " starts to 'tune' effectively at 3,000 rpm and
above, " explained chief engineer Lee. The engine's power and
torque chart bears out his assertion, showing a distinct rise
and leveling to its torque peak between 3000-4000 rpm. Lee
summarized by calling it " an incredible amount of power for
this displacement. "
The LT6's valvetrain, lubrication and thermal-management
circuits are fully optimized subsystems designed to handle
the punishment of racetrack abuse and deliver day-to-day
robustness uncommon to many high-strung performance engines.
Most surprising about the valvetrain is its use of solid
(i.e. mechanical) valve lifters chosen to reduce moving mass
and assure valve performance at high rpm. One of a wide selection
of specifically sized steel lash caps is robotically fitted
for each valve after automated measurement of 32 different
tolerance areas.
Phil Baranek, design release engineer, assures that the
fixed arrangement is good for the life of the engine. That
guarantee may be supported by the unique actuation arrangement
of a diamond-like carbon coating for the rollerfinger
followers and an integrated oil jet for each finger follower
to assure constant and consistent lubrication at this
vital interface.
Variable valve timing of course is part of the equation. The
The LT6's signature
feature: a " flat-plane "
crankshaft that locates
all four throws 180
degrees apart in a
single plane.
8 April 2022
intake valves have 55 degrees of crankshaft authority while
the exhaust valves are variable over 27 degree of crankshaft
authority. The valve timing scheme plays a significant role in
the LT6's emissions profile and surely enhances overall efficiency.
GM did not detail fuel economy figures or confirm if
the engine will be labeled a gas guzzler.
Bill Visnic
AUTOMOTIVE ENGINEERING
BOTH IMAGES: GM
https://www.sae.org/news/2022/03/gm-details-new-flat-plane-corvette-lt6-v8
Automotive Engineering - April 2022

Table of Contents for the Digital Edition of Automotive Engineering - April 2022
