Gibson/Miller
Mark II: The Best Blower in the Business
Born of cooperative brain
storming by aerodynamicist, Tim Gibson, and BME President, Bill Miller, the
Gibson/Miller Supercharger takes an evolutionary rather than a revolutionary
approach to improving performance of superchargers used on large
displacement V8 racing engines.
Tim Gibson, a UCLA graduate
aerodynamics engineer was formerly with Hughes Aerospace, then spent five
years as the Aerodynamicist for John Force Racing and, also, drove the BME
Dragster back in the late-90s. Bill Miller is President of Bill Miller
Engineering, Ltd., the manufacturer of the Gibson/Miller Supercharger, owns
the BME/Okuma/Red Line Oil Top Fuel Dragster and is the only independent in
Top Fuel racing who regularly qualifies at NHRA National Events.
The Gibson/Miller Mark II Supercharger is
catching on. In 2010, John Stewart, Crew Chief for the Lucas Oil Top Fuel
car driven by Shawn Langdon, switched to the Gibson/Miller Mk II . The
results were immediate. The lighter supercharger combined with its greater
air flow improved performance dramatically. Other, more recent converts to
the G/M Mk II are Top Fuel racer, Allen Hartley, as well as Funny Car
veteran Jim Dunn. Image: AutoImagery.
In the early '90s,
racers in the nitro classes tried to raise the blower technology
bar several notches, but the National Hot Rod Association wasn't
buying. With its risk management minions whispering in its ears,
NHRA outlawed both screw-type and high-helix, Roots-type
superchargers putting their potential for significant
performance increases out of reach.
Observing NHRA's
rule-making, but seeing a clear need for a better blower, Gibson
and Miller took a different route to that end. They retained the
traditional, General Motors, 71-series, Roots supercharger
architecture but refined its layout, materials and manufacturing
processes. Consistency is the mother's milk of drag racing, so
the the goal of Gibson's and Miller's efforts was a supercharger
which performs more consistently over a longer time.
Gibson's work
focused on improvements which allowed more air flow through the
blower. This involved changes to the blower case as well as to
the rotors. Of course, more air means you can use more fuel and
burning more fuel makes more power.
Supercharger Dyno Test
Click the arrow to watch a test of a
Gibson/Miller Mark II Supercharger. In this
video, hosted by Bill Miller, you'll learn more
about the special engine dynamometer BME uses to
test superchargers.
A Gibson/Miller Supercharger case is
machined from a large, magnesium alloy casting. The
task takes about a day in the BME Supercharger
Department's Okuma, five-axis, CNC, Machining
Center. Image: BME, Ltd.
One of the headaches
in blown-fuel drag racing can be high wear rates exhibited by
supercharger parts, particularly the rotors' Nylatron apex seal
strips. Most blowers don't control rotor and case flexing very
well and the resulting fluctuations in rotor-to-case clearance
cause rapid and inconsistent seal wear.
"Restripping the
blower" is a frequent, repetitive, labor-intensive, maintenance
task. Because the rotor seals were so limited in durability,
getting consistent supercharger performance is a lot of work and
quite costly, but, even after all the hassle and money, can
still be a crap-shoot. The front line teams in Top Fuel and
Funny Car racing have dozens of blowers they frequently change
and an employee who's only job is to restrip them. The little
guys either constantly work on their blowers or live with the
inconsistency.
As a nitro class
independent running on a limited budget, Bill Miller knew well this
"catch-22" of supercharger consistency. Because he couldn?t afford the
dozens of blowers owned by a big team and his smaller crew was hard-pressed
to do constant rotor seal work; he decided to investigate what caused
superchargers to eat-up seal strips quicker than politicians burn-through
your tax money.
Each rotor lobe has an
apex seal (1) made of Nylatron and two side seals
(2) made of carbon-impregnated Teflon. These strips
seal off the cavities formed by the rotor lobe and
the blower case, preventing the air trapped inside
the cavities from leaking away and reducing the
supercharger's efficiency. Before the Gibson/Miller
Supercharger was developed, in a blown-fuel or
blown-alcohol drag racing duty cycle, the durability
of these strips was poor and their reliability was
inconsistent. As consistency is the mother's milk of
drag racing, apex strip maintenance was a chronic
problem. Image: BME, Ltd.
A standard-helix
rotor set for a 14-71 Gibson/Miller Mark II. They
are designed to be more rigid than other supercharger rotors. They
accomplish that goal through more robust structure, improved materials and
more precise manufacturing.
Image: BME, Ltd.
This investigation took Gibson
and Miller to the heart of a supercharger: its rotors. They found rotor
seals to be unreliable in a dynamic sense because their rotors twist and
flex so much. That unwanted movement caused the rotor clearance to fluctuate
wildly. When it was too tight, the seals were chewed-up very quickly. When
it got too loose, the blower's efficiency tanked due to leakage.
Gibson and Miller designed rotor
improvements aimed at significantly reducing twist and flex and increasing
the system's tolerance for whatever flexing couldn't be eliminated.
Additionally, the blower case and end frames were stiffened, compared to
those of other superchargers. Lastly, aerospace-grade materials were used
along with the precise manufacturing process controls which have made BME an
industry quality benchmark.
The
result of this design and development project was the 1996 introduction of
the Gibson-Miller Supercharger, the most efficient, reliable and durable
Roots blower available for any large V8, racing application. The
Gibson/Miller blower was quickly embraced by top competitors in nitro class
drag racing for its outstanding quality, increased air flow and most of all
it's consistency in performance. It remained in production for several
years.
Thirteen years ago, the
first-design Gibson/Miller Supercharger was a
landmark product. It was a case where blown-fuel
drag racers got improved performance, consistency
and reduced maintenance costs. Image: BME, Ltd.
Besting the Better Blower: The
Mark II
By 2004, the performances of the
BME/Okuma/Red Line Oil Top Fuel dragster and those of the BME Team's
competitors made it obvious that other supercharger manufacturers' products
would soon reach parity in performance with the Gibson/Miller. Additionally,
engine development since the late-'90s in nitro class drag racing had
reached the point where even the Gibson/Miller blower was nearing its
performance limit.
During 2005, Tim Gibson and Bill
Miller began developing a follow-on to their blower. After an extensive
development and test program which took a little over three years, the
improved, Gibson/Miller Mark II Supercharger debuted in January 2009. It
incorporated a number of changes based on Bill Miller's eight years racing
the first version of the blower on the BME Dragster and an exhaustive
dynamometer testing program, part of which you can watch in a video near the
end of this article.
BME President, Bill
Miller, and Troy Buff, Driver of the BME/Okuma/Red
Line Oil Top Fuel Dragster, discuss a prototype
Gibson/Miller Mark II at the Winternationals in
Pomona, California in February of 2008. Image: BME,
Ltd.
Tim Gibson (the airflow engineer,
left) and Bill Miller (the development,
manufacturing and testing engineer, right) have
partnered to produce the best supercharger for
big-bore V8s in drag racing and other motorsports.
Image: BME, Ltd.
The majority of the Mark II
enhancements further improved supercharger durability and consistency.
The first big improvement was a switch from all-magnesium construction
to a more rigid combination of a magnesium case and aluminum end frames.
Gibson and Miller's analysis and testing showed that even though
aluminum's approximate 30% increase in stiffness over "mag" comes with a
modest weight penalty, the result would be a net gain because the
additional rigidity would enable even more consistent sealing and
improved seal life and the weight increase contributed only a modest
amount to the total package weight.
Additional airflow
development done by Tim Gibson resulted in changes to the inlet
side of the blower case and the shape of the rotors themselves
to improve flow through the supercharger at high rotor speeds.
According to numbers gained through testing on BME's "Blower
Dyno", the Mark II is capable of a 10-12% improvement in airflow
over the first Gibson/Miller blower which already had noticeably
better airflow than its competitors. At a rotor speed of 12500
rpm, a Mark II flows an astonishing 3750 cubic feet of air per
minute.
As for improved durability of
rotor seals, the Mark II scores well there, too. BME's
dynamometer testing of the new blower shows that in 10 dyno runs
with a blown-alcohol motor there is only a 1% decrease in air
flow. Race track testing with blown-fuel engines, a more severe
test of the seals, demonstrates seal life of 6-8 passes. That
kind of durability is unheard of with other blowers used on drag
racing engines because they still require seal replacement after
every run
The Mark II continues
Gibson/Miller's track record of making the most efficient,
reliable and durable supercharger available to nitro class drag
racers.
Troy Buff, who's
duties on the BME Crew also include supercharger
inspection and maintenance, has a lot less to do
than the blower specialists on teams not using the
Gibson/Miller. Typically, Buff inspects the inside
and outside of the blower, then reinstalls it.
Image: BME, Ltd.
Gibson/Miller Supercharger
Talking Points
In a Top Fuel
application, such as this 500-cubic inch Brad
Anderson Hemi, the Gibson/Miller Mark II holds
airflow consistency within 1% for typically eight
but as many as 10 runs down the drag strip. Image:
BME, Ltd.
Performance
The Gibson/Miller
Mark II delivers the highest airflow, the greatest boost, the
best efficiency and the longest durability of any Roots-type
supercharger used in a racing application.
Consistency
Saying that a supercharger has
"high efficiency" is merely marketing flimflam if a blower can
only achieve those characteristics for one or two passes down
the drag strip. The Gibson/Miller is designed to perform run
after run after run. In a Top Fuel duty cycle, Mark IIs remain
consistent to about 1% in airflow for 6-8 passes. In
blown-alcohol or blown-gasoline applications the durability can
be a dozen passes.
Design
The Gibson/Miller Supercharger
was designed using state-of-the-art, Computer-Aided Design and
Computer-Aided Manufacturing (CAD/CAM) systems. That allows BME
to make the most technically advanced supercharger available for
big V8s burning gas, alcohol or nitro.
Engineering and Manufacturing
The Gibson/Miller Mark II Supercharger case
is machined by BME's skilled workforce using an Okuma, MU-500VA-L,
five-axis, computer-numeric-controlled (CNC) machining center from a rough
casting of magnesium alloy. The blower's end frames are CNC-machined from
aerospace-quality, aluminum plates.
These CNC'ed components have more
consistent wall-thickness and higher yield-strength than the magnesium or
aluminum castings used by other supercharger makers. These parts provide
maximum stiffness with minimum weight. This rigidity helps maintain the
supercharger's precise clearances over a longer time and the result is more
consistent performance.
A Gibson/Miller Mark II's rotor shafts are
12 times more rigid than those used in other drag racing superchargers. This
increased stiffness better resists rotor deflection resulting from over
7,000 pounds of force exerted on them by the 60-psi manifold pressure in a
blown-fuel drag race engine.
Special, high-speed, low-friction front and
rear gear drives have zero backlash for very-accurate rotor timing. The
rotors are indexed to .001". Precision spur gears eliminate axial thrust and
case deflection produced by the helical gear systems on other supercharges.
Unlike other blowers, the gear cases are sealed, not only to keep the oil in
but, also, to keep blower pressure out, using a unique double-lip rotor
shaft seal. Keeping blower pressure out of the gear cases results in
improved response because, when the driver stands on the gas leaving the
starting line, manifold pressure increases more quickly and reaches a higher
level.
One "secret" of the
Gibson/Miller Mark II Supercharger is the precision with which
its parts are manufactured at BME's factory in Carson City,
Nevada. This sequence shows one of the Gibson/Miller's end
frames being machined in a five-axis CNC Machining Center
operated by BME Supercharger Production Manager, Russell
Findley. Images: BME, Ltd.
Each Mark II has two sets of gears like this which
allow the rotors to be indexed as close as .001".
The gear at the left (the driven gear) is a
two-piece assembly with a vernier adjustment system.
During manufacturing, indexing is adjusted, then
steel rivets are installed through the slots and
holes to lock the adjustment. Image: BME, Ltd.
ARP fasteners are used
exclusively during Gibson/Miller Supercharger assembly. The capscrews and
other hardware are specially designed to provide the correct elongation and
clamping force required by the magnesium case and the aluminum endplates.
Weight
With its magnesium cases and
aluminum endplates laid-out with CAD/CAM and the highly accurate CNC machine
work used in their manufacture, the Gibson/Miller Mark II is the lightest,
most durable, three-lobe-rotor, four-gear supercharger available. A complete
assembly weighs a little less than 86 pounds, 10 pounds less than other
superchargers used in blown-fuel applications.
A Gibson/Miller Mark II 14-71
Supercharger "locked-and-loaded" on BME's Blower Dyno and
dressed for use on an alcohol-burning, 500-cubic inch, drag
racing Hemi. The BME Blower Dyno was a key tool in the Mark II's
development and is used to validate the performance of each
Gibson/Miller Mark II just before it is delivered to a customer.
Image: BME Ltd.
Testing and Validation
The Gibson/Miller Mark II is the
only supercharger which has been tested and validated on a dynamometer using
a test engine capable of subjecting a supercharger to the loads and stress
it would sustain in drag race competition.
Bill Miller
Engineering operates the world's only engine dynamometer capable of putting
full load on racing engines generating up to 8000 horsepower. This engine
dyno was originally built by famed nitro class Crew Chief, Dale Armstrong,
when he worked for former NHRA Top Fuel and Funny Car Champion, Kenny
Bernstein during the 1980s and 90s. After Armstrong left King Racing in
1997, the dyno sat in Bernstein's shop until Bill Miller bought it in 2004.
Miller and the engineering staff at BME refurbished the power absorption
unit and it's 4:1 gear reduction system, added contemporary electronic
controls and a modern data acquisition system and built a facility to house
the equipment which includes a giant pair of mufflers to deaden the sound of
the test engine.
Each Gibson/Miller Mark II
Supercharger is performance-tested on the BME Blower
Dyno before it is shipped to a customer. Bill
Miller, at left, is personally involved in each
Supercharger test run as the dyno test engineer.
Image: BME, Ltd. Image: BME, Ltd.
Besides
making new Gibson/Miller Mark IIs, BME, also,
operates a rebuild and repair service for current
Supercharger customers. Here, Supercharger
Technician, Jack Pierson, prepares a set of rotors
for installation into a customer's blower. Image:
Bill Miller
The BME
Blower Dynamometer was built specifically for use
during development of the Gibson/Miller Mark II
Supercharger. Nowadays it's used for both continuous
improvement and to validate the performance of each
Supercharger before it is shipped. Image: BME, Ltd.
The engine used
to test the blowers is a Top Fuel engine modified with
higher compression ratio, a single magneto and a
blown-alcohol fuel pump. It burns straight methanol rather
than an 90% mix of nitromethane and methanol. The reason for
straight alcohol rather than nitro is the cost, complexity
and engine durability problems typical of supercharged,
nitromethane burning race engines. Running the test engine
on alcohol makes the blower testing more consistent and the
resulting data more accurate. With a Mark II installed, this
engine produces 2020-hp@7100-rpm and 1580-lbs/ft torque at
6500 rpm.
During 2007 and
2008, the Gibson/Miller development staff spent countless
hours testing, developing then retesting the Supercharger on
this dyno. The result is the Mark II's improved performance,
reliability and durability.
Applications
Originally developed for supercharged, nitromethane-burning drag race
engines, the Gibson/Miller Supercharger has excellent performance potential
for offshore powerboats and other endurance racing applications. It also is
good for monster trucks, Bonneville, tractor pulling, dry lakes racing or
any application requiring a Roots-type blower capable of high-performance,
excellent consistency, rock-solid reliability and long-term durability. In
addition to the original, 14-71 size, the Gibson/Miller Mark II is available
in 12-71, 10-71, 8-71 and 6-71 sizes all with either standard or high-helix
rotor sets.
Service
The Gibson/Miller Supercharger is
manufactured by Bill Miller Engineering, the leader in forged aluminum
connecting rod and forged aluminum piston technology. BME has built its
reputation on service, integrity, and engineering excellence. BME not only
sells but, also, services the Gibson/Miller Supercharger. BME prides itself
on quick turnaround of blowers sent in for maintenance or repairs.
