Randakk's
Supercharger Prototype for Honda GL1000
As
I reported recently in the December, 2007 eNewsletter, the
Supercharger Kit is on the road and performing very well.
For
a variety of business reasons, I have decided not to proceed
to production.
I'm
certainly not the first to put a supercharger on an early
Wing. Other parties have done so dating back to the late '70s.
My
goal on this project was to build a better blown GL1000 than
any I've seen on the road. Previous efforts that I've evaluated
have limitations that I hoped to overcome. I believe I have
been very successful from an engineering point of view.
Special
thanks to my good friend Lars Nielsen, aka "Octane" of Denmark
for his invaluable assistance on this project. Lars is an
internationally famous GL1000 enthusiast and prominent technical
contributor to: Naked
GoldWings Forum. Here's a video of Lars on his own
Supercharged
GL1000. Be sure to turn your speakers up! The
video really captures the intoxicating whine of a blower.
Also the fantastic rush to redline!
My set-up works very well. I'm still making small "tweaks,"
but I'm very pleased with the performance and operation. It
has actually exceeded my expectations so far. I'm looking
forward to dyno tests to validate the substantial increase
in performance.
Now
for the bad news. As a parallel effort, I've worked very hard
on the business aspects of this project - struggling to get
the manufacturing costs down to an affordable level so that
I could sell this set-up as a comprehensive kit. Here's the
result of that effort. If I were to commit to a minimum production
run of 10 complete kits, the selling price (with a very thin
margin) would be at least $5,700 per kit. Sadly, I
realized that there is no market for this product at that
price, so I decided not to proceed to production. The price
is actually not that far out of line with what CC Products
was charging for their kit back in the '70s (when you factor
in inflation), but it's still an outrageous expenditure for
an antique motorcycle.
Even
at such a price, I would not recover the R&D costs incurred
so far. Worse, there would be a considerable risk of installation
mistakes, cancelled orders and various other problems on the
buyers' end, plus some level of warranty exposure on a complex
install that I could not fully mitigate. Actually, only one
failed installation out of 10 would put me considerably "upside
down" on this project. So, with regrets - I will not be putting
this into production.
I
will enjoy my creation and look forward to showing it at the
upcoming Rally.
I am very disappointed that I could not get the price down
to "merely expensive." Thanks to everyone who provided assistance
and moral support for this effort!
Randakk's
Supercharger Prototype
"Stack"
height of entire unit easily fits under stock topshelter bodywork...very
stealthy!
Components:
-
Supercharger
- Intake
manifold
- Carburetor
- Air
Filter
- Carburetor
spacer / adapter
- Serpentine
belt drive system
- Special
electric fuel pump conversion
- Electric
radiator cooling fan
- Front
/ rear bracket support systems
- Auxiliary
oil cooler
After
some experimentation, I settled on a slightly overdriven drive
ratio selected to achieve a conservative 4.5 psi boost at 5,000
rpms. This yielded approximately 7.5 psi max at redline. This
fairly conservative setup allows the bike to run on pump gas without
signifcant mofification to ignition timing and no danger of detonation
or excess heat. Premium fuel is required (mandatory). I'm sure
I've left considerable horsepower on the table...striking a reasonable
balance between performance and reliability.
Pulleys
and belts left over from drive ratio experimentation
Target
= 25% horsepower increase at rear wheel (with healthy torque
increase). Once I'm satisfied with all the fine calibrations,
I will dyno the setup to verify the increase. So far, "seat
of pants" subjective assessment of increase is right on
target. The rush to redline is ferocious! There
is no rev limiter and the rider must exercise great care to
avoid over-revving the engine. In the lower gears, it will blow
right past redline in an instant.
Boost
Gauge - Very Entertaining!
This
blower has somewhat lower displacement than the blowers that
have typically been configured for early GoldWings in the past.
This design has advantages in terms of:
- Positive
displacement, twin rotor "Roots type" supercharger
is rated for 12,500 rpms
- Made
from high quality materials - 4340 gears and shafts
- Viton
rotor seals
- Extruded
aluminum center section
-
Each straight-cut rotor has 3 lobes.
-
All parts are precision machined to aircraft specs
- Serpentine
belt system...more durable and tolerant on belt alignment
- Custom-fabricated
idler arm unique to this application (for belt tensioning)
- Self-lubricated
- Custom-length
front drive module engineered specifically for this application
- Robust,
heavily triangulated front blower support arrangement - more
than restores the frame rigidity lost by elimination of the
OEM shroud / torque rods
- Integrated
throttle cable attachment points
- Twin
Heim joint rear blower supports
Randakk's
Manifold is CNC-fabricated from solid billet aluminum
Carburetion:
-
Weber carb with proprietary mods
- Manual
choke retained for easy starts
- Push
/ Pull throttle cables retained for safety
Carb
Spacer / Adapter:
- Exquisitely
machined and cc'd
adapter / spacer for max balanced flow
- Carefully
executed transitions from round carb bores to rectangular oval
blower inlets
- Adapter
/ spacer has o-ring groove in mounting surface for positive
seal
- Phenolic
heat isolator
Fuel
Pump:
- Special
version of Randakk's electric fuel pump conversion. Standard
model described here
Heat
Managment:
- Ignition
timing mods
- High
quality moisture and dust proof electric radiator fan by SPAL
with sealed motor sourced from Italy.
- Full
coverage, high flow, low draw "pusher" fan mounts
in front of radiator. Rated at 650 cfm. Moves considerably more
air than the feeble OEM unit.
- Front
fender modification required for clearance. I looked at many
options, but this was the only practical way to get serious
cooling capability.
- Running
special oil filter adapter (to permit oil cooler) created for
me by Bob Hagerman available here.
Cooler is heavily-modified unit from '82 Honda CB900F. Also
running a Think Automotive competition oil cooler
thermostat (Mocal model #OT/2F-8JIC) connected via Aeroquip
hoses with 8AN fittings. Standard
oil filter conversion kit described here.
Blower
Drive:
- Serpentine
drive eliminates belt "walk-off" that plagues other
designs
- Robust
no-wobble, no run-out drive pulley mount.
- Features
machined bushing / flange with precision boss to mate with OEM
timing gear
- Integrated
outer timing belt guard replacement!
Installation:
The
installation was straightforward, but time consuming. The picture
above shows test fitting of various prototype components and is
a good indication of how "deep" I had to go.
Consider
these details:
- Sound
engine with excellent compression required
- Minor
frame surgery required
- Small
modifications to the top shelter substructure
- Small
trimming of the front fuel tank locating tab
- Front
fender modification required for clearance
- Existing
throttle cables and choke cable must be shortened and new terminations
installed
- A
second midpoint adjuster added to the "push" throttle
cable
- OEM
junction plug removed from OEM cooling fan and transferred to
the new fan's wires
- Holes
cut in timing belt covers for the crankshaft drive pulley
- Slightly
modified ignition advance specs
Other
necessary modifications:
- Electronic
ignition (like Dyna/S)
- Upgraded
coils and wires
- Heavy
duty clutch upgrade
- Braking,
suspension and tire upgrades to handle the new level of performance.
Like the mods detailed here:
- "Later"
driveshaft recommended for '75 GL1000s
For
more information on the use of material from this website, click
here.
Please
read:
Disclaimers
