PLANS | SPECIFICATIONS
| GREENSKY HOME
Mar. 04, 2003
Making The Switch
Rotax 582 UL vs
As we celebrate our Zippy Sport's
twentieth birthday, perhaps a new engine installation is in order. We anxiously
anticipate an HKS-700E powerplant as the ultimate package for our Zippy
Sport. Though the last 582, installed a couple years ago provides
tremendous performance, the negatives associated with a 2-stroke
use must be considered.
Four stroke use on the Zippy is nothing new.
The design prototype was built around a 22 HP Onan, as was used on early
Quickies. The Onan was insufficient and at that time a jump was made to
Cuyuna flavored 2 strokes.
By the time we bought into the Zippy in 1986
there was a full VW installation on the aircraft. After removing the VW,
the Zippy was back to 2 stroke power till 1991 when we installed the little
known, and much misunderstood Rotax 508, (yes, 508) 2 cylinder 43 HP 4-stroke.
The best memory of the 508 was it's comparatively minuscule appetite for
fuel. The 508 was eventually removed from the market, (that's a whole story
alone) and also from our plane. Since then, we have gone through a 503,
532, and a couple 582's. ...A lot of engines, but remember, we are in the
engine biz, and our planes' primary mission has always been that of a
To begin, a decision as to exhaust type, gear ratio, and propeller must
be made. Then motor mount design and construction. We have used the original
Cuyuna motor mount which Ed Fisher build for this airplane on all but one
of the engine conversions performed on this aircraft. It is less than optimal,
so at this time, even though the present mount might be adaptable to HKS,
we, most likely will start from scratch. If you have comments or suggestions,
please call or email.
If we can utilize the empty space behind the firewall and ahead of
the Rudder Pedals, the HKS Exhaust System can be internalized.
Click on Images below to enlarge.
Before cutting the fabric
It's apparent that everything will not fit forward of
the firewall. We also have to deal with Oil Tank, Oil Cooler, and plumbing
Early stages of visualizing potential exhaust placement. Placing the
can behind the firewall would necessitate building a secondary firewall
within the cabin. ...Not something we really wanted to do.
With the Type III headers, (above right) Cowling construction would
be slightly more complicated
Here are a few updates for those following this conversion. In spite
of an original plan to construct an entirely new motor mount, a decision
was made to save time and adapt our original mount for use with the HKS.
Although that has allowed us to source a couple items (Bent Tubing, Straights,
Flanges, and more to come) which potentially may help others with their
installation, I do not believe there was much of a time savings.
Here are some basic "Commandments" on HKS installation
These commandments more or less dictate oil cooler and oil tank locations
on any installation. On our Zippy Sport, the decision to retain our old
motor mount reduces the available locations that are suitable for Oil Tank
and Oil Cooler.
The oil level in the tank (about 2 1/2 inches from the top) must not be
above the oil inlet/outlets of the engine. Otherwise, upon shut down and
storage, oil will syphon from the tank back to the engine.
The oil cooler should be below the oil tank for similar reason.
A third consideration, then, is the exhaust. It was a strong desire,
to use a stock, factory, exhaust system, for best sound, and performance.
(after all, a signature product of HKS is their superbly created High Performance
after market exhaust systems) The type 1, would almost work. That
is the one where the headers come together at the center, below the gearbox
and route back below the engine where they join the collector, and then
meet the transversely mounted muffler via a large ball joint arrangement.
Unfortunately, that would place the muffler directly in front of the only
good location for our oil cooler. Also, the type 1 pipes would not quite
fit under the engine and clear our motor mount.
Rather than modifying the stock pipes, we built a custom, 4 piece header
that joins the factory collector. We have loaded about 20 or so photos
to a dedicated HKS installation picture page. Click .HERE
...Also, a propeller testing/selection page has been created. Click HERE
Do you have time to view some more Cowl-Off Zippy Images?
July 2001, a BD-5 builder spent the day with us using our Zippy Sport as
an engine test bed
How about some pilot's eye images?
are a few shots from a Pilot's point of view taken in NE Ohio December