Rotary Engine Install: Part 2, Page 4
12/26/99
The engine swap is a resounding success with a few unforeseen
bennies along the way. Setup on 30x9.50MTs with a GRS1
tcase, it flat HAULS. I don't like to roach on the
drivetrain, so I haven't done any 0-60 times, but 4th gear
passing is effortless, and it'll bury the 95 mph speedo
easily (gets pretty scary up there). It is returning about
18-20 mpg, where my 1600 gave 23-25, BUT... rotaries like
the lowest octane crap you can find, versus premium, so overall
gas COST is a wash as far as I'm concerned.
One thing I can't get over is how dang QUIET the beast is
now. The motor just humms in the background, versus all the
thrashing and clattering of the old motor. Normal
conversation at 60 with the top up is now possible, and with
the top down, you can't even hear the motor past 30 mph or
so. My stock 91 Sammi is a noisy tin can compared to Mazuki
(now on 32x11.50 SX Swampers ;')
Due to the rotary's excessively heavy flywheel, and flat
torque curve (it makes more torque at 2000rpm than a 1600
does at its peak!), it's a joy to drive off-road in the
rocks. With the motor idling at 800rpm, I can let the clutch
out in 3rd low without stalling the motor. The torque is
there, RIGHT NOW. Plus, the throttle now has a nice, easy,
progressive take off versus the herky-jerky old Weber.
Speaking of carbs, this is THE off-road carb to have.
Uphill, downhill, sideways, it just doesn't matter, it won't
stall out. It's a really *cute* little 320cfm four-barrel
Nikki carb, with vacuum secondaries and dual float bowls.
It is completely mechanical, and self contained, and actually
can be "tuned" to match engine mods. I still need to lower
the floats a little to get rid of some stammering when
severely off-camber to the driver's side, but other than
that, it works great.
Here are a few lessons I've learned (learnt?) along the way:
TRANSFER SHAFT
The single u-joint shaft worked OK, but produced some minor
vibes that inscreased in magnitude as the speed went above
50mph. This system has no "give" in it, either, so if you
bend a tcase arm or tear a rubber tcase mount you run the
risk of damaging the tranny, tcase, or both.
I've since switched to a trick semi-double-cardon-joint
transfer shaft that Tom Wood made up for me using a Mazda
truck slip yoke, 2 Dana 60 flanges, 1 large Suzuki flange and
two Dana 60 u-joints. It is 2-3/4" logner than the single
joint shaft, so I had to move the tcase rearward 2-1/4" to
accomodate it, by building my own beefy tcase arms (not easy).
In the interim, I had gone to a Missing-Link type suspension
using CJ (longer) springs in the back, so mods to the rear
driveshaft were unnecessary, but I did require a 2-1/4"
spacer for the front driveshaft, which Tom also made for me.
This system has proven itself to work. I regularly run
60-70mph cruising speed, and the vibes are gone, plus I
fragged one of my tcase arms drag racing in the sand, and no
other damage resulted from it letting go.
COOLING
The radiator I had made works beautifully, provided it
doesn't get clogged with mud (duh). It seems to have plenty
of capacity in 90 degree heat on the trail all day.
I probably went overboard here, but a double-row with "coarser"
finning would probably do the job just fine and not be quite
so prone to plugging with mud.
The 10" pusher cooling fan and aftermarket "probe" type
adjustable thermoswitch didn't work worth a s**t. The fan
was a AC condenser fan off a Nissan Pulsar, probably in the
600CFM range and LOUD. The thermoswitch shorted out the
first time it got dunked in water. I've since gone to a much
quieter aftermarket 14" 1200CFM fan and wired a VW-type
thermoswitch thru a realy to kick it on,
which works splendidly.
One note about rotary cooling: Although the engine is a
little more resistant to damage from overheating than an
aluminum-head piston engine, they need lots of cooling. A
rotary guru told me they generate about the same cooling load
as a piston engine of twice the horsepower (212 in this case).
And the old trick of removing a stuck thermostat
will cause it to overheat, so I carry a spare.
The larger cooling fan required removal of the hood latch, so
I've gone to racer-type (aluminum) hood pins, which aren't as
obnoxious as I'd originally envisioned. Which bringe me to:
RELIABILITY
Due to its total of five moving parts (two rotors, crank,
disty shaft, and oil pump), there just ain't much to go wrong
with 'em. In a year's hard wheeling I've had the hood raised
exactly ONCE. That was due to the really old plug boots
taking on water in a bottomless mud hole in Attica. That's IT.
Anyone who tells you rotaries are unreliable pieces of crap
is full of exactly that, period. The 1980 and later RX-7
rotaries have one of the best engine reliability records ever
recorded. Not to mention during the early 80's Mazda RX-7s
didn't just win a few endurance races, they DOMINATED the
class for six straight years!!!
Even a hapazardly maintained rotary is a 200,000 mile motor,
and "maintenace" on a rotary literally and ENTIRELY consists
of oil/filter changes, cooling system service, plugs, air and
fuel filters, cap and rotor ....that's IT! Try changing JUST
those items in a piston engine, abuse it to 7500rpm regularly,
and see if it even wheezes out 100,000 miles
before blowing apart.
Consider...
No timing belts to break, no tensioners to seize, no timing
chain guides to self-destruct and hole the block (like in the
"oh-so-reliable" Toyota 4-cylinder motors!), no valves to
burn/crack/drop, no guides to wear out/fall out, no valve
seals to harden and crack, no valve springs to break/weaken,
no lifters to collapse, no valves to adjust, no pushrods to
collapse, no cam journals to wear out, no timing pulleys to
come loose, no little %&#@%! phillips head screws to come
loose in the head and take out a valve, no pistons to hole,
no rings to break, no rods to hole the block, no valve cover
gaskets to leak incessantly, and on and on and on...
I'm toying with the idea to produce a basic kit, which would
include the following:
- front motor and rear tranny mounts
- radiator and mounts
- tcase mounting arms
- clutch pedal (modified)
- very comprehensive set of instructions
This kit would take car of all the welding/fabricating
required, and I would include a list of all additional parts
required, as well as sources for them. Even so, this is not
as easy as bolting in a 1600 into your Samurai, and will
probably take the average "shade-tree" mechanic several days
to complete.
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