Project FI Martin
By Stefan Jung and Mike Simon
After partaking in the oppulent breakfast buffet that the Steigenberger Hotel
(our home away from home) puts out, we get into the car and take A661 to A5
South to A66 West, which connects the cities of Frankfurt and Wiesbaden. You
have guessed it by now: We are in Germany. And on this Saturday in early
October, we are out for a specific CBX experience!
After
we pass the city of Wiesbaden, we leave A66 a few kilometers before it turns
into a two-lane highway, and take the exit for Bundesstrasse B260 or German
Federal Highway 260, commonly dubbed “Bäderstrasse”. This loosely translates
into “Spa Road” as it connects several towns along the way, all known for their
facilities which provide cures for specific ailments through therapies
incorporating waters from local springs that contain certain minerals.
We follow the directions that were given to us and soon reach another road that
goes off to the left and takes us to an in-the-middle-of-nowhere traffic circle
with a strange looking modern monument in the grassy middle. The monument honors
a famous son of the town off to the right, Holzhausen. The man is Nikolaus Otto,
the inventor of the internal combustion engine, and the monument is supposed to
represent elements of a 4-cylinder gasoline engine.
There must indeed be something in the water up there, because we are on our way
to the home of another genius in that field who has his residence in the nearby
town of Nastätten: Stefan Jung. Known in the “CBX–World” – pun intended – for
his awesome alternator modfications, he also got most everybodies attention by
putting together a working (!) fuel injected CBX motor. And that in a “Martin”
frame with a ton of other chassis and body modifications to boost.
Typical
male ego makes me ignore his offer to call him as we enter town so he can pick
us up at a meeting point to guide us to his home, and I try to find him on my
own. After several laps through the narrow streets of downtown and finally
stopping to ask for directions, we arrive at the seemingly correct address.
Nothing, at first, indicates that this place is home to die-hard CBX afficionado
and I am still unsure until I see the rather unpretentious CBX-sticker on the
rear window of a little Renault car parked in the driveway.
Rather than ringing the doorbell, I call him now on the cell-phone and in a
second he comes walking out from the back of the garage building and welcomes us
into the house.We sit down for a cup of coffee (very nice – as it is still in the morning!) and
start chatting a little. Expecting a man with several degrees and maybe a PhD in
engineering and/or other sciences, I am totally flattened when I find out Stefan
is a medical equipment operating, service and maintenance technician and has a
welding certificate from a previous career! Talking about hands-on, passionate
motorcycle re-engineering. We sit for quite a while and I could have listened
for hours to him talking CBX and motorcycles in general, but we came for a
purpose and that was his fuel injection bike. So finally, we move to the garage
to take a look at it. Again, I am in for a surprise. The garage, while only one
car wide, is at least two cars long and shock full of CBXes and parts. The fuel
injected Martin CBX that most of you have seen on pictures from the Euro-meeting
in Switzerland or in other posts by Stefan himself sits right in front and the
owner rolls her out into the daylight, so we can walk around and look at all the
details.
Now, let’s listen how Stefan Jung himself describes the evolvement of his
project:
“It really all started when I heard that Rainer Hoppe from Wuppertal had built a
Moto Martin CBX with fuel injection. Unfortunately, the fuel injection system,
which incorporated a controller originally from Australia, never worked quite
right. The motorcycle was spending more time on the dynamometer than on the
street. As far as I know, the CBX has meanwhile being sold and has been
converted back to carburettors.
Around
the same time, I had been offered a “Martin”. This specific unit didn’t quite
look as one would expect a “Martin” to look - it was done as a chopper, but I
was not going to be too picky…
I soon found out, that not only the looks were odd, but the bike also had
significant technical problems. During an engine overhaul, the camshaft bearing
caps had been installed wrong with the result that the whole engine ended up
full of aluminum shavings and was junk except for the transmission.
On a positive note, the chopper builders had not touched the frame itself and it
was intact, so all the chopper parts came off. After the engine was removed, all
that left was basically the frame and the swingarm. First trials showed that
this could indeed be the base for a sportier motorcycle.
A Suzuki upside-down fork and a CBR900 fuel tank looked promising. Also, a
“Heru” tailpiece styled after the NSR500 fit nice. This way, the rolling chassis
was parked in the corner for the time being.
I could not shake the thought to adapt a fuel injection system to a CBX. It had
to be possible with todays technology and tools. Easier said than done! At
first, I needed to get information about what was available on the market. I
soon decided, that a company abroad would not be a good choice, as sooner or
later the support would lack. Especially, since a privateer with too many
questions would cause too much work. So I discovered “Trijekt”! A two-person
company which procduces fuel injection controllers that are universally
programmable with a mapped characteristic. Everything one would need. Only the
hardware, like throttle bodies, sensors and injection nozzles had to be obtained
elsewhere. I picked Triumph throttle bodies. First impression was good, however,
after the adapters had been welded on to facilitate installation to the cylinder
head, the throttle bodies were warped . The bodies were deformed so bad that the
throttle flaps would not properly close anymore. Too bad. Back to the drawing
board…
Finally,
I discovered the units from the Kawasaki GPZ1100 DFI. The throttle bodies even
fit directly to theCBX intake manifolds, however, out of two 4-piece units, one
6-piece unit had to be manufactured. Very time consuming until everything worked
nice and smooth without any lash and play. I was also able to make theTriumph
throttle sensor fit.
To find all the other components necessary for a throttle body injection did not
pose a major problem. I was able to use the fuel pump and the pressure regulator
from other bike models like Honda CX500 TC and Kawasaki GPZ1100 DFI. As air
intake temperature is an important parameter required for fuel metering, a
sensor had to be adapted to the air filter. Further, the controller requires the
exact engine rpm and the crank position to determine the appropiate fuel amount
and the correct ignition point. To provide this, a gear was installed into the
housing of the ignition pulser. This gear has a notch which sends the data to
the controller via an inductive sensor.
Getting the unit to run, however, turned out to be more difficult than I
thought. After putting everything together, I was going for the first try.
Without any data available - not even talking about a map. Only armed with the
laptop connected to the controller and ready to manipulate the ignition time
with the “+” and “-“ keys, I hit the starter. The engine fired right up only to
to die immediately again after blowing a couple of foot-long flames out of the
exhausts. No restart possible. The spark plugs were totally wet and did not
provide a spark anymore. A new set was installed for another try. Same thing
happens. A reduction in injection time does not yield any better results either.
Great! Almost 2 years of work and then scrapping twelve spark plugs within a few
minutes. Something is substantially wrong. As I can’t find a solution, I call
the gentlemen from Trijekt, who, as always when I am at a dead end, provide fast
and competent help:
“Wrong injection nozzles” is the verdict! It proved to be the right one!
I had only used the fuel mass as a criterion, without considering injection
angle or degree of vaporisation. That kind of data is unobtanium anyway and will
not be revealed by the vehicle manufacturers. I had picked nozzles from a
BMW325i. Unfortunately, these things do hardly vaporize but rather produce a
thin beam of fuel. Which is fine in the car, as it will hit the head of the
intake valve and is being vaporized there. In a CBX, the fuel just runs into the
cylinder. The motor virtually drowns. Through some search, the choice fell on
the 4-hole nozzles from the CBR600. These units vaporize the fuel in a very
compact envelope.
After I obtained 6 units at a used parts dealer – Honda wanted 180 Euro($235.-)
per piece – the second attempt was gioing to be much more successful.
The engine started to run stable immediately. Changes in the injection timing
were recognizable instantly in the changes of the air fuel ratio and lambda value. Up
to 3000 rpm und no load, the characteristic could be mapped easily.
So, the big day of the dyno run came closer. This, of course, is an absolute
must for proper tuning. Thanks to a wide-band lambda sensor, the complete map was
accomplished within one hour, even including several small breaks.
The lambda sensor was installed right behind the collector and provided a very short
reaction time. Storage of the complete map characteristic including additional
fine-tuning on the road took only 2-3 hours. The big advantage of the Trijekt
controller is, that the connection of a PC allows direct access to all
parameters like injection and ignition timing without restriction. In addition,
the unit has a “learning” function which provides automatic correction of map
values according to pre-selected ? values. In other words: The more you ride,
the better it gets. The plug for the PC is conventiently accesible under the
seat.
Here
is a image of the map. Looks pretty simple, however, especially in the mid-rpm
range accuracy is crucial.
So far I have spooled approx 3,000 kilometers without a problem. Including a
trip to theEuro CBX Meeeting in Switzerland, right, Monika?
Well, I am sure you will all join me in giving Stefan a hand for this
extraordinary effort. A truly remarkable accomplishment. I have seen and heard
the bike running myself and I had a really hard time turning down his offer to
take it for a short spin. Besides the fuel injection set-up the bike features
many other unique details which make this a true masterpiece:
Motogadget combination instrument. Electronic speedo and tach. Tach gets signal
directly from engine controller, speedo pick-up is incorporated into
countershaft sprocket.