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I started this project alone
but along the way i have recieved the help and support of many people,
mostly my friend Daniel [Fatty] who was there to bounce ideas off and
who was also doing his own testing but along different designs.
Project Version: V1.0
Status: Failed
Ran hosing into the airbox and sealed it all up. Worked ok but as soon
as I reached speeds of 150kph the mix leaned out and the bike stopped
making power. Did some research and I believe I have found the
problem. As the pressure builds in the airbox the extra pressure throws
the balance out between float bowls and the venturi causing a lack of
adequate fuelling.
Project Version: V2.0
Status: Failed
I was originally
going to
attempt to create a new airbox lower completely encapsulating the carbs
to equalise the pressure but after a friend of mine attempted to
equalise the pressure by running all the carb vent pipes into the
airbox.
I realised that his idea only failed becuase he pressurised the sub air
filter line as well as the float bowls. By pressurising that even worse
performance came about because the slides could not lift at all.
Project Version:
V2.1
Status: Failed
Well, i routed the
float bowl vents into the airbox but was halted
immediately because the pipes that come with the carbs sit right next
to the intake stacks causing a vacuum effect inside the float bowls
causing a no-fuel situation as soon as the carbs switched to needle
circuit.
Project Version:
V2.2
Status: Failed
Lengthened the
vent tubing to place it into the top of the airbox to be
away from the vacuum of the intake. worked a treat right up until the
150kph barrier returned. Defeated i once again returned to the drawing
board and researched the problem.
Project Version:
V3.0
Status: Upgraded
Some research
showed to me that i would encounter fuel starvation again
at speed due to the CBR having a gravity fed,
vacuum actuated fuel supply. This is because that when the intake and
float bowls are at the increased pressure, if the tank is at the normal
pressure fuel will not be able to enter the float bowls.
#1 was to add a
fuel pump to have a pressurised fuel supply line.
#2 was to plumb
airbox pressure into the tank to equalise the whole
setup.
I hate wiring so i
chose to plumb the tank. Luckily a friend had a CBR
tank that already had a VFR tank vent fitted. I ran some piping into
the airbox and also revised the airflow into the airbox with some
smooth bore clear hose and a straighter intake path to improve
efficency. Got it all together and ran terribly due to what i believe
is inadequately sized main jets.
Project Version:
V3.1
Status: Partial
Success
Have sourced some
122 main jets, changed the intake stacks to all long
and completely removed the airfilter so the airbox is completely open.
Took the bike for a test run and idle circuit works perfect but the
transition to needles was less than promising. It was fluffy and
created barely sufficent power delivery. Then the main jets kicked in
and she tried to tear my arms out of my sockets. she accelerated
amazingly and smoothly all the way to redline. Also passed thru the
speed barrier, going past 150 for the first time in the project's
history. I will be retuning with larger jets again and posting the
change.
Project Version:
V3.2
Status: Cancelled
Now that i have
had a partial success and have been working on the tune
i have found a slight problem with the refinement. When the tank is
close to full or full the vacuum that occurs at idle or low speed/small
throttle opening siphons fuel into the airbox. To solve this problem i
was going to create a surge tank to compensate for this but have found
another method.
Project Version:
V4.0
Status: COMPLETE
I have now
finished the whole project and have discovered that i did
not need the tank pressurised at all because i was doing all my testing
with less than a litre of fuel and if i had been using more fuel no
starvation would occur because the weight of the fuel ensures the flow
remains constant.
Stay tuned!
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