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To:
'mail@awol.co.za'
Vmaxers
Knowledge
means nothing if you do not eventually pass it on for the benefit of
others too.Consider the following may be of benefit to other Vmaxers
too.
Those that
know me also know that I take pride in the fact that from the start
I have done all servicing , maintenance and fitment on my Vmax.
Can we improve
the Vmax performance?
Most of us
are happy with the Vmax engine performance.Many make changes.If for
example you change the exhausts(like most of us
usually do)
some minor jetting could be beneficial.Changing(modifying
)the air box will also require some jetting and other changes.The
Vmax is old school and there are no computer aided adjustments
etc.etc thus no power commanders and electronic engine
adjustments.Everything must be done manually by human hand.
More airflow ?
I have
purposely stayed away from individual air filters because the engine
breather flows through the air box and in my opinion the air box is
better in very wet and rainy conditions because it encloses the air
intake and filter.Most people will start by fitting an air filter
that flows more air.This however will not give a substantial
increase in performance because the std air box on the Vmax is
restrictive to air flow in any event.All standard Vmaxes have air
boxes and exhausts that had to pass noise and emission control
regulations in the USA at 4750rpm.The air box and exhaust is a
compromise between being efficient at all altitudes(height above sea
level),at all rev ranges and to keep engine noise and emissions at
levels set by the authorities.
My exhaust
My home town
is approximately 4200 foot above sea level.Some of the neighboring
towns are as low as 3000 foot above sea level. I run the std exhaust
headers with two slip on turn out slash cut pipes (manufactured by
Lu Hao) that are pretty much free flowing and no baffles.I had
specially made up exhaust piping that balance off the two rear
exhausts in the same way that the front exhausts are
balanced.Cylinders 1 and 4 are paired to the left muffler and 2 and
3 are paired to the right muffler thus 4 into 2.
The air box and why ?
Most Vmaxers
have removed the Y piece on their air boxes to flow more air in
conjunction with a K&N or similar type of filter.When I did
this(removing the Y), my range of engine performance was effected.At
4000 rpm the engine was" bogging " and lacked performance.What had
happened?Simple...that engine range was now running leaner due to
more air flow .Solution...remove the needles shim them (thus making
the needle shorter so that it does not stick so deep into the needle
jet and richening up the fueling). This is a very easy procedure
requiring 4 small copper(brass) washers available at most bolt and
nut shops.The effect was a better throttle response and improved low
end performance.I can ride my Max in 5th gear at as low as 1500rpm
and when I twist the throttle there is no lurching or transmission
snatch...it just starts pulling.
Springs
I also are of
the opinion(maybe wrongly) that the diaphragm springs are too heavy
and I have lightened(shortened) them by tying them down with copper
wire(5 coils tied back).It works fine on my bike for more than the
last 20 000 km.
Air box modifications
My next step
in trial and error was to open up the air box with the idea of
flowing more air.Making more power is simple in theory ....flow more
air and fuel mixture to the cylinders.In practice a lot of factors
make this not such a simple procedure.What
might work on your Max might not work on your mates Max.Why....well
he might have a different aftermarket exhaust on that is more or
less restrictive than yours,he may have other main jets ,needle
jets,needle length difference,different needle taper,different float
level settings,different diaphragm spring strength etc. Another huge
factor is height above sea level and it is well known that the best
performance is obtained at sea level with higher octane fuel.
Changing air box changes fueling
In opening up
the air box to flow more air you are making the bike run leaner
because it now gets more air in relation to the fuel.There are
various fueling stages in the engine,depending on what rpm you're
in so changing the air box changes all the fueling stages;
-the main jet
will determine mainly the top end performance(obviously it must be
coupled to the right amount of air flow and height above sea level)
however it also effects the other fueling stages
-the float
level and needles the mid and upper range
-the pilot air
jets effect idle ,off idle and lower range
Running out of air
What I found
was that in 5th gear my Max started running out of breath at 8000
rpm.I proceeded to open the air box up by cutting the hole in the
air box to match the air filter Later ,I proceeded to then cut some
of the material on the inside of the air filter itself and thus
opening the air filter up to its maximum size.
My results as follows
The main jet
of Vboost model Vmaxes is a 152.2 Mikuni jet.The equivalent size
for Dynojet jets is 162.2.My results with air box mods in terms of
top end runs where;
-Std main
jet with Y removed and needle
shimmed =130
mph / 209km/h
-Std main jet
with Y removed and needle shimmed and air box cut bigger
=135 mph
/ 217kmph
-165 Dynojet
with Y on and needle shimmed and air box cut bigger and air
filter cut open to max size =140mph / 225km/h….some
lean surging occurred at 8500rpm and therefore I went to 170 main
jet
-170 Dynojet
with Y on and needles shimmed and air box cut bigger and air
filter cut open to max size =150mph / 240 km/h
Why the Y
Now you may
ask why the Y was replaced.Remember I was in trial and error
mode.Once you cut the air box lid(and the Rubber lips off the K&N
filter) it is permanent.Because the hole in the air box had become
bigger(maybe too big) I needed to replace the Y to restore smaller
size and make air intake leaner.The point is if you want better
performance you need
more air
than simply removing the Y and you need bigger main jets to
cope with the increased air flow.
Take note
REMEMBER all
above works on my bike at altitude from 3000-4200 foot above sea
level and with the setup I run.BE
CAREFUL.We
tried 170 main jet set on my friend Dok's Vmax. He had Y removed
only with shimmed needles and a Marving 4 into 2 exhaust.This
exhaust is probably a little restrictive and has a baffle in.He was
only able to reach 135 mph and stated at that speed the engine was "surging".What
probably was the case was that the engine needed more air in
relation to the higher fueling which only can be achieved by more
air through the air box out the exhaust..
You decide
So as I said
it is not as simple as that.I have merely tried to relate to my
fellow Vmaxers what my personal experience has been and in no way am
I an expert in this field.I provide these observations not to boast
or brag about having a fast Vmax,all Vmaxes are fast.All I am trying
to say that there is possibly more performance available without
going into major engine mods.My deductions are based on what I
saw on on the speedometer( yes speedos do overhead) however I can
assure you that before this my Max had never seen 150 mph on the
speedo .My other deduction was that when cruising at 125 mph / 200
km/h I can now whack open the the throttle and there is an
instantaneous boost of power that propels you forward.In the past
the only difference I could feel with V boost on and Vboost off was
that V boost accelerated you faster and helped a little in the top
end.Now I can feel a difference from 125 mph / 200km/h....without
Vboost from this speed there is little kick but with V boost on from
this speed there is a serious kick. I reached 145 mph sitting feet
forward straight up (with a fly screen)and do not know if that is
the fastest it would go and chose to back off.I cant explain it but
the engine felt free and unrestrained.I would never attempt this in
other than windless days on long straight open wide roads .Maybe now
would be an appropriate time also to fit a steering damper too.
I will be
using my Max at sea level in October 2006 and will know what it
does at lower altitude too.
Finally I
guess the question on everyone's lips are what about fuel
economy...Well it seems that fuel economy might be up a bit. but not
noticeably for me.That being said when riding very hard I tend to
get 11 km to the litre.That equates to about 143 km / 90 miles then
reserve comes on.By that time I in any event stop for fuel and to
stretch my legs.When riding at 120 km/h / 75 mph I generally reach
a distance of 115 miles / 184 km before going on to reserve.All this
to me is irrelevant in any way...If fuel economy were my reason for
riding then a 125 cc would have been my choice of bike.To me the
Vmax is all about old school attitude ,muscle and power.
I hope you
Maxers that read this respond with your own ideas and
observations.Our technical page is about sharing ideas and tips and
is there for the benefit of all Maxers.
Vmaximus
Carl Talbot
ps Keeping
at 5500 rpm in 5th gear I can go 100 miles before the
reserve light comes on.
The
discussion on how Tboost works,the circuit diagram,how to do it etc
is very clear in Terry
Campbell's TBoost Modification article. Apart from
my bike I have done the mod on 3 other Vmaxes for Vmaxers I
know and it really is not that difficult.
I believe that this is a Vboost modification
first done by a Vmaxer named Terry Campbell.Long before the 2007
model Suzuki GSXR 1000 sportbike came with its 3 power settings this
idea already existed and was used by Vmaxers worldwide.I used Terry
Campbells electronics diagrams for T boost however I added a further
option of switching Vboost off entirely.I therefore have Vboost
on/off and a choice of Vboost at 3000rpm or 6000rpm.
Vboost raises the horsepower(at the
Crankshaft) from 100 hp to 145 hp at 8500 rpm.V boost also
increases the maximum torque.If you had to look at the dyno graph
of the Vmax you would see that from 1000 rpm the Hp increases all
the time and peaks at 8500 rpm and then starts to taper
off.Similarly torque from idle increases and peaks at 6000 rpm and
then starts to taper off.Clearly there are two aspects to measuring
the engine performance.
-Horsepower.In
theory,the more horsepower you have the faster a bike can accelerate
in relation to its mass(weight).If you want a bike to accelerate
faster then make more horsepower or put the bike( and rider )on a
diet and loose some weight.Anyway the point is horsepower is what
makes cars and bikes accelerate from 0-220km/h faster(in a quicker
time).Multicylinder engines usually make more horsepower in a given
capacity engine.
-Torque.This
is the measure of an engines ability to do work under load.In other
words the pulling power (at lower revs) or its ability to pull or
push.Engines of higher piston displacement normally make more torque
than smaller ones.Torque is not what causes acceleration.
I have been a spectator at drag racing and it
is not always the car or bike that makes the most horsepower that
runs the fastest quarter mile times.Many things like gearing,rider
ability,having a good launch,rider weight,bike weight,aerodynamics
,good traction and useable power are all factors.When the wheel is
spinning or when a rider is burning the clutch for example all add
up to slower accelleration.
Ok, so why then make Vboost
open at 3000 rpm instead of 6000 rpm ?
The answer lies in the following :
-Riding above 80 km while cruising longer
distances with 3000 v boost effects fuel economy and is only useful
when serious bouts of acceleration are required....I then switch V
boost to 6000rpm.
-Riding at long distances at above 6000
rpm and cruising long distance one can switch off Vboost as it saves
a little on fuel economy .Switching off Vboost cuts engine power
from 145 Hp to 100 Hp (measured at the
crank). Even without Vboost the Vmax is an awesome performer.
-There is no denying that Vboost at 3000
rpm accelerates you faster to 7500 rpm than with vboost activated at
6000 rpm.
-In wet conditions Vboost can be switched
off
-The difference between Vboost on/off in
regard to top speed is that with Vboost top speed is approximately
5-10 mph faster(depending on the wind and steepness of an
uphill).What Vboost really does is it gets you to top speed
faster...thus faster acceleration.
-that unique V4 power and
sound
-that unique style.Vmax is
not a copy of anything...there is nothing that looks like
it....therefore its style can never go out of style or be
outdated.Vmax is instantly recognisable and even today people want
them.
ps Caution
The Vmax does not have a rev limiter and will
keep reving until ..........it destroys itself.
Vmaximus Maximus
Carl Talbot
Kindly forward any complaints
in respect of spelling and grammar mistakes to Mr B. Gates . |
