Dyno
Time with Jamie Bezzina.
STROKED
Hi Jamie,
After reading dyno time I have been wondering
if it is possible to successfully turbo a two-stroke engine.
I have found articles on turbocharging two-stroke diesel
engines for marine applications but not much on petrol
engines. The little bit I have found states that turbo
charging a two-stroke doesn't destroy all exhaust resonances
but you have to place the turbo after the expansion chamber
and match the turbine and housing carefully against the
resonances in the pipe. Would running a passive exhaust
be an option? If possible, what type of turbo would suit?
Dean Riordan, Warwick, Qld
Hi Dean,
Yes it is true, turbo charging
a two-stroke doesn’t destroy all exhaust resonances as
long as you place the turbo after the expansion chamber
and match the turbine and housing carefully against the
resonances in the pipe. Running a passive exhaust on a
two-stroke engine is not a good idea as you are restricting
the standard power while not on boost. It’s hard to say
what turbo would suit as I need to know a few details
like the size of the engine, what the bikes rev range
is, what size carby's etc. I have turboed an old 1985
model RG250 that made just on 80 horsepower and ran a
1/4 mile time of 12.5@118mph. The turbo I used for that
was a small IHI turbo with a modified exhaust housing.
G’day Jamie,
Your Hayabusa is 500-odd horsepower but how much
power would it have without the turbo? The reason I ask
this is because I am considering building a ‘Busa (I have
a wrecked one) but I want to stay naturally aspirated
while still getting big power. How far can you go with
a ‘Busa without turbo power?
Ian Aitkin, Auckland, NZ
Hi Ian,
If I took the turbo off my
bike it would only make 140 horsepower which is less than
standard. The reason for this is because it is a low comp
motor and the whole motor set up is for turbo only. To
get big power out of a ‘Busa, naturally aspirated, you
can get around 300 horsepower. But it’s not suited for
street use, as you would need to run the bike on race
gas. The reason for this is because your compression ratio
would be sky high and it would not be very smooth due
to the amount of engine work needed to get this power.
DRAW THROUGH
Hi Jamie,
After reading Rapid I am seriously considering
my own turbo
project. However before I start I would like to know how
hard it is to set up carb's for a turbo and what's really
involved. My project bike would be a ZX-7R. Is there any
well-known weaknesses with the 7Rs motor or ‘box that
would definitely need attention or is it a straight bolt
on affair?
Mark, Deception bay, QLD
G’day Mark,
Setting up carb's for a turbo
is hard. The reason for this is everything works in reverse.
Boost pressure forces fuel back to the tank and to fix
this problem you will have to get a fuel pump capable
of running at least 3-4psi over your desired boost pressure
and a good fuel pressure regulator to do this. You would
have to find some way of getting boost pressure to your
fuel bowl and blocking off any air leaks on your carbie.
After doing all this you will have to do a lot of dyno
time to get the desired air fuel ratio needed for turbo
charging. As for the ZX-7R running around 7psi boost shouldn’t
be a problem for the bike provided it is in good mechanical
order. You should expect to get around 180 rear wheel
horsepower.
STORM TROOPER
G’day Jamie,
I recently purchased a 1998 Honda VTR1000 Firestorm
as a project and on the things to do list is an engine
rebuild. From information I have been able to find it
seems the cam-chain tensioner is a real problem on these
engines. It has been suggested that a CBR tensioner is
the go and can be fitted. What are the options to fix
this problem? Also, what other modifications are the go
on these engines? From what I have read they seem to be
pretty good and people don't mess with them too much.
I have a pair of Staintune exhausts to fit and intend
to get some later model inlet manifolds which are a different
size (and apparently improve airflow) but apart from that
what do you suggest for a motor that will only see street
duty?
Shayne Faulkner, Brisbane, Qld
Hi Shane,
To be honest I haven’t had
that much to do with the VTR1000 Firestorm but what I
would suggest is to source a cam-chain tensioner off a
later model VTR1000 Firestorm as one would hope the manufacturer
would have fixed the problem. For other modifications
the norm is an after market exhaust system, K&N air
filter, Dynojet kit and a few hours on the dyno should
give you about a 12 horsepower increase. As for another
option a NOS kit and an after market exhaust system and
you could get around a 40 horsepower increase depending
on fuel quality. With the different size inlet manifolds,
I can’t say, as I have not dyno tested them to see if
there is any difference.
WET ONE
Hi Jamie,
Why do people use water injection in some turbo
engines? What are the benefits and why?
Ben Young, Melbourne, Vic
G’day Ben,
Water injection is used to
stop detonation on turbo vehicles or high compression
vehicles. Your vehicle shouldn’t need water injection
unless you have a badly designed combustion chamber, bad
quality fuel, too high compression ratio for street fuel
or too much boost. Basically water injection is a cover
up for not doing the job right the first time.
DUCATISTI
Hi Jamie,
I own a Ducati 999 that is stock except for a
carbon fibre clutch cover (woohoo).
The bike is superb in its current state and plenty powerful
enough but I would like to add a set of pipes, mainly
for the noise. However, owning a Ducati seems to imply
that you have no brain but lots of money.
I have been told that you can’t buy a second-hand set
of Termignioni pipes without the matching CPU and air
filters. Sure you may be able to locate a second hand
set of pipes for about $1000 but the CPU will cost another
$2000! I have also been told that the Termi pipes + ECU
+ filters are the only ones that will really benefit the
bike.
However, I have also been told that a second hand set
would be no problem.
So can I fit a second hand set of Termi pipes to the bike
without the factory CPU and overcome this by fitting a
Power Commander?
For a straight talking magazine like Rapid, this should
be a no-brainer.
Peter Pyriotis, email
Hey Peter,
You’re right, this is a no-brainer. I
have always thought that some Ducati riders get mislead
when it comes to after market parts that aren’t made by
Ducati. You don’t need the factory CPU, you can use any
aftermarket computer such as a Power Commander, S&R
PRO Interceptor, Motec, Haltec, MicroTec, etc. And the
bike can be tuned with ease. You can also fit different
exhaust systems, or anything else for that matter, like
turbos, NOS and superchargers. Your bike is no different
to any other bike.
SUPERCHARGED FJ
Oh Great Bezzina enlighten me with your words
of perverse horsepower wisdom. I’m about to start a project
supercharged FJ1200 and I have a few questions. Do I get
better drive off gear or chain drive and how far will
I have to modify the fuel system.
I'm an older (48) biker and it really gives me a buzz
blowing away the new bikes on an old sport tourer at the
lights. I know I could buy something off the showroom
floor but where would the fun be in that?
Paul Galna, email
Hi Paul
You will get better drive off the crank
using gears as there is no lag or chain stretch. In regards
to power and performance using either gear or chain it
is very hard to notice the difference. As for the fuel
system it’s hard to say as I need to know what boost pressure
you are running and what fuel you are using to determine
what the right set up for your bike is. As a rule, 11.7:1
AFR is a very safe ratio to start with. This way you will
make power without doing engine damage.
PULP or ULP
G'day Jamie,
I have owned six bikes in the last 15 years and
my latest is a 2001 R1.
I've been obsessed with motorcycles all my life and it's
good to see I'm not alone. I Love the R1 and was wondering
if there is anything I can do to improve the exhaust note
without replacing the muffler? My other question is about
unleaded fuels. I have tried both ULP and PULP but I can't
notice any real difference in performance. Is it OK to
run standard unleaded?
Scott Woodroofe, Adelaide
Hi Scott,
For the first question, yes you can modify
the exhaust and get power increases but I would not recommend
you doing so as it is highly illegal and you could cop
a fine for $10,000 from the EPA if and when you get caught.
For the second question you will make more power on standard
unleaded as it burns faster. The higher the octane the
slower it burns, the lower the octane the faster it burns.
If you run a high compression engine (most modern sportsbikes,
including yours) you should run high-octane fuel because
it burns slower and has less chance of detonation. Thus
giving you less power but better fuel economy. If you
have a lower compression engine you should run low octane
fuel, as it will burn faster giving you more power at
the risk of detonation.
BIG BORE
Hi Jamie.
I have a Yamaha SRX250. It handles superbly but
has no guts. I am considering putting a 350 top-end off
an XT or TT 350 on. My question is, will I need to adjust
the weights on the counter-balance shaft?
Tim, email
Hey Tim,
The answer is yes, you will have to get
it balanced and you will notice a great difference in
torque rather than horsepower, which is what counts anyway
(torque sells bikes, horsepower wins races).
FUEL CONFUSION
Hi Jamie
I'm new to riding and have recently purchased
myself a Suzuki GSF250 Bandit. I'm enjoying the time I
get to spend on my bike however when I fill up my bike
I'm getting confused between the various types of fuels
that are available. It seems every service station has
a different type of premium unleaded with a different
octane level. Is there any difference between the many
types of premium unleaded fuels that are available and
is there any particular type or octane level that would
be better to run in my bike?
Rebecca Pethybridge, Bendigo, Vic
Hi Rebecca,
With a bike like yours (low compression)
I would suggest sticking to the standard unleaded (see
PULP or ULP question). This will give you more power as
it burns a lot faster than premium unleaded.
BUDGET BLADE
Hi Jamie,
I currently ride a CBR250RR that I bought for
only $600 and have done up for $2000. I now have a great
L/P plater bike. But after riding for around a year now
I find the bike a bit slow. I was just curious to know
whether you could help me with some ideas on how to get
a bit more from the bike with out breaking the budget?
Josh P, Sydney, NSW
Hey Josh,
Unfortunately there’s not really much
you can do without spending a bit of money. Buying an
after market exhaust, which will give you anywhere from
three to five horsepower extra (after tuning) will set
you back around $600 is the cheapest thing I can think
of.
