Newsletter No 57
17 October 2008
Finally
your long awaited Article on Dynamometers
It is scary
when you see big aftermarket shops closing down. I am talking worldwide here.
Presently I
know of a few struggling ones that were once making a good buck in the 90’s.
“Conversions”
as in wings, spoilers and other “optical” aids are picking up tremendously
whilst the old speed shops are dying.
Technology
is advancing and a lot of “tuners” are falling by the wayside due to inadequate
equipment or not being flexible enough to acquire the needed knowledge.
The proper
Tuners (derived from the Latin Tunare) with state of the art equipment &
intellectual background are in more demand then ever. I recently saw an ad for
a huge operation that went similar to “Automotive technician with
electronic/computer skills wanted. Will be aided by wrench spinners”.
Seeing that
my business is going from strength to strength, aided by having a good Dyno as
a test rig, I want to share the following with you:
First of. A
dynamometer is a tool to measure the torque output on a moving shaft (My
definition, not that of …).
Just like a
workshop should utilize an assized (for instance SABS certified) Torque wrench,
you should also have a Calibrated Dyno...
Either you
have an engine brake that measures Crank output or a rear wheel Dynamometer.
The first I
would love, but is only worth it for some serious funded research.
The latter
you can have in inertia or braking.
The first
will measure your engines accelerative time against a fixed resistance
therefore calculating Torque. Torque X velocity^2 = power
I need a
Braking Dyno, since I want to be able to hold a car at a specific RPM or road
speed. Important for Tuning & research.
Before I
shelled out a significant amount of money on a Dyno I had a look around what I
had worked on before, what was on the market & finally what I could afford.
I knew Hoffmann, Superflow & Triumph quite well with some experience on
other systems also.
After a few
years of searching for the “right one” I finally found a used but not abused
MAHA. This company supplies most of the TÜV & DEKRA stations and have SA
stationed technical back-up. This make has a reputation for accuracy &
durability.
Although the Dyno was sunk
into the ground in 2004 and soon operational it took me quite some time to get
the “ambience” where I wanted it J
Once I did get the Dyno Room
sorted to my satisfaction. I had some fellow SA & European tuners comment
very favourably on its layout & design.
Initially the idea was to
cancel out as much noise internally as possible and at the same time getting
the temperature more stable with a constant high pressure fresh air supply in
front of the vehicle. This is not something cooked up at the spur of the
moment, but rather a culmination of an idea started of over 16 years ago in
These were my (albeit rough) calculations:
Induction noises RPM * cyl /2 /60 = Hz
Exhaust gases move at 200 to 300 ft/sec with pulses in
that running around 1500 to 1700 ft/sec.
Then you have a Luft cooling fan running at 1440 Rpm
and the vehicle fan running at 30 % over the crank speed (1000 to 7000 Rpm
@crank).
Tyres are spinning on the rollers up to 250 Km/h, but
mostly between 30 and 100 kph.
Would you agree, all low Frequency
stuff ?
Early in 2007 I finally got to where I wanted. So
please do check it out !
Finally on the 28’Th May this year, I got my
Dyno certified again. Same as a Butcher has to get his scale assized
When I put your car on my dynamometer to get a
performance graph and figures it needs to have been calibrated by a
professional.
From what I know about 5 Dyno’s in
If you
think this Dyno is my only expense; then check out what a proper 4-Gas exhaust
Analyser costs, as well as an Air Fuel ratio meter, Exhaust gas Temperature gauge,
data loggers, Oscilloscope etc. 2’nd hand you will start at about ½ million
rand if you know your stuff. Of course you also need some back-up equipment. In
case yours is failing or to check your findings.
It would be
even nicer to get my Dyno room running at a constant 25 C temperature, but that
is currently out of my budget and need.
It would
need a bit more than an Aircon. Needed is some serious heat extraction
equipment, probably costing more than the Dynamometer !
Now to what this Dyno can
do and what I can do for you:
I can do an
inertia run by applying a fixed resistance to the eddy current brake (read that
up under Foucault- be careful how you pronounce that in public), called a
Continuous measurement.
Or by
actually braking an Engine for an operator set time at operator set RPM or
speed intervals, called a discrete measurement. The latter is useful if you
want to check your EGT, AFR, Fuel pressure, boost etc.
It can measure 2 pressures on the car with the interface box (either boost
pressure, oil, or fuel- one being 3.5 bar & the other up to 10 bar).
The MAHA
Dynamometer can also load at a certain tractive force which is useful for
checking things like a “stumble at pull-away”, or what happens at the dip in
the power curve etc. In layman’s terms, it simulates driving up a slope.
Of
course I can do a driving simulation or
Engine flexibility test if you can give me: Mass of vehicle, Aerodynamic drag
power, Rolling resistance and tyre flexing resistance.
Other
interesting things you might want to measure are torque converter slip, Road
speed accurately and thereby calibrate your speedometer or Trip counter.
This
particular Dyno incorporates a Data bank where I can store a vehicle’s Standard
power and then the different measurements, whilst doing development,
superimposed on every subsequent run. I.e. The values stored in the data bank can be superimposed in
the background against the current cars test, so that the difference can be
easily seen. Useful in a before and after test !
I do have
the fixtures for Motorbikes, but am not inclined to make us of this at the
present moment.
You might
ask, how can a rear wheel Dyno assume crank power ? Well what happens when I
arrive at the end of the Continuous or Discrete measurement & hit the clutch
pedal; the load cell with measure the negative torque and put that measurement
under your load graph, add this to your rear wheel power, then do some fancy
computations and give you a theoretical Crank force as per a defined norm. It
is quite accurate J Automatics are different but I can
also give accurate readings on those.
Quite often
I get a call where the customer just wishes to have his Kw checked. This leads
rise to the question; why
you would want to strap your car to a Dyno ? To
measure its power ! In the end it cannot do much more than that.
If you
expect anything more than some power readings after just doing a Dyno run
without tuning, you are fooling yourself. So:
You might
want to modify your car and measure the power before & afterward.
You might
want to find out whether your vehicle does generate its claimed power, provided
you can obtain its correct power figures- more on that a bit lower down.
You might
want to check why you have a problem at a particular RPM, throttle position,
road speed etc. Few mechanics will obligingly peer under your bonnet on the
Western Bypass at 250 Kph.
Or you
might want to Tune it all over the RPM range you use. On a BBC you are going to
spend little if any time at 5000 RPM 50 % throttle, whilst on an RSi you won’t
spend a lot of meaningful time below 3000 RPM.
This Dyno
has the facility to connect a fuel consumption meter & a diesel emission
tester. This is more useful on a truck Dyno though, so we have not yet invested
in that.
You should
question if the Dyno is calibrated. We can honestly obtain the Output in
either:
DIN 70020
EWG
ISO 1585
ECE-R 15
Most other Dyno outputs are simply
those of that particular Dyno fulfilling no particular norm. This is similar to
a builder having a home-made tape measure where his meter equals .8765 SI
meters.
So yes I
can give you the correct Din or other type output, but that is of little help
if you do not know what the power was initially & to what norm.
Easiest is
to run a car before & after on the same Dyno to get the improved figures.
Also, in this case most Dynos’ are not self-calibrating, such as mine,
therefore leaving room for “operator adjustments”.
As with any
good measuring device you want to have repeatable accurate results.
As with any
measuring device you have certain limits. If your tyres spin on the road, they
are likely to spin on the Dyno. On bakkies you can throw some weight on the
back for better traction.
If your
Wheel alignment is out your car will be all over the road. I will not allow a
car to be all over my Dyno.
You need
fuel to make power to move your car, even on a Dyno you need fuel- preferably
at a constant temperature i.e. lots of fuel for stabilisation not necessarily
burning J
In the end
what does this mean to you ?
Decide what
your needs as a client are and what you can afford.
If you
intend having repeated runs done, go to the same place & keep records.
See what
guarantee the Dyno operator/tuner will give you on his/her work.
Getting
back to the needs of you, my client:
Maybe you just
want to have your vehicle set-up correctly for optimum power & fuel
consumption- my past newsletters show why this
goes hand in hand.
You are a
hobbyist & want to experiment on your car using a Dyno to determine the
difference every modification makes.
Or you do
development work and need a Dyno to back up your findings- such as some
Workshops, motor sports divisions etc.
There are
different philosophies on Dyno usage.
The
American’s like to do pulls whilst logging that particular data & then do
the adjustments during the stabilisation time.
Dastek
likes us to measure Full throttle to nearly no load at a specified RPM & do
adjustments whilst tuning.
Some
tuners, like me, prefer doing the complete tune on their own whilst others have
one person run the Dyno whilst the other tunes.
A few
operators just use a Dyno to supply their customers with figures to feed their
next bench racing session.
In the end
a Dyno can be a tremendous help for the automotive technician in fault finding
as well as setting up an Engine correctly.
What is
important is that we trust this technology by becoming intimate with it.
I know a
lot of us wish back to the “good old days”, but that will not make the shop
owner money nor make the customer happy.
Now to the bad News
The
We
are expecting increases of between eighteen and twenty percent across our
entire range. This process will take a couple of days to implement and will
commence on Monday, 20Th October 2008. By month end I should
have implemented the new prices.
My
SA suppliers have also increased their pricing on goods that are related to
escalating raw material pricing, such as Steel.
The
only supplier who has not reacted so far is DASTEK. So to tune a car with a
Unichip will still cost between 2000 to 3000 Rand.