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 California. I spent a lot of time interviewing sound engineers, environmental physicists and anybody who has tried to absorb or cancel out noise. Problem is that everybody has tried to please their neighbour, i.e. keep noise contained in its environment. I wanted to reduce the noise in my Dyno room. I guessed most of the noise will be low frequency (below 500 Hz), with the dominating Frequency band runs from about 100 to 400 Hz.

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 Southern Africa are calibrated to an internationally recognised standard. So most the other Dyno operators give you their idea of what the car is pushing out- hardly confidence inspiring.

 

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 Rand has taken a serious beating versus the Dollar and other major foreign currencies over the last couple of weeks. As this is very reminiscent of the way in which the Rand performed against the Dollar after the September 11 tragedy, we know that we can no longer afford to hold our current wholesale pricing, and will have to have a general price increase. This has come at the most inopportune time with Christmas just around the corner.

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.