Dyna Tuning at Steves Auto Clinic
Choose the correct Dyna Tuner to tune your vehicle, 4×4 or 4×2!
Many people talk about Dynos and debate whether or not it is a good thing to have a vehicle Dyna tuned. Most people don`t actually know about dyna tuning, what a Dynamometer is and how it works. Below is a brief description of the basics that you would need to know.
This is how a Dyno works
A chassis dyno is equiped with large rollers, usually sunk into a pit. The car is driven onto the dyno so that the drive wheels rest on the rollers. Dyna tuners all differ with their output figures but how it works is the same.
The car is strapped down so it cannot move laterally or longitudinally, with non-driving wheels choked on 2 wheel drive dynamometers. On a 4 wheel drive chassis dyno, the distance between the front and the rear sets of rollers can be changed to cater for dyno tuning different wheel-based cars. Front-wheel drive cars tend to be more unstable on dynas than rear-wheel drive cars, so when dynotuning FWD cars, small “trainer wheels” are locked into place on either sides of the front wheels. A large fan is placed at the front of the car to cool the radiator and any other heat exchangers located there. The dyna tuner sits in the driver’s seat and operates the accelerator, clutch and brake. The steering wheel does not need to be touched.
The dyno tuner controls speed and other factors via a hand-held pendant that contains controls for load. The simplest test is a power pull.
The ‘ramp speed’ (rate at which the dynamometer lets the engine speed increase) is set and the car is run at very low rpm in the selected gear. Any gear can be used, but second, third or fourth gears are usually selected. The higher the gear, the lower the tractive effort trying to pull the car of the dyno. Very powerful cars are therefore sometimes tested in higher gears, although second gear is most commonly used. The tuner instructs the dyno as to the type of test being undertaken; holds the low rpm in the selected gear and then gives the engine maximum throttle. Flicking a switch allows the dyno to ramp up in speed.
As the engine rpm increases, the dyna’s software draws a trace on a PC screen, showing the power being developed. When the engine redline is reached, the test may be completed or a switch on the controller may be flicked, causing the dyno to ramp the engine back down. Averaging ramp-up and ramp-down power pulls removes the inertia of the dynamometers rollers from the reading.
The comparison of Dynas and a bathroom scale is the best to illustrate this philosophy.
If you follow a strict diet and you want to know if it is working or not, simply stand on a scale. By using your clothes to gauge the result you can easily be misled.
Similarly, by trying to feel if the vehicle’s performance is better or worse by driving it on the road could also be misleading. Choose the correct Dyna Tuners to tune your Vehicle! Better than only being able to test the output of your car, make sure that the Dyna being used has a brake facility. This way you will know if the tuner has the ability to simulate road conditions and enable the tunerto monitor engine-tuning specifications under load.
Many years of experience are definitely the best reference any Dyna Tuner or Dyna Teacher could have. Contact your local SAC Branch.