So How Accurate are the Results from a Rolling Road?
First of all, a dyno is just a good tool for comparing before and after results from a tune, however, even leaving the vehicle on the same dyno and carrying out a 2nd run immediately afterward will generate a different set of results, Celtic Tuning openly demonstrate this with an Audi 2.0 TFSI, nothing changed and runs were carried out back to back, Run 1 = 243bhp, Run 2 = 257bhp so you can see that figures can show significant variations on the same dyno on the same day, actually you could quote either a 19% or 26% gain dependant on which piece of paper you were given, so across different manufacturers and types of dyno, results will vary wildly. Also with so many variables it makes it very easy to manipulate the figures in order to promote their software as one that gives better results.
Setting aside that it’s a FACT that different dynos will deliver different results, and a dyno struggles to repeat the same figures when even carrying out back to back runs simply because of the variability in how the vehicle delivers the power and the variables of the dyno itself, you’d at least expect different dynos to be able to demonstrate the same percentage gains, correct? Wrong. DSPORT Magazine carried out extensive tests across different makes of dyno and the results were up to 12% difference in the gains made, their conclusion was “While dyno figures provide a great point of reference, trying to compare the figures from one dyno to another is futile.”
If you’ve managed to read this far and I haven’t bored you yet, as with all other precision measuring tools, the dynamometer’s readings should be regularly checked for accuracy, due to wear, temperature changes, corrosion, etc. Mechanical and electronic sensors gradually drift slightly away from their original calibration, now I’m a natural skeptic so I’d want to see those maintenance and calibration records before I passed my money over, especially if the environmental conditions resembled that of a garage workshop and not that as a state of the art bespoke facility.
The next most important thing other than the competence of the operator is the entering of a correction factor, take your car in on a nice crisp spring morning when the intake air temps are colder and you make 200bhp for example, go away and return later when the weather is warmer and you’ll make considerably less, the correction factor needs to account for air pressure, tyre pressure, fuel quality, temperature and humidity amongst other things to attempt to provide the same results, whatever time of day you take it.
Let’s take a minute to think about what I’ve said, and then ask yourself if you believe that this really happens at the facility you had in mind?
I believe that we have established that a dyno/rolling road is not essential to having a good quality tune applied to your vehicle, certainly, if you are just looking for good safe gains within the tolerance of the engine and components. It’s also very important to appreciate it is impossible for a rolling road to simulate real-world driving, so unless you own a heavily modified vehicle, or are looking for every last piece of available power to be squeezed out of your vehicle you can save yourself quite a bit of money and get the same result, just without the piece of paper, and in reality, if you can’t feel a significant difference in driveability and driving pleasure the piece of paper is worthless, and no one is going to refund you for Dyno time, whereas if we remap your vehicle and you are not completely delighted on the test drive, there would be no charge.
So yes, our tuning is dyno developed and proven in a bespoke state of the art facility by some of the most experienced people in the tuning business, but also testing is extensively carried out on the road where it really matters.