Rolling Roads, Facts, Fictions, and Pub Talk!

We have been live mapping, and remapping cars here in Somerset now for more than 10 years. We had plenty of Dyno experience in the past, with our first Dyno-Dynamics rolling road arriving in 2007. We have since upgraded the dyno, to an AWD Dyno-Dynamics 450DS.

I thought I'd write a few bits about chassis dynamometers, theyre uses, and the facts and fictions!

Lets first talk about 'Power Runs'. These are the things every 'pub expert', or more lately 'forum elite expert', like to talk about. Now, whenever I get a vehicle in for tuning, I spend 90% of the time in 'steady state mode'. So I'm holding the dyno at specific points in the engines RPM, and tuning it live at that point, then moving on to the next cell in the tune. I'll often do a 'power run' initially, and then a few at the end to show before and after powers etc. Not to mention some very slow runs to gather information.

We're in a country, that sadly, likes to talk about Flywheel BHP. So the first thing we need to get out of the way is this. It does not matter how your 'friends' dyno, or your 'tuners' dyno gives you this figure.... it's calculated based on the information you give it. Guess what? 99% of the time this can be manipulated in one manner or another. Incorrect inertia programmed in, a quick pull on the handbrake... Etc Etc. I find the forum arguments draining, over who's dyno is 'accurate' and who's is not! Guess what, literally, EVERY single tuner will tell you his dyno is the 'Heartbreaker', or 'Dream Destroyer'! It's been the same for literally years, so I'm never surprised by any of it! In fairness, he's going to try and back up his equipment! I know ours ended up costing me upwards of ยฃ150k, so he's likely spent a similar amount, he wants you to know it's better than anyone elses!

So, lets first talk about our 'friend', mr 500bhp. This chap used to reside in the center of the bar on a Saturday evening, shouting about how many BHP his Cosworth made on the local 'rolling road', and moving on to say how 'shit' other dynos are and so on, and so forth! He will always favour the one showing the most power. I mean, lets be fair, this guys probably changed a clutch in his life, maybe he's fitted an intercooler or two, but he's usually a noisy <insert non related job here> who's stood next to a dyno a couple times, but as he's loudest guy we know, he's the self confessed expert right?! Moving onwards a little bit, our same friend, is active on Forums. Even more lately, facebook groups etc. In my experience, these guys are usually defending the tuner whom tuned their car. 'Usually' these arguments start up when someone else has had his/her car also tuned by his friend the tuner, and had it 'power run' elsewhere and it made less power. I don't know why these guys have so much to say about it, I genuinely don't. I see them weekly, and I always do the same thing, ignore them. Smile, wave, maybe even a cheeky little laugh over a cup of coffee. Either way, no point in arguing with them, it's a waste of your breath! ๐Ÿ˜‰ Bare in mind, they've probably watched numerous Youtube power runs too. #expert

So why did I choose a Dyno-Dynamics? Well, a good number of reasons actually. The first being familiarity. Having had the 2wd Version in 2007, it made perfect sense to just move to the newer 4wd. I could jump straight in and get working. Another reason, is Data. The Dyno-Dynamics has an absoute mass of data I can log. It connects VIA CAN to most aftermarket ECU's we deal with, meaning I can log on the dyno Ignition angle for arguments sakes. It has a Mass of analogue channels, EGT channels and so on and so forth. I can also log Knock on the screen live, via CAN & our PLEX Knock Monitor. All on one screen. The PID control for load holding is genuinely epic. I've literally spent hours, and hours with the dyno working very hard, often holding back 500+bhp at every single rpm break in the ECU, and it doesn't break a sweat. The above, are my main purchase points to be honest with you.

I stated earlier, that the 'Flywheel' figure, is always nonsense. It just is sadly. I rarely, if ever, work in flywheel power. The only reasons I run a flywheel power run, is literally for the customer. Most are insistant on it regardless of my groaning! LOL! I read somewhere on the internet years ago, 'It's like measuring your c*ck, and starting at your a$$hole'. Some serious truth here. However you go about getting from the effort at your tyres, to the power at your flywheel, is rough at best. However you do it, it's based on information you provide. Any Chassis Dynamometer, can only measure 'Effort at the TYRES'. It cannot measure anything else. Anything else is calculated, by some means or another.

I also mentioned earlier about 'power runs' and manipulation on various dynos. So, one of the most common ways of 'calculating' our loss, is by 'Run Down'. You'll find many of the Re-Mapping businesses using this method. It makes sense. They will run the car up on the dyno to the limiter, take it out of gear, then the dyno will measure time taken for the wheels to stop turning, and thats you're correction. They will then flash on a new file, modified by themselves or another, and perform the same test again. Nothing wrong with this at all. This is not really what we do alot of though, as I mentioned earlier, 'power runs' for Flywheel power, is not something I do more than a few times on a vehicle. So on this note, if I were a little 'unscrupulous' and wanted my tune to look like it was making more power than it was, a slight pull on the handbrake on the run down, or a touch on the brake pedal, will make the power level go up. The same effort exactly has been applied by the tyres on the way up, but now the calulated flywheel figure is higher. We've made more power now through pulling the handbrake!

The Software in the Dyno-Dynamics was designed to try an counter some of this nonsense. It can correct to various standards, SAEJ95, ATMC2, ATC to name a few. The calculation the dyno uses is based on the engine cylinder size, it's aspiration, and a number of cell conditions, fed from our Weather Station in the corner of the cell. Interestingly, ALL this information is printed on the dyno report. So if you entered that it had 20psi tyre pressure, it would be on the graph! This I love, no messing, the customer knows, it's 100% repeatable time after time. Side note, the amount of standard vehicles i've dyno'd over the years, I can tell you it's always + / - 5%. Despite what our Whattsapp Friend says. Not to mention the 'Heartbreaker' dyno I run. ๐Ÿ˜‰ Interestingly, Dyno-Dynamics introduced a 'Brand-X' mode, whuch runs calculations in a similar manner to mentioned above, it gives higher figures. It prints 'Brand-X', on the 'power run' sheet. Most of us Dyno-Dynamics owners prefer to work out of this mode though.

Another MAJOR factor, are cell conditions. I personally have a Sealed Cell. Plenty don't, but thats up to them entirely. We supply the vehicle with fresh fed air sucked from outside, and through our sealed radiator blower fan. I have four fans at the rear of the cell that are sped up, and slowed down based on barometric pressure within the cell. The cell tries to maintain a pressure of 1000mbar. The rear fans are automatic, and of a closed loop system. This allows for a 'test' that is both safe for the vehicle in question, and also maintains the cell conditions. Why do a test unless the conditions are the same back to back right? It's not even a test if you change parameters.

I never wanted to be the guy who just pokes the back of the car out of the door, getting the same test over and over, is completely governed by wind direction at it's basic level. Engines, or people run well on exhaust fumes!

Mostly, I'm rarely interested in the power figures. The Dyno is a tuning tool. You will have heard that said before I'm sure. But it genuinely is, regardless of brand, it's a tuning tool. As long as all of our tunable factors are correct, the car makes what it makes!

A friend of mine sent me this video a while ago, and it's got some great explanations in there about different dyno's, intertia runs etc etc. If you've got some spare time, have a watch! It's interesting.


Ultimately, I've had people not like the figures that the vehicle has popped out on the dyno screen. So they've popped of elsewhere, usually a 30 year old dyno, or a chinese imported rebranded one, and been much happier as it's read higher.... Who's right or wrong, it makes no real difference frankly, as long as all the data you've pulled off of the vehicle is correct. Lets be fair, the car hasn't changed at all. The little figure on the graph has. I'm always after the area under the graphs, trying to make the tune as best as it can be. It could read in 'fraggles', 'sausage rolls', or BHP for all I'm worried!

Many of the other rolling roads we have used were just not user friendly, gave crazy results, or gave completely different results back to back. Why even bother if it's that different from run to run? We've made a successful business through not selling, or using cheap nonsense, so why start now? After having used various dynos for tuning it was quite a short and sweet decision. The industry standard Dyno-Dynamics rolling road was to be used. I was not interested in any cheap inferior products, repeatable testing is what I'm after. There are many cheaper dyno's about. Hundreds probably, but nothing to the standard I wanted.

UR Quattro on the rolling road
UR Quattro on the rolling road