Dynojet vs Dyno Dynamics: Why Wheel Horsepower Comparison Is MISLEADING 

Almost agree .. obviously fluffing launch and gear changes aside :)

Definitely whp.. Or their version of whp at least 👍

It's the only true (ish) comparison.. Allowing for margin of error between atmospheric conditions and tyres etc 👍

Yeah they but they are a pain to set up, take a long while and again adds a different figure to compare to

👌😂

@@osrsdaily4261 😁😁

Hi. Whifbitz Dyno reads higher whp figures but doesn't show flywheel figures. I normally estimate 20% on top of whp for flywheel figs 👍

@@racedynamix My apologies Duncan, watching the video again you do mention that at Surrey Rolling Road your Forester made 321.4hp at the fly wheel so the fly wheel figures are virtually the same. I knew about the adding 20% and I was doing that for the Surrey 252whp and made it just over 300hp, the dyno obviously has it's own way of working it out. Sorry about that.. 🙄

@@timcoleman3057 at SRR it is 27% iirc but it calculates flywheel figures itself

Not to my knowledge. Race track is the best place.. Have a quiet word with scrutineers and they will normally pop it onto the weighbridge 👍

Thank you.. I will probably change the title to be just wheelhorsepower rather than US V UK tbh.. 👍

The unit with the IT sensor is in the next room tbh so always a bit different to the dyno cell. I will cover the impact of this in a video shortly.. Hopefully that will answer all of the questions you have on it.

Thanks for the detailed comment. Yes, obviously, some details were glossed over but I don't think using a different rpm signal rather than setting off roller speed would have made any noticeable difference but I will test that another day. The point was whether whp could be compared as that is ultimately what is measured. I could also have used a Mustang dyno or Maha dyno or Dyno Developments dyno and got another 3 different figures all of which would be right but all wrong too. The 3 different sets of figures that Dynojet produce (sad, std and uncorrected) also muddy the water greatly too. But this wasn't about saying one dyno is better or worse just that there are differences. The only real way to say 100% accurately is engine out and on a test rig. The UK / rest of the world obsession I think comes back to bringing figures back to figures that the manufacturers state. Ie 265bhp from the factory and it is now 310bhp etc etc. Thank you for watching and commenting, you obviously know Dynojet well.. They aren't that common here. 🙏

​@@racedynamix Torque calculation on dynojet needs engine speed input, as power is calculated from the roller itself. Drive ratio on a vehicle through a run is rarely static unless its really underpowered, using RPM from pickup/canbus will allow torque calculation to track perfectly during tire deformation as gear ratio is changing etc and keep the engine speed axis on the resulting graph accurate. Otherwise you end up with graphs that are skewed on either the high or low rpm in terms of accuracy. I could make the same critisism of most dynos that primarily use gear ratio. This problems gets really noticable the more power an engine makes. The power reading will usually not be affected though on DJ regardless of engine speed input. I try an avoid dynos these days that wont take an RPM/CAN input for some data as it really does help with consistency whilst testing. I'm not expecting any dyno to the read the same either. You will get different results on each for sure, but in my mind every dyno is working of a set of principles based on physics. Rules of physics don't change, so we should be able to expect each chassis dyno to get reasonably similar wheel figures (+ or - 5%) as thats where everyone is measuring from (using the same car). When you get wildy different wheel figures then I start to question the dyno setup as the maths dosent add up. Not saying DJ is perfect, as it has its pros and cons like everything else. I just find it weird that in the UK especially, if I take my car to a chassis dyno I will likely be given a crank figure and any mention of power at the wheels is rarely talked about unless I bring it up. In a way its kind of irrelvant what an engine makes at the crank, because if it only puts out "X" to the wheels then thats more representitve of real world performance. Even engine dynos are a minefield, you will get different results on superflo's vs l&C. Its all rather annoying and takes proper care to ensure some sort of consistency.

The 321 was bhp flywheel figure. The 252 was whp at SRR 👍 Thanks.. I will sort 🙏🙏

All are wrong and all right 🤣 The 321bho was at the flywheel.. It made 252 at the wheels at Surrey versus 277 at Whifbitz 👍

Must have been 🤣🤣

@@racedynamix idea for a video would be to go through the typical turbo range/options for Foz/Impreza owners, especially newage. Power range of a TD04, TD04 hybrids, typical VF30, 34, 35, 43 etc vs TD05-16g, 18g, 20g then popular aftermarket options for 360-500 stock location.

At the flywheel 👍

@@racedynamix both them dynos read wheel hp not crank so something fishy

@@jasonlowther9936 yes and lots of others read wheel horsepower too but they are wildly different aswell. Hence why I did the video.. Whp cannot be compared

It is indeed 🤣👍

First you need the diameter of a hoop-snake and the mass of a drop bear....

🤣