Dynojet vs Dyno Dynamics: Why Wheel Horsepower Comparison Is MISLEADING
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- čas přidán 27. 10. 2023
- Wheelhorsepower (WHP) is a measurement of the actual power put down to the road of cars in the tuning industry... but can you compare it different dynos ? I use my Subaru Forester STi as a test mule to see what it makes on the dyno dynamics at Surrey Rolling Road and on the Dynojet Dyno at Garage Whifbitz
website: www.racedynamix.com
booking: racedynamix.as.me
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I did the same test. Most US dynos use an SAE adjustment so 255 versus 270 is a pretty accurate comparison.
US auto manufacturers use the SAE (Society of Automotive Engineers) standards for measuring horsepower ratings. It says Europe uses SI but if they import into the US they have to convert to SAE for power ratings. Race leagues in the US use SAE. So people in the US use SAE but if you want to compare to foreign dyno results depending on the country you may want to look at Dyno Dynamics.
But if you were to look at the trap speed at 1/4 mile, it would be identical every time, whatever some dyno says. :) ;)
Some of us think that this is the best judge of performance.
Almost agree .. obviously fluffing launch and gear changes aside :)
I think the USA guys always used to like to run more bhp and keep the torque low where as in the uk we like to try and get a nice balance between the two, im talking stock engines with bolt ons mainly here.
Super interesting ..
Even on the bikes here .
We use the same dyno so the comparison between mods is comparable
It's the only true (ish) comparison.. Allowing for margin of error between atmospheric conditions and tyres etc 👍
In the USA I have seen mostly direct bolt on hub dynos I presume there a lot more accurate eliminate wheel traction or loss of it on the rollers great video Duncan thank you 👍👌🙏
Yeah they but they are a pain to set up, take a long while and again adds a different figure to compare to
Always wondered this 🤯
Hi duncan great video as usual, and perfect timing for me really. I just bought a 2015 STI yesterday from what i can see its almost stock with a few tasty simple mods, have quite a few printouts from dynapack dyno it starts out at 240hp ending with 276hp, having never seen a dynapack would this be wheel or crank HP? If you had to guesstimate
Definitely whp.. Or their version of whp at least 👍
just by the sound i guessed 320hp on your dyno lol.
@@osrsdaily4261 😁😁
Hi Duncan...
Just come here to the Algarve and offer us a seafood dinner!
😁
My rb5 used to come home ticking every time I drove it
👌😂
Hi Ducan, great video 👍
Q- Do some dyno have ways to read the weight of a car? to give exact Power to weight ratio figure?
I would be something I'd like to know when the car gets done.
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 👍
Great video! Obviously that you compare UK with US.. But what about the rest of the world?
Thanks for the content!
Thank you.. I will probably change the title to be just wheelhorsepower rather than US V UK tbh.. 👍
Hi Duncan, I know you're saying that all dynos are different but would you be inclined to say that the Wifbitz dyno over reads? When you did the video of tuning the decat bugeye WRX at Surrey Rolling Road you got about 290hp at the flywheel which seems right but if you were to do that with the same car on the Whifbitz dyno surely you'd get well over 300hp! Which surely can't be right for a WRX with a TD04.
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
Feel like you glossed over a lot of details on this. Try using inductive pickup on dynojet rather than Gear Ratio, static gear ratio is so 1995. You will get a more realistic torque value on a DJ using RPM from canbus/obd/pickup. 4WD Linked vs Unlinked DD load implications, CF/ramp/strap style settings for DD. Lots of things that can influence this result further.
Having said that, I could live with a 5% desrepency between chassis dynos & brands using "at the wheels" results, there would be a least a general pattern across brands. I think the bigger problem is the UK loves to add on the the estimated crank power/torque which muddies the waters even further. Look at this example, DD adding on like 29% driveline loss, which seems generous. I think I'd trust the torque value of the DJ a bit more looking at both results.
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.
Great video Duncan. Q1 so all dynos have different readings, so which dyno is 100% correct?
Q2. If you made 321hp at Surrey and 277whp at the other dyno. Why are the US getting higher WHP figures as they are higher than our hp figures and youve shown whp is lower than crank hp. Do they have better fuel?
All are wrong and all right 🤣
The 321bho was at the flywheel.. It made 252 at the wheels at Surrey versus 277 at Whifbitz 👍
At SRR the figure you showed was 321, but in the Whifbitz segment you said the SRR figure was 252 - can you clarify? Also one of your number plate bulbs has gone 👍
The 321 was bhp flywheel figure. The 252 was whp at SRR 👍
Thanks.. I will sort 🙏🙏
All are comparable. That's just what you need to do. There will just be a correction factor.
Quick question for you, every dyno graph I've ever seen at Surrey Rolling Road including this video, the intake temperature is always lower than the Air Temperature......how is that possible? And would that affect the dyno result?
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.
Saw someone in the US post up a video showing he made 420hp on a stock EJ207 with a TD05-16g lol. Not sure where the temp sensor was located, probably in a cup of coffee ;)
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.
It made 321 hp on the first dyno
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
Its all black magic 🤣
It is indeed 🤣👍
And then we add how to work out KW power ratings as used in Australia just to add more depth and compare to US WHP
First you need the diameter of a hoop-snake and the mass of a drop bear....
🤣