And here is a 4wd car - over 130bhp of losses.

Attached is a plot of a fairly low power car.  Inertia was calculated for this car using sweep up and down and comes out at 3.3.

Two runs, one in 4th the other in 5th gear.  As you can see, the wheel results are hugely different.  The flywheels figures are closer but 4th gear is lower than 5th.  My theory is that there is less tractive effort in 5th, indeed the tires run cooler and so the "loaded" loss is less.

Dev

that car particullary was 4%, normally for FWD cars 6-10%. 

Yes, as said, heat could add some extra losses to bearings, etc, but i'd say it's more on acceleration than desacelerating. anyway i think the percentage that add more losses is definitely not too noticable..

Correct, at the end, dyno is a tool for make the best tune for a car.

Walter please don't take this "l Powertrain Losses " forum discussion as a personal attack that is not my intention.

Problem is we have way to many parameter variations to make a unbiased judgement on what engine (BHp) power produced actaully gets back to the axle flanges/wheel&tyres!

But ! 3'to''4% drivetrain losses is definitely not a realistic number.

As stated by Justine the MOI for every engine/chassis/hub_dyamometer tested engine/vehicle combination is significantly different therefore the powertrain losses amongst other factors cause a different % loss.

I don't care if down the road JoeBlow's dyno figures are higher or lower than mine. Im just interested in making the correct adjustments to the engine/vehicle I'm working on.

Amongst us all here in this forum who has a chassis/hub_dyamometer environmentally control test cell that can monitor many other parameters to workout losses. I certainly don't. Heat is a power loss absorber, I'm certian you are aware.

Anyway keep dyno'ing 

Yeah, I had forgotten. 

I will bring back those whp/wtorque dashed lines.

I still have photos i sent you ago long time when was calculating MOI.

MOI calculation

Thats what i meant before when whp lines was more different than actual ones.

whp vs hp lines

yes, the first versión i had set it up 9.8.. until the newest versión needed to put for dynos with 2 hub/brakes, then we talked i have to divide it and it's done. have 4.9 for each hub.

I was really impressive too when i got this MOI, main reason was for using very big brakes..:-D

Oh really, 9.8 that's higher than I thought! So then you are not more sensitive to MOI accuracy than typical roller dynos in this respect.

Indeed, whp is what we measure, and as such will be the most accurate. 

sure, mine has 9.8kg*m2. my old roller dyno was around 13.5 or so. i think it's not really bad for a hub dyno with that MOI.

Yes, definitely think every dyno even for the best calculation would be needed to set MOI for each car. About same whp than hp, i always thought whp is the most important than hp, i means, on dyno hp would be affected by a wrong gear, instead whp is the power you have on the hub/tires always, not matter which gear..

lines should be amazing something like this:

I not means for shadows, i means for different type of lines. i noticed it's a bit different but using normal resolution, it always look the same , if you zoom it a lot yes, you noticed the difference.

Hi Walter, all,

Walter's hub dyno will have less loss than a roller based dyno obviously since there are no tire to roller losses, but 3% is indeed too little.

To be really accurate you need to set the MOI for each car you test. MOI of the drive train is also slightly different in different gears. Note that for a hub dyno with little inertia a slightly wrong setting in the MOI can make quite large effects. You should get the same results (close) in either gear, if the whp is the same. 

The whp and HP graphs are actually visually different, dashed vs non-dashed lines, but it is hard to see unless you zoom in because of the high number of samples. I will see if I can modify that so it is more clear.

if Jostein is Reading, should be good to make different line style for HP and whp  

one time i tested in differfent gears, just for to see how does Will affect to whp (or hub BHP or whatever you want) , almost the same whp, different hps..

was Civic MB3 fullstock.

what i can't remember the gear , i means which gear i used and power i get but i have here the differences..

GearX?? : 121hp/102whp

GearY?? : 112whp/ 103whp.

What i remember too was adjusting noise filter, was ago long time, anyway i can do some test for the next cars. 

Do me a favour next run of the mill standard unmolested vehicle you test  ( manual gearbox)  do  power graph pulls in all the individual gears and scale and overlay the graphs and post the picture of the graph  please.

mmmm i didnt say my dyno is the best, no way, im still say it doesnt just i see many dynos readings wrong or having problems with readings as Reading wrong losses by tire deformation,etc.

Ok, you choiced a car i cant remember somethings exactly but i Will tell you experience with this car..

That car , customer fitted a old 820ti rover T-series, with 220 engine head, he rebuilt it. we just wiring the whole car because he tried to run with oem ecu and didnt work properly, many cutted wires in the chassis,etc, we wired everything and after to see didnt work properly with 3 ecus he has, 220 turbo, 820 one, other i dont know which one was , made downpipe, fabricate rear motor mount, ic pping ,etc.

Finally after to do many research found Emerald was the best option for this car. after many emails, finally we ordered a P&P ecu, including he have a map tuned already, so everything was really easy, that map has comments , i can't remember exactly but was about 250hp. yes, they use dyno chassis. coincidance? well, we upload the map, put on dyno, always start tuning in steady mode, after first pulls, got only 199hp, was stock boost, this car has oem boost controller so was very easy to do, started to raise up the boost, was 3-4 psi more, i can't remmeber exactly really, so we got about 224hp, (im checking all dyno pulls right now ), that was first day, then for second day we go for more boost, then got 250hp, 251hp, 252hp, after more pulls , go slow to 248 and 246hp, just by IAT was too highs, checking external temperatures was 38-39ºC.

You say, it's not posible only gearbox has that 3% , yes sound really crazy, i can't remember what gearbox he used, i know he told us that gearbox is still weak, but the best he can install it, very small gearbox, what i 'd say im pretty sure in a dyno chassis,including tires there Will be more drivetrain looses. maybe whp was hight? i really dont think so, even i'd noticed in high drivetrain looses.

the first year after rebuilt my dyno, using yourdyno, every car i tested, always compared with other dynos, i was very paranoic with these because i wanted the best dyno (who doesnt wanna it?) then made a lot comparing, affortunatelly you can see tons of dyno pulls for many cars on YouTube and was comparing, and really the results was very close, after 3 years, i know everything is good, you can see in some dynos only read whp making 150-155whp b16s with bolt ons.. and other dynos only read hp, you can see yourself in YouTube readings 170-175hp, that's what the numbers i get normally with these EGs/Eks, B16s with bolt ons… same for other cars...

that's just my experiance, this tool years for design, for learn more about dynos, indeed, i had before a roller dynos (i Will rebuild it and sell), learned a lot, still learing, i dont have any dynosheets for comparing with the other dyno, complete industrial state got burnt, many shops including my old shop, roller dyno was ok, just wires and pneumatic system was damaged, (plastics,etc).. what a  tragedy.. im up after many years. for example.
Thats was my experiance with this car, so you can make your own conclutions. i'd like to go with 4WD i'd like to see what drivetrain looses i can see for 4WD cars..

Im pretty sure if i test in other gear, i'd get different drivetrain looses..the best one for to get "close Reading" to hp in a dyno chassis is to test using the gear closest 1:1.... still repeat, im not saying i have the best dyno, no way! but my goal as always in my life, try to learn, and to make things good. that's just my 2 cent. (as US ppl would say, does it? :D), pretty sure running with tires, you Would get more drivetrain looses, i'd say +4-5% depend of tire size/Wheel weight/total weight of tire-Wheel.

PS: sorry for edite it, just Reading and found some wrong words, i means, my english isnt my first language and i dont write correctly in many times. sorry!