Article on Dyno Drivetrain Loss

[**Ghost**]

http://www.twinturbov8.com/dynostuff.htm

have a look at this article.

I cant vouch for its acurracy obvioiusly, but from the way the author has written the article it doesnt seem like a "bragging rights" article

Just thought it'd be interesting and useful (if accurate) to put to rest all those arguments as to whether USA dynos really read more HP than ours and what (as a general rule of thumb) we lose through our drivetrains

[DynoDave]

http://www.twinturbov8.com/dynostuff.htm

have a look at this article.

I cant vouch for its acurracy obvioiusly, but from the way the author has written the article it doesnt seem like a "bragging rights" article

Just thought it'd be interesting and useful (if accurate) to put to rest all those arguments as to whether USA dynos really read more HP than ours and what (as a general rule of thumb) we lose through our drivetrains

The article is writtin by Todd Wilks who is no longer with us,those figures are very close to what ALLMTR996 put up in another thread a few weeks ago. And it is what I have been telling you guys for the last 2 years.Aussie dyno's read real power at the wheels not only a 5-9% loss.Rule of thumb is that if an engine makes 160kw at the flywheel it will make 160hp ATW (119.38kw) on a Dyno Dynamics dyno but I know most on here like KW readings.
Regards Dyno Dave

[**Ghost**]

so the article is accurate if i'm not reading dave's words wrong?

Alright i'm shakey in mathematics, but

if

%Loss x 160kw = 119.38kw at wheels

this means

the "rule of thumb" % loss = 1- (119.38/160) = 25% (rounding up)

so using this as an example

in other words a stock b16a (which everyone is so obsessed about) in from factory specs shoudl be putting out

118 flyheel figure x 0.75 = 88.5 kw at wheels

in my personal experience this is accurate as i dyno'd 89.9 kw at wheels when my car was stock except for a intake box

[DynoDave]

so the article is accurate if i'm not reading dave's words wrong?

Alright i'm shakey in mathematics, but

if

%Loss x 160kw = 119.38kw at wheels

this means

the "rule of thumb" % loss = 1- (119.38/160) = 25% (rounding up)

so using this as an example

in other words a stock b16a (which everyone is so obsessed about) in from factory specs shoudl be putting out

118 flyheel figure x 0.75 = 88.5 kw at wheels

in my personal experience this is accurate as i dyno'd 89.9 kw at wheels when my car was stock except for a intake box

So there you go another good piece of information the way this forums going these days I will not have to say anything anymore.
Regards Dyno Dave

[**Ghost**]

lol @ dave making himself more obselete bit by bit :P

Just to clarify things above though... we have

1. The Article by the late Todd Wilks (which is reliable if i'm reading Dave's word's right)

2. The opinion of our becoming obsolete dyno-guy, who has been dyno-ing for 10 yrs? (was it 10yrs or 15 i cant remember u mentioned it somehwere)

3. My personal dyno run with stock B16a + intake "proving" the formula

Since all 3 above reference to AUSTRALIAN DYNO DYNAMICS type DYNOS... is it reasonable in EVERYONE"s opinion here we should sticky this and get ppl to read this b4 they ask "What does my engine pull at the flywheel?" or "y did i only make xxKW" or "y did USA car with same mods and lower octane fuel pull more than my car"?

just a caveat on this info... its a RULE OF THUMB... not designed to be 100% accurate.

if you are absolutely pedantic you need to take out ur engine and do a engine dyno :P

[Weq]

I concour with all this.

But be weary of DD dyno's im america, they have been 'calibrated' for american standards

[Boost]

alot of tuners here use the roller dynos... but not many use the dynapacks.

[iamhappy46]

The above link is now dead... So if it was covered in the article, please forgive me...

I have been involved in a discussion with a few Americans. They claim that our dynos are out of whack... Based on: a 400Hp@crank engine making 300Hp@wheels, would be dissapatting 100Hp(75Kw or 750x 100W light bulbs!) of energy thru the gearbox. As energy cannot be created nor destroyed, where the hell is our power actually going? 75Kw of Heat and friction is rather unsettling...

I believe the 25% drivetrain loss figure to be accurate, as stated by DD in post #2. But when actually presented to me in that way, it is down right disturbing!

I can link the discussion if required...

[EfiOz]

25% for a front driver is about right and it's probably more like 30% for a RWD. Most of the extra loss in a RWD is from the diff pinion spreading load into the diff side bearings. As the final drive in a FWD is a helical travelling in the same direction, you don't get this effect. Then there's the extra inertia although you can get around that by running a real slow ramp rate.

Proper race cars with straight cut gearboxes and light weight drivetrains can get down to 10-15%. An F3 would be about 10%, a GT1 would be around 15%.

I've got a heap of paper here from Lars at Rototest in Sweden regarding drivetrain loss. The other funny thing is it gets less in higher gears, as a generalisation. Although the rolling resistance goes up with speed, the spreading force in the gearbox and diff gets less.

It's not hard to see the 25% heat loss. Especially when you've been stuck in a poorly vented dyno cell with a 650HP car, mapping it in steady state. The heat from the exhaust and dyno retarders is bad enough. I've logged gbox and diff temps on a couple of racers |'ve mapped on chassis dyno's and it's amazing how quick the temp comesup once you put a bit of load on it.

Interesting comment about the "American" calibration on the DD units. They have been known for their aggressive marketing stance in the past..........

[Weq]

this information is 100% right. American dynos read engine HP, and not wheel HP.

[aaronng]

There are rolling road/chassis and hub dynos in the US.
Hub dynos read higher because there is no loss from speeding up the wheels. What confusion is there? If you can't compare dynos of the same brand but located at different locations because of atmosphere conditions, then why are we comparing different brands?

With regards to the 300 whp from a 400 crank hp car, the 100hp is lost in the drivetrain and in the dyno itself.

[EuroDude]

where the hell is our power actually going? 75Kw of Heat and friction is rather unsettling...

The more components the power goes through (the clutch, gears, differential etc..), the more energy is used to keep up the momentum. Using lightweight drivetrain components helps reduce the power loss.