hi

lol know where ur coming from

cya

PS : opinions are like a**hole we all have one

The accuraccy of a dyno all depends on the technician who callibrates that dyno. It must be refferenced to something. Depending on that refference (and a few other things which are purely related to the equipment itself) you end up with different readings.

There is a standard as to what 1 horsepower is. But being able to interperet rotational motion from linear motion isn't always the easiest thing. Especially when that rotational motion is being transferred through gears and shafts which all have a mass and a given size.

There is no way to be able to interperet engine power and torque from horsepower and torque at the wheels.
For one: The dyno operator would not know all of the mass of the moving parts linked from your engine to the rollers. He also would not know their sizes, centers of mass, radii of gyration and coefficients of friction. The software to work all of this out on the fly probably isn't yet developed and it is far too complex for the average joe to even try to understand.

You could suggest that the engine be taken out of the car and dynoe'd on an engine dyno. Then put back in the car and dynoe'd on a chassis dyno. This has merit but that thought is shotdown pretty quickly because its a fairly expensive exercise. Not to mention that many engine dyno's provide different readings. Also the conditions in an engine room are very different from that in an engine bay. The airflow is different. The air temp is different too. Not to mentioon air pressure and all sorts of factors.

Chassis dyno's when properly calibrated and maintained are a precise tuning tool which will only give you a precise reading at the driven wheels of your vehicle and that is it. Nothing more nothing less. Unless you know how to interperet torque/hp curves into numbers down at the track peak numbers are only for bragging rights or to boost the profile of your car for a sale (many junior habibs and ricers fall for this trap by bragging about their mates car purely because of how much rwkW it has).

Engine dynos are the same but they give you more of an indication as to how your engine will perform regardless of the car it is being installed in or what the rest of the drivetrain is.

And chassis dyno's do not cost half a mil as previously stated otherwise it would not be worthwhile to buy one. Last time I checked a chassis dyno was 50k and an engine dyno was 110k.

hi
sorry about that , that was a honest typo i ment fifty thousand DOLLARS onwards for a 2wheel drive and a 4 wheel driver starts anything between 135,000 AUD to 185,000 AUD depending on the configuration u buy
yes engine dynos start at 110,000 AUD onwards agian depending on the dyno you buy water brake or eddy current.


let me get things inperspective so people understand what i'm saying


if ur run a car on a dyno dynamics dyno eralvet who the operator is say a EL falcon 6 cylinder you will get a rear wheel kwatt reading of approximately 105 to 110 kwatts

yet run the same car on a DTS dyno and you will get approximately a 17 to 20 % greater reading

so my question is once again

WHAT IS THE CORRECT READING ???? THATS MY MAIN CONCERN i dont not care about all this shootout software and correction factors nor the operator nor the tuning aspect REMEMBER THIS i should be able to run my car on any bodies dyno thats PC controlled and should be able to get a reading within 2 to 5 % variation Remember there PC controlled .amd supposed to be a scientific piece of equipment.

lets get some figures in here if anyone is willing to share the dyno information

a) we need some cars that have been run on a dyno dynamics dyno

b) we need the same car without any alterations on them that have been run on a DTS dyno

lets see what the results are

then you will see what im trying to say
forget about the tuning aspect thats not my arguement LOL

cya

Although I am not a dyno operator -Is anyone here?

I would say that the problem is broken down into a few areas.

1) Your engine does not make the same power all the time - air temp, coolant temp, altitude, fuel quality, parts wearing in/out, ecu learning etc. Even if you can put in compensation values how do you know how your engine responds to changes compared to another? I could see an easy 5-10% variation here

2) Mechanical factors like tyre rolling resistance. Drivetrain losses. Things like changing the diff or extra weight in the back would make a difference. But small since you can largely control them 1% variation.

3) Dyno variations, I asume they use a strain gauge on a shaft, that would need to be calibrated using some reference weight or load. Is this ever done? As they get older the sensor charteristics will change. + The dyno has bearings, moment of inertia etc with their own losses that will change as the machine ages. another 8% here

4) Measuring technique. Do they just pick the highest peak, or average over a few readings or what? Is the engine acellerating through the load points or being held at constant RPM. Even if there is a standard for one type of dyno, another type might have a completely different technique. Sampling rate? Big variation here probabily 10%.

I think we can see where the variation comes from. It doesn't matter if it costs $50,000 or $50,000,000 these things are still going to be there.

hi
some interesting pionts there

I'm talking new dyno's ( ie new dyno dynamics and a new DTS ) zero waer and tear

as for the vehicle being tested I'm talking the same vehicle all the time

yes air temp is a big influencing factor

I'm willing to donate dyno time for anyone willing to run there car on my dyno dynamics dyno if they have a result from another workshop that there car has been tested on a DTS dyno and i will post the results in here and remember i dont play around with the nudge factor LOL

then u will see what i'm saying

does anyone have a mate in the industry that has a late model DTS dyno we can compare the results and do the runs on the same day and at sea level would be interesting to see the variation

cya

So you have one of these?

What do you have control over and how are measurements made?

What are these 'nudge" factors?

I would be very interested to hear how it all works.

Sorry mate..

I was just toying with the guys.

I do not know if there is a standard that all dynos meet ?Even in the dyno dynamics range of dynos there are many questions in my mind as well as to finding meaning in their figures.
Many have seen me post that in one day I went to 3 dynos.All were dyno dynamics.In blacktown I got 112 rwkws.I went down the motorway to Granville and pulled 128 rwkws.I then proceeded to Silverwater where I got 147 rwkws.
This exercise was not cheap,but it taught me a lesson..

I think that if you want to really know what power figures that you have ring ford or holden engineering and ask what is their method of engine dyno?

There must e some legal rules that their power figures must not be misrepresented.

Dyno dynamics dynos do not give repeatable results from place to place.
However you get a general idea after a few dynos where your power level is at the back wheels.The average method descibed elsewhere is not a bad way to do it.

As has been said again and again, there a FAR TO MANY VARIABLES in play to make a chassis dyno a CORRECT or even TRANSFERABLE measure of power/torque.

By transferable I mean, able to be compared across other dynos, or indeed in extreme cases other runs on the same dyno (different conditions acting here).

There are MANY dyno 'standards' around (I quoted standards because there's far to many to be called a standard).

Quote: http://www.dyno.com.au/shootout.htm
"The fact is, a (quality) dynamometer is fundamentally a diagnostic tool. So the accuracy of power measurement in an absolute sense is generally not critically important. "
(from DynoDynamics themselves)

In short there is no CORRECT dyno measurement.

DynoDynamics go forth to say their ShootOut mode is a set of standards and operator training that should enable transferability between other dynos also run in ShootOut mode. This doesn't make them correct, just REPEATABLE - which in itself is one step towards what everyone is after, a way to say "mine is bigger than yours" and have proof.

My personal expereince, between two MDX dynos, 102RWKW one day 114RWKW another, no new mods between them.

That being said, take you're ET or TS and cars+drivers weight and try these two fomulae. See how these compare to your dyno runs.

Weight in Lbs
---------------
(ET / 5.825)^3 = RWHP

or

Weight in Lbs
----------------
(TS / 234) ^ 3 = RWHP


ET in seconds
TS in MPH

I found the ET formula compares closest with my dyno runs.

It's generally accepted that TS is a pretty accurate measure of horsepower, more so then ET in my opinion. I'd much rather get a timeslip then a dyno printout, seeing as no matter what you do, 400m is 400m...

Yes I agree the TS is a really good measure of the power to weight of a car and those formulas actuall work well for a wide range of weights and powers this side of 300rwkw plus drag cars.

They work better than most dyno's for estimating power in my opinion.

hi

lets have a better look at my question

easy example
if i have say a 10 kg weight and use scale Scale1 and it measure 10kgs i would expect another brand of scale to measure the same so Scale2 should measure 10kgs as well if i used the same weight if these 2 scales have been calabrated and meet a standard

so lets get back on the chassis dyno situation im talking two different brands of dynos here Dyno dynamics and Dynamics test systems (DTS) botH manufactures of dynos and both based in melbourne victoria dont know the sea levels in relations to each other other than one is in frankston which is close to sea level and the other based in lillydale which i assume is slightly above sea level dont know and havent bothered to look it up.

they both use strain gauges to measure force YES do we agree here
so if i had a 10kg weight and place it on the strain gauge (load cell) exactly the same distance from the center of the electricl retarder those strain gauges should read the same voltage do we agree on this

THEN MY QUESTION IS AGAIN WHY DO THESE TWO DYNO MANUFACTURES READ DIFFERENT IF THEY BOTH RUN THE SAME CAR ON THEM ???

I HAVE DONE THIS TEST ALREADY AND I KNOW THEY DO READ DIFFERENT????

SO GUYS BEFORE U START TELLING ME THE PHYSICS PLEASE READ THE QUESTION AGAIN

SHOOTOUT SOFTWARE MMMMMMMMMM WHAT AM I SUPPOSED TO BELIVE THIS IS A STANDARD lLOL

Why dont you ask the guys that make the dyno?