The AUSubaru.com.au Forums

check this out
http://cgi.ebay.com.au/G-TECH-PRO-RR-IN ... RCH:AU:101

what about it?

never seen 1 befor thats all
you want them seats
dibs

LOL , sorry I am a bit sus on how this could really work , has any one had any real expreience with this .

Mike.

They work by measuring G forces (acceleration) and uses Newtons 2nd law of motion to calculate power (force)

Force = Mass x Acceleration

All you do is enter the cars weight (mass), find a flat piece of road and floor it. It can then calculate via the G forces it measured and the weight you entered how much power you car has.

its physics, force = mass x acceleration.
This must simply have a accelerometer sensor, similiar like those
brake testing machines have come rego time...
the rpm hookup then enables it to give a similiar graph like a dyno
sheet.

How well does the particular device work though? if it requires requires
full on input like on a race track? well that may cost more than a dyno session ay? or illegal activity on roads.

haha......someone beat me to it! i got disrupted so didn't post earlier.......

Force = Mass x Acceleration. Well that would be sufficient in a perfect situation, but unfortunately there are a number of factors which act on the car, including wind resistance, friction, incline ect. THis would mean the "horsepower" display would be underestimated.

Pretty simple device if it only bases its calculation on 2 set points. Also, fuel, driver and load weight would change things again. Its bullocks to say its better than a dyno. It would have to take in dragco efficiency of the car, tyre width, pressure ect. All sorts of things to be accurate

Well come to think of it, this thing probably gives the best 'real world' because acceleration depends on things like traction and wind resistance.

Compare say a Nissan Pulsar with a 300kw engine and FWD to a Subaru Impreza with 250kw and AWD.

On a chassis dyno the Pulsar is gonna look quicker

But on the road with this portable dyno, the Impreza is gonna have the advantage of traction and thus will be quicker

well yes, a simple read out of g forces (acceleration) as measured by an accelerometer would show which car is infact better. But by the same token, a speedo is merely the sum of the previous acceleration of the vehicle, thus already showing that at any given point, the car is winning.

Sorry, hard to explain.

All it means is you can't directly compare this graph with a dyno graph, its still relative comparisons only to using the same measuring device. This can also be said for dynos, as different garages may have the dyno calibrated differently...so you can't compare absolute results.

i have used the older version of the G-tech, but more as a quarter mile timer without having to go to the drags. not always accurate, as in the quarter times given weren't the same as the timing gear at the dragstrip, however the error was consistent.

not actually a bad tool to check if a mod made a worthwhile change or not, or to compare cars to each other. I would only quote power figures with 'measured with a g-tech' as a disclaimer

theclick wrote:Force = Mass x Acceleration. Well that would be sufficient in a perfect situation, but unfortunately there are a number of factors which act on the car, including wind resistance, friction, incline ect. THis would mean the "horsepower" display would be underestimated.

The "real" horsepower of the drivetrain would be underestimated for its true value if you always ran your car on the spot. This device seems to allow a "real life" measurement of the car's horsepower as an overall unit, not just at the wheels as a dyno gives you.

Suparoo wrote:Well come to think of it, this thing probably gives the best 'real world' because acceleration depends on things like traction and wind resistance.

Compare say a Nissan Pulsar with a 300kw engine and FWD to a Subaru Impreza with 250kw and AWD.

On a chassis dyno the Pulsar is gonna look quicker

But on the road with this portable dyno, the Impreza is gonna have the advantage of traction and thus will be quicker

I'd hate to get my car dyno'd, find out its got more power at the wheels than a mates car - only then to be whipped by him at the lights...

Also I wouldn't be dyno'n my car cos it would be a waste of money. But this unit could be a bit of fun on the weekend between mates...

Cheers

Bennie

I have the cheaper earlier model than the one pictured there and as long as you get the wieght pretty much on the money they are a good indication. said my Liberty had 130kw and when dynoed it had 125.2kw ATW so it wasnt off by much.

We've been using them for years. Very handy for measuring the effectiveness of mods, especially exhaust where more noise can make the car feel faster. I've seen independent tests where the 1/4 mile function is damn close to drag strip times.
I prefer the older model though. It's easier to use.