Caporegime
because some people fail to understand the difference between dynometers with one roller and two.
Mini OcUK Rolling Road Day: Powerstation Saturday 22nd January!
- Thread starter Gibbo
- Start date
Permabanned
Can you educate us then, without the use of Wikipedia.
Caporegime
People have always read on the internet that the only true figure is the power at the wheels figure, that the power at the fly figure is a figure generated to massage people's egos by looking bigger. And that the only true indication of a car's power is the power at the wheels.
The american's are very much in this mindset, its not uncommon to hear people on american forums talk only of RWHP - rear wheel horsespower. Very rarely do they quote crank horsepower.
However in europe we nearly always quote the engine power instead of the power at the wheels. As a result the Maha dyno that powerstation use has been geared up to produce a more accurate engine horsepower figure by using two rollers. Whether you believe this works or not is up for debate. I've no idea if its true or not, but thats what Maha who make it think.
Because the wheels have two contact patches, there is more resistance at the wheels than you would get in a real life. You could possibly choose to take account of this, and quote an accurate power at the wheels figure, but powerstation choose not, and use it purely as a figure for calculating the crank horsepower.
However, because people see power at the wheels figure that are horribly inaccurate, they conclude that the dyno itself must be horribly inaccurate also. This is not true, the Maha dyno that PS use is not intended to quote accurate power at the wheels figures. It quotes it on the graph purely for reference. Maybe they should remove it to avoid confusion ? who knows. Its german and you know what those crazy germans are like ...
But anyway, main point is the Maha Dyno doesnt produce accurate power at the wheels figures and aims instead to produce accurate power at the flywheel / crank figures.
The american's are very much in this mindset, its not uncommon to hear people on american forums talk only of RWHP - rear wheel horsespower. Very rarely do they quote crank horsepower.
However in europe we nearly always quote the engine power instead of the power at the wheels. As a result the Maha dyno that powerstation use has been geared up to produce a more accurate engine horsepower figure by using two rollers. Whether you believe this works or not is up for debate. I've no idea if its true or not, but thats what Maha who make it think.
Because the wheels have two contact patches, there is more resistance at the wheels than you would get in a real life. You could possibly choose to take account of this, and quote an accurate power at the wheels figure, but powerstation choose not, and use it purely as a figure for calculating the crank horsepower.
However, because people see power at the wheels figure that are horribly inaccurate, they conclude that the dyno itself must be horribly inaccurate also. This is not true, the Maha dyno that PS use is not intended to quote accurate power at the wheels figures. It quotes it on the graph purely for reference. Maybe they should remove it to avoid confusion ? who knows. Its german and you know what those crazy germans are like ...
But anyway, main point is the Maha Dyno doesnt produce accurate power at the wheels figures and aims instead to produce accurate power at the flywheel / crank figures.
Soldato
Be sure to tell them that so they can, like, seasonally adjust the result to your satisfaction without a doubt.
Caporegime
funny because my dyno operator didn't even know what engine my Vectra VXR had in it, let alone how much horse power it produced - yet the maha dyno still estimated i was running with 1/2 hp of the manufacturers quoted figure.
Exactly the same for all 4 of my cars, unless they are looking up the cars before hand?!
You going to be coming via the Willy Wicket again?
Associate
I'll come and spectate if I have a car by then 
Soldato
I know we've had this here eleventy million times, but...
I'm sorry but I don't buy that. What a Rolling Road measures is power at the rollers. It then does some funky maths to work out a power at the flywheel estimate.
Anyways, having the engine out on a calibrated bench dynometer is better than any rolling road - be it one roller or two
.
Soldato
Might come and spectate actually, could do with a good day out.
Soldato
Let's wear our uniform.
Man of Honour
Man of Honour
As best I can tell, it doesn't even do that, because you could only measure that with a full-chat launch, and actually you spin up the speed relatively slowly. ANY dyno run is effectively calculated, even at the rollers. However, you are correct that the conversion to flywheel figures bears little resemblance to the calculated wheel figure.
M
Caporegime
Courtenay sport have a Dynojet which uses one roller. Quite popular make too.
http://www.courtenaysport.co.uk/rolling-road/info_17.html
Caporegime
I'm sorry but I don't buy that. What a Rolling Road measures is power at the rollers. It then does some funky maths to work out a power at the flywheel estimate.
Anyways, having the engine out on a calibrated bench dynometer is better than any rolling road - be it one roller or two
Don't buy it then, makes no difference to me. But thats what the Maha people have told the operators at powerstation. You've got to get away from thinking that the figure it quotes on the page as "power at the wheels" is some kind of definitive figure that is universal across dynos - its not.
And it seems to work just fine to me, as my standard car was spot on. It later produced pretty much the same figure (within 1 bhp) on courtenays dynojet rolling road which uses one roller. I don't know enough to know whether what they say is true or not, but all i know is it works.
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Mustang dyno's are a single roller as are dynojet, very much ones used in US and tend to give quite accurate at the wheel power figure. Problem as there a single roller they only work for RWD or FWD vehicles.
Powerstations rollers are fine for me, generally they are accurate within 2-3% of cars manufactured claims either way.
My last run the car got 378BHP, it should have been 366BHP I believe standard but with 40,000 miles on the clock its possible the engine has found more horses over its lifespan or its just the powerstation rollers been a couple of percent out or I got a very good car, who knows. There are also people who on these days get pretty much on the mark figures and some cars don't make their quoted figures.
Then there is also when was the dyno last calibrated from when we were last there, it may have just been due a calibration which could mean it was quite a bit out or it may have just been recently calibrated meaning it was pretty much spot on.
There are too many variables and to debate or trying to work it all out would probably just be one headache, for me its a good day out and it will satisfy my curiosity.
On the whole stock cars seem to get very close to the manufacturer claims, so the dyno can't be that bad.
Am looking forward to meeting a few of you there, going the pub and taking some trips out in the other cars.
Soldato
Soldato
And last time I went, they seemed pretty much spot on as I got it done again with a decat, and gained 3-4bhp.
Shame it isn't summer though, as I really enjoyed seeing the Citroen C5 on fire at the side of the road, and also having to drive home at 50mph as a boost hose literally exploded on a spirited drive with agw_01.
Fun times...
Shame it isn't summer though, as I really enjoyed seeing the Citroen C5 on fire at the side of the road, and also having to drive home at 50mph as a boost hose literally exploded on a spirited drive with agw_01.
Fun times...
Soldato
I think you've been in the car post remap since the map was done back in sept 2009.OK cool shall let them know there is 2 of us running so far.
Anyone else coming to run or just for a mini meet? As if enough of us we can always pay a visit to the usual pub and do a few test drives.
Be good to see how your Exige feels after the remap Neil.
Neil.