Dyno Dynamics rolling road, accurate?
#43
Testing the future
i don't see why christian couldn't just do a quick test and answer the question if he doesn't know the answer already from his extensive use and knowledge of his equipment?
#46
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All the runs on the Gooon have been done in 5th, when I questioned the operator about this I was told that it would make very little difference, maybe 5bhp lower compared with 4th gear
Intrested to see some back to back testing though
Intrested to see some back to back testing though
Last edited by Ratty; 30-03-2009 at 12:17 PM.
#50
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I suspect that there will be a significant difference between runs.
Unfortunatly none of the tuners will admit this as it will lead to people questioning the accuracy of load cell dynos that measure coast down to give flywheel figures.
I stopped thinking DD RRs were much cop when their UK importer publicly stated in a mag that a load cell dyno is far more accurate than a inertia dyno.
Unfortunatly none of the tuners will admit this as it will lead to people questioning the accuracy of load cell dynos that measure coast down to give flywheel figures.
I stopped thinking DD RRs were much cop when their UK importer publicly stated in a mag that a load cell dyno is far more accurate than a inertia dyno.
#51
I suspect that there will be a significant difference between runs.
Unfortunatly none of the tuners will admit this as it will lead to people questioning the accuracy of load cell dynos that measure coast down to give flywheel figures.
I stopped thinking DD RRs were much cop when their UK importer publicly stated in a mag that a load cell dyno is far more accurate than a inertia dyno.
Unfortunatly none of the tuners will admit this as it will lead to people questioning the accuracy of load cell dynos that measure coast down to give flywheel figures.
I stopped thinking DD RRs were much cop when their UK importer publicly stated in a mag that a load cell dyno is far more accurate than a inertia dyno.
#53
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As long as you know the inertia of the drum and have accurate speed measurement of it f=ma does the rest.
#54
Perfectly true in terms of "raw" data though.
As long as you know the inertia of the drum and have accurate speed measurement of it f=ma does the rest.
#55
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The DD rollers seem massively inaccurate when not used properly..
(but i guess most RR would be)
Par exmplé :
friend has Williams clio (heavily modded)
was mapped on a Friday, and made over 240 bhp..
The very next day, the car was driven to another DD rolling road, and the car made
not much over 200 bhp
this car then went on to do a 13.2 second 1/4 mile at 105MPH about a week later
with no changes (no major suspension mods either)....
make of that what you will, but i think it'd take closer to 240 bhp to do a 13.2 1/4 mile than 200
* Edit. the lower figure was recorded with the RPM pick up not used, but done on wheel speed etc.. sounded like a cowboy method to me lol
(but i guess most RR would be)
Par exmplé :
friend has Williams clio (heavily modded)
was mapped on a Friday, and made over 240 bhp..
The very next day, the car was driven to another DD rolling road, and the car made
not much over 200 bhp
this car then went on to do a 13.2 second 1/4 mile at 105MPH about a week later
with no changes (no major suspension mods either)....
make of that what you will, but i think it'd take closer to 240 bhp to do a 13.2 1/4 mile than 200
* Edit. the lower figure was recorded with the RPM pick up not used, but done on wheel speed etc.. sounded like a cowboy method to me lol
Last edited by pee vee; 30-03-2009 at 01:43 PM.
#58
Happily retired
Interesting thread. There are so many different factors that would need to be accounted for when going from rolling road to rolling road. But, at the typical power levels that joe blogs has on the street, i cant see a couple of degree's of ambient temprature making a whole lot difference to the eventually BHP result.
IMO, rolling road figures can be manipulated by the operator anyhow, and as somebody mentioned, they really do mean diddly squat other than maybe pub talk or a riugh guide to what level of tune your car is at. How the car drives on the road is what should really matter, or how it performs on track/strip.
Just my 10p's worth
IMO, rolling road figures can be manipulated by the operator anyhow, and as somebody mentioned, they really do mean diddly squat other than maybe pub talk or a riugh guide to what level of tune your car is at. How the car drives on the road is what should really matter, or how it performs on track/strip.
Just my 10p's worth
#60
So because I want to put my car on the rollers its all pub talk, get real man the one thing my car aint is pubtalk. Mark has replicated his Dyno figures within 1% on the rollers he uses & in one case left immediately for Brunters & ran a new Topspeed record hardly pub talk. They only mean diddly squat to someone who hides behind your statement & dont get out there & prove the Dyno & RR figures are correct Please dont tar me with your brush.
He is just talking about cars in general where people bang on and on about BHP and never do anything with them, as you DO do something with yours, surely it should have been obvious to you that you therefore werent in the category of people he was talking about?
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Well i have always wondered about this as i put my saff on a RR up here....it runs grays and 34-36psi peak on the roads and when it went on the RR it was run in 3rd gear and i was really upset with the result as it struggled to make stage 3 power, But when i read the printout it only hit about 26ish psi not anywere near what it makes on the road.....
Ive always thought if it was run up in 4th would it of loaded the engine up more in turn gaining more boost and giving me a higher BHP figure......?
Ill try and find the printout.....
Not sure what kind of rolling road it was but im sure it was C&B old one so if anyone knows what kind that was....
Ive always thought if it was run up in 4th would it of loaded the engine up more in turn gaining more boost and giving me a higher BHP figure......?
Ill try and find the printout.....
Not sure what kind of rolling road it was but im sure it was C&B old one so if anyone knows what kind that was....
#63
Professional Waffler
i agree that an inertia dyno is much easyer to get an accurate power figure from, as you say its simple physics! but if the mass isnt large enough to provide the load required to get to peak boost, what can you do about it?
#65
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It's not actually that simple. You do need loading to allow the car to produce boost.
We run most cars in mode Shoot_4 which is actually intended for N/A, as opposed to Shoot-4F, which is the mode intended for Forced Induction. We have done ALOT of experimentation and we have found this to be the way that the car produces the closest boost curve to what it does on the road as the ramp-rate is slightly slower.
There is alot in the way the car is strapped down too. It is as others have said, a Dyno is only as good as the operator. That is in no way intended to be an attack on any other specific dyno operator, but I think we experiment more than most.
We can actually run Gary's Evo to within 4-5bhp in 2 separate sessions on different days, which, given the fact that we are talking about 650+bhp, is quite a close margin.
We run most cars in mode Shoot_4 which is actually intended for N/A, as opposed to Shoot-4F, which is the mode intended for Forced Induction. We have done ALOT of experimentation and we have found this to be the way that the car produces the closest boost curve to what it does on the road as the ramp-rate is slightly slower.
There is alot in the way the car is strapped down too. It is as others have said, a Dyno is only as good as the operator. That is in no way intended to be an attack on any other specific dyno operator, but I think we experiment more than most.
We can actually run Gary's Evo to within 4-5bhp in 2 separate sessions on different days, which, given the fact that we are talking about 650+bhp, is quite a close margin.
#67
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So because I want to put my car on the rollers its all pub talk, get real man the one thing my car aint is pubtalk. Mark has replicated his Dyno figures within 1% on the rollers he uses & in one case left immediately for Brunters & ran a new Topspeed record hardly pub talk. They only mean diddly squat to someone who hides behind your statement & dont get out there & prove the Dyno & RR figures are correct Please dont tar me with your brush.
Fancy a pint Rod?
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Sad but true
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It wasnt exactly helped when a GTR Reg mod got a slap at TOTB (not by me I hasten to add..... I was beaten to it! )
I think they may have all kissed and made up but I still cant login.
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Madrod, firstly my comment wasnt aimed at you in the slightest, for one i dont even know who you are, so chill mate. I was merely trying to put myy opionion accross that a lot of people find out there bhp level merely to boast down the pub to their mates. for a mucky old Ł5 i'll knock a rolling road graph up for someone on excel so they can boast to their mates that there saxo 1.1 forte is making 207bhp @ the wheels at 0.7bar of boost
#72
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chip,i imagine the tuners dont want to come on to this thread because they are fed up with all the argueing that ends up between them all.
tbh sometimes i think the numbers we chase are bullshit. i was discussing this with my mate jay last night,we are sure we would be better off having a car that we know is fast on the road rather than knowing the figure is higher than someone elses, rod is right when he says it matters on the tarmac
so many different results on the rollers from different people that the only true answer is the cars side by side on the road
tbh sometimes i think the numbers we chase are bullshit. i was discussing this with my mate jay last night,we are sure we would be better off having a car that we know is fast on the road rather than knowing the figure is higher than someone elses, rod is right when he says it matters on the tarmac
so many different results on the rollers from different people that the only true answer is the cars side by side on the road
#73
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bang on!!
i could do a run and post graphs but im sure someoe on here will find something i did wrong and ill never hear end of it.........
i could do a run and post graphs but im sure someoe on here will find something i did wrong and ill never hear end of it.........
chip,i imagine the tuners dont want to come on to this thread because they are fed up with all the argueing that ends up between them all.
tbh sometimes i think the numbers we chase are bullshit. i was discussing this with my mate jay last night,we are sure we would be better off having a car that we know is fast on the road rather than knowing the figure is higher than someone elses, rod is right when he says it matters on the tarmac
so many different results on the rollers from different people that the only true answer is the cars side by side on the road
tbh sometimes i think the numbers we chase are bullshit. i was discussing this with my mate jay last night,we are sure we would be better off having a car that we know is fast on the road rather than knowing the figure is higher than someone elses, rod is right when he says it matters on the tarmac
so many different results on the rollers from different people that the only true answer is the cars side by side on the road
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#79
Interesting topic.
IMO Gary's Dyno use and knowledge is impecable as are his tuning skills so I will take his readings as being as scientific a test as we can get for free on a mere forum and would hope you all appreciate him using up his valuable time to create and collaborate the information for us.
IMO Gary's Dyno use and knowledge is impecable as are his tuning skills so I will take his readings as being as scientific a test as we can get for free on a mere forum and would hope you all appreciate him using up his valuable time to create and collaborate the information for us.