Chip

iTrader: (3)

Not if you can vary the resistance like on a set of rollers, to give it longer to spool up in the lower gears.

Chip

iTrader: (3)

Id be interested in info from non tuners too if anyone had it, but they dont seem to, and the tuners who do, dont seem very forthcoming.

As Rob says, we'll just do it ourselves, no problem!

foreigneRS

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?

scoooby slayer

iTrader: (4)

will be interesting to see the results of this, some hard facts of what the difference actually is

Luca

iTrader: (2)

Any questions or theories you want checking /answering JKM will be able to test and prove for you boys.

Now ring them up and book the runs, be great to see what its running now

sbd16v

hold on a second

i said nothing about publishing the findings

Chip

iTrader: (3)

Its not "couldnt" its "wouldnt"

Chip

iTrader: (3)

Indeed, secret squirrel FTW yo!

Ratty

iTrader: (1)

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

Garage19

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.

Chip

iTrader: (3)

Id sooner trust an inertia dyno personally, but maybe that quote was presented out of context and he was referring to a DD setup specifically due to the number of corrections it can make, perfectly possible that what you read wasnt exactly as he meant it.

alistairolsen

lmao at this thread!

"Is the sky blue or black?"

"I think the sea is purple"

Garage19

Its the fact that you shouldn't need any corrections on an inertia dyno just Newtons Second Law that makes them accurate.

As long as you know the inertia of the drum and have accurate speed measurement of it f=ma does the rest.

Chip

iTrader: (3)

Thats not the case at all if aiming at a repeated DIN type measurement which takes into account pressure and temperature and attempts to allow for it.

Perfectly true in terms of "raw" data though.


Well, almost, it wouldnt take account of friction in the drum bearings, but im sure that effect wont be massive.

pee vee

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

Chip

iTrader: (3)

Using wheel speed shouldnt effect the BHP, but will make a massive difference to what the torque figure is and where it appears if they get the calibration wrong.

I agree with you that 105mph sounds more like 240bhp to me BTW.

Cam

Chip,
I would advise you ask the same question on the GTR Register as the Dyno Dynamics head honcho/importer guy frequents there

Rod-Tarry

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.

Chip

iTrader: (3)

I dont suppose you could PM him and ask him to view this thread?

I would imagine this board has a big enough readership to interest him commericially?

Chip

iTrader: (3)

Wow, what a massive over reaction, he wasnt talking about you specifically like you have taken it to mean.

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?

lawnsy

iTrader: (1)

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....

cossie4i+

iTrader: (15)

Im going to book mine in to my local DD RR and see if the figures are the same as TOTD.

Not that bothered about exact figures more interested if it makes power above 5800 and dont flat line again.

Steve

GARETH T

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?

Tim

iTrader: (1)

run better boost control,so you always get full boost no matter what ?

Christian and Beccy

iTrader: (14)

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.

Chip

iTrader: (3)

And what variation do you see when you run gary's car in 3rd gear versus 4th then mate?

Cam

Fancy a pint Rod?

Cam

I'm banned for life from there after a minor disagreement with the admin over not being allowed to mention Keith Cowies achievements
Sad but true

Chip

iTrader: (3)

They want people not to mention the fastest skyline in the country on a skyline forum?

You gotta be kidding!

Cam

All Forum politics over Keiths breakaway forum and that I was a mod on there when Keith started it.
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.

Kev83

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

Bullett

iTrader: (2)

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

GaryEvo

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.........

Bullett

iTrader: (2)

exactly mate.it doesnt matter who you are or what you do someone will always have a problem

Garage19

Will DD RRs give ATW readings?

It would be really interesting to see flywheel in 3rd and 4th and then ATW in 3rd and 4th.

Garage19

Never question anything. Thats a great attitude. Suppose you would still be happy thinking the world was flat.

Chip

iTrader: (3)

yes they will


Gary, dont be such a fucking girl about it, if you know that how you operate your rollers is correct then there will be nothing anyone can criticise anyway.

GaryEvo

let me get some stuff out the way and ill sort it

Stu @ M Developments

iTrader: (12)

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.

It's Czech Mate

Edited by Stu. Unnecessary.