EIL132

Can you comment on this

"from the looks of the pics the rolling road you went to was the older type where the cars wheels sit inbetween 2 rollers. the modern and most accurate rolling roads have a set up where your car sits on top of a single roller (looks scary when u see a car doing 100+ mhp perched on top of a single roller! )

the old style rollers are not accurate its a well know fact i m afraid variable like how hard the car is strapped down etc can alter the readings dramtically.

if u want a true and probably disapointing reading you need to go to one of the modern rollers i think there is only 3 in the country and they are all used by prodrive,noble,cosworth etc because its is well know in the trade that they are the only ones that give 'true' readings"

Billabong

I believe the thinking behind this is that on the road you have 1 contact patch per tyre, obviously with two rollers per wheel, you have two contact patches. And if strapping down is such an issue, then that surely applies to all rolling roads, as a car doesn't need to be strapped down on the road.... (I know aerodynamics come into play on the road )

BUT, as for 'true readings' on rolling roads in general...... that's a whole other subject in itself, regardless of type.

As for Cosworth etc. I'm pretty sure they use engine dyno's for development purposes. If they use RR's, then that would probably be for comparative purposes and in conjunction with engine dyno results, not 'power runs' as we know them. (And which part of Cosworth??)

I guess the source of the quote would be pertinent too....

EDITED TO ADD: I'm no RR expert

foreigneRS

what a load of bollocks. all rolling roads are accurate in what they measure - torque at the rollers.

the differences come with what the losses are and how they are measured or estimated.

there's so much misunderstanding of rolling roads (chassis dynos to give them their correct names) for what is essentially a very simple device

Gary Osborne

a company i used to work for over here had a dynapack 2500 chassis dyno. these are the way forward for mapping cars imo . it can hold any engine at any given rpm with all the power you can throw at it and theres is never a chance of wheelspin because its bolted to the hubs of the car. it could in theory stop a 1500 bhp engine dead in its tracks (not that you might want to!) it also imo lets the car move about under load as it would on the road as there is no strapping involved. its awesome to see a big bhp car squat as it comes on boost

Billabong

Just to add to the discussion if we're moving on to hub-dyno's:

http://www.wrc-tech.co.uk/services-r...ynamometer.htm

Gary Osborne

now forgive me if im talkin through my arse but they are talkin about real world situations and "road load" etc.

so they are basically saying an engine dyno is not the proper way to map a car either?

im sure the likes of abbey motorsport, JUN, and apexi have a bloody good reason for using dyna packs to map their world famous cars

JohnnyB

well lets look at the dyno pack setup, not perfect as heat increases oil thins?

eddie current roller are the best, is just a question of holding the car down.

my I suggest Dyno dynamics

Billabong

Most tuners have their preference - usually depends on what equipment they have.

IMO, the best way is to engine dyno, and then tweak in car on the road/test track. Engine dyno's are invaluable for R&D, where FACTS can be ascertained as to the effectiveness of a modification - highly repeatable and accurate.

JohnnyB

yes bill i agree if you want a very close to correct reading then use a engine dyno, but in the real world taking your engine out for a tune is inpractical.

most RR give you an basic reading, but thats not the point of RR the main + is for tuning no matter what people say and you can make some nice cash from a RR day

Gary Osborne

very true mate but they are water cooled so they can last quite a while before losing accuracy and as most cars cooling systems wont cope with prolonged mapping sessions without gettin a rest or whatever, the dyno is also getting a chance to cool down

Billabong

I agree Johnny, but when you have accumulative R&D data, you can tune engines further without the need for an engine dyno' as you already know what works and doesn't - if you've been meticulous with your R&D and already tested certain things....

JohnnyB

yes saphcos, but if I spent 60 odd k I would not use dyno pack stuff as I would like to pay back my loan and dyno packs are not great for RR days, thats were money is being made.

JohnnyB

yes Bill, but if you can get enough wind in the front of a car on the rollers. you can get the engine mapping time right down, yes not perfect, but better than the shit chips going about these days.

GUZZLER

iTrader: (3)

a lot of the time Prodrive use Power Engineerings rollers

Gary Osborne

i know what ya mean alright . the first and only rr day we had was pants . got through about 12 cars or so and then gave up.

but it didnt matter cause my bosses daddy paid for it! jammy cunt. and the only reason i like them so much is because of a bad experience sittin in the boot of a supra with 3 others and like a fuckin plank dropped me leg across the exhaust

anyway ive just seen the title on this thread so i think ill

JohnnyB

saphcos if you can get a Dyno Dynamics to slip then I will give you head

pee vee

JohnnyB
i have a tractor puller that i need dynoing,, it has at least
50000000 Nm of torque (ass dyno estimation)

so
do you spit or swallow ??

JohnnyB

lol

they handle 4000 bhp, but that is tooooo much

JohnnyB

I spit

Gary Osborne

johnny b . i think you picked that up wrong . used to have 2wd rollers ...... burnt the fuking leg off meself ..... now i like hub dynos

pee vee

JohnnyB

EIL132

On topic,

"a modern single roller rolling road does not suffer with all the wheels spinning,loading the rollers problems that older style rollers do.

a dyno bench test is excactly what it says it is a BENCH test. Unless the engine has the correct mainfold and full system connected on the bench you will not get a in car output

a rolling road that doesnt give a accurate figure is still a good tool and aslong as you always use the same rolling road you will tell if any modifications you have done have worked. remeber if a rr is 10% out for example it will always be 10% out so you will see a improvement if there is one to be seen.

another good way of seeing how much bhp your car has is to run it at santa pod ignor the time but look at what the terminal speed is if its crossing the line at just over 100mph its got around 210bhp per ton is the general rule of thumb"

JohnnyB

yes and no, my car is reported to produce 226 bhp, i could not make more than 96 mph on the 1/4, must admit zorst was blowing

foreigneRS

that's a fairly useless way of evaluating any tuning that you've done as it wouldn't show you where and why any gains have been made

you will NEVER get enough wind in the front of a car on the rollers. i run a climatic wind tunnel where we test automotive air conditioning systems. look what you need just to get 70mph worth of wind over the front of the car

here's our 220kW motor



that drives this centrifugal blower



to generate a wind speed up to 70 mph out of this nozzle

Stu @ M Developments

iTrader: (12)

Fooking love that Nick

JohnnyB

now thats a blower

foreigneRS

even though it's massive, it can still only do 70mph over that nozzle size. our newer place in germany can do 100mph over a 2.5 x 2.5m outlet. that uses an axial blower.

as i say, our places are for use for testing air con, so don't need massive speeds. proper wind tunnels for aerodynamic testing like at MIRA etc have far more powerful blowers. one place has 4 propellors from a ww2 lancaster bomber

that just shows you what a waste of time some of the fans that they put in front of the car during rolling road shoot outs are. look at this desk fan that they were using at santa pod classic ford show the other weekend

foreigneRS

you could try and argue that an electric fan on the radiator is no bigger than that desk fan. but they are placed on the radiator to directly suck or blow through it. something like that desk fan will just blow around it.

and usually when your engine is producing max power and needs the cooling the most (or just after) it is travelling at speed so has the wind going through the radiator. during fast driving, an electric radiator fan should not come on whilst on the move, only when you come to stop.

GARETH T

best photo ever

dojj

iTrader: (3)

he was on about bhp/ton
how much does your car wiegh then jb? don't forget to add yourself into the equation and i'm sure you won't end up with much more than about 180/ton

Stavros

The rollers they talking about arnt hub dynos like dynapacks, they the single roller mustang dynos, like what GTART have...

http://www.mustangdyne.com/MD-1750-series.htm