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RR Result at RS Tuning
- Thread starter kevo66
- Start date
172Cup
Not interested in ownage!
The biggest issue I have are losses recorded on most rolling roads do not match the data I have for drivetrain losses nor do they match my experience of what a standard engine will make on an engine dyno.
What some people are seeing as a gospel figure from a rolling road is completely different to what I've seen from an engine on an engine dyno, from an engine simulation (and believe me these days they are sodding accurate!) or from live data.
However Rolling roads are a tool and people shouldn't forget that. Look at the gain or loss a change makes on the same rolling road not what the car makes on different rolling roads. Percentage change means much more than head line figures but people forget this.
DD's get labeled as cheap rolling roads but they are very clever - okay they guess losses but the algorythm they use to guess it is very, very good at getting close. To give you some idea TT Duratec 2.5 - engine Dyno 377bhp, DD Rolling Road - 372bhp, Dastek Rolling Road - 401bhp, Brosters Rolling Road (albeit with the engine in a different spec), went off the end of the scale.
The Dastek was massively optimistic, the DD slightly under what the engine dyno said. The engine dyno obviously is never going to be 100% absolutely bang on (every OEM engine dev bloke has their favourite test cell ;-)) but its certainly a good benchmark.
Broster is bang on with his comment regarding sticking calipers etc. and yes a Maha will show this up as a low wheel figure vs a high fly figure - however the number of plots posted on here with 20 - 25% losses is just crazy, you justs can't get rid of that much power through a FWD gearbox.
Don't get hung up on headline figures, look for the improvement it shows but be sensible with it - if you've got a standard 197 with a different air filter and a loud exhaust and the rollers say you've got 200bhp its best to take it with a pinch of salt ;-)
Cheers
M
Last edited:
172 5HED
All,
I thought this post had had its day but it seems people want to drag it back up and chat s**t!
If you want to see, feel, touch, have a go in, doubt, jizz on or whatever else you want to do to my car, I will be attending various track days in it this year. This was the main reson I modded it, not for "pub bragging rights", I have a life.
Feel free to put your money where your mouth is cos I know damn well I will. Matt, Paul Naith et al.... thanks agian for your help on this "waste of money".
I thought this post had had its day but it seems people want to drag it back up and chat s**t!
If you want to see, feel, touch, have a go in, doubt, jizz on or whatever else you want to do to my car, I will be attending various track days in it this year. This was the main reson I modded it, not for "pub bragging rights", I have a life.
Feel free to put your money where your mouth is cos I know damn well I will. Matt, Paul Naith et al.... thanks agian for your help on this "waste of money".
E39 M5 & Corsa track
so your comparing the engine with a difference spec?
also at the time our software wouldn't plot above 360bhp...... this is now fixed and it plots to 720bhp
i assume this is the noble your talking about?
It wasn't a dig!!!!!! Was to point out it had been on yours, hadn't got a headline figure but that didn't matter anyway as the spec had changed. Engine was the same spec on the Superflow ED, DD and Dastek before it ran out of oil ;-)
My comments regarding DD roads are that whilst they use a calculated loss rather than a measurement of coasdown I have found them to be accurate when compared to an engine dyno. Okay they 'guess' but they 'guess' well - unless the engine dyno was massively out but if it was we're all buggered for working out what power our engines are making!
Lets face it we all favour different makes of rolling road and we all find certain aspects of specific rolling roads more useful than others. It's why I say look at the percentage change between a pre modification and a post modification reading. Even if the rolling road is hugely optimistic or massively pecimistic you'll still have a solid indication of what effect the modification has had. If you look at the different ways in which various types of rolling road measure wheel torque then they're never going to agree completey with each other, however in wheel torque/power terms they do get pretty close - its the calculated fly figure and the drivetrain losses that concern me. If we all worked off wheel power things might be a bit more simple? As its least thats a direct calculation from measured wheel torque.
Cheers
M
It is a direct calculation between wheel torque as measured, and wheel power, but the effects of roller diameter, traction efficiency of the roller, tyres pressures, rolling radius, temperatures, strapping method/force etc etc or anything affecting rolling losses means that it will still never be a true fair comparison.
E39 M5 & Corsa track
totally agree, people need to realise that a rolling road is primarily a tool for tuning a car and fault finding seeing the gain from a modification as you say.
Thats still nearly 200kg's heavier than stock quoted figures surely?
182
not a 197 dude, sounds about right with driver and fluid tbh - though cant remember which model he said he owned
Very true but it does remove the optimisitic flywheel power calculation issue where depending on who's software you're using you can see 25% losses or 10% losses through the drivetrain.
Different rolling roads will never read the same figures as you say but removing the biggest 'margin for error' would help - quite a few graphs posted here, including the Dastek ones, show pretty sensible wheel figures - but then a 20 - 25% drivetrain loss.
Cheers
M
It is Clio 197, curb weight is 1280 with 50L of petrol.
