Stupid Things Petrolheads Say
Discussion
zakelwe said:
Chapppers said:
Even if he was talking about rolling roads, all the test are calibrated to the transmission losses, drag and mass of the vehicle by doing "coastdowns" (time taken in a given gear or neutral to slow down to rest) in the real world before hand. As the vehicles are developed, they're also updated with the latest coastdown data.
For instance, all the cars in the JLR range have the same basic engines now, and the heavier ones get higher CO2 figures. It's not magically adjusted afterwards, the heavier cars just have different coastdown data fed into the (EU certified) rolling roads.
What's this "in the real world beforehand" you talk about for calibrating for the test? For instance, all the cars in the JLR range have the same basic engines now, and the heavier ones get higher CO2 figures. It's not magically adjusted afterwards, the heavier cars just have different coastdown data fed into the (EU certified) rolling roads.
Surely a test should be in laboratory conditions, hence the description, what it does on the tin.
Andy
The calibration could be done a week or a month beforehand, not directly before the test by the way, as long as the same car is used the weight and aero won't have changed.
zakelwe said:
That doesn't sound very controlled to me, what track do they use? How do they negate different wind directions or temperatures? Is your track enclosed?
You also said
"And weight does have an effect. the more a car weighs, the more friction the tyre produces, the more fuel is used, and the higher the CO2 output"
Well the 1.6 Elise uses a Toyota engine and at 876kg it produces 149g/km CO2. The Toyota Avensis also uses a 1.6 Toyota engine and although weighing 1445kg only does 152g/km CO2.
My bet is that 2% increase is nothing to so with the 160% increase in weight and is due to some other factor only dependent on the engine.
http://en.wikipedia.org/wiki/New_European_Driving_Cycle <- if you want to read how the test is performed - looks like either way works - however they do dial in weight, suggesting it has an impactYou also said
"And weight does have an effect. the more a car weighs, the more friction the tyre produces, the more fuel is used, and the higher the CO2 output"
Well the 1.6 Elise uses a Toyota engine and at 876kg it produces 149g/km CO2. The Toyota Avensis also uses a 1.6 Toyota engine and although weighing 1445kg only does 152g/km CO2.
My bet is that 2% increase is nothing to so with the 160% increase in weight and is due to some other factor only dependent on the engine.
In your example, The 2% increase will be due to a whole load of things - while the elise is loads lighter, its probably running stickier rubber on wider wheels, an LSD, a lower ratio gearbox, mid-engined inefficiencies (pumping water to the front etc) and a less smooth shape all of which will suck economy from the car.
Edited by 5lab on Thursday 12th May 16:18
5lab said:
http://en.wikipedia.org/wiki/New_European_Driving_... <- if you want to read how the test is performed - looks like either way works - however they do dial in weight, suggesting it has an impact
In your example, The 2% increase will be due to a whole load of things - while the elise is loads lighter, its probably running stickier rubber on wider wheels, an LSD, a lower ratio gearbox, mid-engined inefficiencies (pumping water to the front etc) and a less smooth shape all of which will suck economy from the car.
It will almost certainly have a different ECU tune too.In your example, The 2% increase will be due to a whole load of things - while the elise is loads lighter, its probably running stickier rubber on wider wheels, an LSD, a lower ratio gearbox, mid-engined inefficiencies (pumping water to the front etc) and a less smooth shape all of which will suck economy from the car.
Edited by 5lab on Thursday 12th May 16:18
g3org3y said:
Mastodon2 said:
"RWD is superior" - not an absolute truth, not by a long shot.
Worth checking out EVO Mag's Letter of the Month. "FWD is wrong wheel drive, would rather have a 116d over a Clio Cup".But don't make the mistake of confusing 'things written in EVO' with 'facts'.
busta said:
g3org3y said:
Mastodon2 said:
"RWD is superior" - not an absolute truth, not by a long shot.
Worth checking out EVO Mag's Letter of the Month. "FWD is wrong wheel drive, would rather have a 116d over a Clio Cup".But don't make the mistake of confusing 'things written in EVO' with 'facts'.
My point was to highlight that one shouldn't be surprised that a certain petrolhead group subscribe to such a philosophy if the magazine held in such high regard proclaims it 'letter of the month'. More fuel to the Wrong-WD fire as it were.
busta said:
g3org3y said:
Mastodon2 said:
"RWD is superior" - not an absolute truth, not by a long shot.
Worth checking out EVO Mag's Letter of the Month. "FWD is wrong wheel drive, would rather have a 116d over a Clio Cup".But don't make the mistake of confusing 'things written in EVO' with 'facts'.
EDLT said:
That needs to be added to the list. Its no better than quoting Clarkson imo.
It's much better than Clarkson quoting.They're not 100% accurate obviously, and a lot of it is just opinion. But they are not 90% bulls
t like pube head is.That letter of the month got on my tits too.
zakelwe said:
My bet is that 2% increase is nothing to so with the 160% increase in weight and is due to some other factor only dependent on the engine.
Gearing, aerodynamics and rolling resistance.The cars are either tested on a test track to produce a coastdown curve in two directions to negate wind resistance, or they use measured data like aerodynamic drag from a wind tunnel and tyre rolling resistance from a rig.
The test is done by putting the car on a rolling road with a roller size chosen based on the cars weight (which is in increments of 100-200kg IIRC) and the coastdown force applied to the rollers as a resistance to reproduce the real world drag.
The car is then 'driven' over a simple speed profile that includes several accelerations and decelerations, some fixed speed periods and some stationary periods.
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