Estimate & list your aero drag.
Discussion
I'm interested in aero drag. If you are as sad as me then use the following calculation to find out much aero drag your car has...
Vehicle height(m) x width (m) x 0.8 = estimated frontal area
Multiply your estimated frontal area by the Cd to get your estimated CdA.
Here's my car
BMW E30 318is
A = 1.38 x 1.646 x 0.8 = 1.82 m2
Cd = 0.35
CdA = 1.82 x 0.35 = 0.637
Frontal area estimate calculation based on "Prediction of Vehicle Reference Frontal Area"...google it if your interested.
Vehicle height(m) x width (m) x 0.8 = estimated frontal area
Multiply your estimated frontal area by the Cd to get your estimated CdA.
Here's my car
BMW E30 318is
A = 1.38 x 1.646 x 0.8 = 1.82 m2
Cd = 0.35
CdA = 1.82 x 0.35 = 0.637
Frontal area estimate calculation based on "Prediction of Vehicle Reference Frontal Area"...google it if your interested.
No need to estimate. It's all on here: http://www.carfolio.com/specifications/
This is mine:
Drag coeff: 0.350
Frontal area: 1.98m^2
CdA: 0.69
E46 330Ci BTW.
This is mine:
Drag coeff: 0.350
Frontal area: 1.98m^2
CdA: 0.69
E46 330Ci BTW.
MartinQ said:
No need to estimate. It's all on here: http://www.carfolio.com/specifications/
This is mine:
Drag coeff: 0.350
Frontal area: 1.98m^2
CdA: 0.69
E46 330Ci BTW.
Interesting..both the E30 and E46 have the same Cd!This is mine:
Drag coeff: 0.350
Frontal area: 1.98m^2
CdA: 0.69
E46 330Ci BTW.
Says he, trying to get the thread moving!
kambites said:
My Elise:
Frontal Area: 1.6m^2
Cd: 0.407
CdA: 0.651
Wow, the Cd is surprisingly high. I wonder how the Opel version measures, I'll have a quick search.Frontal Area: 1.6m^2
Cd: 0.407
CdA: 0.651
edit..found it
Around 0.37/0.38.
Frontal area...not sure but found the CdA..0.592...wow, big difference to the Elise.
Edited by Kawasicki on Monday 9th December 10:14
Kawasicki said:
Frontal area...not sure but found the CdA..0.592...wow, big difference to the Elise.
Hmm, I've found the Elise listed as 0.59 somewhere too so maybe I've got the figures wrong for the Elise. Or maybe that's roof on vs roof off; or soft-top vs hard-top;...ETA: Actually reading around a bit, it would seem that it's never really been measured properly. Lotus state 0.36 for the drag coefficient (giving 0.579 overall); independent test results seem to vary significantly. Looking at their top speed and power figures, I can believe the Elise is very similar to the current 3-series.
Edited by kambites on Monday 9th December 10:25
kambites said:
Kawasicki said:
Frontal area...not sure but found the CdA..0.592...wow, big difference to the Elise.
Hmm, I've found the Elise listed as 0.59 somewhere too so maybe I've got the figures wrong for the Elise. Or maybe that's roof on vs roof off; or soft-top vs hard-top;...ETA: Actually reading around a bit, it would seem that it's never really been measured properly. Lotus state 0.36 for the drag coefficient (giving 0.579 overall); independent test results seem to vary significantly.
Edited by kambites on Monday 9th December 10:21
Interesting post, as this will make some people realise how much of a joke the Government Official mpg (& CO2) tests are... In the official test, the car is on a rolling road with no wind resistance at all - so Cd has no influence on the results.
In the real world, aerodynamic forces start to overtake friction/inertia at about 50 mph on a level road (obviously faster uphill and slower downhill, but they tend to balance out for most journeys. In a small aerodynamic car (particularly heavy ones, like my old 996 Turbo), fuel consumption is way better than official figures on a long motorway run, with the cruise control set - even if way above the speed limit)... However, my Supercharged Sport was a bit of a shock... At about 75 mph + the cumulative average fuel consumption actually got worse, the further you travelled at a steady speed on cruise!!! One memorable journey through Belgium/France, heading directly into a wind of around 30-40 mph, I averaged 14 mpg, with the Cruise Control set at just 120 kph (it was very wet).
Manufacturers used to boast about their Cd, before the compulsory emissions test / taxation, now, it is almost completely irrelevant from a marketing perspective: Much better to spend the engineering budget on clever electronics to 'cheat' your way through the emissions test
e.g. twin scroll turbos, that are cleverly designed to produce no load until you press the accelerator 1 mm further than they do on the official test and such like
In the real world, aerodynamic forces start to overtake friction/inertia at about 50 mph on a level road (obviously faster uphill and slower downhill, but they tend to balance out for most journeys. In a small aerodynamic car (particularly heavy ones, like my old 996 Turbo), fuel consumption is way better than official figures on a long motorway run, with the cruise control set - even if way above the speed limit)... However, my Supercharged Sport was a bit of a shock... At about 75 mph + the cumulative average fuel consumption actually got worse, the further you travelled at a steady speed on cruise!!! One memorable journey through Belgium/France, heading directly into a wind of around 30-40 mph, I averaged 14 mpg, with the Cruise Control set at just 120 kph (it was very wet).
Manufacturers used to boast about their Cd, before the compulsory emissions test / taxation, now, it is almost completely irrelevant from a marketing perspective: Much better to spend the engineering budget on clever electronics to 'cheat' your way through the emissions test
e.g. twin scroll turbos, that are cleverly designed to produce no load until you press the accelerator 1 mm further than they do on the official test and such likekVA said:
Interesting post, as this will make some people realise how much of a joke the Government Official mpg (& CO2) tests are... In the official test, the car is on a rolling road with no wind resistance at all - so Cd has no influence on the results.
This is not true.There are two stages to the test. The main "cycle" part is indeed carried out on a rolling road but the car also does a "drag run", down from a certain speed and the rate of deceleration is factored into the figures.
I'm also impressed if you managed much above the official extra-urban figure in your 911 (comparing a motorway run to the combined figure would be ludicrous).
Edited by kambites on Monday 9th December 10:33
kVA said:
Interesting post, as this will make some people realise how much of a joke the Government Official mpg (& CO2) tests are... In the official test, the car is on a rolling road with no wind resistance at all - so Cd has no influence on the results.
In the real world, aerodynamic forces start to overtake friction/inertia at about 50 mph on a level road (obviously faster uphill and slower downhill, but they tend to balance out for most journeys. In a small aerodynamic car (particularly heavy ones, like my old 996 Turbo), fuel consumption is way better than official figures on a long motorway run, with the cruise control set - even if way above the speed limit)... However, my Supercharged Sport was a bit of a shock... At about 75 mph + the cumulative average fuel consumption actually got worse, the further you travelled at a steady speed on cruise!!! One memorable journey through Belgium/France, heading directly into a wind of around 30-40 mph, I averaged 14 mpg, with the Cruise Control set at just 120 kph (it was very wet).
Manufacturers used to boast about their Cd, before the compulsory emissions test / taxation, now, it is almost completely irrelevant from a marketing perspective: Much better to spend the engineering budget on clever electronics to 'cheat' your way through the emissions test e.g. twin scroll turbos, that are cleverly designed to produce no load until you press the accelerator 1 mm further than they do on the official test and such like
I think vehicles are tested for coast down performance...and the performance in that test determines the drag loads on the fuel economy test dyno. In the real world, aerodynamic forces start to overtake friction/inertia at about 50 mph on a level road (obviously faster uphill and slower downhill, but they tend to balance out for most journeys. In a small aerodynamic car (particularly heavy ones, like my old 996 Turbo), fuel consumption is way better than official figures on a long motorway run, with the cruise control set - even if way above the speed limit)... However, my Supercharged Sport was a bit of a shock... At about 75 mph + the cumulative average fuel consumption actually got worse, the further you travelled at a steady speed on cruise!!! One memorable journey through Belgium/France, heading directly into a wind of around 30-40 mph, I averaged 14 mpg, with the Cruise Control set at just 120 kph (it was very wet).
Manufacturers used to boast about their Cd, before the compulsory emissions test / taxation, now, it is almost completely irrelevant from a marketing perspective: Much better to spend the engineering budget on clever electronics to 'cheat' your way through the emissions test
e.g. twin scroll turbos, that are cleverly designed to produce no load until you press the accelerator 1 mm further than they do on the official test and such likeHere is one of mine, it was the first production car to do 100mpg, (with 81g of penguin killing ability) I can squeeze a bit more out if occasionally, but 80-90mpg is the norm.
By modern standards its not that great in the aero works & has a large frontal area too
Year 2000 VW Lupo 1.2TDI 3L
Drag coefficient 0.290
Frontal area 2.00 m²
CdA 0.58
By modern standards its not that great in the aero works & has a large frontal area too
Year 2000 VW Lupo 1.2TDI 3L
Drag coefficient 0.290
Frontal area 2.00 m²
CdA 0.58
Gassing Station | General Gassing | Top of Page | What's New | My Stuff