Reduce drag on an Astra...
Discussion
http://www.pistonheads.com/sales/2383687.htm
Pretty pointless thread but had to post this advert i found. Made me chuckle...
"have for sale my Astra Eco4 diesel. It is the LS spec in metallic silver with the 1.7dti engine. Being the Eco4 version it has been designed to maximise fuel economy and benefits from the following spec;
REAR SPOILER TO REDUCE DRAG
UNDERBODY PANELS TO REDUCE UNDERBODY DRAG
Higher ratio 4th & 5th gears
Low drag tyres
With these features the car has a C02 rating of less than 119g/km meaning £30 a year road tax with well over 50mpg easily
Isn't the case of a spoiler to increase drag?!?!
Pretty pointless thread but had to post this advert i found. Made me chuckle...
"have for sale my Astra Eco4 diesel. It is the LS spec in metallic silver with the 1.7dti engine. Being the Eco4 version it has been designed to maximise fuel economy and benefits from the following spec;
REAR SPOILER TO REDUCE DRAG
UNDERBODY PANELS TO REDUCE UNDERBODY DRAG
Higher ratio 4th & 5th gears
Low drag tyres
With these features the car has a C02 rating of less than 119g/km meaning £30 a year road tax with well over 50mpg easily
Isn't the case of a spoiler to increase drag?!?!
kambites said:
gazmutd said:
Isn't the case of a spoiler to increase drag?!?!
No, it's to reduce drag and/or lift. Wings generate drag, spoilers generally reduce it.Edited by kambites on Wednesday 12th January 11:04
gazmutd said:
I'm new to the technical sides of cars, so bear with me, but how does a spoiler reduce drag?
By severing the airflow, creating a clean break in the flow over the back of the car so you don't a laminar flow down the back of the car, and hence don't get a low pressure region behind it. gazmutd said:
Pretty pointless thread but had to post this advert i found. Made me chuckle...
Only because you're clueless.Have a look at any of the modern "green" cars like the VW Bluemotion and the likes.
Vauxhall were very much ahead of the times with the Eco4 - even considering the piece of junk engine they were using.
gazmutd said:
ah i see. learnt something new today. I look a bit stupid now 
Does this have much affect on the average passenger car though?
Depends on the exact aerodynamics of the car. It certainly played a significant role in reducing lift off over steer in the mk1 TT. Most modern cars are tuned in wind tunnels or computer simulation so the bodywork itself provides an effective spoiler effect. Does this have much affect on the average passenger car though?
If you look at the back of the mk1 Elise, you can see where Lotus had to graft an integrated spoiler into the bodywork because they found that the shape produced dangerous amounts of rear-end lift.
ETA: If you look at any of the modern "eco" versions of cars (like the Polo Bluemotion), they generally have spoilers.
Edited by kambites on Wednesday 12th January 11:18
spoil·er
[spoi-ler]
–noun
3.
Aeronautics . a device used to break up the airflow around an aerodynamic surface, as an aircraft wing, in order to slow the movement through the air or to decrease the lift on the surface and, as a result, provide bank or descent control.
4.
Automotive . a similar device for changing the airflow past a moving vehicle, often having the form of a transverse fin or blade mounted at the front or rear to reduce lift and increase traction at high speeds.
spoilers usually create drag but in a nice way and most of the time only work efficiently over 70 mph which for fuel economy you don't want to be. Smooth underfloor is good for reducing drag but can create lift so that is probably what the spoiler is for to counteract this. But it is an Astra so proabably PR b
t
Buy an Elise
[spoi-ler]
–noun
3.
Aeronautics . a device used to break up the airflow around an aerodynamic surface, as an aircraft wing, in order to slow the movement through the air or to decrease the lift on the surface and, as a result, provide bank or descent control.
4.
Automotive . a similar device for changing the airflow past a moving vehicle, often having the form of a transverse fin or blade mounted at the front or rear to reduce lift and increase traction at high speeds.
spoilers usually create drag but in a nice way and most of the time only work efficiently over 70 mph which for fuel economy you don't want to be. Smooth underfloor is good for reducing drag but can create lift so that is probably what the spoiler is for to counteract this. But it is an Astra so proabably PR b
tBuy an Elise
james_tigerwoods said:
I'm never convinced that a spoiler on a mass produced car like this does anything anyway...
At steady cruising speed they can, they can also aid high speed stability as not all places in the world have a 70mph speed limit.Maybe an odd ball example, but the classic Range Rover V8's had a front spoiler (with foglights in), this was worth upto 2/3mpg at motorway speeds according to LR. Not a huge number, but on a vehicle that usually averages 12-17mpg, and extra 2mpg is a reasonable percentage.
It's also part of a compound affect, a single spoiler on its own might not produce significant results, but combine it with all the other also non significant gains that can be achieved in a cars aero properties and rolling resistance and it can all add up to a rather more noticeable result.
kambites said:
gazmutd said:
ah i see. learnt something new today. I look a bit stupid now
Does this have much affect on the average passenger car though?
Depends on the exact aerodynamics of the car. It certainly played a significant role in reducing lift off over steer in the mk1 TT. Most modern cars are tuned in wind tunnels or computer simulation so the bodywork itself provides an effective spoiler effect. Does this have much affect on the average passenger car though?
If you look at the back of the mk1 Elise, you can see where Lotus had to graft an integrated spoiler into the bodywork because they found that the shape produced dangerous amounts of rear-end lift.
ETA: If you look at any of the modern "eco" versions of cars (like the Polo Bluemotion), they generally have spoilers.
Edited by kambites on Wednesday 12th January 11:18
CraigyMc said:
kambites said:
gazmutd said:
ah i see. learnt something new today. I look a bit stupid now
Does this have much affect on the average passenger car though?
Depends on the exact aerodynamics of the car. It certainly played a significant role in reducing lift off over steer in the mk1 TT. Does this have much affect on the average passenger car though?
Interesting you mention the TT. The Mk1 TT had a recall and I heard that the rear spoiler, although offering downforce, was not the whole story as they did some suspension mods to avoid lift off oversteer. A friend who had this recall done, was told that he didn't need the spoiler if he didn't want it, as the suspension would suffice. So he didn't and the car looked great and drove brilliantly.
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