the Fast And Furious people

[Good53X]

Hmm...

Alright, let's correct some thinking here.

Cars are wedges. The shape of a car provides downforce. Thus, the faster a car is moving the more downforce acts on the front of the vehicle. At the same time, the rear window and trunk of a vehicle often create a vacuum behind the car as it moves through air, and this vacuum actually produces lift in the rear of the vehicle aswell as drag. Spoilers and wings not only act to produce downforce, but reduce lift and 'spoil' the vacuum drag. This will cause the vehicle to 'tuck down' as you hit higher speeds, and many enthusiasts will know the feeling I'm talking about.

In addition, the faster a vehicle travels the more inertia it has, and the less its overall weight is involved with its velocity, wind resistance becomes much more of an issue - this is of course once acceleration has started to plateau. The added downforce won't make the vehicle slower at all.

The whole "wing/downforce/RWD" arguement doesn't make much sense - mainly because traction is most often lost off the line - where you will have no downforce. At speed it is extremely EXTREMELY rare to lose traction save for uneven surfaces. I say traction due to torque because that is the only situation that drive wheels are involved, and thus RWD is an issue. Losing traction around corners is more dependant upon weight distribution. I find it important to note that RWD cars carry driveshafts that run the length of the vehicle, differential assemblies and halfshafts, often now CV joints connecting the engine to the rear wheels - this additional weight in the rear of the vehicle will tend to negatively affect performance around corners... however this doesn't mean that somehow RWD cars get more benefit out of a spoiler/wing.

Lastly, strapping a basset hound wouldn't add 60lbs of force to the vehicle, it would add 60lbs of weight, which would have a negative effect the cornering of a vehicle. It would also negatively affect your acceleration, where downforce only comes into play at speeds where it is preferred.

[DGthe3]

Originally Posted by Good53X

Lastly, strapping a basset hound wouldn't add 60lbs of force to the vehicle, it would add 60lbs of weight, which would have a negative effect the cornering of a vehicle. It would also negatively affect your acceleration, where downforce only comes into play at speeds where it is preferred.

Ummm, weight is a force that acts down just like the negative lift that aerodynamic devices create (spoiler downforce). So adding 60 lbs of weight to the rear of a car will affect both the weight distribution and the downforce. Technically speaking, a Chevy Suburban has more downforce (5600 - 6300 lbs) than an F1 racecar driving at top speed (3000+lbs). However the 'burban cannot upside down on the roof of a tunnel like an F1 car theorhetically can because of aerodynamic forces that exceed the weight of the car.

[z28camaro2471]

Originally Posted by DGthe3

Ummm, weight is a force that acts down just like the negative lift that aerodynamic devices create (spoiler downforce). So adding 60 lbs of weight to the rear of a car will affect both the weight distribution and the downforce. Technically speaking, a Chevy Suburban has more downforce (5600 - 6300 lbs) than an F1 racecar driving at top speed (3000+lbs). However the 'burban cannot upside down on the roof of a tunnel like an F1 car theorhetically can because of aerodynamic forces that exceed the weight of the car.

While weight and downforce aren't entirely mutually exclusive, adding 60 lbs of weight is not the same as adding 60 lbs of downforce. Weight is part of the object's mass that at speed will try to overcome the force of gravity. Downforce is an external force pressing down on the object. When downforce exceeds an objects gravitational pull it can overcome gravity. This is why a Formula 1 race car could theoretically run upside down. An upside down Suburban would have "upforce" equal to the objects mass and instantly crash to the ground with a force equal to 3 tons or so.

Downforce is a product of air movement and acts independently from gravity. Weight is driven entirely by mass and gravity.

[DGthe3]

Originally Posted by z28camaro2471

While weight and downforce aren't entirely mutually exclusive, adding 60 lbs of weight is not the same as adding 60 lbs of downforce. Weight is part of the object's mass that at speed will try to overcome the force of gravity. Downforce is an external force pressing down on the object. When downforce exceeds an objects gravitational pull it can overcome gravity. This is why a Formula 1 race car could theoretically run upside down. An upside down Suburban would have "upforce" equal to the objects mass and instantly crash to the ground with a force equal to 3 tons or so.

Yes, thats kinda what I was trying to say but in a much better turn of phrase.

Also, adding weight tends to hurt handling because of the increased inertia, while aero downforce hold the car to the ground increasing its cornering ability.

Getting back on topic though, while cosmetic spoilers (ie 90% of those that you see on cars on the road) do still provide these bennefits to a small degree, they generally do not make a significant differance on things like a 124 hp Saturn

[z28camaro2471]

Originally Posted by DGthe3

they generally do not make a significant differance on things like a 124 hp Saturn

Agreed!

[AFSNightrod]

I read somewhere that the C5.R racecar in theory could run at 185MPH completely upside down and still hold the road due to the amount of downforce that is generated. Just thought that I'd throw that out there.

[stovt001]

I was just joking about strapping the poor little basset hound down in the back. Didn't want to turn it into a serious debate. It would obviously produce different results than a spoiler (bad weight distribution, no aerodynamic benefits, an unfortunate wet spot in the trunk...)

Another thing that confuses me with big spoilers on FWD cars - If you're adding downforce to the rear wheels, you're adding more traction at the back and possibly reducing traction at the front by unloading the wheels. Now FWD cars as a general rule tend to understeer at the limit anyway, as the front wheels are tasked with both driving and steering. Now if you add traction to the rear wheels (the ones that don't turn) at the expense of traction at the front wheels (which need to do two jobs with what little traction they have) then aren't you just making understeer worse?

And yes, when you have these guy's driving their mom's old Civics with a few bolt on mods and a fart can exhaust, a spoiler really won't make that much difference. Some, but not as much as it would on say, a well running Supra. Assuming they are both pushed to their limits, the Supra would obviously make better use of the downforce.

[DGthe3]

Actually, adding downforce at the rear doesn't do a whole lot to the front end. lets say the car makes 100 lbs of downforce with a spoiler located 2 feet away from the rear axel on a car with a 9' wheelbase. It will create 300 ft-lbs of torque about the rear axel. that means that 9 feet away at the front it will reduce the weight by 22 lbs. On a civic that means means the weight at the front wheels will go down from about 1600 lbs to 1578. Not a big deal. Even if you moved the spoiler farther from the rear axel by 2 feet (hanging past the back end a bit now) and doubled the force it exerts on the car, you still have under than 100 lbs less weight on the front.

[stovt001]

Thats actually pretty much exactly what I was saying. It will have a small unloading effect on the front end, but really what you want to be doing is making the front end stick better, not slightly worse. And lets face it, wicked oversteer is way more fun and way sexier than understeer.

[DGthe3]

Originally Posted by stovt001

Thats actually pretty much exactly what I was saying. It will have a small unloading effect on the front end, but really what you want to be doing is making the front end stick better, not slightly worse. And lets face it, wicked oversteer is way more fun and way sexier than understeer.

I'm not sure why I never did the math on it until then.

and for the other half of what you said, in Nascar they have a saying, loose is fast!

(in case you don't know, oversteer=loose=back end sliding out; understeer=tight=car going straighter than you like)

[stovt001]

Think back on the last time your buddies or some girl said "That was such an awesome set of donuts you just pulled off" or "Holy crap, you just drifted your car sideways half a block!" Felt great didn't it?

Now think back on the last time your buddies or a girl said to you: "Wow, that was so cool when you pushed your car hard through that turn and it just stopped turning and plowed straight off the road into that ditch!" Oh wait, that's right, something like that has never, once, in the history of driving, happened.

[RiceRocket]

Sorry....it's 66lbs of downforce at 90MPH.

http://www.mkiv.com/publications/roa...3/rt393_03.jpg

[Myka]

Funny stuff.

Of course, there are a lot of imports that deserve respect. I think most of you are familiar with them, so I don't need to list them. This guy was talking about the 16 yr old that has a civic with neons under it. Not much to consider, it was just a silly bit that he does as a comedian.

[DILLIGAF]

I once had a kid in a V6 camaro scream out the window to me "American Muscle!!!" I laughed at him at the next light and proceeded to show him how much "American Muscle" my saturn has. though not too impressive, a 250hp (at the wheels) 3000lb car is decently fast!