Modifications That Dont Work

[Izso]

Hey Leo : i have a question. Why would a FWD car need downforce at the rear? Wouldn't it be more beneficial to have a front diffuser or something to push down the front part of the car to provide more frontal grip? I'm thinking rear gt-wing on a FWD will result in drag regardless of whether it's working or not. Pushing down the rear of a car that has no drive at the rear wheels only causes more friction there no?

 

[xtremeleo]

speaking of downforce how does ground effect apply to a road car? from what i learn, making the air flow under the car smooth produces greater ground effect (pulling effect towards the ground) by putting a cover under the car to make the air flow smooth.. i've seen someone here in zth who put an aluminium sheet under his MR2 (forgot the link sorry)..

my question is, will this be better than a spoiler?

as the only increase in drag is caused by the tire.. imo, this is better than a spoiler as it doesnt produce drag at low speed, only when the air flow around the vehicle is fast, the effect takes place.. im still learning so please add on or correct me if im wrong..

its a good observation sir, higher airflow creates less pressure in the path it goes through, simply taken from bernoulli's principle, googlee it up if u have the time. so, if u smoothen the airflow beneath the car, it creates a low pressure area underneath the car. this pressure is comparatively much2 lower then the pressure exerted on top of the car, and dis difference in pressure pushes the car downward for dat extra grip. dat mr2 put an aluminum foil underneath for the same reason, to decrease the value of 1. drag; produces by airflow going through rough edges / surfaces underneath there 2. produces a downward suction by what ive explained above.

the best about dis mod is, it doesnt create the drag like what a spoiler will. u can even use the flow to help straighten the car by introducing a series of.. sirip (?) underneath there, its like the rudder in boats, but again, dis will only work up to speed, and again, it doesnt produce much drag like again, the spoiler or a GT wing wud. the ground effect wud be further enhanced if the vehicle is lowered, but not too much as u need sufficient airflow to flow underneath the car for this to take effect. at least, that is what i understand on the subject matter

---------- Post added at 09:54 AM ---------- 6 hour anti-bump limit - Previous post was at 09:40 AM ----------

Hey Leo : i have a question. Why would a FWD car need downforce at the rear? Wouldn't it be more beneficial to have a front diffuser or something to push down the front part of the car to provide more frontal grip? I'm thinking rear gt-wing on a FWD will result in drag regardless of whether it's working or not. Pushing down the rear of a car that has no drive at the rear wheels only causes more friction there no?

a front diffuser, hmm.. i think i remember beieng told about it by a supra owner dat a UK spec supra is equipped with this tech; the active spoiler will only be deployed at a certain speed, to decrease the value of drag at low speed.

the thing with a FWD is, when u accelerate, most torque is channeled through the chasis to the rear end of the vehicle, so the front tyre will indeed lose much traction, compared to a RWD vehicle.

a spoiler / GT wing in a FWD can be benificial when achieving certain speed, especially when the rear part is much lighter then the frontal part. at this threshold speed, depending to the suspension setup, the car may experience noticeable bounce, which may elevate u from the ground and render u outta control of the vehicle. the downforce during dis time helps in keeping the car planted, but if the value is appreciable. at this particular moment, the downforce seems to be more important; to keep the car planted on the ground for safety reasons, then the extra friction u mentioned.

its a good topic sir, tq

 

[HKS-GT2835R]

its a good observation sir, higher airflow creates less pressure in the path it goes through, simply taken from bernoulli's principle, googlee it up if u have the time. so, if u smoothen the airflow beneath the car, it creates a low pressure area underneath the car. this pressure is comparatively much2 lower then the pressure exerted on top of the car, and dis difference in pressure pushes the car downward for dat extra grip. dat mr2 put an aluminum foil underneath for the same reason, to decrease the value of 1. drag; produces by airflow going through rough edges / surfaces underneath there 2. produces a downward suction by what ive explained above.

the best about dis mod is, it doesnt create the drag like what a spoiler will. u can even use the flow to help straighten the car by introducing a series of.. sirip (?) underneath there, its like the rudder in boats, but again, dis will only work up to speed, and again, it doesnt produce much drag like again, the spoiler or a GT wing wud. the ground effect wud be further enhanced if the vehicle is lowered, but not too much as u need sufficient airflow to flow underneath the car for this to take effect. at least, that is what i understand on the subject matter

---------- Post added at 09:54 AM ---------- 6 hour anti-bump limit - Previous post was at 09:40 AM ----------



a front diffuser, hmm.. i think i remember beieng told about it by a supra owner dat a UK spec supra is equipped with this tech; the active spoiler will only be deployed at a certain speed, to decrease the value of drag at low speed.

the thing with a FWD is, when u accelerate, most torque is channeled through the chasis to the rear end of the vehicle, so the front tyre will indeed lose much traction, compared to a RWD vehicle.

a spoiler / GT wing in a FWD can be benificial when achieving certain speed, especially when the rear part is much lighter then the frontal part. at this threshold speed, depending to the suspension setup, the car may experience noticeable bounce, which may elevate u from the ground and render u outta control of the vehicle. the downforce during dis time helps in keeping the car planted, but if the value is appreciable. at this particular moment, the downforce seems to be more important; to keep the car planted on the ground for safety reasons, then the extra friction u mentioned.

its a good topic sir, tq

the topic gets interestingly better!

here i found a rather large pic, so i put a link lah

http://www.vasanth.in/content/binary/1306371943__CDG_Air_Flow_graphic.jpg

a gud link oso --> http://www.gmecca.com/byorc/dtipsaerodynamics.html

cun eh?

 

[xtremeleo]

hahaha, havent heard "naca" for quite sum time jugek, like in the text book ler di. thanx for the link sir, a very good read indeed..

---------- Post added at 10:19 AM ---------- 6 hour anti-bump limit - Previous post was at 10:16 AM ----------

ohh, the best aerofoil design shud be a flat plate fyi, it produces the least drag when air flows around it. hmm, dat sounds just like in the text book years back, lol

---------- Post added at 10:38 AM ---------- 6 hour anti-bump limit - Previous post was at 10:19 AM ----------

If we consider that a flat plate has a Cd of about 1.0, an F1 car really seems inefficient, but what an F1 car lacks in aerodynamic drag efficiency, it makes up for in downforce and horsepower.

Probably the most popular form of aerodynamic aid is the wing. Wings perform very efficiently, generating lots of downforce for a small penalty in drag. Spoiler are not nearly as efficient, but because of their practicality and simplicity, spoilers are used a lot on sedans.

Wings, by their design require that there be no obstruction between the bottom of the wing and the road surface, for them to be most effective. So mounting a wing above a trunk lid limits the effectiveness.

a nice read indeed..

 

[arturo]

a little visual aid on underbody flat paneling

BAD

GOOD

 

[tofu_manic]

elo mr. leo! ive read people use the terms spoiler and wing interchangeably

ive also come across definitions of spoilers, saying that it is something the 'spoils' drag; reduces drag

and wings are something that adds drag

confused noob here haha hope u can clarify

 

[xtremeleo]

tofu manic = noob? naah!!!

spoiler doesnt spoil drag sir, but rather airflow.. the way i see it, it delays the separation / departure point, so the turbulence dont reach the low pressure area just at the rear of the car as fast as if the car isnt fitted with a spoiler. err, iam i making sense to sir?

both add drag, but the gt wing produces more, depending on the location

 

[papagoines]

Wow... getting better and better

found some links to share
Undertrays, Spoilers & Bonnet Vents series (it improve flow but more beneficial to engine bay cooling?!?!)

http://autospeed.com.au/cms/A_2159/article.html
http://autospeed.com.au/cms/A_2160/article.html
http://autospeed.com.au/cms/A_2162/article.html

Modifying Under-Car Airflow series
http://autospeed.com.au/cms/A_2455/article.html
http://autospeed.com.au/cms/A_2456/article.html

Ultimate DIY Automotive Modification Tool-Kit series (dealt with flows and pressures)
http://www.autospeed.com/cms/search/index.html?keywords=Ultimate+DIY+Automotive+Modification+Tool-Kit&x=17&y=11

 

[xtremeleo]

starting to change to "mods dat work", lol

---------- Post added at 11:33 AM ---------- 6 hour anti-bump limit - Previous post was at 11:28 AM ----------

err, continuing.. looking at the subject matter of grounding cable, u need to trace the grounding point before fixing it permanently there, especially for old cars ler.. electrons isnt scattered "sekata" (what word ler for english? dah tua laa, lupaa.. ohh, evenly!!), scratch dat, evenly in a structure. sum point has higher electrons density then others, u need to search for these points through out the chasis for the grounding cable to be able to work properly

 

[arturo]

i have a question on wings too here...is it safe to assume that if the wing is just simply a flat piece of material simply angled to create a push down effect(like the windscreen), then this will create useless ratios of downforce VS drag?

what if the wing is a reverse wing with the front end only just slightly angled downwards? will this create a much better ratio of downforce vs drag?

i asked cos i noticed almost all aftermarket wings are just basically just flat pieces of materials either angled downwards at the front or have that shovel shape. another thing i noticed is almost all supercar wings have that reveresed wing shape...just try googling n u'll get what i mean...

xtremeleo...i think i have to start calling u leo(is this ok?) la...very hard to type yr full nick heheheh...i had no idea at all about the grounding thing. i understand that electricity always chooses the path of least resistance n distance but how to find out where to place the grounding points? use a static checker?

 

[xtremeleo]

its never useless of u know what it is for and where to apply it sir..

xtremeleo...i think i have to start calling u leo(is this ok?) la...very hard to type yr full nick heheheh...i had no idea at all about the grounding thing. i understand that electricity always chooses the path of least resistance n distance but how to find out where to place the grounding points? use a static checker?

leo is okie, but hommies usually call me angah jer.. indeed, electricity always choose paths of least resistance, but it also depends on the shape / surface. electrons usually gethers around sharp edges, dats why u'll see all those lightning rods like on the twin towers are shaped sharply. tajam woo, facing the sky summore.. ehem, dont mind "him", continuing.. because of this pointed structure, the electrons moving across the buildings' surfaces are prone to gather here, and attract lightning to strike there then anywhere else on the earth's surface.

the same goes to grounding effect, in time the chasis may be corroded, oxidized, broken, etc as to break the electrons' normal path, so they seek another path to complete the circuit. most of them will close the circuit, but there are few dat will gather at sum points in the chasis, dis is where u can observe dat there is slightly a drop in negative charges, and tracing and connecting them to the proper cathode makes the electrical system fresh again. u rnt giving the engine more power, but rather rejuvenate it, dats all.

 

[^pomen_GTR^]

this working or not??

well..it was all back to the purpose..for show or for go....

http://jalopnik.com/5397825/huge-front-wing-compensates-for-scion-tcs-fwd/gallery/

 

[xtremeleo]

ginormous!!!!! hahahaha, and the word is in the dictionary pulak tu, iam LMAO!!!!! reminding me of the story mosnters vs aliens, ginormica (or sumthing, lol), hahaha..

front and back summore!!!! hahaha

ehem, shooo.. dont mind "him".. seems a go to me, since a 900hp FWD dragster needs all dat downforce to help the tyre grip at high speed. it wudnt do shite if the car is just about to launch off, like i said, the downward force isnt appreciable above certain speed

 

[dabok max7]

ginormous!!!!! hahahaha, and the word is in the dictionary pulak tu, iam LMAO!!!!! reminding me of the story mosnters vs aliens, ginormica (or sumthing, lol), hahaha..

front and back summore!!!! hahaha

ehem, shooo.. dont mind "him".. seems a go to me, since a 900hp FWD dragster needs all dat downforce to help the tyre grip at high speed. it wudnt do shite if the car is just about to launch off, like i said, the downward force isnt appreciable above certain speed

Well I think U forget 1 tiny fact which is velocity effect to the aerodynamic force... and for certain current development in aerodynamic effect already contribute to the handling of the car.. but it seem U kept mention it only effect on above certain speed:hmmmm: . and because U always mention about certain speed before the downforce have it effect can U clarify it how fast it need to go before aerodynamic force taking effect? because based on this equation:

F=1/2 x p x v^2 x Cd x A which is
F~ aerodynamic force drag
p ~ air density (1.23 kgs/m3)
v~velocity of the vehicle (m/s)
cd~ drag coefficient
A~ frontal area of vehicle

it means with 36kmh =1m/s, with 4m^2 frontal area and have of cd 1.05 (if the vehicle have box design for it frontal area and body design heheh) already generate 2.583N.. and must remember with kuasa dua (iskh lupa lak bahasa english apa dia heheheh) already create parabolic graph where v>0 condition...
still this is only a matter of simple equation and not taking many item into consideration..but still it worth taking account to...especially when it come to velocity... but again it only based on my opinion la sir.. maybe U can correct me if I'm wrong la...

and 1 more thing
about grounding effect, did height of the vehicle also play role in its effect...:hmmmm:

 

[xtremeleo]

i apologise if i give u the wrong impression, but it only gives favorable value of downward force when the speed is above a threshold, its doesnt have much fucntion below dat speed but to create unnecessary drag.

i wud post the link where active spoilers such as on those veyrons only activates from a certain speed onwards, but i cant access youtube from the office. can sumbody search for it and post it here? id appreciate it much, tqvm in advance.

u have the exact formula to calculate downforce sir, the thing u need to take into account is the weight of the car, airflow beneath the car, and if the weight of the can be overtaken by the lift value at a certain speed. if this lift < weight, then the car will still be planted on the ground, definitely. u need d extra downforce when weight is about to be outnumbered by the lift value, before this threshold point, that extra downforce generator will only add drag because the downforce value isnt appreciable. dats not taking the ground effect of the vehicle, all this helps but for maximum acceleration u dont need dat additional drag, as to y the veyron doesnt employ the spoiler until its needed.

kuasa dua is square btw, lol (aku pun lupa jap tadi, hahaha)

ground effect will be better if the car is closer to the ground, but not to a point dat appreciable airflow cant flow through. dis reminds me alot to ayrton sena's accident, just a simple problem / mistake but made us lose a legendary racer

 

[arturo]

and 1 more thing
about grounding effect, did height of the vehicle also play role in its effect...:hmmmm:

i can help answer this...remember Ayrton Senna? the great F1 driver who crashed his F1 car and died? during his time, F1 cars heavily depended on the ground effect for downforce purposes and what they found out the lower the front part of the car is to the ground, the higher the downforce subjected to the car in its entirety(rear will be higher to create a low pressure area below the car) there is however a limit to how low the car can be lowered without damaging it when racing so they compensated for this by installing stiff curtains that draped down. this reduced the gap that air could pass thru the fronts n sides...he crashed cos the curtains lifted and the pressure difference was lost which caused him to loose control suddenly and without warning.

and if my memory hasnt failed me...lotus had already used this ground effect for downforce back in the 70s...

so yes...height of the bottom of the car does play a part but not till a height that no air passes under the car.

another factor in the ground effect...front of car lower than rear of car = good.

aiyak....i took too long to reply leo aredy reply hahahah

n to add the veyron spolier facts...
http://www.bugatti.com/en/veyron-16.4/technology/speed.html

To create the optimum aerodynamics, the Bugatti engineers developed three configuration modes. In standard mode, used for speeds up to 220 km/h, the rear spoiler system is completely retracted. In handling mode, used at higher velocities, the vehicles nose is pulled down and the monumental rear spoiler deployed. This produces an additional 350 kg of downforce without compromising the Veyron’s exceptional turn dynamics. And then there is the top speed mode for velocities beyond 375 km/h, which is activated before the engine is started. At top speed mode the front diffuser flaps are shut to make the underbody absolutely level, and the spoiler is completely aligned with the chassis, forming a tearing edge – thus, the Veyron is perfectly adapted for top velocities. The downforce is reduced to minimize the strain on the tires, which is already considerable. The car is held down on the road by its own weight and the downforce

 

[xtremeleo]

it means with 36kmh =1m/s, with 4m^2 frontal area and have of cd 1.05 (if the vehicle have box design for it frontal area and body design heheh) already generate 2.583N.. and must remember with kuasa dua (iskh lupa lak bahasa english apa dia heheheh) already create parabolic graph where v>0 condition...

from this equation, at 36kmh (1m/s) it only generates a mere 2.5N of downward force, at 72kmh (2m/s) it generates a mere 10N, at 108kmh (3m/s) 22.5N, at 144kmh (4m/s) 40N, at 180kmh (5m/s) 62.5N, so on and so forth. u see, if we are not taking the ground effect into calculation pun, the downforce created by a cardboard box (not taking its weight into account here, just imagine its like a 1000kg) pun seems negligence. we have to take into calcuation jugek really all the other factors surrounding the area of question but dat shud be sufficient to show y i said the downforce is needed after a certain speed (i think dis wud be the correct term to use, "after") is achieved

---------- Post added at 04:24 PM ---------- 6 hour anti-bump limit - Previous post was at 04:17 PM ----------

the weyron deploys its flappy spoiler (lol) and squat for top end speed, memang crazy baii.. i dont care if any other car can beat the speed of a veyron, but they wont be able to beat the technologies dat define veyron from the rest of the pack. the others wont be as stable and safe, plus 407kmh top speed wasnt achieved with the engine full potential pun. tweak dat up summore and bugatti made faster top speed. was it 437 or 467 eh? lupa laa..

 

[arturo]

the veyron 16.4 SS fastest recorded speed is 434kmh...but normal production units are limited at 258kmh "to stop the tires shredding" ! hahaha

the wing placement is also important. those GT guys knew what they were doing when they placed the wing at about roof level cos the air still hasnt seperated at that level. those wings that are placed near to boot level cannot use the air flow effectively since most of the air at that level is just turbulence caused by the rear windcreen dropoff

but in the end...all these needs a lot of airflow testing to get the right angles n placements n sizes...in short, kedai aband spoilers would definitely do more harm than good...

 

[dabok max7]

from this equation, at 36kmh (1m/s) it only generates a mere 2.5N of downward force, at 72kmh (2m/s) it generates a mere 10N, at 108kmh (3m/s) 22.5N, at 144kmh (4m/s) 40N, at 180kmh (5m/s) 62.5N, so on and so forth. u see, if we are not taking the ground effect into calculation pun, the downforce created by a cardboard box (not taking its weight into account here, just imagine its like a 1000kg) pun seems negligence. we have to take into calcuation jugek really all the other factors surrounding the area of question but dat shud be sufficient to show y i said the downforce is needed after a certain speed (i think dis wud be the correct term to use, "after") is achieved

---------- Post added at 04:24 PM ---------- 6 hour anti-bump limit - Previous post was at 04:17 PM ----------

the weyron deploys its flappy spoiler (lol) and squat for top end speed, memang crazy baii.. i dont care if any other car can beat the speed of a veyron, but they wont be able to beat the technologies dat define veyron from the rest of the pack. the others wont be as stable and safe, plus 407kmh top speed wasnt achieved with the engine full potential pun. tweak dat up summore and bugatti made faster top speed. was it 437 or 467 eh? lupa laa..

ok I get Ur point on top speed cruising for vehicle. and seriously I'm too lazy to put overall equation including weight of vehicle, downforce effect, etc (because that equation only for overall and basic equation of drag force heheheh and we have different kind of equation for total measurement in aerodynamic) and too lazy to search back my books relate to aerodynamic.. and the equation just to show the effect of the velocity with the aerodynamic force...and 10N already give 1 kg load on ur vehicle...nevermind on that..

how about cornering and breaking in influence of aerodynamic? I dont think when U taking corner can go about above 200kmh right? :hmmmm: and 1 more thing is about influence of side skirt? can anyone explained to me...

and yup agree with U la without proper measurement of aerodynamic flow all the item add in for aerodynamic accessory only create extra drag with little downforce rather than extra downforce..and it seem that our discussion is already out of topic heheheheh...but still it good discussion....

 

[arturo]

sideskirts is something like that curtain/apron used to lower the car loh n keep the lower pressure air under the car n stop the higher pressure air from the sides going under the car n ruining suction. but seriously...ground effect is not very practical for road cars...look at the height of those speed bumps n pot holes n undulating roads....