How Come R32s Have Such Crappy Drag?

[iplen]

Not sure if it is true... but... pretty confident a Kombi has a lower CD than an E type Jag.... CD can also have a fair bit to do with the way air leaves the car would be keen to know if the N1 bits effect the R32??? I have also noticed a massive difference going down hill in my R32, pop it into neutral and it damn near stops dead, however wheels seem to spin pretty freely when it is on stands. 1989 Patrol though could roll forever, before front hubs etc were done, rather than being CD related, pretty sure this was just a result of wheel momentum.

[bozodos]

fat gf's are more noticable when driving RB20 powered cars LOL. Mine already weighs 1500kg, but tbqh it dosen't get pushed around on the road as much by wind, trucks going past etc as the old VN!

[TurboDoseBro]

Yeah I guess there are many factors (a given). However I recall reading an article quite a while ago on autospeed.com saying that one way to measure the effectiveness of your drag is to go on the same stretch of road, same weather, conditions etc etc and accelerate to ~140km/h and let go of the accelerator, then time how long it takes to drop back down to 100km/h. This only works for the same car, but my old Subaru (newer actually, 2004) had basically the same gear ratios and roughly same weight, added AWD, and still noticeably would drop down slower from 140km/h if i ever tested it. I know cause there is a point on the freeway where I always coast, that had larger and heavier wheels than stock, compared to stock 16" GTS-T rims and tyres.

[Nee-san]

More to the point I guess is there any proven way to improve the cars performance with 1 type of body kit over another or perhaps or even paint finishings.

ie Kiwi yachtsmen use lanolin on their hulls to improve the boats slip through the water & powerboaters use it for better fuel economy-not possible on the car but??????????

That would be to overcome the skin drag of a fluid of a an element, Skin drag accounts for a very large proportion of fluid resistance read (way higher then frontal area or CD).

[waxracing]

To much drag= not enough boost

Seriously if you think you can feel it then it may be time to turn out the torch and pull the sheets back

The swelling will go away

I drive a pathfinder and sure it effects up high when i drive and drive it fast 130k and above you can feel it pushing the wind

But it would have a cd of 1 or maybe greater

[mad082]

Not sure if it is true... but... pretty confident a Kombi has a lower CD than an E type Jag.... CD can also have a fair bit to do with the way air leaves the car would be keen to know if the N1 bits effect the R32??? I have also noticed a massive difference going down hill in my R32, pop it into neutral and it damn near stops dead, however wheels seem to spin pretty freely when it is on stands. 1989 Patrol though could roll forever, before front hubs etc were done, rather than being CD related, pretty sure this was just a result of wheel momentum.

back in the late 80's or early 90's the volvo race cars were station wagons because they had a lower CD than the sedans.

how sleek a car is has little to do with CD as turbulance can dramtically affect it.

[syfon]

The only car i know of that you can feel the wind resistance when driving at freeway speeds is my dad's old 1988 Suzuki Sierra. It's a bloody red metal box with 4 wheels and a 66hp 1.3L carby 4cyl. Mind you, if you're doing 100km/h and there is s slight crosswind, that thing will just tip over haha

[Equinox]

To much drag= not enough boost

Seriously if you think you can feel it then it may be time to turn out the torch and pull the sheets back

The swelling will go away

I drive a pathfinder and sure it effects up high when i drive and drive it fast 130k and above you can feel it pushing the wind

But it would have a cd of 1 or maybe greater

Greater than 1. Yeah right. It'd be in the 0.4x range somewhere. The frontal area will be alot greater than an R32 however.

[Galois]

As mentioned freeway speeds just wont be enough to notice the affect of Cd alone. Drag, however, also includes the skin friction and the means by which the air leaves the car (also mentioned before).

There's a topic somewhere on sau comparing fuel usage which has testimates from people who have experimented with tyre width, apparently it makes a HUGE difference to fuel economy, and hence overall drag on the car.

I find with the gtt that downhill on the freeway I still need throttle when everyone else is braking, that's because of the gear ratio's as well, 3200 rpm at 120km/h, massive engine braking.

Cd is a method of oversimplifying a shape, it's not greatly useful in normal applications, esp on 20 year old cars.

Edited September 9, 2010 by Galois

[Galois]

skyline wind tunnel:

http://il.youtube.com/watch?v=V6ewoDeUo5U&...feature=related

the turbulence at the back is present on all cars to a degree, it can perform one of two actions:

1. It can create a buffer for air to flow over, much like it does on a ute with the tail up (reference: mythbusters haha)

2. It can create a point of lower pressure, pulling the car back. Not much, but just a thought

Edited September 9, 2010 by Galois

[waxracing]

Greater than 1. Yeah right. It'd be in the 0.4x range somewhere. The frontal area will be alot greater than an R32 however.

Do a search on sarcasim I know it wouldnt be anwhere close to 1

[TurboDoseBro]

More to the point I guess is there any proven way to improve the cars performance with 1 type of body kit over another or perhaps or even paint finishings.

ie Kiwi yachtsmen use lanolin on their hulls to improve the boats slip through the water & powerboaters use it for better fuel economy-not possible on the car but??????????

Well cars actually do have a trick or 2 up their sleeves for better aerodynamics. It's called vortex generators / fins. You will mainly find them on Evos and WRXs (mainly evos).

They look something like this (but not limited to):

http://www.amsperformance.com/cart/images/...exGenerator.jpg

This basically alleviates some of the air turbulance / air suction at the back of the car, stabilizing it and giving slightly better drag.

The other thing is rear diffusers. I'm sure you know this one.

Also Galois, that 'wind tunnel' video wasn't much lol, only showed the effect of the rear air turbulance. The underbody of the car plays a major part in fluid dynamics too. Reading your posts, you should have no problem understanding that as you're from an engineering / science background.

Edited September 9, 2010 by TyresBro

[Galois]

Also Galois, that 'wind tunnel' video wasn't much lol, only showed the effect of the rear air turbulance. The underbody of the car plays a major part in fluid dynamics too.

Yeah not a great video, but might help someone with visualising the are effects over the car. The underbody is the most important part, very few new supercars have a wing because the underbody of the car is so highly developed for working air.

The ground effects cars in f1 pulled the highest g forces ever and were banned due to dangerously high cornering speeds. Current f1 cars have a rear diffuser built into part of the safety arrangement which caused many teams to be upset when the design was introduced last season.

Not really adding anything onto to what you said mate, just some examples.

Why the interest in the drag coefficient? It doesn't mean much except at top speed?

[TurboDoseBro]

Well actually this topic hasn't been covered yet. Also theoretically it's not just top speed, it is accelerative capacity as well. Example: Car A that has Cd of .5 will start exponentially slowing down from 140km/h and top out by 200km/h compared to Car B with 0.3 Cd which will probably start from 160km/h and top out by 220km/h or so (both example figures) assuming same everything except Cd so basically Car B achieved what Car A could do at the same amount of time but higher in acceleration and speed. Also i believe drag makes a smoother and easier ride

[zebra]

fat gf's are more noticable when driving RB20 powered cars LOL. Mine already weighs 1500kg, but tbqh it dosen't get pushed around on the road as much by wind, trucks going past etc as the old VN!

Soooooo...1500kgs of Girlfriend plus 1400kgs of R32 plus fuel and you...no wonder the old rb20 struggles.

[Nee-san]

Cd is a method of oversimplifying a shape, it's not greatly useful in normal applications, esp on 20 year old cars.

+ 9000.

[Galois]

Soooooo...1500kgs of Girlfriend plus 1400kgs of R32 plus fuel and you...no wonder the old rb20 struggles.

bahahahahahaha i thought that too!