Increasing downforce while reducing drag?
 

I know there's got to be some ways to reduce lift and give downforce while reducing drag.

Tire spats are one of them, and I've installed a pair on the rear end of my '91 Ford Tempo using material from my front license plate holder (which actually cover the whole width of the tire!)

I've seen data showing that vortex generators allow air to stay on the surface of the rear of the car better, and improving the effectiveness of spoilers (as shown by studies on the Mitsubishi Lancer Evolution VIII).. But what if you don't have a wing?

Discuss lift-reducing and downforce-making aero tricks!

To save reading through spam posts, here's a list so far:

1. Roof-mounted vortex generators when a rear wing/spoiler is present

2. Tire spats

3. Rear diffuser

4. Front Air Dam

How fast are you driving that you actually need downforce? :p

PS: I'm not sure I know the answer :)

Well, Ben, it could be a function of vehicle weight and tire contact patch. If I were driving on bicycle tires, with a fairly hefty vehicle, I'd want some downforce as well.

I'd probably not be concerned about it if I were driving the average vehicle though, since more downforce at speed equals more power necessary to continue propulsion. (It's the same thing as adding weight at speed.)

Lift creates drag, and so does downforce. Some aerodynamic improvements (such as a kammback over your trunk) will reduce drag and lift at the same time, others (such as deleting cosmetic wings) will reduce downforce and drag.

Downforce and lift are mostly a distraction here. A few lbs added to or lifted from the tires will have a tiny effect on mpg. Pursue drag reduction whether it removes lift or removes downforce.

I'm actually more concerned about stability at highway speeds. Next month, I'm going to be taking a 600 mile trip on I5 into Oregon, and I want to know I'm not going to lose control because of traction loss from aerodynamic lift. Downforce and lift may be just a distraction in the city or around town, but on a freeway where average speeds are around 80 MPH, it plays a vital role.

You could have a car with a super-low Cd, but if it lifts at speed, you're not going to have any control if you need to suddently stop or swerve into another lane to avoid an accident.

Browsing the threads, I've seen a bunch of great data on Cd, but almost nothing on how they affect lift or downforce.

For example, tire spats force air away from turbulent rotating tires. Without them, air would be pushed under the treads, creating a super-high pressure zone at the base of the tires. With the spats in place, that high-pressure zone is reduced, thus reducing lift.

Vortex generators can reduce drag (6 points on the Evo VIII), and increase downforce when a non-cosmetic spoiler is present. If it generates lift or downforce without one, I haven't a clue.

This thread is for ideas that both cut drag and cut lift. Know any good tricks?

tire spats - interestingly, our '09 Vibe has a pair located just in front of the front wheels...barely the width of the tire itself...little airdams for each wheel.

Ah, a fellow Tempo owner. ^^ Mine's a 2nd Gen, though.

Obviously, cars can't "take off", because their power source is connected to the ground. But I beg to differ- Lift does make a difference. I'm seeing a little bit too much of an MPG obsession here when control at speed needs to be taken into account.

Look at the Audi TT- Even a seasoned rally driver died on the autobahn from loss of control due to lift.

True enough.

So, do you have any data on the Cd of the 4-door Tempo? I haven't a clue what it is.

escort transaxles fit as well, and may have longer gears/final.

You, Sir, are correct. You need the mounts, transaxle, pedals, shifter and linkage, and the clutch kit/flywheel. It's about a $250 conversion from u-pull-it yards.

A 3.0/3.2 transmission will also bolt up to the block, but might not fit in the car's chassis, even though they came with optional 3.0's. I think the 2.3 is a bit longer than the 3.0, but I might be wrong. I do know that when putting the 3.0 into an Escort, you're shoe-horning everything to make it fit, and the Topaz isn't THAT much bigger under the hood, that I remember.

I'll just add that lift, like drag, increases as the square of speed, so there is 4X as much lift at 120 as at 60. I doubt that there is a production sedan that can ever loose as much traction to lift as it does to mild rain, let alone ice.

i'd exeriment with an undertray, wheeldams op perhaps an airdam.

especially an undertray is a great update to any car, as it smooths out the air going underneath, but it has the added benefit of blocking out road and windnoise, and keeping your engine bay much cleaner. subjectively i'd also say that it makes my car feel a bit more stable. everytime i drove the car without it since it was fitted it felt as though the car was less stable. could just be the noise, but it's a great thing to have.

i've once experimented with windstrips for doors to seal up the panel lines between the hood, and while i didn't see a massive FE increase from this and they didn't stand up to the rain, i'd swear the car was a little more quite, wich made it feel... smoother.

experimenting with wheel airdams i found certain setups can also alter the feel of the car... these things are difficult to get right especially since the low drag and a stable feel sometimes come from different designs.

if you want to drive a normal car hard, than the first thing you'd need to upgrade are the suspention , the breaks and the tires... these things keep you from going of the road. but keep in mind that widers tires are a huge source of aero drag

the opel calibra went from 0.26 to 0.29 because wider tires where fitted, and the new mercedes e class coupé has Cd's from 0.24 up to 0.29 depending on what size tires are fitted.

I suggest you do this, using 3/4" plywood for stability. Don't forget your K&N.
http://i282.photobucket.com/albums/k.../DOWNFORCE.jpg

A kammback creates lift while reducing drag. A "diffuser" at the rear underside creates downforce while reducing drag.

stability
 

Ford has already spent a few million dollars in wind tunnel development time to make sure the Tempo won't have stability issues at posted speeds.It's good that you're thinking safety,it's just that Ford can't afford for you or anyone else in a Ford product to get out of shape in a crosswind gust.

TO STAY ON TOPIC: THE LIST SO FAR!

1. Roof-mounted vortex generators when a rear wing/spoiler is present

2. Tire spats

3. Rear diffuser

4. Front Air Dam

I'm taking in the information, thank you very much. No need to be rude.

I was also trying to steer things back on topic.. I'm sure at least the moderators would appreciate that.

i think lunarhighway pretty much hit it on the head already

#1 you dont have one so dont worry about it
#2 try it
#3 make an undertray instead, then you could try it, without a smooth underbody it could only create drag
#4 try it unless youre trying #3

personally on my saturn i've extended the air dam so that its wider, and extends in front of the tires so its like i have tire spats in front. i haven't been able to detect any change in mileage good or bad. but i kept it on because the car seems less affected by cross winds when driving on the highway or interstate. if it improves handling any other way, it has been undectable to me.

i would also like to improve my mileage while improving handling of my own car (or as you think of it, reduce drag and improve down force) but i don't think down force or lift matters much below triple digit speeds, and if you're going that fast, you'd probably let down force trump drag anyway. if you have plenty of ground clearance for where you normally drive, and if lowering springs are available for your car, buy some. i'd like to when i can afford doing it... my tires are needing to be replaced soon, so i've been looking for tires that have the best grip and least rolling resistance.

btw, anyone know of a better tire for that in a 175 70 14 than michelin harmony that isnt worthless in snow?

Tire Search Results

There's two studless ice and snow tires on the bottom, and some sticky summer treads on the 1st page for 175/70/14. Enjoy!

Hi

Are you trying to improve FE, too? The spats you are referring to -- are they wheel skirts, or deflectors? (A pic or two would help.)

Nobody has mentioned a front upper grill block and/or a gasket under the front edge of the hood to seal the gap. This will reduce drag and it may even improve cooling. It might reduce front end lift, too?

A rear deck spoiler will only increase drag and it'll do squat for lift. Turbulators will add more drag, and do squat for lift.

A front belly pan (or a full length belly pan) will lower drag much more than a chin spoiler, and it would not increase the frontal area.

A Kamm back would reduce drag, and probably lower rear lift.

Here's my spats:

http://i3.photobucket.com/albums/y93...y/DSCF0837.jpg

http://i3.photobucket.com/albums/y93...y/DSCF0840.jpg

http://i3.photobucket.com/albums/y93...y/DSCF0838.jpg

Wait... Blocking airflow will cool the engine? You've got it backwards, dude. Blocking the grille makes the engine run hotter. Just ask NASCAR drivers when they pull tape off their grills during a race. More airflow=cooler engine. Less airflow=hotter engine.

The cosmetic rear spoilers don't do much of anything. However, a decent spoiler will in fact reduce lift by creating downforce. This is if they're either shaped like an upside-down airplane wing, or like the old NASCAR lip spoilers. Granted, they do generate drag.

However, a full belly pan covering the engine results in a hotter engine, reducing efficiency and lowering the life of the engine and parts. Vents/loveurs for the engine bay would be beneficial.

There are cases where blocking grille openings actually will increase airflow through the radiator, though I can't think of any right now.

Putting a gasket between the hood and upper rad brace is a well known way to improve cooling, as well as a tray under and around the radiator. Most of the air that goes into your front end doesn't really go to cooling your engine.

If you want to compare apples to apples, leave NASCAR out of the street car arena. NASCAR autos have tuned inlet ports on the front of the car that allow just the right amount of cooling based on the size of the opening without sacrificing aerodynamics the way street cars do.

Blocking your grille properly could allow air to flow through the radiator uninterrupted by cross-flows under the hood, which would improve cooling over stock. This is part of the reason that newer cars have radiator trays above and below, and a large part of the reason for adding fan shrouds to radiators.

A full belly pan also does not necessarily result in a hotter engine, as long as your cooling system is adequate and you have adequate airflow to vent the system into open air.

Do you have evidence to back up what you're saying about a hotter engine having reduced efficiency and less life? Seems funny, because many engines run overcooled OEM style, and end up getting better efficiency once they're allowed to run at some nominally higher temp.

"By taking sumptuous amount of cold air directly to the engine it provides the engine with abundant oxygen. Cold is important too because for a given volume more air will fit in if it is cold and less will fit in if it is hot. This abundant oxygen ensures that the fuel is combusted very well and fuel left unignited due to a lack of oxygen is reduced. The fact that a higher percentage of the fuel is combusted means you get a better fuel efficiency. And the fact that more fuel is burnt in every engine cycle means you get more power. Often extra power is at the cost of lower fuel efficiency but a cold air intake manages to do both."

Cold air intake improves engine life

Cold air=dense air=greater efficiency

This isn't a secret, really.. It's common fact elsewhere, but even simple things become foreign with such fixation on MPGs alone.

Same with cooler engine parts meaning longer life. Does an overheated engine run well? Obviously not. Continuous heating over time has the same effect as one burst of heat. Look at slow cooking versus high heat. They both end up cooked, it's just a matter of when.

All engines have an optimum operating temparature. This is when they're "warmed up." Anything beyond it is less than beneficial.

"Cooling is also needed because high temperatures damage engine materials and lubricants. Internal-combustion engines burn fuel hotter than the melting temperature of engine materials, and hot enough to set fire to lubricants. Engine cooling removes energy fast enough to keep temperatures low so the engine can survive."

http://www.answers.com/topic/engine-cooling

1. Answers.com is hardly a technical data source, and should not be treated as anything close to such.

2. You still haven't proven that a warmer engine is necessarily going to "live a shorter life" compared to a cooler one. The problem with this statement is that it assumes that everyone already agrees that a warm engine is actually a hot engine, which it is not.

A cold air intake doesn't necessarily increase horsepower. In some cases, the same gains could be made (at WOT, obviously) by simply removing the air filter and air box.

Where exactly does a CAI make gains at less than WOT? Show me that? If colder air is really making more HP in the capacity of the CAI, then even at part throttle, there should be enough excess air density to make more power compared to the same throttle with OEM intake.

Obviously, an engine has a limit to the amount of heat it can stand before it starts to grenade, even over a long period of time. Engines run most efficiently when they're not wasting heat, which tells one that the excess heat created either needs to be utilized, or not created in the first place. Since combustion creates heat, and ICE's aren't truly all that efficient, having a warmer engine means that less energy is sent through the engine as heat, and more as power. There is a reason that cold engines don't run well.

Saying that anything beyond "warmed up" is less then beneficial is just a cop-out statement, which shows that you're probably regurgitating information from someone else's mouth. You can't confirm that "warmed up" is an actual operating temperature, nor can you confirm that if "warmed up" were a concrete state in terms of temperature, that it would be the most efficient state for all applicable scenarios. Without being able to prove any of that, this statement needs no further review, as in the looking glass of scientific scrutiny, it holds no weight whatsoever.

If cooler engine parts mean a longer life - again, a generalized statment - why does the engine need to be warmed up? Now you're contradicting yourself...

I'm not even going to start on the non-scientific (or even considerably credible) nature of the CAI article.

Please, continue this discussion when you can find real evidence and studies to back up what you're saying.

You could do the same and provide evidence instead of having none and attacking mine.

Who's contradicting themselves?

Also, removing the air filter? Anyone with half a brain knows that the particles getting into the engine from that would ruin it.

If you actually read my post, you would have understood what when I said cooler, it means relative to blocking the air intakes into the engine compartment and the vents underneath such with a full belly pan.

As I said, and I'll repeat, all engines have an optimum operating temparature, and it varies from engine to engine. There is no definite number for all engines, and it's asanine to think so.

And I'll repeat again, try overheating your engine constantly and see how long it lasts.

Dyno chart for a 2006 Ford Mustang GT, with stock intake, and CAI:
http://www.knfilters.com/dynocharts/57-2565_dyno.pdf

Same test on a 2006 Chevorlet Corvette Z06:
http://www.knfilters.com/dynocharts/63-3060_dyno.pdf

Gains all across the powerband, but more noticeable at high RPMs.


I'll lay it in common sense that even an elementary student can understand:

For gas to blow up, it needs oxygen. When air is cold, it's dense, meaning there's more in it for a given space. If cold air goes into an engine, there's more oxygen to blow up the gas. This makes sure there's a bigger boom. Bigger boom means more power.

Clear enough?

So - I'm not in the position to provide evidence, as I'm the one questioning what you've provided. It's a rather simple process.

I run my engine with no air filter, and it's not ruined. In fact, I've been doing this for about 9,000 miles now. While I don't recommend that others do it, because of the obvious perceived danger, I also know that it won't "ruin" your engine in any short amount of time, relative to average engine life.

If you feel that I misunderstood something, it may be because you were less than clear about it. I, however, doubt that there was a misunderstanding. I'm sure you were referring to blocking the air inlets of the grille, which, in most OEM "real world" scenarios, are far too large to allow for adequate cooling.

Once again, A full belly pan won't necessarily cause your engine to overheat, provided you have a means to vent the engine's excess heat into open air. That means doesn't necessarily have to be the bottom of the engine bay, nor does it have to be the hood.

You're correct in saying that engines have an optimum operating temperature, I didn't dissuade from that. What I mentioned was that it was very neglectful of you to say that "warmed up" was that optimum temperature. You simply cannot apply such a broad term to something so precise without further explanation, and you also cannot say that the OEM setting is always necessarily best for optimum performance or efficiency, to place the cue on either side of the scale, especially considering that such has been found to be false on so many occasions, both here at EcoModder and in most performance communities at large.

What one can be quite sure of, though, is that OEM's will make every attempt to compensate for "worst case scenario", even though it doesn't apply to the largest subset of consumers. What this means for you is: on average, your vehicle, when in OEM condition, will not run at it's best efficiency or performance, will not perform at it's peak in all conditions, and, at least in some capacity, has room (lots of it, usually) for improvement over OEM configuration.

To combat your previous non-sensical assessment of CAI's with more non-sense:

Most OEM's won't cover engine damage that could even remotely be associated with intake stream modification or manipulation. Go ahead and verify it.

OEMs won't cover ANY modification of the engine that isn't replacing OEM parts. I'm quite sure your lack of an air filter isn't covered either, so what you said is pointless.

Also, here's a challenge for you- Take apart your engine, especially in the air intake, and wipe it down. You'll see how much gunk is getting in there.

Give it another 10,000 miles or so. Without an air filter, you're going to need an overhaul. I'd bet money on that. It's recommended air filters are changed every 12,000 miles.

"I'm sure you were referring to blocking the air inlets of the grille, which, in most OEM "real world" scenarios, are far too large to allow for adequate cooling."

That makes absolutely no sense. Go ahead and pull off your front facia. I'm sure you'll be running plenty cool from all that air hitting the radiator. If you said "small," it would make sense.
Unless the engineers are complete idiots, a large grille allows a large ammount of air into the engine compartment and through the radiator, thus allowing better cooling than a smaller grille. Common sense.

As if it hasn't been made painfully obvious, the engineers are covering "worst case scenario", and yes, you can easily OVERCOOL your engine by removing the fascia from the vehicle, which would put it outside it's efficient range, which is apparently not what you're going for... so that statement is pointless. Were you going somewhere with this discussion?

You'd bet on my engine needing an overhaul, and you'd probably lose. 10,000 miles is a very short time.

In case you'd like something else to under examine, I also don't change my oil on a schedule. If overhaul was imminent based on my lack of air filter, I should see buildup in the oil, correct? I'll take a pic for you tomorrow. Hell, I'll even text it to you. It's just starting to lose it's golden color - and it's been in there, with the same filter, for ~9,000 miles as well.

A large amount of air doesn't necessarily afford more cooling capacity, either. I'll let you do the searching to quantify that - you might begin to understand how a grille block could make an engine operate more efficiently.

When you really want help, we're here, but you've been afforded plenty of solicited advice/information, and you don't seem to accept it, both here and elsewhere, as I've been informed by others.

Once you figure out whatever it is you really want, please, by all means, show us the Nobel prize in your category.

first off, click on the "65+ Efficiency Mods" at the top of the page and spend time reading through them, might find some new ideas, or at least the logic behind them.

i thought the overcooling thing was about having more air flow over the radiator than needed, not the actual coolant temp which would be controlled by the thermostat. on most stock vehicles in most conditions there is much more air flow to the radiator than needed to keep the vehicle running at the temp regulated by the thermostat. so grill openings, or part of openings can be covered to make the car more aero without making it run hotter.

if your cold air intake is working properly and your getting that extra oxygen, anything with an oxygen sensor will adjust the fuel mixture. now you can make more power for any given throttle opening. sweet right? but it still takes the same amount of power to hold your car at any given speed going down the road, so you dont need to use as much throttle. this car has to be efficient now right? well wait, closed the throttle more...crap thats where the oxygen gets in.... what were we trying to do again?

Hi,

Thanks for posting the pictures -- I would call them deflectors.

With a fully ducted cooling system, you can cool the engine with a LOT less air. NASCAR has found that 16 sq. in. of intake for each 100HP is adequate. That is an opening 4" x 4" to cool 100HP engine. Small opening = less drag.

Not all of a large grill is necessarily taking IN air! If the lower part of the grill is more efficient at taking in air (as it is), then on some cars at least, the upper part of the grill has air flowing OUT. That air does not flow through the radiator, and will not cool the engine -- it only adds drag.

Have you read the Hucho book "Aerodynamics of Road Vehicles: From Fluid Mechanics to Vehicle Engineering"? I have started to read it, and you should check out the chapter on the internal engine bay air flow.

Also, see my xA build thread, dude: http://ecomodder.com/forum/showthrea...mods-2969.html

Thank you, Neil, for properly expressing what I referred to as "cross flows". I couldn't think of what I wanted to say to that effect last night.

Now to get back to the original topic- Reducing drag while simultaneously reducing lift.

Hi Hermie,

I think what we need to worry about is drag -- we do not have enough lift at normal speeds to really worry about, IMO.

An upper grill block will reduce drag, and probably reduce lift; as I said before.

You should try to find the Hucho book at a university library -- I borrowed a copy from MIT (via my wife who is a librarian). It'll knock your socks off with the sheer volume of detailed info about vehicle aerodynamics.

I'll look for it, thanks! ^^

I'm also thinking about taking my car to the track on weekends once in a while, so I'm looking to make my car the best of both worlds- fuel efficient through less drag, but handles at speed through reduced lift/increased downforce. I don't want mods that'll increase lift, because performance at speed will be dramatically reduced.

I probably should have made myself clearer from the start to avoid the rudeness some people have posted...

If I can get Stickers to run 30mpg highway from lowered drag, but have zero lift or net downforce, I'd be more than happy.

The trade-offs for street use usually leave a bit of lift. If you want to race occasionally, bolt on a big wing at the track. A really smooth belly pan, and an arrangement to lower the front might be another fine combination.

We Take Audi's Tamed TT for a Spin - First Drive Review - Auto Reviews - Car and Driver

So it turns out a car for which lift actually was a problem at high speeds was only experiencing 148lbs before they added the spoiler. I'm surprised that's even though to make a big difference in handling though.

So what kind of lift would you get a 65mph? About 1/4 as much as 125mph?

The Audi TT in question was notorious for high speed lift-off snap oversteer due to the style-over-function design. After that incident (not the only one), the optional rear spoiler was installed on all of them by the factory.

My 1983 Subaru GL sedan was a similar style car to the Tempo with a likely comparable drag coefficient. I had few stability issues until it was topped out at "P" (the P in MPH at the bottom of the 85 mph speedometer), which worked out to be around 110 going by the tachometer. At that point, it would move around a little in crosswinds, but could still keep in a lane sawing the wheel like a '50's movie racecar driver. Where it bothered me was on on-ramps at speeds over 80, with significant understeer, so I added a front airdam. Got slightly better mileage which was probably within a margin of error, but it did add straightline stability and cured the understeer (at least the lift-induced understeer). What it also did (besides scrape the occasional driveway when I forgot to enter at an angle) was increase oversteer to a level that was fun in the dry and a little hairy in the wet. A tree fell on it while I was driving down the street, so I never got to put an adjustable rear spoiler on the trunk.

Wow, I'm glad you're okay.

I'm definitely adding an air dam then. Tomorrow I'm going to look for material.

I'm going to balance it with a rear lip spoiler, with vortex generators to aid airflow onto the rear deck, which should improve the spoiler's properties and reduce drag at the same time.

*points up*
These are the exact mods I'm talking about. XD

So, anyone have any wind tunnel data on the ecomods here, by any chance?

Front undertray. My '08 Honda Fit was squirrelly around the big rigs on the freeway. Then I put a Beatrush front undertray on the car. It is now much, much more stable at speed, in crosswinds and so forth, plus it handles the offramps better.

Oh yeah -- 1 to 2 MPG improvement in fuel economy.

i'd vote for an undertray to. it's a little more involving than an airdam, but it has so much advantages. even my first relative small one made out of a sheet of coroplast made such a difference in the way the car felt, it seemed more stable and quite. i once drove a day or two with my current dam removed the car felt wobbly and unstable... and while my car has a terible ammount of oversteer, the dam actually gives is the stability that allows my to toss it around a sharp corner or roundabout. it will still oversteer at some point but i've never found this to be a problem with in normal driving, even at high speeds

it also protects your engine from debris and dirt

what i most certainly recommend you do is to evaluate your mods.

you could do several things. first of all record your milage and work out if there's any change, but don't draw conclusions to soon... the best thing to do is do A-B-A testing over the same track, as weather and traffic all influence your results. if you have a fuelcomputer that tells you your milage instanly thay's even better.

you could also do some diy tuft testing especially on the vortex generators that should tell you one or two things
this aoutospeed article has some nice info on how to tuft test