Spirited Driving Question
 

Wasn't sure where to post this question/discussion topic so General it is.

So went on a nice backroad out of the way except for some Bikes like to frequent it to do some therapeutic driving. Was reflecting back on the drive, so on the curves I am sure the spoiler is not deployed automatically.

So I AM curious if when on a back roads, A/X, or track driving with lots of twisties would it be better to manually deploy the spoiler or not? Car felt nice a solid but traction is key to better times.

Regardless if you consider it a spoiler to 'spoil' the airflow over the vehicle (thus reducing lift) or a 'wing' to create addl downforce or both...

If the opposing force is not prevalent, specifically copious airflow volume vis-a-vis vehicle speed, then the wing/spoiler is merely a decoration. It's deployment is speed dependent for a reason... and I'm sure has A LARGE safety margin (~ 72MPH deployment and 55MPH retraction limits as I recall).

Think of it another way... You build a treadmill wide enough to accommodate a jet airplane's landing gear. You then put a jet on said treadmill and crank up speed so the jet's wheels/tires rotate as fast on this special treadmill as they would on a tarmac/runway during take-off. Does the jet take off? Of course not.

Good luck :)

I get that the auto deployment and the function and its is there for a reason to add traction, but they also added a manual deployment button for a reason.

Deployment speed is 72Mph and retract is 55 Mph, so that means you might need it or you might not in that range to get more traction.

My question is pointed at that specific speed range on a curvy road. If you are going from between 35 Mph to 85 Mph and hitting a curve a 55 ect.. the in between range I would think just deploying the wing would help keep you planted. At a lower speed I could not see it making you unstable.

So I will mark you in the No leave it in auto mode column.

My theory is that if you are driving more aggressive then you should just deploy the wing manually to have the benefits of the extra down force in the curves. Normal driving with wife and busy street leave it in auto mode to stabilize at high speed.

I am really interested in hearing from the track guys and their opinion.

About the only time I raise the spoiler with the switch is when I wash the car and I want to dry the area where the spoiler retracts. Other than that it goes up and down based on speed.

PS . . I'm not a track guy. :)

Thanks nice and to the point! So thats 2 in the auto only mode.:D

I am a track guy and, politely, you missed the answer entirely. BTW most AX courses, below extreme expert level, rarely if ever see speeds in excess of ~ 60MPH and even then only in very short bursts. So, AX is likely slower than a continuous curvy road you're driving. Nor did I suggest deploying below 55MPH or at slow speeds would make the vehicle unstable.

Simply this is a matter of physics. There's a world of difference b/w driving 35MPH vs 85MPH; at 35MPH, the rear spoiler, due to LACK of air flow/volume, will provide ZERO benefit. Where as being fully deployed at 85MPH would start to provide some benefit. But, and it's been greatly debated countless times, is said benefit spoiling of the airflow or using the airflow to increase downforce? They are NOT the same ;)

Anecdotally, I once had a 997 C2S with front aerokit but not accompanying rear aerokit/wing. Porsche advised the rear aerokit wing was necessary for stability purposes, but I ignored their 'requirement'. Everything was fine, stability-wise, on the vehicle at speeds up to ~ 125MPH. Up from there the back end would get wiggly... not so noticeable on an incline where the g-forces are compressing the car into the pavement. However, a fast downhill like the back straight of Mid-Ohio got 'exciting' on more than a few occasions...

Regardless, correct, I'm in the No leave it in auto-mode column. But if you feel deploying provides benefit then by all means deploy the spoiler when and wherever you feel it will help as having confidence in your equipment does aid you in being a better driver.

I'd be curious to know the answer to this if you can loop back after testing:
If you manually deploy then exceed 72MPH and subsequently reduce speed back below 55MPH, will the spoiler automatically retract?

Good luck :)

Yeah use the auto criss as an example, I get the idea fast more wind more down force.

So my question simply is the any extra down force at lower speeds or not, which we still have no definative answer to that question. If it creates down force when its deployed must have some at 40 not as much as 85 of course.
So is there a point where it has no affect? What if you are going 50 and dring into a 35 mph head wind? Lol

Note in Owners manual says manual mode is active until its manually retracted.

Retracts about 50 Mph according to manual. Comments in the manual seem more concerned that it is deployed over 70 for stability. And referes to it as a spoiler, to be affective it has to build a high pressure point to force the car down.

Curious to here more input

First off, I am a track guy.

Pre-production models of the 1st Boxsters did not have a spoiler. Porsche discovered at high speeds (WELL into triple digits) the back end began to lift. :eek: So as a last minute addition, the rear spoiler was drafted into production. It was defn needed on a vehicle that supposedly has a 160-170mph top speed. I would assume Porsche chose 75mph for it to deploy because of research they did, but don't know that for a fact. It may deploy at that speed because it would have a smaller, less adverse effect at that speed than popping it up at 100, IDK. The rush to get the problem solved before production began may be why the spoiler looks like an afterthought.

When I'm tracking my CSS, I manually set my spoiler to up. This is because the tracks I drive incl runs up to 130mph and several corners in the 30-50mph. The spoiler would be going up and down multiple times per lap. Since it's a mechanical device, I don't want it failing on one of those 130mph blasts.

Would not having the spoiler come up at 75 or 85 cause you to crash violently? Probably not. Would it provide any effect by having it up when driving 35? No. Can you drive it that slow with it up? Sure.

Burg - on my 987.1 CSS, when the spoiler is manually deployed, the spoiler stays up until you put it down manually. It does not operate on speed. Can't imagine they did it differently on a 986.

Ah now we are getting to the heart of my question. I am Sure no stability issue with slower, but is there a traction benefit?

I suppose the 70 or 75 point was some type of tested safety zone.

Anyway, can you dicern more traction when taking the lower speed corners with the spoiler up, or not?

In theory should have some, but what does buttometer say?

I ask here as I have no oputunities for a driver course! Thanks

This thread started me thinking... I am not an aeronautical engineer, but I do grasp the basic concepts of downforce, drag (etc) and understand the purposes and advantages of a retractable spoiler. That being said, I can mentally picture the benefits on a coupe, but what about a convertible? In my "brain wind tunnel" I can envision a smooth air stream over a hardtop, but without a top, wouldn't the airflow be so disturbed that any effect would be greatly negated? Or am I just seeing this wrong and that the downforce provided by a spoiler is independent of the slipstream over the vehicle?

I think too much...or if you asked my wife, not enough. ;)

After more researching, I think I see what Berg is getting at. Depends on the desighn if its a spoiler it disturbs air flow to eliminate the air currents causing lift, and does not generate downforce. Where as an air foil generates down force. Looking at a physics page on spoilers and air foils, the boxster appears to have an air foil. The owners manual says its a spoiler, but the appearance is more airfoilish. Lol

Found another discussion on Pedros board, which did not help seems there is no agreement if it creats down force or not.

So I revert back to the buttometer ansew does it feel more planted or not?

And thanks for adding one of the classic engineering brain experiments to the mix. LOL. I've always contended that a model plane on a treadmill won't take off (it's not moving through the air, hince no pressure change and no lift) BUT you said jet. A jet engine moves air, so even if the wing isn't moving through a medium, the jet is moving air over the wing producing *some* lift. Would it be enough to take off? Doubtful, but reason would say that if it DID move enough volume of air to sufficiently reduce pressure, then lift would occur. Think of a model plane in a wind tunnel...the planes forward motion (same as with the treadmill) would be zero, but relative speed through the air would still create lift...theoretically if the fan in the wind tunnel was mounted on a sufficiently sized wing, it would lift itself. With that, back to our regularly scheduled programming... :)

all air at front of car has to get to back of car at same time, regardless of whether it goes (a) over, or (b) under car.

distance under car is shorter than distance over car.

hence, physics says air traveling over car has to travel faster than air under car in order to arrive at back at same time.

faster air has lower pressure.

car gets sucked up by pressure difference.

just like an airplane wing.

at slow speeds effect is negligible.

at high speeds you start to see impact.

ways to mitigate:

- front splitters and side rocker panels reduce amount of air under car.
- rear diffusers lengthen under car distance and reduce effect.
- spoilers (not wings) disturb airflow and move 'delamination' point (where smooth, 'laminar' flow over hood, windshield, and roof, separates from car and becomes 'turbulent' flow that no longer contributes to lifting effect) further forward.

all this to reduce lifting effect caused by 'wing' shape of car.

there is also downforce - this is different - this is where you get air to push the car down:

- front canards
- venting radiators upwards
- venting fender liners
- wings (reverse airfoils) on rear of car

Quite honestly at road speeds you won't notice any difference. I've driven the same sort of roads with the regular spoiler and one replaced with a Cayman style wing. You will notice more 'traction' difference with better tyres and balancing the car correctly through a corner.

Thanks this is type responses I was looking for, somewhere we drifted off into a very interesting physics disscusion on aero dynamics.

The wheel spacers i just installed actully added some traction, she doesnt try to break traction as soon in the roundabouts. I put brand new tires last year Michelin Sports 2’s or 3s I think, next time might look for something stickier.

So no noticable effect!

Don't use Pilot Sport3. Pilot Sport2 is an old tyre now. Pilot Sport4 is the latest equivalent version. Pilot Sport4S is the new version of Pilot Supersport. Or for proper sticky which work well in Spain but cost more and you get less tread depth try Cup2.

Might be PS4 I got, I just went to my tire guy I always use asked for PIlot Sports. I might try the cups next time, as it was the PS were just over 800 euros. Certainly made the car ride and handle much better. I swear it had the original rubber on it.

Ummm... b/c at the end of the day it's all about physics.

Just like spacers... as spacers themselves per se can't "add" traction... oh nvm

Good luck :)

No. You're pushing insignificant amts of air over the spoiler at low speed to feel any effect. If there was a benefit at slow speed, Porsche would have it pop up at a lower mph. Speed thru a 30-50mph corner is influenced more by:

what tires you're using
what pressure you're running in your tires
whether you're running a stock or modified suspension
what line you take thru the corner

Be aware that Cup2s are not very good in the rain. They are track tires that "can" be used on the street. But their forte is dry track tire, not necessarily a street tire. If you're buying Cup2s, you should be running it primarily on a track, not the street.

You may have had PS2s, which is an old design and not a great tire IMHO - rides rough and takes significantly longer to warm up on the track than SuperSports or Conti DW.

Well...

An aircraft engine (model or full size) moves air, not the wheels. Once inertia on the treadmill is overcome, the amount of forward thrust to balance the forces of the tread on the wheels is minuscule.

If one is arguing that forward thrust is applied only to overcome that tread to wheel friction and hold the plane stationary, then it won't lift off. However, the amount of power needed to hold it stationary is tiny.

For example, if the plane needs to be moving forward at 60mph to take off, and treadmill is moving at 60mph in the opposite direction, the amount of power needed to take off would be almost exactly the same as it would without the treadmill.

The Mythbusters did it. ;)
https://m.youtube.com/watch?v=YORCk1BN7QY

What were we talking about? :p

In your opinion of course. I have used my Cup2s only on the road and even in winter and rain. Cup2 are fine in the rain a long as it isn't torrential or with big standing water. In the UK it can rain any time any day of the year. Also here and Europe there are a fair few standard cars released as standard on Cup2 or other manufacturer equivalent tyres. We get a bunch of hot hatches that you don't get on these and of course in the same stable the GT4.

My GUESS is the real benefits are at an even much higher speed than 70 or 75. Look at all the cars on the road with no spoilers and no issues at speed in that range and much higher. things get drastically different in higher speeds these cars are capable of. I understand that the shape of the car has everything to do with it. Porsche needed the spoiler to make the car safe at a much higher speed but didn't want to put a spoiler on that no one would see work until ultra illegal speeds(in the usa) so they made it come on at speeds that are legal. As far as the low on speed, once you determine you up speed you need a big gap for the down speed to prevent frequent up and down of the spoiler.

As mentioned, the rear spoiler doesn't create downforce, it cancels some of the lift. That is a big difference. That is where the spoiler gets it's name, it "spoils" the lift.

I track my 986, and it doesn't feel loose in any of the real corners, some of which are up to 75 - 80 mph (130 kph). However, there is a flat-out kink that I take at about 125 mph (200 kph) where the back end definitely does not feel as planted.

The spoiler is up at that speed, so I bet it if I lowered the spoiler it would be exciting, in an unpleasant way. Could I handle it? Yes, because I would expect it to behave that way every lap, and I'm an experienced racing driver. For an average driver on the street, it would be alarming, and a high percentage of drivers would probably not be able to handle it. That's why Porsche put the spoiler on, just as they set up the car to understeer. Customers crashing their cars because they spin easily would be bad for business!

To answer the OP's question, the spoiler won't make any difference at under speeds under 200 kph!

This.

I sometimes feel that one of the reasons Porsche put a retractable spoiler on the Boxster was to avert possible high speed problems, like the ones that haunted Audi in the early TT models.

Just sayin'.............

TO

For me We get so few rainy days where I live, unless my daily is in the shop I don’t drive my boxster in the rain. Actually get so hot I worry about tar road patches getting slippery. We are already in the 40s here.

Of course it'll fly. What I can't believe is that the guy at the yoke and throttle believed that it would not! This guy's a pilot?? :eek:

Isn't the downforce necessary to cancel the lift? That's the ying and yang of it. No? Can't have one without the other. The spoiler is solid, so when the air hits it... it pushes down. No? Isn't that downforce? Absent that downforce you couldn't cancel the lift. No? Tell me I'm wrong. I'd like to know. Thank you.

You are wrkng unfortunately. The answers to your questions are in the main already above.

Would you believe us if we told you downforce is lift?

^^^ This. Is. Awesome. ^^^

https://www.indiatides.com/wp-conten...neva-Debut.jpg

see where the airflow departs from the roofline - that is where the air over the car transitions from smooth laminar flow into turbulent flow. at the rear, between the smoke and the car, picture air just swirling around with no cohesion.

note how the smoke has the shape of the upper half of an airplane wing. imagine the air under the car forming the lower half of the wing. the closer that transition point is to the front of the car, the less airfoil shape you have. conversely, the closer to the back it is, the more it looks like a wing.

ever notice how a big ship pushes a bow wave ahead of it? how does the water know the ship is coming? ditto spoilers. they create a larger pocket of turbulent air, which pushes the transition point forward and decreases lift.

the turbulent air has no cohesion, so does not provide any downforce by hitting the spoiler and shooting upwards. in fact, the air directly in front of the spoiler isn't even moving backwards at that point - it is just confused air.

this is why, if a car has a real, effective wing, that wing is high enough to grab the laminar airflow above the car. and realise that it is an upside-down wing, designed to use that clean air to produce negative lift that pushes down on the car.

this is also why the porsche gt3, etc., have both a spoiler (tailbase) and a wing - they serve two different purposes.

I was looking for a picture similar to this demonstrating the 986 air flows, but no luck. The website i did find had a 911 with similiar picture as this one. But the site gphad some diagrams of nascar setup, which explains the concept well. Nice pic. Rk!

I really miss Fred and hope he's doing okay. Check out this thread around post #67 for some interesting pics with the spoiler up.
http://986forum.com/forums/boxster-general-discussions/65306-boxster-986-aerodynamics-%40180km-hr-4.html

..and his Flickr:
https://www.flickr.com/photos/gtcollection/with/32407835180/

Thanks for linking to this thread...I read through it some time ago, but forgot about it; this should close all discussions regarding airflow... ;)

Regarding Fred...doesn't anyone have another social connection with him? He was a prolific poster, then just disappeared. I do hope it's nothing health related.

Fwiw....
 

...in "Excellence Was Expected", the original designers and engineers for the 986 explained the spoiler in interviews with the author.

The designer wanted the rear end of the Boxster to drop like the rear end of the 550 Spyder, RS60, et al.

The aerodynamicist wanted the rear or the car higher for better aero--less drag, less lift at high speed.

The spoiler that pops up on the 986 was a solution that solved BOTH issues.

The pop up spoiler allowed the designer to design a rear end that sloped DOWN like the original racing Spyders, and still have the ability to raise up at speed and "spoil" the rear end lift, like a Gurney Flap.

Like others have posted above, it does not push down on the rear end, but it keeps the rear end from LIFTING at high speed.

For an autocross, no advantage.

:cheers: