Spirited Driving Question

[Cunningr]

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.

[Burg Boxster]

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

[Cunningr]

Originally Posted by Burg Boxster

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.

[paulofto]

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.

[Cunningr]

Originally Posted by paulofto

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.

[Burg Boxster]

Originally Posted by Cunningr

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.

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

[Cunningr]

Originally Posted by Burg Boxster

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

[husker boxster]

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. 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.

[Cunningr]

Originally Posted by husker boxster

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. 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

[MWS]

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.

[Cunningr]

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?

[MWS]

Originally Posted by Burg Boxster

... 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.

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...

[The Radium King]

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

[edc]

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.

[Cunningr]

Originally Posted by edc

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!

[edc]

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.

[Cunningr]

Originally Posted by edc

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.

[Burg Boxster]

Originally Posted by Cunningr

... somewhere we drifted off into a very interesting physics disscusion...

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

[husker boxster]

Originally Posted by Cunningr

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?

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

[husker boxster]

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.