Can the mph that raises the rear spoiler be changed?
 

Can the mph that raises the rear spoiler be changed? If possible I'd like to change it to 100 mph before it raises.

Thanks!

Porsche says that the car becomes unstable and dangerous without the added down force from the spoiler over 75 MPH. So I doubt that there would be an easy way to do this.

IIRC, it is hard coded into the ECU to deploy the spoiler at 75mph.

So, my best guess to work around this is either modifying the speedometer input to trick the ECU that 100mph was 75mph (without screwing up the speedo displays in the cluster) or modify the ECU code itself.

Maybe someone else knows more and will jump in...

On the Boxster it is a spoiler, not a wing. It does not produce down-force, it disrupts the airflow over the car and reduced the tendency of the car's aerodynamics to act a wing and lift.

A wing will produce down-force and actually push the rear of the car down. This needs to be co-ordinated with the suspension

why does it matter at what speed it raises? You can't see it when it's up from inside the cabin.

Because it creates unnecessary drag on the car, plus I don't really care for the looks of it in the up position. It doesn't go back down until you slow to 50 mph. It's easy to hit 75 and then travel a long distance at a lower speed and the spoiler stays up for no reason. Yes I know about the manual raise and lower button at the fuse panel door, but that's PITA.

I'd rather it not deploy until I hit 100 mph or even 85 mph. Was hoping maybe the Durametric could set this function.

Guess I could buy one of these. http://www.ebay.com/itm/261698591779



.

Even with the switch, once the spoiler has been automatically deployed I don't think You can override the function.

Just cut it off from the Porsche's system and built your own. Hardware: Arduino + automotive 12vdc relay ($20). Hand code one simple condition in your arduino backend (e.g. if >150mph then PIN#HIGH else PIN#LOW end)

The speedo analog signal can be tapped from the OBDII harness, and so its ground.

But you knew all about Arduino did you? If not it takes a day to learn on their site (ask their million-members-forum for support if you ever need lol)

Ah! I see! I havn't ever really researched it. Just what I've read in my owners manual. Thx!

It keep the car from lifting at higher speeds. Probably does add some negligible drag, but that is what it is supposed to do.
Porsche put it there for a reason!

Why are you concerned with drag anyway? Are you trying for a high speed record?

In any case, if you don't want the spoiler to deploy, you probably could get inside it and disconnect the gears and while the motor would still work and therefore no CEL, it would not move.

There probably are alternate methods as some have added fixed wings and disconnected the spoiler and have no codes.
Do some searching here, on boxa.net, boxster register and rennlist boxster forum

I want the spoiler to come up, but I don't think it's needed at 75 mph.

Why am I concerned with drag? Because this is my DD and that causes fuel economy to go down and drag isn't the only thing, I think it looks tacky when deployed for no reason.

I rarely hit 85 mph, but 75 mph is easy when the highway speed is 70 mph and you need to get around another car. So here is this spoiler up for no reason and doesn't come back down until 50 mph.

For safety reasons raising the speed at which it goes up is risky. My thought is that instead the speed at which it drops back down be changed. Instead of 50 let's say 65 or maybe even 70. I always thought the 25 gap was a bit much.

Fuel economy, really? slow down a bit, that will improve your fuel economy.

I get around 27 mpg on the hwy doing 75-80, so I don't know what you expect. A Boxster is not an economy car and was not meant to be one
Besides the spoiler at worst has a negligible effect on fuel economy

The spoiler comes up at 75 for a reason. I am fairly certain that Porsche did a lot of wind tunnel testing and determined that 75 is where it is needed.
The spoiler is up FOR A REASON!!!

Basic aerodynamics are in play here. the shape of the car acts like an airfoil (wing). when air flows over the top of a wing, it moves faster than the air below the wing and creates a partial vacuum. this causes the wing to move towards the partial vacuum, in this case up. by disrupting that airflow over the top, it prevents the partial vacuum and therefor prevents the car from lifting. It is exactly how the wing on an airplane works and why they deploy spoilers on landing.

A proper wing on the back of a car is in fact inverted and the airflow is faster on the bottom, causing down-force. In a car you need to counteract that down-force with springs (adjustable coil-overs)to push up a bit

They probability have the down set at 50 so once it is up, its not constantly moving up and down

That is probably a better idea. To change the speed at which it drops. Installing that button would probably be the easiest way to drop it back down.

I was really hoping a tool like the Durametric could change the spoiler operation speeds. I have not had enough time to explore what all the Durametric can do.

Fwiw, I picked up 1-2 mpg by going to an underdrive pulley.

That's already on my to do list, didn't know it helped mpg though, thanks.

I need to change out the metal impeller water pump I installed when in a pinch last summer. So I'm going to do the UDP and Low Temp Stat at the same time.

Hey don't mess with the 'active aero' man. That's right folks our cars were SO ahead of their time- so be proud of that sweet little, variable flap!
Kram- just think about what those huge GT2 air suckers are going to do to your aero...How about rigging up some slides that limit airflow through them above say, 50 MPH?

The bumper replacement is on hold. http://986forum.com/forums/general-discussions/55530-goy-my-new-front-rear-bumpers-wheels-way.html#post433870

You do make a valid point on that, but the cooling benefit would be worth it, plus it looks sweeeeeeet! The rear spoiler sticking up doesn't look sweet to me, but yes it's a nice and needed feature. I believe the slots in the upper portion of that front bumper would allow the air to escape and give front down force too. So that would probably reduce mpg too, not sure at what speed that would come into play though.

Like I said, this is a DD mostly, but I do take her out to some nasty fun twisties now and then. Hence the lager wheel and tire upgrade and ROW M030 suspension.

The rear spoiler isn't just about mpg, I think it looks tacky when up and I only want it up when needed. Seems the dash button control would be my best option.

Yaaa, I kinda like the function of the spoiler even if it is unattractive. It "spoils" both lift and drag in the rear which keeps the car planted at speed and also improves mileage. If it ain't broke, don't fix it. I can't even see mine while driving so it doesn't bother me at all. :)

Can you explain more how the extra drag the spoiler puts on the car actually improves mpg?

Seems I'm not the only person to think about this.

http://rennlist.com/forums/987-981-forum/624522-anyone-ever-disable-their-rear-spoiler.html

Interestingly in that thread it says the Durametric can disable the spoiler. Will have to dig into this some more, would be nice if it could change the speed settings too. Crud, just realized the person said Durametric Professional and I have the Enthusiast.

Byprodriver even posted in that thread he wished his spoiler raise speed could be changed to 80.

It's a physics thing. By breaking the lift it also partially diffuses the aft vortex behind the car. A major source of drag. The same is true in a standard pickup truck. All the homies drive around with their tailgate down thinking it will improve gas mileage but it has the opposite effect. Having the tailgate in place creates a pressure zone known as a separated bubble that significantly improves the aerodynamics. Both concepts were proven in the wind tunnel.

I think that applies when another car is drafting the car in front of it. I'm am however going to read up more on this.

http://www.strangeholiday.com/oops/stuff/annurev.fluid.38.050304.092016.pdf

39 pages, I'm all for learning something new.

Dynamic: air speed, wind force, direction, turbulence, density....

I think spoilers are a scam LOL great marketing none the less ;)

Was that using your butt dyno?

You need some kind of an airfoil to get down-force. Again, it's aerodynamics/physics. I don't think air flowing through those vents will give you down-force.

LOL, until you design and make some super duper cool illuminated one

Next project????

You don't need a dyno to figure out mpg.

I couldn't find anything the aerodynamic of racing link showing that having the spoiler up would increase mpg. It did mention drafting would cause the car in front to have less drag.

Sure they can. Why do you think Porsche added them to the GT2 and GT3 cars? The new Z06 does it with vents on the hood.

I was being sarcastic about the butt dyno
The problem is that to calculate MPG, you need to have constant conditions, speed, etc, so using a dyno actually would be a good way to get a good caculation

as far as less drag via drafting, again it comes down to aerodynamics and physics. Drafting produces a partial vacuum and effectively sucks the car behind in. Please someone correct me if I am wrong

Sorry, but the front vents are for cooling the brakes and radiators, they don't produce down-force. The front apron/lips generates down force, not the vents. I would guess the same is true for the Vette, cooling. I could be wrong, maybe someone can comment differently

I'm talking about the vents at the top of the bumper. They make the air flow more closely to the contour of the car.

Check out this video, skip to about 5:25

2015 Chevrolet Corvette Z06: We Speak to the Men Who Made It – Video – Car and Driver

Also on the drafting, it does affect the aft vortex behind the car.

http://www.onebadwheel.com/img/artic...s-drafting.gif

A little bit of science and aerodynamics:

https://www.youtube.com/watch?v=TKH1DyV9vNU
Pickup Truck Tailgates | Fuel Economy - Consumer Reports News

In the youtube video it says the spoiler on the Porsche creates more drag at the rear of the car.

" the redirected air leads to a lower pressure zone behind the car, which can increase drag"

Having the spoiler up will not improve the mpg.

I've used an app to track mpg for a few years now. When the UDP went in, average mpg went up by 1-2.

cool
That is a fair calculation. Does it track your speed or shift points?

in that time have you changed tires or tire pressure?

The app is Dash Command. It tracks speed, and if you set it up, shift points. I check the tires pretty regularly, so no issue there. FWIW, I see mpg go down in very cold weather, but that's expected. Seems pretty accurate.

You can bypass the oem system and use and two relays and a Porsche window switch and manually control the wing. The wing motor wiring works the same as a window regulator. It has 2 wires on the motor -up and down. Reverse polarity to move in the other direction. I have also in the past used dei window controllers to wire the wing to alarm remote controls. Your sitting having some coffee when some people come to admire your Porsche. You hit your remote switch and the wing goes up.

I guess we will just have to agree to disagree then. Tailgate up always improves highway gas mileage on a pickup. The Boxster spoiler operates under the same principles. Separated bubble.

The air flow over a truck bed is completely different then the air flow over the rear of a Boxster. You're video proved it would lead to more drag on the car.

And if the spoiler created more drag, why did the car with a spoiler outperform the car with no spoiler in straight line testing??
1st- Car equipped with wing
2nd- Car equipped with spoiler
3rd- Car with no spoiler or aero device.

Hmmmm... Still so much to learn Grasshopper. :)