Can the mph that raises the rear spoiler be changed?

[Topless]

Originally Posted by KRAM36

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.

Anyone ever disable their rear spoiler? - Rennlist Discussion Forums

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.

[KRAM36]

Originally Posted by Topless

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.

[Nine8Six]

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

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

[JayG]

Originally Posted by j.fro

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

Was that using your butt dyno?

[JayG]

Originally Posted by KRAM36

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

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.

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.

[JayG]

Originally Posted by Nine8Six

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

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

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

Next project????

[KRAM36]

Originally Posted by JayG

Was that using your butt dyno?

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.

[KRAM36]

Originally Posted by JayG

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.

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.

[Topless]

Tailgate Up or Down

[JayG]

Originally Posted by KRAM36

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.

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

Originally Posted by KRAM36

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.

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

[KRAM36]

Originally Posted by JayG

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.

[Topless]

A little bit of science and aerodynamics:

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

[KRAM36]

Originally Posted by Topless

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.

[j.fro]

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.

[JayG]

Originally Posted by j.fro

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?

[j.fro]

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.

[madmodz]

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.

[Topless]

Originally Posted by KRAM36

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 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.

[KRAM36]

Originally Posted by Topless

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.

[Topless]

Originally Posted by KRAM36

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.