the effect of pop up lights on drag

[PSH]

An interesting article that has been shared on FB , the author has used the 951 body in his simulation although I would guess that the effect on other models would be similar.

http://theansweris27.com/porsche-944-headlights-aerodynamics/

Pete

 

[blade7]

I very rarely use my 944 at night but I wouldn't mind a couple of projector lamps under perspex instead of the pop ups, or in place of the side lights in the bumper.

 

[924Srr27l]

Interesting article Pete

The original pop up assemblies (Binnacles / Motor / connecting bar) also weigh about 18kg, the GTS replacements 2kg !

Aero drag was another reason for me choosing the 24 over the 44 because it has less frontal area width



I also added a small angle "Gurney Flap" on top of the bridge style rear spoiler to disturb the wake



R

 

[PSH]

I don't raise the headlights often, perhaps on dark country roads...the side lights with their bright LED's are enough for normal roads

 

[graham.webb]

That's really interesting...surprised it's not more than 6%.

Some years ago I bought a SAAB 9-5 Estate and was shocked at the amount of spray sucked in behind, so decided to fit mud flaps. Result? Fuel consumption increased by 10% Sublime to ridiculous, I know, but anything causing drag has an effect!!

BTW I often drive on fogs in marginal light conditions, just to be more visible.

 

[tscaptain]

I presume the 6% increase in drag is based on the 35m/s (near enough 70mph)speed quoted? As drag increases by the square of the speed it would be less at slower speeds and considerable more as speed increases above 70. Although as we're talking 944s here I guess that's not an issue [](Only kidding)

 

[Peter_Bull]

I presume the 6% increase in drag is based on the 35m/s (near enough 70mph)speed quoted? As drag increases by the square of the speed it would be less at slower speeds and considerable more as speed increases above 70. Although as we're talking 944s here I guess that's not an issue [](Only kidding)

Now now Alan - kidding or not that's just plain teasing and you deserve the onslaught which will duly come []

 

[PSH]

It's ok Pete...some 951's need that little bit of extra drag to slow us down a little..I took a look at the 997 turbo specs....interesting... Roger yes the 924 is a little more slippery than the 944...IIRC the drag coefficients are 0.33 and 0.35 respectively....the weights you note is interesting although not surprising, there is a fair bit of gear related to the pop ups under the bonnet

Pete

 

[924Srr27l]

Roger yes the 924 is a little more slippery than the 944...IIRC the drag coefficients are 0.33 and 0.35 respectively....the weights you note is interesting although not surprising, there is a fair bit of gear related to the pop ups under the bonnet

Pete

Maybe my cd is a tad less than .33 then with the front lower spoiler, rear spoiler and the smaller section mirrors

replacing the huge heavy Original Flag ones which are over 5kg a pair !

I split the car into 3 sections and have reductions as follows:

Section :

3. 112Kg

2. 70kg

1. 68kg

Does an objects Mass affect aero dynamics ?

R

 

[tscaptain]

The fun is also poked at myself as the owner of a pop up headlight 928. I knew there must be another reason for having them - airbrakes! Saves on pad wear too...[]

 

[PSH]

The fun is also poked at myself as the owner of a pop up headlight 928. What with the drag from the headlights and the 1980s autobox, 320 horses feels like 220......what's the Cd for the 928? Must look it up.[] Anyway Pete, not all 951s are created equal, are they?[]

oh, I don't know, they were all created pretty equal, even the heavy ones... how they are today though is another matter entirely....

Pete

 

[924Srr27l]

The fun is also poked at myself as the owner of a pop up headlight 928. I knew there must be another reason for having them - airbrakes! Saves on pad wear too...[]

1990 Porsche 928 S4 .34

2005 Aston Martin Vantage- .34 2003 Aston Martin DB9- .35 1997 McLaren F1 GT-.32 1999 BMW Z8- .39 2005 Bugatti Veyron- .355 2007 Ferrari 599 GTB- .336 2002 Ferrari Enzo- .36 1995 Ferrari F50- .372 1991 Jaguar XJ-220- .36 2001 Lamborghini Murcielago- .33 2003 Porsche Carrera GT- .396

R

 

[924Srr27l]

R

 

[tscaptain]

The fun is also poked at myself as the owner of a pop up headlight 928. What with the drag from the headlights and the 1980s autobox, 320 horses feels like 220......what's the Cd for the 928? Must look it up.[] Anyway Pete, not all 951s are created equal, are they?[]

oh, I don't know, they were all created pretty equal, even the heavy ones... how they are today though is another matter entirely....

Pete

Yes indeed, poor choice of phrase. Of course they were all created equal but didn't all remain that way!

 

[Sandspider]

I seem to remember seeing somewhere that popping up the headlights increased fuel consumption by about 1mpg!

I modified mine so that the headlights didn't pop up when the sidelights were on, looks better to my eyes and more fuel efficient.

 

[Sandspider]

I seem to remember seeing somewhere that popping up the headlights increased fuel consumption by about 1mpg!

I modified mine so that the headlights didn't pop up when the sidelights were on, looks better to my eyes and more fuel efficient.