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How important is the 991 rear spoiler for stability/downforce?
I have a 991 born with the SportsDesign ducktail rear spoiler, and I'm considering replacing it with a regular rear spoiler, but my car isnnt born with the rear spoiler buttons or cabeling, so the regular rear-spoiler will be non working.
My question: How important is the 991 rear spoiler for stability/downforce? Will I able to feel a meaningful difference below 160mph?
160? Aerodynamic effects can be noticeable at as low as 50 mph. That said, as Churchill demonstrates, "can be" is not the same as "will be."
Porsche spoilers are NOT cosmetic. A good driver will notice and appreciate. In other words, its not the spoiler. Its the driver.
160? Aerodynamic effects can be noticeable at as low as 50 mph. That said, as Churchill demonstrates, "can be" is not the same as "will be."
Porsche spoilers are NOT cosmetic. A good driver will notice and appreciate. In other words, its not the spoiler. Its the driver.
Below are numbers (in MPH and pounds) for a 991 GT3RS (stolen from 991 GT3 forum), i.e. for a car with huge aero. What do you think the numbers are for the little flap that pops up on a 991? 90 lbs at 80MPH for the big RS wing. Just guessing, but does the 991 flap produce even 30 lbs?
How do you know there is no lifting spoiler wiring in the car? There are common features accounted for in cars that may not be used by options, but are included in construction or wiring
If it had no wiring, I would add something that would make it work even if it was some manual on/off.
There are wings and then there are spoilers, A wing like on the GT3-RS, develops a downforce and has the structure below it to transfer those pounds to the car. A spoiler on the other hand "spoils" the airflow that passes from the roof and over the rear deck area. On a 911, a low pressure area develops on a spoilerless car and cause a lifting effect. the spoiler disturbs this flow, and eliminates much of the lift.
Yes, you will feel the effect of not having a spoiler at speeds below 160mph. Drive an older, spoilerless 911 at 100mph, and you will feel the effect of the rear getting light
Porsche are not known for adding 'bits' that are not necessary. And given that they engineered the spoiler to adjust position if the sunroof is opened, I am going to say that it absolutely has a functional use and not just for looks.
I wish the red light on the console spoiler button came on when the spoiler flap automatically raises at 75 mph. I hate to advertise to a knowledgeable Porsche enthusiast Highway Patrolman that I am exceeding the 65-70 mph speed limit. Can't see it any of the mirrors when it is raised up.
I’d say that for road use, balance is more important than absolute downforce. So if you want to add a little wing on the front hood to add lift there, you can probably go without the back wing without noticing any problems in normal highway driving. You’ll have a lower limit on high-speed sweepers I’m sure, but you might not notice that unless you’re a racing driver.
Interesting subject ..... as I understand things, the typical car shape creates lift at the rear of the car so a spoiler, diffuser or anything else at the rear of the car would be helpful if it reduces the lift let alone added downforce.... on the chart on this thread I don't know if it is actually measuring a reduction in lift or actual downforce - I would guess give the subject car it would be actual downforce - meaning it is providing enough downforce to "cancel" the lift and then some....
Everything I have read about airflow has demonstrated a reduction in lift to some degree with a spoiler.........
How are you getting up to 160 mph in Washington State? Most people can't get that high on a track, let alone on a normal road.
For the street, you don't need a deployable spoiler. It's a bit of a gimmick but it looks cool (kinda). For performance driving up to 160mph you need it.
Originally Posted by Scottish Pete
I wish the red light on the console spoiler button came on when the spoiler flap automatically raises at 75 mph. I hate to advertise to a knowledgeable Porsche enthusiast Highway Patrolman that I am exceeding the 65-70 mph speed limit. Can't see it any of the mirrors when it is raised up.
I agree. In a 991.2, you can see the spoiler in the side mirror if you are sitting tall in the seat. With the sunroof open, the spoiler lifts even higher and is clearly visible in the rear view mirror. It blocks half of the window.
02-18-2018, 02:58 PM
How important is the 991 rear spoiler for stability/downforce?
