IrishAndy

Skimming the manual the other day I read that the higher downforce setting (steeper rear wing angle and removal of the front underbody panels) is not permitted for road use. It was news to me until I read it. Has anyone tried this yet for track use?

ShakeNBake

I don't why it would matter other than impacting MPG, and slightly changing the alignment (toe) by compressing the suspension ever so lightly. The 997 4.0 had a higher factory rake (higher rear height than the 3.8) because the springs were softer and the car came out of the box on the higher downforce setting.

fishing

I noticed that too. I found it odd. I would like to try the higher downforce at the track.

jphughan

Almost undoubtedly some regulatory issue requiring cars to be run on the road that allows them to meet their advertised metrics, such as MPG.

vantage

Agreed, Porsche probably has to say that for regulatory or liability reasons. it's not a huge difference anyway.

I recall reading somewhere (apologies if incorrect) that the front fender vents on the new 991 RS are technically not legal so they are blocked off as delivered and the customer needs to remove them.

IrishAndy

Very interesting. So, who's going to be the first to switch to the max downforce setting. Has anyone done it already?

Also, has anyone seen a comparison of the downforce numbers in both settings? Everything I saw/read said '200 pounds' amd I'm assuming that's for the high downforce setting?

RealityGT

I don't understand the need to modify anything without first testing the Driver & Cars limit first... Unless most of you have already pushed the gt4 to its limit on a track, then if-so, my apologies and I look forward to hearing more of your impressions on this requirement.

fishing

Owners are welcome to do what they like.
1. Maybe they like tinkering
2. Maybe it makes a fast sweeper a bit faster for them.
3. Maybe they wonder if it's enough to help high speed braking.
4. By doing this, you are not modifying the car. It is still completely stock.

With your logic, you would have to say many GT4 buyers should still be in a base Caymans. Everyone bought this car with their individual intentions on how to enjoy it.

IrishAndy

Nicely stated. I do understand the logic that you should 'grow into' a car before making numerous modifications, but I also don't see this as a modification; rather an alternative standard setting that's easily switchable (for those with a jack or a ramp).

Personally I'd love to hear the opinion of anyone that switches to the higher downforce setting and whether there are any disadvantages on the street (e.g. materially higher wind noise).

By the same logic I switched on the stiffer PASM setting before I fully knew the limits of the car. I wanted to see what the effect would be in normal driving. On my beaten-up local roads it trashed the ride quality, so I turned it off. Now that's just a button on the console but the logic is similar. No harm, no foul.

ChrisF

Does anyone know how much downforce the standard setting produces?

The feeling of downforce is PROFOUND if you haven't driven a car at speed before. I expect it will be the same on the GT4. First time I felt it in the GT3 was awesome. Experiment away!

matttheboatman

I saw that and didn't understand the logic either. Could it be the high downforce setting adjust the wing to block too much rear visibility - therefore a CYA liability warning???

My intentions are to find the perfect track set up within the existing limitations (without changing parts) and leave it there for the street.

Archimedes

I was under the impression the higher downforce setups require higher speeds to achieve grip. Hence why they might not recommend it for the street. There's a good article out there about this on the new Viper ACR with the high downforce setup.

supercup

Factory media information has quoted 220 lbs of downforce (at least that is the number I recall) - but I don't know if that is in stock trim or with the wing and splitter settings maxed out?

BGB Motorsports

If you aren't going 90ish + mph through the corner, you're going to have a hard time feeling the effects of aero changes on the car. If you're trying this one the street, shame on you! Obviously some more rear wing would help under braking as you decel from 130 + mph down to your entry speed via the increased rear drag that reduces the rear end's wanting to lift more when you're standing it on its nose. I am not condoning trying this at the intersection by your house though.

I think that the single biggest thing folks get confused over is something that helps reduce axle lift vs. something that actually generates downforce. The Cayman R rear wing on the 987.2 was a good topic for this differentiation; it was used to reduce lift. The rear wing on the GT4 however is used to create additional downforce. The heavier the car and the driver, the less effect the added downforce has at the bottom end of the range of required minimal speed.

It's very easy to notice one car's having more power than the other on a race track once you hit 110 mph because drag is really beginning to become a factor at that point.

jphughan

Downforce certainly increases with speed, but I don't believe a higher-downforce setup would produce LESS downforce at a given speed than a lower-downforce setup. Higher downforce setups also often require more power to reach a given speed since they typically increase drag, but that apparently isn't a hard and fast rule. AP says that the 991 RS for example increased downforce relative to the GT3 without increasing drag coefficient.