OT:911R
05-13-2016 | 10:17 PM
#2536
Rennlist Member
Joined: Apr 2002
Posts: 14,140
Likes: 14
From: New Zealand
Thanks for the insight Jack! I believe you are probably right. As I never drive at 150mph in a straight line (even on our longest track straights here in NZ) Ill ditch the idea. Id probably bend or buckle them on my first bumpy early morning B road raid anyhow ;-)
05-14-2016 | 03:09 PM
#2539
Burning Brakes
Joined: Apr 2012
Posts: 1,157
Likes: 92
From: Port Orange, FL
Ha! I've been there and done that. Years ago.
And you know what? It doesn't work.
I tested mine in a straight line and got good numbers. But then at the track it made the car unpredictable and weird. The more research I did, the more it looked like a diffuser has to stay in a very specific (and low) position near the ground in order for it to be effective in corners. Production car springs -- even stiff ones -- just don't reduce body roll enough for that to be possible.
And yet, manufacturers keep putting diffusers on performance cars. I cynically concluded that they were just decorative nonsense -- something like brightly-painted calipers.
It wasn't until after I'd driven the 911R that I realized I was partially wrong. I still don't think the 911R's diffuser would be very effective at a track (or in any corner, for that matter). But I'll bet it reduces the light, floaty (and potentially dangerous) handling a production car gets in straight-line, high-speed driving. Since my own car is limited by gearing to 140 mph, and since I don't have an autobahn near my house, there's no reason for me to put one on again. But for 911R owners who might want to see what 200 mph feels like, I'll bet the diffuser is something that the safety guys at Porsche like a lot. My guess is that its sole function is to make the car more stable above 150 mph (or thereabouts). Nothing bad about that -- but it's also not something that's going to dramatically change your lap times, like a wing can.
And you know what? It doesn't work.
I tested mine in a straight line and got good numbers. But then at the track it made the car unpredictable and weird. The more research I did, the more it looked like a diffuser has to stay in a very specific (and low) position near the ground in order for it to be effective in corners. Production car springs -- even stiff ones -- just don't reduce body roll enough for that to be possible.
And yet, manufacturers keep putting diffusers on performance cars. I cynically concluded that they were just decorative nonsense -- something like brightly-painted calipers.
It wasn't until after I'd driven the 911R that I realized I was partially wrong. I still don't think the 911R's diffuser would be very effective at a track (or in any corner, for that matter). But I'll bet it reduces the light, floaty (and potentially dangerous) handling a production car gets in straight-line, high-speed driving. Since my own car is limited by gearing to 140 mph, and since I don't have an autobahn near my house, there's no reason for me to put one on again. But for 911R owners who might want to see what 200 mph feels like, I'll bet the diffuser is something that the safety guys at Porsche like a lot. My guess is that its sole function is to make the car more stable above 150 mph (or thereabouts). Nothing bad about that -- but it's also not something that's going to dramatically change your lap times, like a wing can.
The larger Crawford Wing was by far the most effective change in both reducing
oversteer and stabilizing high-speed threshhold braking - which I attributed as much to its drag as to its downforce. A MUCH larger flat front splitter (1/8th inch flat aluminum plate) protruding 6-7 inches out from the front) also was very effective in reducing understeer.
05-15-2016 | 06:17 AM
#2541
Pro
Joined: Apr 2012
Posts: 601
Likes: 7
