997 digital speedometer display
Rennlist Member
Joined: Apr 2007
Posts: 1,924
Likes: 28
From: Tejas Hill Country
I was out at Harris Hill Road a few weekends ago and found myself alone on the track for a bit. With no traffic to contend with, I decided to pay closer attention to my corner entrance and exit speeds as I experimented with my line around the course.
I was pretty surprised to discover that the digital speedometer has just enough of a lag that it made it less useful for taking speed snapshots during hard braking (as I was entering a corner). It's not anything I've ever perceived during normal street driving but it was definitely noticeable out at the track. In particular coming into turn four at the end of the long straight you have to brake very rapidly (aided by a steep uphill). In my C2S this translates into 105mph down to under 50mph. What I'd see was that I'd be accelerating at WOT then apply the brakes hard -- the digital speedometer would increase just a tick, lagging the application of the brakes, before it would begin to then decrease to show my acceleration.
I sure wouldn't call it a problem. It's definitely an edge case -- rapid change in speed on a track when I was unusually concerned with the precise speeds. Still, it was a little surprising. I switched to using the analog gauge which suffered from all the caveats others have mentioned in the thread but had no perceptible lag.
My guess is that the lag is a necessary byproduct of "smoothing" in the digital display that Porsche employ to stabilize the inherent miniscule variations in speed that exist in reality. The display is probably an averaged number of the past 20ms of samples or something. (total speculation on my part)
I was pretty surprised to discover that the digital speedometer has just enough of a lag that it made it less useful for taking speed snapshots during hard braking (as I was entering a corner). It's not anything I've ever perceived during normal street driving but it was definitely noticeable out at the track. In particular coming into turn four at the end of the long straight you have to brake very rapidly (aided by a steep uphill). In my C2S this translates into 105mph down to under 50mph. What I'd see was that I'd be accelerating at WOT then apply the brakes hard -- the digital speedometer would increase just a tick, lagging the application of the brakes, before it would begin to then decrease to show my acceleration.
I sure wouldn't call it a problem. It's definitely an edge case -- rapid change in speed on a track when I was unusually concerned with the precise speeds. Still, it was a little surprising. I switched to using the analog gauge which suffered from all the caveats others have mentioned in the thread but had no perceptible lag.
My guess is that the lag is a necessary byproduct of "smoothing" in the digital display that Porsche employ to stabilize the inherent miniscule variations in speed that exist in reality. The display is probably an averaged number of the past 20ms of samples or something. (total speculation on my part)
