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I just wrapped up the L2 course at Spring Mountain and was using the PDR the entire time to keep track of my lap times and see how I was progressing. For the second half of day 2 the SM folks also put a transponder on your car and give you your lap times at the end of the day.
I was feeling pretty good about getting a 1:59.2 according to the PDR but when I got my printout from the transponder it showed that lap as a 2:01.2. All the other laps I compared were pretty close between the transponder and PDR so what gives?
I pulled up the Cosworth toolbox and compared my "fast lap" with another lap that was close in time and could see where the time delta between the laps suddenly jumped 2s at about 28s in to the lap. If you look at the video side by side you can literally see the lap time on the video jump backwards 2s and then continue counting.
Perhaps there was something specific to this car at SM but seeing this anomaly has really shaken my confidence in the PDR system. I'm going to go back and look at my other fast laps to see if this anomaly occurred there because without the transponder data I don't think I would have noticed. Has anyone else seen this?
On the plus side, it looks like the 1:59.9 lap I ran earlier in the day was legit so at least I broke the 2 min barrier on the extended N/S course.
I just wrapped up the L2 course at Spring Mountain and was using the PDR the entire time to keep track of my lap times and see how I was progressing. For the second half of day 2 the SM folks also put a transponder on your car and give you your lap times at the end of the day.
I was feeling pretty good about getting a 1:59.2 according to the PDR but when I got my printout from the transponder it showed that lap as a 2:01.2. All the other laps I compared were pretty close between the transponder and PDR so what gives?
I pulled up the Cosworth toolbox and compared my "fast lap" with another lap that was close in time and could see where the time delta between the laps suddenly jumped 2s at about 28s in to the lap. If you look at the video side by side you can literally see the lap time on the video jump backwards 2s and then continue counting.
Perhaps there was something specific to this car at SM but seeing this anomaly has really shaken my confidence in the PDR system. I'm going to go back and look at my other fast laps to see if this anomaly occurred there because without the transponder data I don't think I would have noticed. Has anyone else seen this?
On the plus side, it looks like the 1:59.9 lap I ran earlier in the day was legit so at least I broke the 2 min barrier on the extended N/S course.
I've had the same thing happen to me, but just once as far as I can tell. I didn't have a transponder but it looks like just about 2 seconds.
Thanks Operations. We had what I suspect was an unusually fast class. While traction wasn't great with the wind and the cold there were 4 of us that dropped below 2:00. One guy even managed a 1:58.3.
Yet again the crew at SM was able to quickly identify my weaknesses so I have a lot to work on this next season.
I just checked my previous fast laps and it looks like my 1:16.8 lap on Summit Point main was also a PDR anomaly. You can clearly see around 20s in to the lap the time jumps 2 seconds. I'll have to post a retraction in the fast laps thread.
Thanks for being honest and coming forward with this info, now all of the lap times posted with just the PDR are in question unless you have a transponder to verify it with.
Thanks for being honest and coming forward with this info, now all of the lap times posted with just the PDR are in question unless you have a transponder to verify it with.
Yeah, it's disappointing. Particularly if you are looking at lap times while on track to get a feel for what works and what doesn't. If you're really consistent I imagine you would notice a sudden 2s improvement but with traffic and the lack of consistency most of us have it would be tough.
If you have the ability to load the fast lap up in Cosworth and compare it with another lap the anomaly is easy to spot. I'd encourage anyone posting a fast lap to do this first as a check. However, if you're just watching it on youtube it can be really hard to spot.
Below is a screen shot from the Cosworth toolbox. If you look at the time delta line on the chart you can see that it goes near vertical at about the 30 second mark. If you see that, double check the video to see if you checked up or something. If you didn't do anything major at that point just watch the time and you'll see it skip back.
When I had my ST2 Z06, I used a Race Pak G2X. I would compare lap times from the NASA Transponder, they were always pretty consistent but rarely matched exactly. The differences however were usually in the hundredths and if I remember correctly not over 2 tenths off at the most.
Sounds like we may have another ask Tadge question in the making.
You may have noted I did not post my PDR recorded lap time of 1:16.35 recorded at SP because it seemed too much an anomoly after a lot of 1:18s. My Ruf Porsche has turned a 1:16.6 at SP with 100+ hp and 400 less pounds than the Z07 so it made me also question the Z07 lap time. While the Ruf has aero it has no electronics except ABS. At first I thought the Z07s aero and electronics made it as fast as the Ruf at SP, although there was a bigger disparity at VIR, with the Z07 running 2:04s and the Ruf in the 1:59s.
I am off to Sebring with the Z07 after the Rolex 24 with a new DeWitt radiator so I will see how the lap times hold up. I do have a portable AMB transponder so if that system is up and running I can get an AMB to PDR lap time comparison.
I am still waiting for DeWitt or LG to build an oil cooler for the Z07 with an A8.
They weren't giving this information when I took my class. That's very cool.
Did you take L2? They only use the transponders for the afternoon of day 2 in the L2 class. Even then they don't give you times until the end of the day.
I just wrapped up the L2 course at Spring Mountain and was using the PDR the entire time to keep track of my lap times and see how I was progressing. For the second half of day 2 the SM folks also put a transponder on your car and give you your lap times at the end of the day.
I was feeling pretty good about getting a 1:59.2 according to the PDR but when I got my printout from the transponder it showed that lap as a 2:01.2. All the other laps I compared were pretty close between the transponder and PDR so what gives?
I pulled up the Cosworth toolbox and compared my "fast lap" with another lap that was close in time and could see where the time delta between the laps suddenly jumped 2s at about 28s in to the lap. If you look at the video side by side you can literally see the lap time on the video jump backwards 2s and then continue counting.
Perhaps there was something specific to this car at SM but seeing this anomaly has really shaken my confidence in the PDR system. I'm going to go back and look at my other fast laps to see if this anomaly occurred there because without the transponder data I don't think I would have noticed. Has anyone else seen this?
On the plus side, it looks like the 1:59.9 lap I ran earlier in the day was legit so at least I broke the 2 min barrier on the extended N/S course.
Which track were you on? North/south, west or east?
01-17-2016, 02:25 PM
PDR Lap Time Anomaly
