[SgtRick]

Went yesterday to the track to run the quarter mile for the first time. Turned on the PDR and it recorded the run at 11.90. The car ran 11.391 @ 123.4 mph. Are the PDR's only an estimate, or does it need calbration? Thanks.

[Tricksta]

Originally Posted by SgtRick

Went yesterday to the track to run the quarter mile for the first time. Turned on the PDR and it recorded the run at 11.90. The car ran 11.391 @ 123.4 mph. Are the PDR's only an estimate, or does it need calbration? Thanks.

The PDR would start the timer as soon as you touch the gas pedal and are off the brake I believe , so any wheel slip would play into your ET on PDR , where as the track time wouldn't start until you crossed the lasers, so wheel slip wouldn't effect your ET on the track.

[Tricksta]

Also, what was your RT if you don't mind? I'd assume if you add your RT to the ET you would get close to the 11.90 the PDR had.

[SgtRick]

Originally Posted by Tricksta

Also, what was your RT if you don't mind? I'd assume if you add your RT to the ET you would get close to the 11.90 the PDR had.

.039 red

[SgtRick]

Originally Posted by Tricksta

The PDR would start the timer as soon as you touch the gas pedal and are off the brake I believe , so any wheel slip would play into your ET on PDR , where as the track time wouldn't start until you crossed the lasers, so wheel slip wouldn't effect your ET on the track.

That makes sense. I had/still have a gyro type device that does the same data as the PDR, no overlay, just records the data. It starts as soon as the gyro senses the movement instead of when the wheel breaks the beams. Thanks for the help.

[Tricksta]

Originally Posted by SgtRick

That makes sense. I had/still have a gyro type device that does the same data as the PDR, no overlay, just records the data. It starts as soon as the gyro senses the movement instead of when the wheel breaks the beams. Thanks for the help.

no problem.

[Badmojo]

It usually reads a couple tenths slow, since the PDR starts as soon as the car moves and the track timers don't start until the front tire leaves the timing beams. Was the 0.5 sec difference repeatable?

[SgtRick]

Originally Posted by Badmojo

It usually reads a couple tenths slow, since the PDR starts as soon as the car moves and the track timers don't start until the front tire leaves the timing beams. Was the 0.5 sec difference repeatable?

All the times were off. I just watched another video where he ran 11.48 and the PDR said 12.10.

[Badmojo]

Are your tires the factory height?

[Vigilante375]

Originally Posted by Tricksta

Also, what was your RT if you don't mind? I'd assume if you add your RT to the ET you would get close to the 11.90 the PDR had.

RT doesn't mean anything for us regular joes that attend the drag strip. Time doesn't start until the front tire leaves the beam.

If the strip has it setup how pro drag racers race then yes it would matter.

[Tricksta]

Originally Posted by Vigilante375

RT doesn't mean anything for us regular joes that attend the drag strip. Time doesn't start until the front tire leaves the beam.

If the strip has it setup how pro drag racers race then yes it would matter.

it would matter in this case, because the RT is the time from when it hits green to when the first lasers are triggered, and if the PDR is starting its 1/4 mile time as the wheels start to spin, then technically you could add the RT of the track to the tracks ET time and get close to what the PDR gives as an ET.

[Indyblue98]

OP's time difference seems too much to me,
But don't think the reaction time would be the answer.
That launch was not a half second delay.

Used the PDR a few times at the Track
1st was in a 2016 Z06
Later with 2018 ZL1 both cars were reading within 0.1 on time vs Track Timers.

Z06 ran a 11.34 at 124 reaction time 0.023

ZL1 was 11.8 at 122 reaction time 0.13

Both Cars Stock except Green Air Filters and 91 Octane fuel here

[Vigilante375]

Originally Posted by Tricksta

it would matter in this case, because the RT is the time from when it hits green to when the first lasers are triggered, and if the PDR is starting its 1/4 mile time as the wheels start to spin, then technically you could add the RT of the track to the tracks ET time and get close to what the PDR gives as an ET.

And yet his RT was a -.039 (red light). Doesn't add up to the ~.6 difference of his 2 ET's. 9/10 times us regular joes at the drag strip will never see the pro timing light where if you're reaction time does matter. Unless it's one of those bracket events or whatever.

I used to think the same thing about reaction times but I was shown different and learned. He could have sat there for 10 seconds before he got on the gas and he still would have ran a 11.3.

I haven't taken my car to the drag strip so I have no insight on the PDR vs track timing.

[Tricksta]

Originally Posted by Vigilante375

And yet his RT was a -.039 (red light). Doesn't add up to the ~.6 difference of his 2 ET's. 9/10 times us regular joes at the drag strip will never see the pro timing light where if you're reaction time does matter. Unless it's one of those bracket events or whatever.

I used to think the same thing about reaction times but I was shown different and learned. He could have sat there for 10 seconds before he got on the gas and he still would have ran a 11.3.

I haven't taken my car to the drag strip so I have no insight on the PDR vs track timing.

This conversation was strictly about why PDR would be different than a track timer. The RT would not be the sole contributing factor, but does play into the time difference.