PRE-Z06

I can't shift as fast as an a8, but in my experience between switching from being optimally geared for the 1/8 at the top of third like the c7z is or running steeper trans gears resulting in a shift to 4th right before the traps resulted in a lower mph though not a slower ET...looking forward to your tire comparison test results.

DRLC5

Was this at PBIR? I thought one of the sides reads slow? Is this correct?

Snorman

It's a combination. The right lane reads slightly low but the left lane is probably ~3+ mph fast with a 125-130 mph car. And that means fast relative to other tracks too. We have lots of vbox data, and when the track trap speeds are equal and higher than vbox data, the track is wrong. Track averages over last 66', vbox measures at 1320', so vmax.
Do you ever wonder why certain people almost always post left lane slips only?
S.

JoesC5

Is the problem related to the timing lights on the two different lanes or the track condition of the two different lanes?

4VFTW

i've made countless passes in both lanes at PBIR and never seen any discrepancies in my MPH from lane to lane ....ymmv

Snorman

Then your car is an anomaly. Post time slips from same day both lanes with car numbers and date.
I can post up data of vbox vs. PBIR left lane and track trap speed is well over 2 mph faster than vbox. Right lane passes are 2-3 mph slower than vbox same day. OSW track speeds are 2-3 mph slower than vbox in 130+ mph cars.
S.

Sharkgray

Yes I just have to get them uploaded. Been hungover today. The will be up tomorrow

Well I agree with this. Everyone was complaining the traps speeds were low. A Porsche turbo S that usually runs 138-139 mph had. Best of 132 that night. 104 in the 1/8

They say the right lane reads slow. Unfortunately all 3 of mine were in the right lane

Good point. I will test this next time out.

It's crazy that a friend and I were talking before the runs and said yeah let's run the left lane. It just ended up me being in the right all 3 passes. There was some ricer event going on so people were pouring in. I did my 3 passes all within 30 mins and left. I will go back in the next couple weeks.

Snorman

I could look back at all of my timeslips from my GT-R at PBIR over a few years. Or could look at some of a friend's data. This is my old GT-R that I sold to him. Granted, it's a 140+ mph car, but there is no way track trap speeds should be higher than vbox speeds. The track averages over the last 66' of the quarter mile. vbox reads vmax at 1320', which is always higher as the car accelerates.
S.

Dabigsnake

Is it possible he's lifting right after the first finish light and not running it through the full trap. That will not hurt et, but slow MPH. I agree trap speeds should be higher w those e t s

Sharkgray

Run1, Run2 and Run 3........ clearly shows the MPH times were off

Run 1 10.77 @ 125
http://vid1167.photobucket.com/album...psxaripr1a.mp4

Run 2 10.78 @ 124
http://vid1167.photobucket.com/album...psv32oueej.mp4

Run 3 10.29 @ 123
http://vid1167.photobucket.com/album...ps1ufr4ase.mp4

I tried to embed them but have no clue........

FrcFed8

Do you keep short shifting second gear or is it in full auto doing that each run?

Sharkgray

No its in auto each time. But you can see my speed was faster before I even went through the traps. Look at the cones

ZoratZ06

Interesting...I don't know if there is any 'lag' in displaying the PDR data...but in run 3 at the exact time the PDR shows 11.00s 1/4, the speedo is showing 128mph. Don't get me wrong, sometimes the speedo's are off...but 5 mph seems a lot. So maybe you're right, maybe the MPH's were off. Btw, seemed like a 'decent' launch.

Snorman

You can probably frame through the video and see where the cones and breaks in the Jersey wall are for the trap speed timers...those are at the end and spaced 66' apart. Ultimately, there is no easy way to determine what the trap speed 'should' have been. But by using something like a vbox can give you real data to compare between tracks, lanes, etc..
S.

Sharkgray

Thanks
Pulled a 1.64, 1.63, and a 1.61 on stock rubber.
Cars feels great, Just received my Corsa X from NorCal. Gonna put that on and done. Wait for the colder weather. Not trying to get caught up in the mph. It clearly shows was above 125 like 10 feet before the cones.

Dabigsnake

Sure seems like your PDR is showing 130 mph at the second trap cone, on your first run. ?? My analytical mind asks if mph is off, how do we validate the E T ? That system may need calibrating or some thing. GREAT runs regardless. Sure wish we had a track w good prep around here.

FLC6

Here is the final word!!

PBIR's right lane shows 3MPH LOW on the right lane. PERIOD!

The left lane shows 1mph high.

Vbox's always show higher trap speeds on the street than at the track.

4VFTW

okay , if you insist...

now about your Vbox...

Snorman

How about my timeslips? Like you, I have more showing the same data from when I've ran there for the Streetcar Drags over the last several years.

Very, very similar incrementals, and 1320' ET within .002 and there is nearly a 3 mph difference in trap speed from the right lane to the left.
S.

Enzom

Isn't the trap the average of the speeds taken at the two measuring devices roughly 60 feet apart at the backend? You will always hit the second device at a speed greater than your trap shown on your slip