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M2 Technical Topics > Track / Autocross / Dragstrip > BMW M2 sets Laguna Seca lap time of 1:40.88 at hands of BMW DTM driver Martin Tomczyk

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      03-22-2016, 11:39 AM   #67
Laertes
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For what it's worth, I have a full data acquisition system in my track car (Racekeeper) w/ 10hz GPS. Before I had this, I used the Harry's Lap Timer app on my iPhone, using the built in GPS. Just for the heck of it, I tried them both at the same time last year, and it was pretty amazing how accurate the iPhone based lap timer was. It was within 0.1 sec (and sometimes less) on ALL laps. I have to assume from this that the app, though only sampling position at 1 hz, extrapolates from that what point in time you crossed the start/finish line. It doesn't just wait until the first position fix after you cross the line and call it good, it figures out how far past the start finish you are at that fix and then uses your velocity to figure out what the time was when you went past the line. Clever.

I'm less skeptical about the lap time based on the timing device than I am about the fact that there was a passenger. At a short track like Laguna Seca the effect is less than at someplace like VIR, but I'd still bet it's a second/lap difference or so. Laguna Seca is a HP/Braking track, and both are very affected by weight in the car.


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Originally Posted by Robin_NL View Post
Then 1:38.88 sounds fine with me.



About the laptimer: Why should BMW and Porsche use that stuff then if it's far off? Please explain...


Cheers
Robin
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      03-22-2016, 11:52 AM   #68
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That was always expected.
m2 will be likely match to the Cayman S or GTS
981 CS = 981 Cayman S.



The GTS is going to give it a good battle - the S might be a little down on power - it will be interesting to see.
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      03-22-2016, 12:37 PM   #69
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Originally Posted by oj34 View Post
...

I wouldn’t expect Randy Probst going faster than Marting Tomczyk (of course same conditions and correct timing assumed).
Tomczyk is an great driver, to be sure, but Randy Pobst (there's no "r" in his last name) has a huge number of production, street-car laps under his belt at Laguna Seca. Race car drivers rarely get the kind of practice that Randy has had at a single track. MT has published some statistics on Randy's speed and consistency at that track, and it's just off the charts. He also holds more records than anyone at Laguna Seca. Much of this can be attributed to the fact that he gets so much seat time there. If anyone can beat Tomczyk's time, it's Pobst.

So, I'll take that wager. I think Pobst will put up a time that beats Tomczyk's. It may only be by a tenth, but I think he'll beat it.
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      03-22-2016, 01:21 PM   #70
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Quote:
Originally Posted by Laertes
For what it's worth, I have a full data acquisition system in my track car (Racekeeper) w/ 10hz GPS. Before I had this, I used the Harry's Lap Timer app on my iPhone, using the built in GPS. Just for the heck of it, I tried them both at the same time last year, and it was pretty amazing how accurate the iPhone based lap timer was. It was within 0.1 sec (and sometimes less) on ALL laps. I have to assume from this that the app, though only sampling position at 1 hz, extrapolates from that what point in time you crossed the start/finish line. It doesn't just wait until the first position fix after you cross the line and call it good, it figures out how far past the start finish you are at that fix and then uses your velocity to figure out what the time was when you went past the line. Clever.

I'm less skeptical about the lap time based on the timing device than I am about the fact that there was a passenger. At a short track like Laguna Seca the effect is less than at someplace like VIR, but I'd still bet it's a second/lap difference or so. Laguna Seca is a HP/Braking track, and both are very affected by weight in the car.


Quote:
Originally Posted by Robin_NL View Post
Then 1:38.88 sounds fine with me.



About the laptimer: Why should BMW and Porsche use that stuff then if it's far off? Please explain...


Cheers
Robin
Agreed, I've done track days using the tracks own lap timer modules together with using the M Laptimer app and the results are way less than a tenth out. For example my fastest lap on my local circuit was a 1:30.999 according to the circuits timer and 1:30.97 according to MLaptimer. In fact my AIM data logger using a higher GPS sampling rate was less accurate against the two above. I wouldn't doubt M lap figures.
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      03-22-2016, 03:06 PM   #71
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Originally Posted by bradleyland View Post
Tomczyk is an great driver, to be sure, but Randy Pobst (there's no "r" in his last name)
Sorry for the "r". Probst is a common name in Germany and so I typed it almost automatically.

Quote:
Originally Posted by bradleyland View Post
So, I'll take that wager. I think Pobst will put up a time that beats Tomczyk's. It may only be by a tenth, but I think he'll beat it.
Wager taken I'm drinking beer
However, comparing times will be difficult (passanger yes/no, conditions, timing equipment, ...)
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      03-22-2016, 05:55 PM   #72
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Quote:
Originally Posted by oj34
Quote:
Originally Posted by bradleyland View Post
Tomczyk is an great driver, to be sure, but Randy Pobst (there's no "r" in his last name)
Sorry for the "r". Probst is a common name in Germany and so I typed it almost automatically.

Quote:
Originally Posted by bradleyland View Post
So, I'll take that wager. I think Pobst will put up a time that beats Tomczyk's. It may only be by a tenth, but I think he'll beat it.
Wager taken I'm drinking beer
However, comparing times will be difficult (passanger yes/no, conditions, timing equipment, ...)
I thought it was Probst for the longest time

Good point on the passenger. I keep forgetting that. I'll give you a two beer handicap haha
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      03-23-2016, 03:24 AM   #73
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Originally Posted by bradleyland View Post
I'll give you a two beer handicap haha
I'm fine with that
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