jittsl

Had a great time. This was my first time at TWS and first time with Lone Star Region. As I plan to run the Clubrace in March I thought it would good learning to do the DE.

Pleasantly surprised that TWS was a great track. My only other experience with a converted NASCAR track is NHIS. NHIS basically sucks and had nothing in common with TWS. The Texas track has a great combination of very fast, **** puckering corners and thinking persons combinations and the Boxster seemed right at home. I really enjoyed it and would recommend giving it a go to anyone.

I also really enjoyed the way Lone Star ran the event. There was a comfortable casualness about the organization yet it seemed as though everything ran effortlessly and effectively. Met lots of great people not the least of which was Mike "mglobe" who generously spent time orienting and instructing me.

Can't wait for the Clubrace and I can't wait for the next DE with LSR at TWS.

Veloce Raptor

Lone Star, not Longhornn.

Sorry we didn't meet, Laurence. Mike told me you were there, and every time I walked over to your car to say hello, you were not there.

See you there in March.

jittsl

Sincere apologies. Long drive home to San Antonio - not really, but brain is faded.

I MEANT LONG HORN REGION

Looking forward to meeting you as well and in March I will make sure we do.

onefastviking

I thought we were the "Big Huevos" region, but I guess we could also be nicknamed "long horn" region as well.

Sorry I missed you as well, but I too will be there in March. Just ask Globe to point us out next time, it's always nice to put a face with a name and always great to meet another Rennlister in person.

The TWS events are wonderfully ran events, always over 220 participants yet always seem to run effortlessly, and the track, TWS is a hidden gem.

See you at the track !

mglobe

It was a pleasure to meet you Laurie, & I had a blast riding with you in your SpecBox. I'm glad you enjoyed "our" track and our DE organization so much. It's a track that I wish more people would get the chance to appreciate. Look forward to seeing you at the club race in March, and hopefully many more times at TWS for our DE's. Welcome to Texas!

ervtx

As usual, the weather was an integral part of the experience. Cats and dogs and hail (oh my!) and cars floating down the streets on Friday night. A dry and fast track by Saturday afternoon. Bone chilling wind on Sunday morning. A second dose of rain for the drive home. Typical.

It was good to run CCW again; I think it had been over a year since the last time I got to run in that direction. I'm increasingly disappointed with Harry's Lap Timer Pro. The speedometer data is constantly lagging real time, and then spurts ahead to catch up to the new coordinates. Harry says that I enter T1 at 138, whereas my speedometer consistently reads 150 just prior to lifting. So the velocity reading is useless; makes me wonder about the lap timer.

Car gets an A+
Driver gets a B
Harry gets a C

jittsl

My 04 996 GT3 has a +5% error when timed against mile markers which means I would have an actual 142 against a shown 150 so I wouldn't throw it out based on it reading 138. Try this test - take your GT3 out on the freeway and run 10miles (or more if you have the time - the more miles the better the measurement) against freeway mile markers. Travel at a precise 60mph (set your cruise control). Measure the amount of time that transpires. Exactly 10 minutes to travel 10 miles at 60mph (1 mile / minute) means you are spot on. Obviously the amount over or under will allow you to calculate the percentage error. Now repeat the process on a different piece of freeway to see if you get the same result. Sometime the mile markers are just in the wrong place.

The actual lap time looks about right and I cannot imagine how it could get time wrong unless it is starting and finishing in a different place- it does however look about right.

The G-force metering I would ignore in terms of accuracy other than for comparison purposes. Cell phones simply do not have highly precise accelerometers.

PS NICE LAP! Now all I have to do is get my 170hp SpecBoxster to run that pace and I should be competitive.

Veloce Raptor

Russell, most OEM speedometers indicate optimistically, with varying amounts of error. That said, there is a hardware add on for Harry's that ups the pathetic 1 Hz refresh rate, and gets rid of a lot of that lag.

DCP

I was annoyed by the lag too. I bought an GPS attachment and used it for the first time this weekend. I have not had a chance to study the videos yet, but it does appear to work far better. This is the one I bought: https://www.emprum.com/index.php

Waco Racer

I got to come hang out a little on Saturday and I had a great time! It was nice meeting some new people, sitting in on a classroom session, visiting with some friends, and seeing how a well run DE event is done.

onefastviking

Glad you finally came out !
Now we need to get you in a P-car. I think what we discussed with NASA to get some crossover between NASA and PCA racing would be great. The more cars racing the better, and the more local, or more opportunities, to race closer to home is always a great thing. No need to spend all that money on traveling to far away races when we have such great tracks so close to us.

ervtx

I have previously calibrated the OEM speedometer using the method Laurie described. When the speedometer says 60, the calculation says 63. I have also calibrated the OEM speedometer against the GPS receiver in the iPhone... when the speedometer says 70, the iPhone says 74. That would suggest that that my speedometer reports pessimistically.

Note also the lap time durations as indicated by the quicktime file information compared to the HLTP lap times in the screen shots below - each one taken at the last frame of the video file; i.e. at the start/finish line; a point well before my top speed at T1 entry, btw). The HLTP lap times are consistently 1 second higher than the quicktime duration. Does that mean that HLTP is even more pessimistic than my OEM speedometer? That would be hard to believe, since that would imply that my actual top speed is more like 155 (doubtful), and my actual lap times are closer to 1:58 (wishful thinking).

I'm more inclined to think that the GPS receiver in the iPhone is working just fine (as proven by the 70/74 calibration), and that it is the HLTP software that introduces the discrepancies, especially when trying to keep up with acceleration and deceleration. And even with the added hardware, the lag effect in HLTP's speedometer never goes away, so I'm not encouraged about relying on it for specific sector times if not for the whole lap.

onefastviking

No experience with Harry's so I can't say on it, although on other GPS lap timing devices some can be as much as 3 meters off.
Depending on how things fall it could even be 2 sections of 3 meters off, so 6 meters, or approx 20 feet off, that is enough to give you some weird speed and lap time differences. Throw in a week, or slow, refresh rate and I think there is your differences.

And as VR stated, OEM speedos are always optimistic.

Also don't forget if you have changed tires from OEM. Not all tire brands have the same dimensions too.

jittsl

There is no doubt that there are far more accurate ways to measure lap times than hanging your telephone off the windscreen. Gives you a pretty good indication though. I'm sure the experts here can make recommendations as to the best systems they will however cost a lot more than $40.

I was really surprised at the video quality (given the investment). Will that work on my 3G or have I finally found a really good excuse to trade up to the 4?

ervtx

Yep, I have a Performance Box that has gathered dust since I discovered Harry's, and I'm concluding that Harry's is not nearly as reliable or accurate for data acquisition.

Just to clarify, my issue is the data lag. Just watch the T2 to T3 sequence. HLTP's speedometer indicates that I am decelerating from the T2 apex to T2 track-out, and accelerating in the T3 braking zone. Tire sizes, OEM speedometers, and GPS issues aside, that is just plain WRONG!

Edit:

The problem is not just the HLTP overlay speedometer. The actual data log indicates a lag as well. See the snapshot below which shows increasing speed in one of the hardest braking zones in the CCW configuration.