Low Cost Video Telemetry Solution
GeorgeCo was at the track again mid-November for the NCC BMW CCA Fall HPDE at Summit Point Motorsports Park. GeorgeCo drove the MINI on Friday/Sunday and the Porsche Saturday in between. This was GeorgeCo’s first drive of the Porsche at the track. The car is larger and heaver than the MINI, but really accelerates well out of the corners, even on the not-so-grippy full-tread summer tires that came on the car. We still have some issues to sort out, but the car is progressing nicely. More on that later. First the MINI.
We’ve been working on a (relatively) low-cost video telemetry system and have finally worked most of the bugs out of our set-up. The video above uses an iPhone 4, Optrix-HD iPhone Mount, Harry’s LapTimer software, External GPS sensor, and a PLX-Devices data-interface. The iPhone is used for video capture and accelerometer function. It captures OBD-II data from the PLX-Devices Kiwi WiFi and combines it with 1 meter accurate GPS data from the external GPS device via Bluetooth. Ho, ho-ho, ho…. The iPhone does the post-processing and overlays all of the data on the video. In this video, I’m tracking down my friend John who is in the red E30 which is prepared very similarly to the old GeorgeCo E30. I like this video because you can see the driver’s hands, whether he’s looking ahead into the corners, and the telemetry shows revs as well as how much of the lap is spent on full throttle (less so in traffic.) I need to work on getting a brake sensor.
The second video was filmed in the Porsche 996 Carrera using a ReplayXD camera mounted on the sunvisor. This is an example of how you can combine video from external sources. The initial video was exported to an iMac and then uploaded to the iPhone via iTunes. It was then imported to LaptimerPro for overlay with Laptimer data. We didn’t have the OBD-II data connection working on this day, so the only data sources were the accelerometer and external GPS. The key to this process is to find the key video frame at the end of the timed lap so LaptimerPro can match the data-stream correctly. In this video, the Porsche is on Summer Street Tires which have no grip on the cooling track.
This third video shows the value of video as a learning aid. I followed my friend (and newly minted instructor) Dave for a few laps. He eventually went off in turn 1 when his tires gave out, got a nice mud bath, then almost went into a tank-slapper when he came back on. Fortunately he got his act together and we had some distance between us. The final shows what it must have felt like from his point of view…
Porsche Custom Tune Baseline
Finally finished base-lining the Porsche today. We lost a month of preparation due to the accident repairs, but finally finished all of the tasks necessary to establish a baseline and get the car out onto the track next week. We even managed to fix the broken vanity mirror on the passenger side visor. The last step in the process was completed this week when we took the car down to Behe Performance to get it on the Dyno. Since we are starting to run out of time before the next trackday, we had them finish the remaining maintenance tasks and put the car on the Dyno to see what we have to work with. They inspected the suspension (nice to get a second opinion after any repairs), flushed the brakes, changed the transmission oil, and aligned the car as well.
The initial results were a bit disappointing. The initial runs on the Dyno showed only 221 hp at the wheels and 207 ft lbs of torque; peak torque band was pretty narrow. After Behe worked his magic, however, horsepower is up to 236.9 and torque up to 217 ft lbs. More importantly, the peak torque band is wider, with more than 205 ft lbs from 4400 to 5600 RPMs as opposed to only 4700-5300 before the tune. The 2000 Carrera had 300 bhp when it left the factory. If you figure a 15% drivetrain loss, that amounted to about 255 hp at the wheels. Considering that this is a twelve year-old car with 68,000 miles that means it’s down about 8% from new. That’s probably not too bad, especially considering the nature of dyno testing where weather conditions and fuel quality can impact results.
PICgauge Optical Belt Rib Gauge Tool
I found this tool the other day on iTunes of all places and I thought it was very cool. It’s called PICgauge. It’s an app for iOS devices (5.1 or higher) that lets you gauge belt wear on your engine’s serpentine belt without removing it from the car. As the belt wears the gaps get deeper and wider so the ribs get smaller relative to each other. Eventually the belt starts to ride only on the ribs and may start to slip.
The measurement process is very simple: Grab a silver or white Sharpie and draw a line across the ribs of your belt and take a picture of it with your iPhone without using the flash.
Open the picture in the PICgauge app. Tell the app how many ribs your belt has and use two fingers to resize the photo to fit between the lines.
Mash the “measure” button and you’re done. The app finds the boundaries of each rib, measures them relative to each other and tells you if you’re OK, marginal, or kaput. Pretty cool.
Repairs Complete
While we wait out the Frankenstorm, here’s a picture of the Porsche fresh from the shop. (Click the photo above for the complete set.) All repairs have been completed; no suspension or sub-frame damage found. The car looks terrific and we can’t wait for the roads to clear up and take it out for a drive. We’ve been gathering parts this past month: new headlights, clear side-markers, and a new intake were installed yesterday. New serpentine belt, coil-packs, plugs, and rotors will have to wait until next weekend.
Porsche Progress Report 4
One small piece of trim prevented the completion of repairs to the Porsche last week. New ETA is next Tuesday. (Can’t attache the trim, can’t put in the window. Can’t put in the window, can’t attach the door panel…) Since the garage was empty, we repainted and put down a new floor.
So today we went back to the skidpad with some of the instructors from the local BMW club. This would have been more fun with the Porsche, but the MINI is plenty chuck-able. In this video, I’m working on the Scandinavian Flick. In one case, I manage to get the back out more than 90 degrees and still recover. Also listen for the sound of terminal understeer towards the end. I wanted to see how well the camera would pick up that sound.
