Spokane is coming so soon. It really crept up on us. We have our 8 driver line up ready to go, now we just need a working car.
Our regular readers will remember our last post on chris’s efforts to integrate the race capture pro system with our car. Yet another antenna for our already busy roof. This time, for GPS.
The real time cell module and race capture pro unit are mounted to the top of the tranny tunnel.
New water temp sensor. This time with a real harness!
Works pretty good. For sensor hook ups we currently have: battery voltage, accelerometer, GPS, tach, water temp, and oil temp. There’s a lot more we can do but we lack the time to develop and test before the next race. There are some bugs (can’t reset my password, can’t get firmware to flash, tach signal is 2x too fast) but its still a very “young” device. It’s to be expected. I imagine it will all get fixed soon, maybe even before Spokane.
The next major project up was the rear diff. Not much to note other than we put new seals and bearings in it and slapped it back in. No major drama.
That meant new gear oil and tranny oil. Brake fluid, water, and engine oil were all flushed too. We also did a full brake service with new rotors and pads in the front and new pads in the rear.
While burping the water Jamie noticed that the radiator cap on the radiator was leaking! It was weeping a drop or two every second. You could even hear it suck air with the system closed. I think we found the source of our water mystery! A new water cap was installed and voila no more air in the system after it cools.
The challenge has been how to mount and enclose them. These are normally sold as retrofitting kit to take place inside your stock headlights. I decided to use some cheap EMI off-road lights.
The fronts are glass which requires us to tape them up. This time I used 3m clear bra instead of packing tape. Much better.
The first test drive didn’t go so well. This shot is with the lights pointing as high as possible.
The pattern and light output is great just not so much on the adjustment. The center lights also bounced around like crazy. I solved the bouncing with an all thread support. I think I fixed the adjustment with a BFH taken to the mounting brackets. I’ll test them again soon.
Spokane is likely to be in the high 90s. The Cool shirt is going to be critical for us. We took some steps to improve it to hopefully ensure its successful operation. Its been moved forward slightly and bolted down through the bottom of the car. This will allow us to change the ice without removing any straps.
The blue valve on the side will drain any excess water out of it. During the pit stops before, we would have to bail this water out with a cup. Its still leaking a bit. Hopefully I was able to reseal it properly this time.
Micah rigged us up a new cover for the radiator inlet. No more 10lb of tape!
Micah also got some non-slip surface applied to the new pedal riser.
The window net rules haven’t changed this year, but their enforcement has. John has clarified the requirements to cover any gaps a hand can fit out. Were going to short cut the engineering to get a fancy larger net in and just put a small window in instead.
We just got our Race Capture and so I came down to Eugene to help Leo plug stuff in. Two pretty important sensors in our car are the oil and water temperature. I wanted to be able to replace the old sensor AND gauge without adding another hole to the coolant system so I decided that I needed to not just hook up the sensor but also make a compatible gauge so the driver can read it. I’m going to divide this write up in several sections: characterization of our sensor, the instrument amplifier, and the gauge it self.
I started with the same GM sensor that Autosport Labs sells, the TX3 (aka SU109, SU102. Full disclosure, I’m using the SU102 because that was the one I could get fastest. I hope they’re all actually the same.).
Assuming the sensor was an NTC thermistor (an extremely safe bet), I went ahead and characterized the part in a very precise (but annoyingly not too accurate) oven.
The Temperature sensor was immersed in mineral oil along with a calibrated thermometer and placed in a precise oven.
After leaving the sensor for a few hours between data points I measured the resistance of the sensor as well as the thermometer reading.
With a working model for the temperature sensor I could now model the full circuit, which would allow me to choose resistor values analytically.
Leo and I decided to specify the working range of our instrument be 150-250F (I lost the C vs F battle). Since the best way to read a thermistor with a voltage sensor (such as race capture) is with a wheatston bridge I needed to choose three resistors. One to sit below the temperature sensor on the bridge and a pair to use for the reference voltage. The series resistor needs to be chosen in such a way as to maximize the linearity of output voltage vs temperature. In order to do this I derived the output voltage vs temperature function with the series resistor value as a parameter. After some basic math I ended up with a choice for the series resistor of 240 ohms and the following map from output voltage to temperature (in C),
which when plotted looks something like this:
The relationship between voltage divider output and the sensor temperature in C. Inside of [1,3] this function is very linear!
Remarkably, this is pretty close to what we wanted already, an affine map from voltage to temperature. How accurate is a linear approximation of the above? To find out I fit a linear function to the equation above and plotted the error (difference).
In the operating range (shaded) the measurement linear model error is less than 1C.
The last thing I needed to do was to “stretch” this so that 150F (65.5C) reads 0v and 250F (121C) reads 5v. To accomplish that I used an instrument amplifier(IA) circuit (these come as premade ICs that only need one external resistor for $5-$15 but I didn’t have any around so I used opamps) to take the difference from the reference side of the wheatstone bridge to the measurement side. Resistors for the reference side of the circuit were chosen s.t. the voltage difference equals zero when the sensor is reading 150F and the gain was chosen s.t. the IA output was 5v when the sensor is 250F (I used an equivalent resistance instead of firing up the oven again).
Now that I had a 0-5v output I was able to use a standard 5v gauge I picked up from sparkfun. All I needed to do was replace the backplate with numbers that read 150-250 instead of 0-5v and was done.
The original faceplate was scanned and then traced over to create this rescaled faceplate.
Last step was to breadboard everything, test it and then solder it and put it in a box.
The prototyped sensor and gauge ready to be soldered and packaged
Here is the gauge in its final resting place. Firmly attached and easy for the driver to see. Looks way classier than the sock-wrapped-oil temp gauge.
Just a quick work update from a couple of weeks ago. We had a bit of oil burning/very light smoke in the car from the thunderhill race. Enough to bother the driver. It looks like our home made OMP block off plate was leaking. I pulled it out, cleaned it up, and reinstalled.
The big job for the day was pulling out the rear diff. The input shaft oil seal is leaking pretty bad. We race on it like this for hours.
You can see the culprit here.
We decided the pull the whole thine apart to inspect for damage. Here are the surfaces for the output shaft seals.
No chunks, should be good for a ghetto rebuild. We also made number panels! We used the required chumpcar stickers and mounted them to removable sheet metal. That way they could be taken off for non-chump events, and we can be sure they got good solid adhesion to the car. Our doors aren’t exactly flat.
This post may be a record in blog procrastination for me. Here is a write up for our last event all the way back in February .
This event was run by Star Projects (http://www.starprojectsevents.com/) as a “Rat Race”. It’s very similar to ChumpCar and Lemons, same concept. This is our second rat race. The attendance tends to be pretty minimal but the events are cheap and the schedule worked out perfect for us. It’s also nice to get back to thunderhill for another event!
The race format is unusual for us. An open practice day on saturday and an 8 hour race on sunday. They also announced some kind of qualifying event for saturday! Our first ever!
As our car looked for this event. A bit of a mess, but isn’t it always?
We started saturday off with a track tour. People like talking about racing, even if it digs into their actual track time. This seemed to go on forever. The bright side was that we got an opportunity to take some good pictures.
The back hill from the observation tower.
Looking back from turn 5 back down the front hill:
Same hill looking forward.
We sent micah out first for practice. He hadn’t raced here before.
After some time, he came in reporting a clunk. We looked over everything and concluded that it must have been the rear tow hook flopping around. A couple quick twists and we were back out.
Learning the track. Everyone got lots of time in the car. No major issues to report. We borrowed a stig from another team and learned we have many many more seconds to find in the car . Thanks for the humility Ryan.
Qualifying would be a 20 minute sprint race. Having set the best lap time during practice, Matt was selected as our quali driver.
They packed us up and threw a green. It was an all out push for the 20 minutes. Matt took and early lead and kept it for the whole session. Got us qualified first!
Saturday was another beautiful day. I went out first to take the green flag.
I held our lead into the first turn but lost it after this harassing integra pushed his way through. My tires and brakes warmed up and I felt comfortable pushing it to the limit. It seemed too much to drive fast enough to keep me behind him and I regained the lead after a couple of laps. I held it all way way through for almost 2 hours. The entire time, with that integra in my mirror.
We were planning a full 1:55 at least but at 1:50 or so, I got fuel slosh and starvation on the top of the back hill. I had to come in a bit early for our stop which was a real threat to our fuel strategy. If we couldn’t split this race into 3 stops, and had to take a four, we would surely be in trouble. It turns out the integra had almost the same fuel issues for us. Orders were given to the rest of the drivers to shift at 6k (instead of 7) to try to save fuel.
It worked out. We were able to rebalance our pit stops and make it work.
There is a list of things to do following laguna. Nothing major, but lots of little stuff.
I fixed the battery problem!?!.. maybe. I reinforced the mounts a bit to make it more secure. I also got new “purpose built” longacre battery terminals with proper boots! It’s more secure now as are the cables.
Next up is the case of the disappearing coolant. There have been many different stock configurations for the coolant systems on these cars. Multiple cap options, over flow tanks, ect. We have always just attached whatever and it worked. This upper coolant cap (by the thermostat) was replaced with a unit that didn’t have any kind of vent. You can see here where it would have been.
I have replaced it with a unit with a vent. Hopefully this will allow the system to expand and contract properly.
Next up is the big job. The front rear diff mount. These constantly break and I think we have always had one in some kind of state of failure. There has been a funny “slack” in the driveline recently. It’s noticeable from a stop. We checked u joints in the drive shaft (and switched to our spare just in case) and axles. There doesn’t appear to be anything wrong. What we did find, is that this diff mount got worse.
It ended up being a pretty big job. The full rear suspension had to be removed and dropped to get access (the diff mounts to the rear sub-frame). It’s supposed to go like this:
There was so much play at the point where the drive shalt met the diff that you could easily (with poor leverage) push it up an inch. We replaced the unit with a good stock piece and its much more solid now.
Unfortunately in the process we stripped one of the exhaust manifold to cat-back bolts and damaged the threads on one of the lateral links (the one we bent at sonoma) so now we can’t get a nut to thread back on it without just spinning the ball joint. Both parts we have no spares for so they must be sourced.
3 steps forward, 2 steps back. That’s still progress right?
Time for another winter trip down to sunny California. The regular team was busy so we partnered up with Dirty Little Freaks Racing. Rae and Jamie joined me in our car for the new years eve event with Chump Car at Laguna Seca.
Prep for this event was pretty light. We put another brand new factory wheel bearing set on the driver’s front. We swapped out our drive line for the spare (the u joints seemed to be getting a little sloppy). We flushed the brakes, put new pads on the front, and turned the front rotors. Also, another water flush.
Worried about the weather in the pass we made it down a day early and got to hang out for all of tech. No major drama on the trip but this had to be near our sane limit for towing. A good 12-13 hours for the trip. Lots of familiar faces, some new.
We thought we were in with a good shot for the win. Unfortunately due to our success at the ridge, we carried a 5 penalty lap MOV into this race. In an 8 hour race and nearly a 2 minute lap, thats pretty significant. Our plan was to stay out there, keep putting in good laps, and see where we land. Any significant stumble (extra pit stop, mechanical issue, ect) and we would out of the running for sure. With only three drivers, we would need four stints to make it through the day. I would be taking the first and last.
The first hour went great. I was in second place after Southworst (a fox body mustang who was blindingly fast). Due to being state owned land (I think its a park?), laguna seca has a ridiculously low sound limit of 92db. This is monitored and managed by government staff who aren’t part of the track or the event. No fudging the numbers here. Even though our car is one of the quietest (in my opinion), we ended up getting a sound violation. It meant a black flag and a seriously amount of time in the pits. We could get the violation only one more time, before we would be forced to trailer it. Luckily our pit neighbors with the rockstar team hooked us up with some pipe and a welder and we made this beauty.
The sound station is on the passenger side! In addition I started to have some issues with the radio a couple of laps before coming in. We discovered that the battery terminal was cracked about about to fall apart. It had come loose again.
We improvised another terminal out of a spare grounding strap and got to car together for Rae to head out. Unfortunately our 30 minutes in the pits threw us all the way down to 21rst.
She had a good uneventful stint. Jamie was next out and she also got a good solid stint in. They took great care of the car, and I think for the first time, I got back in the car with the brakes feeling as good as I had left them!
We ended up in 12th, which is great considering the issues.
Chumpcar runs three “chumpionship” races a year. One for year of the US regions. Our west coast race was held at historic Sonoma Raceway (once Infineon and before that Sears Point). To qualify for the outright win, you had to podium in a race 6-18 months before. Since our win at The Ridge was <6 months ago, it qualified us for the 2013 event not the 2012 event. We were allowed to compete, but only in the “not qualified” class. Track time is track time though .
Our team for this event was Erik, Chris, Myself, Wade and Dave (one of erik’s team mates). Wade and Dave were both new to the team. Dave had lots of experience with the track and racing and wade had none at all. A good diverse group!
To prepare for this race we had done a lot of work to the car. Following the win from the ridge we have more than a couple issues to sort out. First we sorted out the bumper / front end damage. Turns out it wasn’t too bad at all. All we did was remove the bumper and generally pound/bend it all back into place. Remounted and it was good enough.
Next up was the transmission issues. An after race inspection found:
The blue/green stuff was all the gear oil…
Our theory is that since the gear oil was so old (over year!) that we just cooked all the antifrothing agents out of it and it blew out that vent there. This cooked all the bearings and synchros and we had to have it rebuilt. So we put it all back together and it wouldn’t shift into 5th or reverse. You couldn’t even get it to pass the gate to the right. Turns out the tranny needed some kind of adjustment (the shop did it, I never could get them to explain it in a way that I could figure it out). The odd noise was still there. They determined it to be the throwout bearing. I check out the throwout bearing while we had the tranny out and it seemed ok.
Back under the car, tranny back out.
Where I found this…
Which might have been the problem all along. *sighs* That fixed all the problems though.
I decided it was time to preemptively replace all the wheel bearings as well. Most of these bearings on the car have 20 + years of service and HUNDREDS of race hours on them now. I know what its like to loose a set during a race and its not fun. It’s time to get some new ones it. I went with the mazda factory units. Unfortunately mazda in their infinite wisdom did not make the races (the surfaces that the bearings touch in the hub) removable. If you ask the factory, you have to buy a whole new hub ($400+!!!!). Turns out with some well placed grinds you can get the races out on their own.
With the notches ground to be able to punch out the race.
All cleaned up and ready for reinstall.
Packing the bearings up with this nice redline grease and reinstalling.
Unfortunately while getting the transmission out we broke the starter. The bolt to remove the main power harness just spins. There was no way to get the wire off. There must be some kind of captive internal nut that got loose. So we had to cut the wire. Luckily I have a couple extra wiring harnesses and we just replaced that individual wire. No worries (good idea micah!).
The last project before out trip down to california was to finally sort out the tow rig. I had been towing with a ball mounted on the bumper that was on the truck. It was some kind of aftermarket bumper. Much thicker and it attached to the same points a receiver would. I assumed that it meant it was rated like a receiver. I was wrong. We took it off and its pretty much just a bumper. It’s amazing that the trailer didn’t rip it off. I got a factory bumper for a junkyard, a receiver off rock auto, and some very nice folks at Husky Tow hooked us up with this top of the line anti-sway weight distribution hitch.
It made the trip down to sonoma great! The semi’s don’t push us around at all anymore. The front doesn’t float nearly as bad. It almost feels like the trailer is leaning into the corners with you. We showed up rather late friday. Just before tech was closing. It was a mad rush to get the car tech’d and the trailer unloaded. Not emergencies though.
We had Dave and Wade practice driving and getting in/out of the car. No major issues but I’m glad we practiced. The first couple of attempts weren’t very coordinated. We got to bed early friday to get caught up on sleep for saturday.
This event was run over two days as a single race. There would be breaks for lunch (crazy local corner worker’s union rules, also I think they don’t like ChumpCar very much) and then a break over night between saturday and sunday. No working on your cars during lunch, but you could over night. We started saturday with high hopes. The weather was great, but a little cold and slick in the morning. We decided to send dave out first. He has, by far, the most experience with the track. The thought was that he would be best equipped to deal with the changing conditions.
The team watching from the grand stands.
Dave did great and kept us high in the single digits on the same lap as the lead. Chris was up next. He took us to the lunch break and we held a good position in the rankings only 4 laps behind the lead. After lunch, wade was up. This being his first time on a track, in the car, or racing wheel to wheel ever, he had a lot to take in! He managed 30 minutes before he started to get a little motion sick and we had him come in.
I was next out. We were starting to slip down the order a bit as the leaders gained on us. At the end of my stint we were 9 laps down. Not qualifying for the real win, I wasn’t too concerned. This weekend was more about fun for us than anything else.
Erik was in last. The last time I had been to the track was with erik’s team in early 2010. It was one of the first races erik help staff for chumpcar so he didn’t get to drive. This was his first time on track!
There was a bit of an incident. I’m going to try to take it easy on erik, I know he feels bad. This is the first time hes had one of these.
In the last turn, the hair pin before the front straight, he got on the power too early and the back end kicked out… into a k-wall. Here are some pictures from that night. You can see the marks from where the tires impacted the wall and rubbed along it.
See that gray dust covering the yellow line? That’s oil dry. The impact broke a motor mount and slamed the oil filter into the brake booster and broke the oil filter. This caused all of our oil to be pumped straight out. Luckily erik immediately hit the kill switch and saved the motor. Good work erik! We got her towed in and started work.
First problem, bent rear link.
BFH saves the day.
Problem two, wheel/tire damage. We switched to our spare wheels/tires. The tires ended up being salvageable. One of the wheels as well. The other is in the big scrap heap in the sky now.
Problem three, broken oil filter. Not only did it take out the filter, it also broke the threaded bit off the mount. Had to replace the mount on the block (luckily they bolt on and off!).
Problem four. Broken front lower ball joint. We had a spare.
Problem five. Loose wheel bearings. (Note: Factory service manual isn’t good enough for racing spec, make them a little tighter )
Problem six, loose body work and radiator ducting.
Problem seven, alignment. We did the best we could with string, tape measures, and eyeballs.
And got really close. Better than I expected. We put erik back out with 15 minutes left in the day.
And he got 8 more laps in before having another spectacular failure. They parked him on track until the race was done for the day and towed him in. Originally though to be brake failure turned out to be this:
We did have a spare!
We couldn’t find anything else wrong, so we cleaned up the grease off the brakes and had a couple beers.
The next day, erik was due to go out next (since he barely had any time on saturday). We got him in the car and noticed that the oil pressure gauge wasn’t working. The sensor wire had fallen off, and reinstalling it, broke. A terminal was quickly bent into roughly the right shape and crimped.
Erik started to get a little motion sick. We decided it was best to switch drivers. We had to have dave get suited up quickly and in the car. We managed to get him in and ready to go for the green flag!
Dave also had a bit of an incident. He got pit maneuvered in the carrousel. No major damage (the course workers didn’t spot the other car ) but the positive terminal popped off the battery and he couldn’t get the car started again and had to get towed in. We quickly popped the terminal back on and sent him back out.
Chris was up next and had a great full stint and said the car was running better than ever! Repairs successful! He took us to the lunch break again.
This time, with the help of some anti-nausea meds, wade was able to stay out well over an hour! He picked up over 10 seconds during his stint. A great improvement. I got a good solid hour in after that, before giving the car back to erik. He finished the race up for us without any more contact .
Awards! Some how through all the carnage we managed to finish 29th overall and 10th for the non-qualified class and even got a little prize!
All in all, a good solid race! Lots of problems but we made it through in one piece to race another day.
Let me apologies to the families of anyone who was holding their breath for part 2 of this race report. They would have long since parished.
At last we reported our scrappy little rotary had clawed it’s way into the race lead. Our guest driver, Sam, had just gotten in for our fourth stint and reporting issues shifting. The issue wasn’t going away and there was still a little over 7 hours left in the race (not even half way yet!). Sam did his best to keep it together. We debated over reving the engine vs shifting in and out of fourth. He tried keeping it in third but was getting destroyed on the straights. He eventually was able to get fourth to work (2nd wasn’t super important).
Sam managed to run a full two hours keeping our original minimalist pit strategy. He even kept us a two lap lead. We called him in for his pit stop and this happened:
Sam tired to get around this volvo and cut in on their inside and t-boned them as they turned in (Sorry guys!). Immediately after he knew it was the wrong move to make. He dove into the pits immediately and we got to work on his pit stop.
The damage wasn’t too bad. The brake duct was intact. The fiberglass bumper corner was broken off. The headlights were spared. The bumper doesn’t have a ton of structure in in any more due to all the years of hits and such. It slid over to the left but was still firmly attached. We got a couple zip ties back on the bumper and fender and put erik out.
He reported the same issues that Sam had with the transmission. He left it in 3rd for some time still manged to maintain a 1 lap lead but it was closing. It was very tense in the pits. There was nothing we could do. The situation looked dire. I took a walk to cool off. Went a visited some friends whos race wasn’t going well. Driver over rev’d their motor and completely cooked it. Boost in peace fellow oil burner.
Back in our pits the cooking continues. Our tranny was only getting slightly better. Erik reported that if he rev matched perfectly he could shift. The synchros were clearly not working properly. He got frustrated with the pace and eventually got the 3/4 shift working again. BSD racing, who was in 2nd catching us, took a short stint and pitted out of 2nd. That opened up our lead, now from Squirrels of Furry. Giving us a very healthy 5 lap lead.
Maybe we could do this!
Micah was in next with another solid pit stop by the team. He also managed the tranny fairly well. He maintained our 5 lap lead.
Erik had a steak.
We decided (well, me really) that our best shot at winning would be to put myself in for the last stint. I was the most sympathetic driver of the car and tended to stay out of trouble the best. That’s exactly what we needed. I think we figured that with out lead we could even loose 10 seconds a lap and still take the lead.
I got out there and didn’t have too much trouble with the tranny. It wasn’t right clearly, but I could shift pretty well. Strangely the upshift from 3 to 4 was more difficult than the downshift from 4 to 3. We had a decent 15 minute red flag in the middle of my stint so I got a nice break. The time went by quick and the headlights worked great.
Then the race was over…
What can I say. Winning rocks! Thanks so much to everyone who has helped us get here. It’s been years of work and it feels amazing to see it pay out. Thanks to our drivers! Thanks to our crew! Thanks to all of our friends! Thanks to all the shops that have helped us along the way.
Our next race is the Westcoast Chumpionship (which we don’t qualify for the running of, so it will be a fun run) at Sears Point in early December. See you then!
Were back at The Ridge! This time, were racing with ChumpCar.
This is quickly becoming one of our favorite tracks. Short tow (<5 hours), nice long track, great local facilities, and AWESOME owners. This is going to be a big race, over 60 teams (50% more than our last race with lemons). Lemons also splits up their racers into three classes A,B,C. Were an A class car. When an even distribution that meant we only had ~20 cars racing with us in the lemons race. ChumpCar is essentially all class A. That’s 3x as many people racing with us!
The team for this race had four drivers, some regulars (my self, Micah, and Erik) as well as one newbie, well I say newbie but he makes us look like newbies with all his experiance, Sam. Our support crew for this race was Chris (taking a break from driving) and Adam (chump chef extraordinaire).
Scheduled race time was from 8am to 10pm saturday. The race would include a light fog (not really an issue at all) and at least 2 hours of full night racing. All in one day.
We showed up early friday to help setup and do a little volunteering for the race.
After most of the cars were through tech, we started getting ready our selves. We had lots of little things to get done (Registration, Taping Glass, General Check). During the check, I found us to be low on clutch hydraulic fluid again. I put erik on it. He quickly discovered the root cause.
The slave cylinder was completely soaked in fluid. The boot was full. Look how nasty that is. Luckily, since we decided to pack on the spare motor we also had a spare slave!
We also got the lights aimed.
Everything looked ready to go, so we packed it in early and got some sleep.
Due to the early start time (8am!) we got to the track at 6am when it was still dark.
Adam got up extra early to get a super awesome breakfast going.
I took the first stint 8-10am. The 14 hour race would be broken into seven 2 hour stints to maximize our time on track.
It took a little while to get heat in the tires. Early on I got 4 wheels off in turn 2 when I took the turn way too quick. I turned it down a bit and kept it on the road after that. The new wider tires (Mustang 17×9 wheels with 245 tires in the front and 255 tires in the back) really made it a lot easier to keep consistently fast times.
At the green flag we started the race in 14th and slowly started working my way up the field. By the time I pitted on lap 49, we were all the way up to second place. I ended up with my best time of a 2:07.36. Pretty good!
Erik was in next and after our pit stop we were back down to third. He worked us up to second.
Car #13 was in the lead and putting some pretty impressive lap times in. They had a mechanical issue (fuel pump I think I heard) and had to retired letting us inherit the lead. He got our fastest lap of the race at 2:07.314!
Micah left the pits in fourth and quickly took back all of our former positions while everyone else pitted. Right back into the lead! Micah kept the car steady and safe and held the lead for his entire stint building us up a 6 minute lead.
Sam was up next. It didn’t get any time to get ready to be in the car. He didn’t even see the driver’s seat until he was about to get in to drive. Quickly adapting he held our lead. He started reporting issues with the gear shifts. Clearly something was wrong. We had a similar issue over a year ago in spokane. It would go into gear but it was hard to get it in and very notchy. Doing the math, with most of the race left…
Warning: If you don’t like graphs stop reading now.This race was the first time I was able to actually collect real usable data! last time I forgot the GPS antenna at home and the time before that the logging software had a bug that made it crash every 3-5 minutes making data collection possible. I’ll let Leo post about the actual race results events. This post will focus on just the data I collected. TL;DR; I want some neat numbers version:
Fastest lap 2:07.2 (according to official timing it was 2:07.3. This discrepancy is probably due to somewhat different start/finish lines.)
Maximum cornering Gs: 1.3-1.4G (noisy data, so i can’t give anything closer than that)
Maximum Speed 110 MPH (95.7 knots)
Sum of best three sectors (“best possible lap”): 2:05:05
All the data collected came from two sources. A Droid X cell phone (Leo’s old cell phone) gives us accelerometer data (“Gs”) and stores all collected data on its micro SD card. GPS is provided by a 20Hz Venus GPS chip wrapped in custom electronics (because I’m a cheapskate and would rather build it than buy it) and a bluetooth transciever, which allows wireless communication between the cellphone and GPS.
>Custom Bluetooth 20Hz GPS. It’s not a looker but it works.
Some of you may recallthat I have plans to add more data inputs. That hasn’t happened yet, but now that I have Gs, speed, and location done it’s next on my list (right after adding live sector times for the driver for immediate feedback).
In order to interpret the data I needed a track map and at least a start/finish point. As it turns out the ridge is so new that aerial photos of the completed track are not available on any maps services I know of. Mapquest (remember them!) and bing both show partly cleared land and googleshows only a dirt track. Since a dirt track is the best I can get, thats what I used to map out The Ridge.
Next I sectored the track. I tried to place sector boundaries at the turn-in to corners; the idea being that it would make them somewhat independent from one another (ie a compromised sector shouldn’t compromise the next sector). Finally I’m ready to put the logged data into my magic visualizer. Its all written in MATLAB right now to prototype algorithms.
A walk through data
I’m not exactly sure how present all the data I collected in a blog post. I’ve spent a good part of today looking at laps and data and I think I could spend a lot more time looking at it. I figure presenting some laps in chronological order is as good as anything. Every plot shows turn numbers so for reference sake here is the official track map.
>The Ridge Motorsports Park map with turn numbers.
Leo was our first driver out. Its typical for chumpcar to do a running start will all the cars spread out around the track. The problem was that the car setting the pace was horribly slow so instead of spreading out everyone bunched up instead. Around the second pace lap Leo radioed in saying that the pace lap was painfully slow, moving at <40mph much of the time. The data confirms it; it was SLOW. Interestingly you can see in the lateral force graph what looks like ringing. This is leo “getting heat into the tires”. I think the consensus is that this doesn’t do much but when you’re going 40 on a race track you gotta pass the time somehow. This lap clocked in at a blistering 3 minutes 48 seconds. Next are some of Leo’s early laps overlaid. In black you can see an early lap that is less confident with several areas (especially the blind uphill around T9-T11) that are much slower than the following lap (red). You can see the confidence build in the next lap.
>Black: lap 9; Red: lap 10
Comparing the black lap above to Leo’s fastest lap and you can see the progress made in 30 laps. Faster everywhere!
>One of Leo’s first laps vs his best. Lots of improvement after he gets into the grove.
So, what if Leo wanted to know where to improve. A quick search for the best sector 2 brings up Sam’s in lap, which is three tenths faster. Comparing the two we see that turn 10 can be taken 10kph faster. Interestingly, third gear tops out at close to 130kph, and there is a characteristic change in the slope of the speed graph (acceleration) indicating that Sam used fourth gear and Leo did not. So now we know conclusively, yes after T8 you do use 4th gear!
>Leo’s Best lap(Black) vs the best Sector 2(red). We won’t mention the blip in Gs right at T13 *cough cough* [Note: the two points where speed goes to zero are at pitin/our pit spot and pit out]
Last is Leo’s best lap (Black, 2:07.3 ) vs Erik’s best lap (Red, 2:07.2) (they’re the top two laps for the day). Whats interesting is that while it looks like Eric’s sector 2 is faster, it turns out Leo did it faster by a tenth. What this goes to show is that faser isn’t always better. making the track 3m shorter at 100kph gets you more than a tenth of a second. You can actually see this at T9 where Leo and Erik are going the same speed but Leo’s lateral forces are higher meaning he’s turning tighter. I think that’s enough graphs. If anyone wants to see other data and its not too annoying to get then I’ll happily post it.
I started processing the location data. Here’s Leo’s best lap vs Erik’s best lap. Its important to note that the GPS is only accurate down to 2.5m (according to the manufacturer) so comparing two lines can be deceptive, but its interesting to look at.