Traqmate GPS data analysis from Autobahn South

[Hornswoggler]

Analysis Intro

 

This thread will document the analyzing of GPS data gathered at the track between two different cars with different drivers. The data was gathered using a Traqmate GPS data acquisition device during a NASA HPDE at Autobahn Country Club South course (located in Joliet, IL). My intention is not so much to compare drivers or cars (although hard to avoid) as to learn from each other and learn from different lines taken by the same driver/car combo.

 

I welcome anybody to perform some of their own analysis and please feel free to share. To view these data files, you'll need to download and install a copy of Traqview, the traqmate analysis software. You can get a copy HERE and the Adobe-format user guide HERE. This software is very easy to use and VERY informative!

 

Link to the data files:

Zip File

 

I forgot to change driver and vehicle, so while the filename has my car and name in it (i renamed it), the data file will say Joe and SRT-4. When in doubt, look at the file name. You can change this and save as an analysis file, but the .tqm files are read-only. Sorry for any confusion.

 

 

This is a short intro to how I see this analysis going, or atleast the things I am looking to compare. As we get more familiar with these tools and learning what provides the most useful information, this plan may be adjusted. This is my planned table of contents:

 

Table of Contents:

 

I. Analysis Intro

II. Segment Analysis (multiple posts)

III. Best lap comparison

IV. Same driver, different lines

 

 

Driver and Car Intro

 

One of the challenges here is trying to identify differences between the two drivers vs differences between the two cars. It's hard not to compare both, but when possible, I am trying to differentiate between the two. To introduce the vehicles and drivers:

 

The Red Dot will be Me (Collin) in my 1997 BMW M3. This car is fairly well modified from stock with the intention of optimal performance at track events like this (non-competitive HPDE's) while still being a fairly refined street car.

 

Key mods/specs:

- 246 RWHP naturally aspirated. 7,000 rpm redline

- ~3,150 lbs with half-tank gas and no driver

- Toyo RA-1 comp-r tires 235/40-17. Shaved to 6/32nds

- definately lower than stock, corner-weighted, and lots of negative camber (-3.3 front, -2.5 rear)

- Stoptech 332mm front brakes with Cobalt SpecVR front pads. Motul RBF600 brake fluid

- Traction Control (ASC) has been physically removed from the car (disabled).

 

Collin's driving experience:

- Doing HPDE events since 2003, ~3-6 driving days per year

- Some autocross experience. Been to three auto-x events plus Mazda Rev-it-up event in 2004.

- 176 lbs.

 

The Blue Dot will be Joe in his Dodge SRT-4. Joe is an avid autocrosser and this is his second HPDE and first time at Autobahn CC.

 

Key mods/specs:

- mopar stage 3 coilovers (KW v2)

- -1.5 camber front, -.5 camber rear

- mopar front/rear sways

- Hawk HPS brake pads, Super Blue ATE fluid

- Avon tech tyres r 225/45 16

- vehicle weight 2,880 lbs

- expected stock power ~230 fwhp and 250 ft-lbs torque. 5,800 rpm redline

 

Joe's driving experience:

- second season of autocross

- second HPDE driving event (first event was at Gingerman)

- driver = 185 lbs

 

 

The Track and Conditions

 

Autobahn Country Club is a fairly new facility (opened late 2004?) in Joliet, IL. They have both a North and South course which is sometimes combined for a full course. Both courses are very fun with the South course being a bit more technical/challenging but still easy to pick up. I enjoy both north and south course but do prefer the south course.

 

The first data file (ABCC South 97 M3 Collin 2.tqm) was the first session of the day, and conditions were dry. Later in the afternoon, it started to drizzle, which turned into a consistent light rain for the rest of the day. I believe Joe's SRT-4 run was a little damp, and the last session (ABCC South 97 M3 Collin 5.tqm) it had been lightly raining for the previous 1-2 hours. Fortunately, the course did not suffer very much although not exactly ideal for fastest times. Either way, we make do with what we have

 

Cliff Notes

 

For those who want Cliff Notes on how we did with laptimes and such, here is a summary. I plan on doing a full lap analysis after I am done with the segments, but here is a quick overview:

 

Best laptimes:

 

Joe in SRT-4: 1:48.025

Collin in M3: 1:45.575

[Hornswoggler]

Segment 1 Analysis

 

With the overwhelming amount of data to compare and analyze, my plan is to tackle the course segment-by-segment, and experiment with what makes most sense to convert the data into useful information we might all learn from.

 

Lots of tools and charts here, some variables to take into consideration, and definately some learning to do on this end. Anybody feel free to take a stab at doing some of your own analysis and post here with your thoughts/results. Also, would be nice to see some other cars from Autobahn South... if I find some of these data files on the net, I'll post a link.

 

The first segment I am analyzing is the turns 1-2-3 complex. I consider these turns interconnected as one and two kinda arc together, turn two feeds into three, and three is most important of this combo because it leads to the 837 foot straight (third longest geometric or "true" straight on the course).

 

Picture of the first segment:

 

 

I am comparing Joe's 13th lap (3rd session of the day) against my 10th lap in the second session.

 

Data from this segment:

 

Collin M3 Joe SRT-4

Segment time: 0:20.450 0:20.650

Entry speed: 95.44 mph 90.08 mph

Exit speed: 88.86 mph 88.10 mph

Max Brake: 1.05 g's 0.98 g's

Max Accel: 0.333907 g's 0.332186 g's

Distance travelled: 1965.8 feet 1951.3 feet

T3 apex speed: 67 mph 64 mph

T3 exit speed: 74 mph 72 mph

 

 

 

Driving line through this segment:

 

After the braking zone for turn one, the M3 (red dot) has a slight lead:

 

This lead is soon lost as Joe (blue dot) takes a shorter line through 1-2:

 

The M3 is carrying more speed through the apex of turn 3, catches-up:

 

Since turn 3 leads to the straight, I want to take a snapshot of data here. Let's look at the traction circles:

 

Collin (97 M3) friction circle at T3 apex:

 

Joe (SRT-4) friction circle T3 apex:

 

Slightly more acceleration from the M3, and lateral grip was about even.

 

Both cars lifted between turn 2 and three, but Joe (SRT, blue dot) slowed down a bit more so the M3 (red dot) carried more speed through three:

 

 

 

Acceleration and Braking zones from this segment:

 

Collin braking and turn zone

 

Joe braking and turn zone

 

The black spot between 2 and 3 is probably a gear change from 3rd to 4th.

 

Analysis:

 

I really liked Joe's line through turns 1-2, he took the shortest path and didn't seem to give up much for corner three entry setup. I think I was able to keep up in the M3 because of hardware, while Joe drove this corner a hair better. Coming into turn 1, Joe did a better job of hugging the left-hand edge of the track and his earlier turn-in helped shorten the course by a few feet. The variation in driving line could have just as much to do with GPS antenna placement, although I think we both put it on center of trunklid.

 

For turn three, definate speed advantage at apex for the M3, which allowed it to gain back any time lost from the "longer" driving line.

 

I was definately braking later in the M3, using shorter distances to brake but much less trail braking.

 

Our driving was surprisingly similar! Not an exact mirror copy, but fairly close behaviors. Lots still to learn...

[GAC]

Collin,

 

This is great stuff, really. Keep it coming. I'm going to get data aq at some point, but I've been leaning AWAY from the GPS-based stuff. Still, interesting nonetheless...

[Mr PS]

Dan, I had both the G2x and AMB transponder at the July WSIR event.

 

Comparing lap times from both systems, they are within 0.005 of each other. Can't complain too much about track mapping either.

[Mr PS]

Colin,

 

Question about the velocity vs distance plot. Is that GPS MPH or wheel speed MPH?

[bnewport]

FYI,

We have quite a bit of telemetry for around 11 tracks right now at trackpedia. Follow this link for a list of tracks with data

 

http://www.trackpedia.com/wiki/Category:Tracks_with_Telemetry

 

We're interesting to providing our logger to drivers doing tracks we don't have so if you'd like it then send me an email at [email protected]

 

Thanks

Billy

[kbrew8991]

Dan, I had both the G2x and AMB transponder at the July WSIR event.

 

Comparing lap times from both systems, they are within 0.005 of each other. Can't complain too much about track mapping either.

 

and some of that you can chalk up to the differing start/finish lines unless you happended to get very precise coordinates for the track's T&S loop (which isnt nessecarily under the painted line)

[GAC]

Dan, I had both the G2x and AMB transponder at the July WSIR event.

 

Comparing lap times from both systems, they are within 0.005 of each other. Can't complain too much about track mapping either.

 

Wasn't really thinking that the lap times would be different...but a G-Force sensor provides data in a way quite different than a GPS-based system.

[Hornswoggler]

... but I've been leaning AWAY from the GPS-based stuff. Still, interesting nonetheless...

 

I did some research on a lot of the sub-$3k data-acq products out there, and one thing that jumped out at me is the difference in products depending on the intended use.

 

For race teams with larger (than my) budgets have some great non-GPS systems to choose from, but from what I could tell, they require significantly more installation and interpretation seemed to require quite a bit more work. If I were a competitive race team, i would have spent more time shopping in this segment.

 

What seemed to meet my needs best, being just a HPDE guy (non-competitive... mostly looking to have fun, but now getting to the point where I am looking to go faster via improved driver skill), I was drawn to the GPS (G2xtreme or traqmate) systems for a number of reasons:

 

- Cool maps for TrackVision overlays

- MUCH easier to plop it into somebody else's car to have data to compare against (ala M3 vs SRT-4 in this thread)

- No trackside beacons required (some HEDE's don't allow them)

- easy to "share and compare" data files with other ppl on the net

- Traqmate software has really impressed me so far. Software is the reason I went with traqmate over G2X (although I'm sure both get the job done)

- definately cheaper than "pro" data acq.

- I did not want to replace my guage cluster/console (i am driving a street car)

 

I did a feature comparison (via the internet, lol) between a handful of systems and this is what I came up with:

 

 

I guess most of those are GPS-capable. The rest of my spreadsheet (harder to attach .xls files) has non-GPS stuff, I think. Still, way out of my budget and I needed something more newb friendly.

[Hornswoggler]

Wasn't really thinking that the lap times would be different...but a G-Force sensor provides data in a way quite different than a GPS-based system.

 

Most of the GPS systems also have accelerometers. It somehow combines the data from both.

[kbrew8991]

Dan, I had both the G2x and AMB transponder at the July WSIR event.

 

Comparing lap times from both systems, they are within 0.005 of each other. Can't complain too much about track mapping either.

 

Wasn't really thinking that the lap times would be different...but a G-Force sensor provides data in a way quite different than a GPS-based system.

 

If you get a system like the G2x I've borrowed from the Trackpedia guys, you get the best of both worlds imho since it uses g-force and GPS to provide data

[Hornswoggler]

Colin,

 

Question about the velocity vs distance plot. Is that GPS MPH or wheel speed MPH?

 

It's either GPS or accelerometer... no wheel speed sensors installed.

[Hornswoggler]

Segment 2 analysis

 

Segment 2 (by my definition) is the area after turn 3 and before turn 9.

 

For this segment, I am using Joe's 13th lap from his session vs my 6th lap from the afternoon (last) session. things are pretty comparable going through turn 4, and the position into turn 5 is VERY similar... but if you look at the traction circle, you'll see my car (red dot, 97 M3) just as far to the right, but a lot further down. Both cars in this screenshot are travelling 65 mph but with me applying more power, it is about to change:

 

 

Also in that picture are stats on this segment (i.e. segment time, exit speed, max accel/speed, etc.)

 

 

Coming into turn 6, between my later braking and having been on the accelerator out of five, I have a slight edge and travelling 7 more miles per hour while we are both braking. My braking zone is also a little later, which helps with the difference in speed.

 

 

By increasing the acceleration threshold of the "Brake and Turn Zone Map" from the default of .10 to .15, the difference in being able to put power to the ground is more noticeable:

 

 

This could be either a heavier foot, or the ability of RWD to put the power down. I do get on the power sooner coming out of turn 6.

 

Exiting turn 6 I have a slight lead:

 

Which keeps growing as I build on that speed, and plant my foot through turn 7 (slight kink) coming into turn 8:

 

 

For segment two, my fastest run through here was 0.950 seconds faster than Joe's fastest run. Driving lines seemed very similar, but I was probably able to put more power down with the RWD advantage. I don't think either of us lifted for the kink.

 

Here are the G's over distance: