e46 M3, e36 M3's and SRT-4 at Autobahn North, Data Analysis!

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e46 M3, e36 M3's and SRT-4 at Autobahn North, Data Analysis!

Postby Hornswoggler » Thu May 17, 2007 5:45 pm

I. Analysis Intro

Last year, some friends and I went to Autobahn Country Club in Joliet, IL to attend an HPDE on the North Course with AMS. While the event had a bumpy morning (was AMS' first time organizing an HPDE event, definately a learning opportunity) we were able to get in some smooth running sessions in the afternoon. The weather was very nice out and it turned out to be a good day.

I brought my Traqmate GPS data acquisition device so I could capture lap data for this analysis and any future review. One of the great things about the Traqmate is being able to quickly and easily swap this device from one car to another, which makes for some very fun comparisons. While two cars or drivers can put down similar laptimes, its interesting to compare the data and see how they may have accomplished this in different ways. With a full sessions data at your fingertips, it makes a metric like laptimes seem so, well, one dimensional. :D

Since comparing my own runs/laps against each other gets pretty boring (not enough variables!), we took advantage of the Traqmate's portability and captured data from a few different cars in different sessions. Starring in today's analysis is three M3's and one SRT-4. All four of these cars are street cars but plenty of go-fast track goodies. All four drivers were very capable and experienced.

My analysis here is going to be inspired by some of my favorite car mag issues where they perform handling comparisons or sports car shoot-outs using a road course and data. I will be looking at everybody's best time through a certain segment, so not to focus on the fastest lap. Later I will combine fastest segments for each driver and put together a theoretical fastest lap for everybody, and compare vs their actual fastest lap that session to give a feel for each drivers consistency. Also keep in mind there were other cars on the track as this was a non-competitive HPDE driving event and passing was only allowed on two straights.

Table of Contents:

I. Analysis Intro
II. Participant Introductions
III. Segment Analysis
IV. Theoretical best lap (combining best segments from the session)
V. Thoughts/conclusions

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

II. Participant Introductions

Stars of this showdown:

- Me (Collin) in my 1997 M3
- So in his 2002 M3
- Trevor in Tim's 1995 M3
- Joe in his SRT-4

Key mods/specs on the participants

Collin and his 1997 M3
Ground-Control coil-overs 450F/525R
Camber plates (-3.3* front, -2.5* rear)
Strut tower brace
Ground-control rear trailing arm bearing (solid)
GC front lower control arm bushings
est. 3,200 lbs
Engine/performance/drivetrain mods:
246 RWHP naturally aspirated 3.2L I6. 7,000 rpm redline (Eurosport OBD-II cam kit)
UUC lightweight flywheel, e34 M5 clutch
Toyo RA-1 comp-r tires 235/40-17 all around on Kosei K1's
Stoptech 332mm front brakes with Cobalt SpecVR front pads. Motul RBF600 brake fluid
Rear pads are Hawk HP+
Driving experience:
Four years of HPDE's
Advanced run group
Limited Auto-x

So and his 2002 M3
PSS9 coil-overs
est. 3,400 lbs
Stoptech BBK 14 inch rotors
Performance Friction "97" compound Front brake pads
HP+ Rear brake pads
245/40/18 Toyo RA1s all around on stock wheels
Driving experience:
Four years of HPDE and Auto-x
Advanced run group

For Trevor in Tim's 95 M3
Sway Barbarians sway bars
GC coilover kit 500 front and 600 rear
camber plates with about -4 degrees up front and -3 in the rear
Rear seat delete and no CD player, not sure on weight (Tim, any est?)
Engine/performance/drivetrain mods:
cone filter
fan delete
3.46 rear differential
17 inch GT2 wheels
235/40/17 hankook RS2 Z212 (non comp-r tires)
Hawk HP+ front and rear on stock type brake setup
Driving experience:
2 skip barbar schools including (including laguna seca)
6 years of Auto X and Track Days
Audi club instructor certification
FTD of the weekend at the Chicago ZOOM ZOOM LIVE EVENT (2006)
CVO motorsports director

Joe and his SRT-4
est. 2,900 lbs
Had passenger on this run! est. 180 lbs weight burden.
Engine/performance/drivetrain mods:
Stock (est. 230 fwhp?)
Driving experience:
Two years of auto-x, one year HPDE's

Best Lap-time Summary:
So: 1:14.350
Collin: 1:15.975
Trevor: 1:16.650
Joe: 1:19.325

III. Segment Analysis

This performance comparison was done at the Autobahn Country Club in Joliet, IL. We drove the North Course, which is a 1.46 mile course with 9 turns. Most of the corners on this track are very fast, except turns 2 and 6, both are pretty tight. My favorite turn is #9, a full-throttle carousel leading to the front straight. The track runs clockwise.

Here is a picture of the North course with colored segments for analysis:

Segment one = Purple
Segment two = Brown
Segment three = Red
Segment four = Light Blue

Segment One

Segment one (Purple) includes the braking zone from the main straight, the fast left-hand corner of turn one, and the sharp right of turn 2. Turn one is very interesting because that was the turn with the most difference in driver technique. Where So and I would brake before turn one, accelerate through, then brake for turn two, Trevor would take a different approach and brake slightly later but through the turn. I always learned to do my braking in a straight line (the safest approach) although have used trail braking for getting more rotation. Will be interesting to see which technique is faster. Turn two is the slowest turn on the track.

The best results for segment one were from the following laps:
Collin - lap 4
So - lap 11
Trevor - lap 9
Joe - lap 3

Data from Segment one:

Segment Two

Segment two (brown) includes three corners, a fast right-hander, a fast left-hander, and a fast right-hander. There is plenty of time between corners to let the car settle so these are fairly gradual transitions. One important thing to note is there was oil spilled right on the driving line of turn four earlier that day, so some drivers may have been a little extra cautious on that turn (I know I was!). I call these the cojones corners as vehicle speed through this section is usually more limited to driver comfort than actual hardware, lol. This segment ends with the third longest straight on the course.

The best results for segment two were from the following laps:
Collin - lap 7
So - lap 9
Trevor - lap 8
Joe - lap 2

The reason Trevor was consistently slower coming into turn three (compared to the other M3's) was because he started his braking zone a little earlier, probably back in segment one. I checked all of Trevor's other laps to verify that the low entry speed was not a fluke.

Data from Segment two:

Segment Three

Segment three (red) includes turn 6, a long straight, and turn 7.

Turn 6 is the trickiest corner on the track as it looks like two geometrical turns and you must know to throw away the first apex or else you run out of track on exit. Another thing that made turn 6 challenging this day was all the mud and debris on corner exit which meant a more conservative line to stay on clean pavement. Here is my driving line through turn 6:


The straight between 6-7 is the second longest straight on the track. I will also be measuring top speed reached on this segment. Turn 7 is a fast left-hand turn... all day it felt like I could keep taking turn 7 faster and faster with plenty of room to track out. This segment will punish those who do not get a good exit from 6.

The best results for segment three were from the following laps:
Collin - lap 10
So - lap 10
Trevor - lap 8
Joe - lap 3

One thing I noticed, comparing Collin and Trevor's braking zones is that Trevor would brake earlier and longer than Collin. While many make the case that the stock M3 brake system (sans pads and fluid) is more than sufficient, I believe some timed was gained by Collin's upgraded brakes (stoptech 332mm front, Cobalt SpecVR pads). When Trevor reached his max speed of 97 mph on the straight between 6-7, Collin was travelling at 99 mph and only gained 1 more mph before he started braking. It also appears that Collin's 97 M3 has slightly better acceleration as Trevor had a slightly better exit from 6.

So gained most of his time here on the entry to turn 6 (better/later braking?). Joe loses .3 seconds to the other three cars on turn 7.

Data from Segment three:

Segment Four

Segment four (light blue) includes two right-hand turns (8 and 9) followed by the longest straight. Turn 9 is my favorite turn on the track and I love powering through the carousel at full throttle.

The best results for segment four were from the following laps:
Collin - lap 6
So - lap 4
Trevor - lap 7
Joe - lap 2

Data from Segment four:

Very similar segment for the three M3's. Collin seemed to gain ~.1 seconds over Trevor by taking a tighter/shorter line on the exit of turn 9 (reducing distance travelled by 9 feet). In this mini-segment (see picture below), each driver took the following distance between segment markers:


Collin (blue line): 1144 feet
So (red line): 1148.9 feet
Trevor (black line): 1152.8 feet
Joe (green line): 1147.7 feet

Is nine feet of distance a big deal? How much time is that worth? Is a shorter but slower line quicker than a longer but faster line? I really don't know the answers but have to figure since Collin and Trevor's speeds were similar, the shorter line would have to win.

Theoretical best lap

By taking everybody's best segments and adding those times together, I put together everybody's theoretical best laps (compared to actual fastest lap):

Collin: 1:15.600 vs 1:15.975 actual
So: 1:14.150 vs 1:14.350 actual
Trevor: 1:16.275 vs 1:16.650 actual
Joe: 1:19.175 vs 1:19.325 actual

Being .2 to .4 seconds away from theoretical fastest lap is actually pretty good! Says something for our consistency, especially since we don't drive that track everyday and considering the traffic.

Thoughts and Conclusions

Man, lots of data to take in. Feels like everytime I do one of these analysis, I learn a little more and my approach gets a little better.

For my thoughts, I'll mention what I think each car was doing right or what they should consider doing next to catch-up with the next fastest car. Starting with the fastest driver...

At the track and after seeing So's wicked fast laptimes, I thought for sure it was his extra horsepower and gearing advantage really starting to shine now that his brakes are really working for him and his comp-r tires really seem to make a big difference. So and I have done four events together this year and we both did Blackhawk but at separate times. I am very impressed with how much faster he is today than he was at start of the season, both car development (his M3 is new to him this season) but also I see a big difference in driving skill. It feels like we kind of drive each other to go faster but also help each other go faster at the same time (all while having fun!). My hats off to some very fast (relatively speaking atleast) laps. Looking at the data, I don't think its just the horsepower, and So consistently was braking later and almost always had a faster corner entry speed. He was able to carry that speed onto the straight, where his extra power was just the icing on the cake. By braking later, So would pick up an extra .1 seconds here, .1 seconds there... it starts to add up and really makes a difference. Must have been much closer to threshold braking, or could be enabled by those wider front tires.

The one corner that So did better than everybody else was turn 5. While the apex info for all the cars was pretty similar, his corner entry speed was the highest, which I believe gained him about .4 seconds... a lot for one turn. So also had a fast entry into turn 4. Maybe in the future I will add corner entry speeds for segment 2 as it does tell part of the story.

If there were any corners for So to improve on (atleast relative to this crowd), the only corner he was really matched (and slightly beaten, looking at just the corner) is turn 9. We'll just have to find some faster drivers for So to compare data with next year, haha.

Collin: (me)
So where else can I catch So? Looking at my own opportunities to improve, I was about .3 seconds off So and Trevor's pace in turn one. My concentration was all about getting the car settled and slowed for turn two, I didn't put much effort into making the absolute most of turn 1... but now that its been pointed out as a slow part for me, I know to work on that next time.

I overslowed for turn 4. While I was cautious because of the oil on the track, there was more grip in that corner than I was taking advantage of. I could gain about .2 seconds by entering turn four about 5 mph faster. My current technique is to slow for the corner then accelerate through, where I should be slowing less, but feathering the throttle through so my exit is about the same speed (as my entry is not grip limited). I always listened to the DE mantra of "slow in, fast out" but it looks like there is time to be gained! :)

I'm going to start following So's lead and start braking a lot later, hehe. Also, next set of tires I am going to step-up to 255's instead of the 235's I currently run (hoping for more grip). I think my car accelerates at a very similar pace to So's (not quite as fast, but surprisingly close), my car seems to grip just as good... i'm gonna work on my technique. ;)

Trevor: (in Tim's car)
I think the #1 disadvantage this car had vs the other M3's is tires. While on good street tires, they didn't seem to have quite the grip of the Toyo RA-1's on both Collin and So's cars. Lateral acceleration was close, but not quite. The biggest gap on the friction circle, however, was deceleration g's. While Collin and So both consistently hit 1.2 g's in negative acceleration (braking), Trevor was more around .9 g's. I'm sure tires are a part of this, but braking system as a whole could be a contributing factor. I don't think Tim (owner of the car) really believes me but oh well, lol. Here are some friction circles from both Trevor and Collin, note how they are similar in the lateral and forward direction, but the top of the graph (deceleration) the peak just isn't there for Trevor. Yes, tires are a part... but if tires were that much of a disadvantage, the car would not have the same lateral grip either. (unless street tires handle lateral grip better than deceleration grip? I might learn something here)


Start with tires, then consider brakes. We could always capture more data next season once Tim upgrades to RA-1's or similar. Fortunately we can make these kinds of fact-based decisions with the ability to capture and compare data. If this car could late brake like So's, there is a lot of time to be gained.

Joe had a passenger and was at a disadvantage. Not sure how much the 180 lbs handicapped him, but it would be unfair to not give some sort of correction factor or credit for the extra burden. How much did this weight matter? Not really sure. I have a feeling we are going to be capturing more data next year to get more apples-to-apples (and hopefully not in the rain either!).

I think Joe has some wider tires and maybe lighter wheels planned for the 2007 season, this should help. Also, I know its a LOT cheaper for Joe to add power than any M3, LOL. Throwing more power at the car could be the great equalizer.

Biggest corners of opportunity for Joe were the cojones corners of 3, 4, and 5. Carry more speed into those turns, and you'll gain quite a bit of time.

While Joe didn't have the lateral grip of even the street tire M3 (Tim's), he DID get higher deceleration numbers. Not sure if this was Trevor's driving technique (not used to ABS?) or a more aggressive brake pad in the SRT-4. Joe's max braking was .1 g harder (1.0g) than Trevor's (0.9g).

Ditch your passenger, get some more grip, maybe add some cheap power, and see ya next season Joe!

That's all I got for now. Anybody feel free to post their own input or questions. Thanks for reading!

Andre' Surles
Team Traqmate
Posts: 651
Joined: Mon Feb 07, 2005 5:53 pm

Postby Andre' Surles » Fri May 18, 2007 12:23 pm

Wow! Thanks for posting, great read and great analysis! Those M3's are fast, I would have loved to see the times of a first gen M3 with an equal amount of work. It will be interesting to compare the latest V8 M3, as BMW is quoted as saying its 'substaintially faster'...at least around the ring. Hope the weight penalty and electronics don't lead it down a gee wiz why am I so slow path.
Thanks again for posting, great job, nice details. Have fun out there.
Andre' Surles
Track Systems
Redline! Redline! Redline!

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