Data Loggers (Spec DL1) - Getting Started and using them for Driver Analysis

[Maxx]

EXPLANATION

I needed to do a "get you started" guide to using the DL1 for driver analysis for a
driver i'm working with who is currently overseas (only conversed with via email).
We are looking to work together next year in the UK but he wanted to buy a DL1
so he could get into data-logging and analysis and I may also be able to help him
remotely (by analysing his data).

So, seems like he may be in a similar situation to some folks on here who have either
bought or looking to buy a DL1 so I may as well post it here.

REQUEST : More than happy to answer questions and have comments but could
you just hold back for the rest of today, so that I can get a few more sections up.

Even if you don't own a DL1, I will be posting a link to download the data file discussed in this
post and a link where to download the DL1 Analysis Software, so ANYONE can have a look
at the actual software.

THANKS

Although the actual steps are for the DL1 the concept is the same for other products
that also provide g-force data (via accelerometers) i.e. Driftbox.

INSTALLATION & SETUP

First you need to fit the unit in your car. As I transport mine around quite a bit
and swap from car to car I have the power cable terminated with a 12v cigarette
lighter plug.



They can be bought at places like Halfords or Maplins etc. Here is a link to one at
Maplins Online (go for the fused one @ £2.49)

http://www.maplin.co.uk/Module.aspx?...hter&doy=22m11

You then need to mount the DL1 somewhere in the car, ideally flat and secure, I tend
to use velco and some duck tape to secure as I move the unit around. It does come with
brackets if you want a more permanent solution. If you bolt it direct to the chassis/
floor just make sure it is protected from excessive vibration by placing some foam rubber
underneath.

The GPS antenna is best as high as you can get it and as flat as you can get it with
no obstructions. It will work almost anywhere that it has "sight" of the sky but the
more GPS satellites it can lock onto the better [and more accurate] the signal. For a
Saloon the very best place is on the roof. It is magnetic but should be secured with
duck tape. People have had much success with mounting it in the windscreen (a la SatNav)
and even beneath GRP body panels (i.e. Elise)

There are ways to set the DL1 to automatically start logging based on certain events
(i.e. once the vehicle exceeds a certain speed) but that's too much to go into here, full
details in the help files. I prefer to press the button to start logging, that why I can
check I have a GPS lock.

You know you have a GPS lock when the GPS lock light starts flashing, this can take up
to 30 seconds. Make sure you are NOT in a garage as you wont get a GPS lock and even if
you are very close to a large structure, you may struggle.

Once you have your Power light, Status Light and GPS Lock light on you are ready to
start logging.

TIP: If ever your unit fails to give you the Status light (without which it won't let
you start logging) I have always found this to be related to the data card. Simply
reformat the card (FAT) and this fixes the problem.

The help file within the analysis software will have further and more detailed information
plus there is an excellent Knowledge base on the DL1 here :

http://www.race-technology.com/wiki/...p/Hardware/DL1

If you have a laptop computer or can beg/borrow one I think it is well worth taking one with
you to the track, even if you are not intending to do anything with the data, at least you can
check that logging is working OK and you are getting decent GPS accuracy.

You will need a CF Card reader if your laptop doesn't already have one. You can either get a
CF-Card Adapter to fit into your PCMCIA socket, like this one from Mapline @ £10 :-
http://www.race-technology.com/wiki/...p/Hardware/DL1

Or a USB card reader like this one from DABS @ £9 :-
http://www.dabs.com/ProductView.aspx?Quicklinx=4S34

You can of course test the unit first by fitting it into your road car (assumes you have gone
the 12v plus route) which may help you sort out any issues before you get to the track.

[Maxx]

NOTE: All images are clickable for larger view


BASIC ANALYSIS - Lap & Sector Times

So, we've got the software installed, logged some data and now ready to load
it into the analysis software.

NOTE: You should make sure your analysis software is up to date, especially
if it says 6.<something> as the release no. Version 7 is available from
the RT site and has many enhancements and bug fixes from version 6.x

What I do is copy my data onto my laptop first rather than read direct from
the cars. The data is stored on the Compact Flash card in directories named
like so (by default) "RT071127" the last 6 number being the date in YYMMDD
format. I create a DL1 folder on my laptop and copy these over as is so I
have different folders for different days loggings. I suggest you do the same
for ease of use, lets assume we have created a folder C:\DL1 and copied our
days logging into it.

When you load the software it will ask if you want to load the default
layout, always say YES to this.

The first thing to do when you load up the analysis software is to do a
File->Set Default Paths and change all of them to C:\DL1

Then do a File->Load Logged Data and search for the folder you want and
select the files that you want. You can select up to 20 files top load
in (but would suggest doing them 1 by 1 at first, seeing the results each
time).

You should see a screen like so :



The cuts you see on the track map are not off-track excursions but area where
the GPS lock has been lost and later recovered.

The thing you will want to do after this is to find out your lap and perhaps
your sector times. You need to just take a guess at where you think the start
line is if you want to do it based on the s/f line but my preference with
lap and sector markers is that I have them just before the braking zones of
all the corners as I am mainly interested in analysing the cornering stats.

Again it is mainly a guess at first but you can alter them later when you have
access to the g-force data. For this first example we will select the lap marker
but allow the DL1 software to define our sectors for us.



Here is the bit of the screen we are interested in, we use the button to the right
of the hand to mark the start of the lap. Click on it and draw a line across the
part of the track you want your lap marker to be at. A box will pop up with
"Marker 1" as the title and show a tick box which you need to select to use that
Marker as the Lap Market. It will then ask you if you want to automatically add
sectors now, you should say YES at this stage.

What you then end up with is a screen like this ..



.. that shows a marked up trackmap and a lap & sector times table. Note that the
fastest sector in each run will be shown in bold, if you load more than one run
the fastest sectors out of all the runs loaded will have a PC next to it. A total
of the fastest sectors is used to determine the Fastest Theoretical lap which is
shown at the top.

NOTE: The sector markers shown are "custom" ones I did, not the automatic ones.

The sectors you see that show n/a are because there has been some sort of GPS
anomaly and the data cannot be relied upon.

NOTE ABOUT ACCURACY & OPTIONS

I'm not sure what the default is but there is an option to either use GPS+Accel,
GPS only or Accel only to draw the trackmaps. These can be found by selecting
Data-Analysis Options and on the Mapping tab you see 3 tickboxes.

I generally run the software with just the first option ticked. The above map
was however generated with the first and second box ticked (i.e. ignore accel
data when drawing trackmap). If I revert back to only have option 1 ticked it
introduces an oddity into the trackmap like so :



The most accurate method should be with just option 1 ticked but if you get
anomalies like this you can play around with the settings to get the most
useful trackmap.

Now lets start looking at some specific data other than the times themselves.

Firstly, tick the Interactive box on the trackmap, this allows the trackmap to be
based on whatever selections you make in the lap and sector times table and will
come in useful later. Then click on the fastest laptime, the 1:29.25, notice we
now have graphs at the foot of the screen and that particular lap (line wise)
highlighted on the trackmap.

BASIC LAP COMPARISON GRAPHS

By default the quick graphs at the bottom contain long accel (braking/accel),
lateral accel (cornering), speed and time slip %. The first 3 should be fairly
obvious, time slip is (by default) measure against the Best Theoretical Lap.
Even though a sector time might be slower than the best sector time, it may
still have been faster at some stage and you can easily see where you have
gained lost on the fastest sector.



If you click on another lap time (lets say the next lap, the 1:34.43) you can
see that both lines are shown on the trackmap and both "traces" are shown in
the quick graphs. We can easily see here that the major time loss was early on
as the time slip % shows this very well and is confirmed by the speed graph.
The rest of the lap does not look too dissimilar



We can highlight up to 5 different laps which show up on the trackmap and in the quick graphs.

[Maxx]

Sample Data File and Analysis Software Download Link

As mentioned in the first post, anyone can try the steps discussed in this post by downloading the analsysis software and the sample data file used. Later in the post there may be other datafiles you need to use and these will also be made available.

The software can be downloaded from here : http://www.race-technology.com/downl...ea_2_7453.html

I've uploaded the data file to a filehost site, not used this one before so any problems, please advise, download link :- http://www.filefactory.com/file/e788f4 click the big green [ FREE DOWNLOAD ] button at the foot of the page.

In order to follow the above more accurately, you should create a folder called C:\DL1
In that folder create another folder called RT071127 and unzip this file into it.

[Maxx]

FURTHER ANALYSIS - SECTORS

We can also analyse the data at a sector level. Instead of selecting the
laptime, instead click on a sector time. Lets pick the fastest Sector 1 time
on lap 10. Notice that the trackmap, now in interactive mode "zooms in" on
our sector and shows the driving line. Now select Sector 1 from lap 11, this
is the one we saw earlier had a big time loss.



We can easily see from the trackmap that on lap 11 we took a different line.
If we look at the quick graphs below we can see that we actually took more speed
into the corner (Speed graph, 3rd one). We can see this also in the first graph,
the long accel [g] which is our braking/accel g-force and the deceleration
starts later.

Looking at the 2nd graph, the lat accel [g] our cornering g-forces, we can see
that we don't pull quite as much lateral g on the way in but then things start
to get a bit out of shape (essentially this looks like a bit of a "tank slapper".

We can see that, because of this we lose further speed and our time-slip %
starts to drop (we were actually ahead at one stage, by braking later).

When we actually click anywhere in the graphs or on the trackmap windows we get
a pointer which is shown in the graphs and on the trackmap. You can drag this
pointer back and forth and see exactly what is happening with the various items
on our graphs and how it relates to where we are on track. A very useful feature
also is that on the trackmap, you get a visual representation of the amount
of long and lat g we are pulling via the coloured lines, the longer the line,
the higher the value. In the following screengrab you can see the difference
between the fast (black) lap and the dodgy (red) lap.



The red lap shows deceleration and higher cornering force, if we move it forward
we would see those cornering forces go side to side.

Of course, the differences here are quite obvious but we often have to look a
little deeper to find those extra few 10ths per corner that add up to that
special lap.

It's beyond the scope of what I'm going to write here to get into that in any
depth but it is useful to look at the 2 areas of analysis that the analysis
software can give us and see why it is easy to follow a red-herring if you
rely on line data only.

Again, I have had to try and find an extreme example in the data file you have
access to already so, lets look at sector 2 on laps 16 & 17.



Looking at the line we can see a big difference, the black lap (slowest) appears
to take the often seen VERY wide line out of Sear corner at Snetterton. Looking
at line and speed alone it just looks like it's a slower option but the g graphs
tell us the real story. The black lap was actually faster up until close to the
apex (see time slip graph, No 4). Then we appear to lessen the cornering g
(straighten up) and lessen the acceleration g (see dip in graph 1) then getting
back to full acceleration.

I'm 99.9% certain that this is caused by another car being in the way on the way
through Sear and the driver backing off a little and taking the wider line and
then going past.

It's not a brilliant example but does show the possibility to follow a red-herring
if you don't look at all the information.

Before leaving this section it's worth looking at one more which is a not a
sector spoilt by traffic, just driven differently. We are going to look at
Sector 6 (Coram) on laps 5 & 10 which are about the quickest 2 and only .08 of
a second difference.



Looking at the line the is no discernable difference between the 2. but the
g-force graphs show that we drove the corners differently. On the black lap
we eased off a bit more at one stage, which allowed us to use a little more
acceleration grip up the level where it again ran out etc. This also shows
on the speed graph and on our time slip graph.

As it happens this has very little impact on Coram itself as it is such a
long corner but had the corner opened up half way through we may well have
been quicker on the black lap by getting better acceleration out.

Hopefully we are starting to see that the g graphs are much more useful in
figuring out what is going on, what way is the fastest and why, more than just
looking at line, plus, as we know from pervious posts, the line can be quite
inaccurate.

Before moving on to more in-depth g-force analysis lets just make our
sectors easier to interpret and save ourselves having to redefine them each
time.

Select Data->Lap & Sector Options. Go onto the Sector Setup tab, make sure
"Define Sector Automatically ..." is NOT checked. You will then see your
laps and sectors listed like so :-



Click on each sector and select Edit Sector and give each sector
a meaningful name, for the Snetterton sectors this would be something like
this :-



When you now display your screen you will see the Lap & Sectors Table now
looks like this :-



You should now save this by selecting File->Advanced Load/Saves->Save Markers/Sector
choose a meaningful name and the file is normally stored in the DL1 folder.

To load that file back at any time, select File->Advanced Load/Saves->Load Markers/Sector

I have attached the file I use to this post, just unzip it into your DL1 directory.
If sector names do not show, remember to check the "Define Sector Automatically ..." is
NOT checked in Data->Lap & Sector Options.

NOTE ON SETTING UP YOUR OWN SECTORS

If you decide you'd like to add you own track markers you can setup the sectors yourself
(or add to existing one) by going into the same option and click in a blank sector and
Add Sector Definition You enter a name and the start and finish markers. Note that
these do not have to be sequential, you can add a sector from for example Market #2 to
Marker #7.

[m3Chris]

Maxx - many thanks for that. I will be getting one early next year prior to my first trackday - I think Stephen is selling them on here. I'm sure I will need to read this again once it is fitted.

Nice that you can play with the data prior to buying.

[Maxx]

Glad your enjoying it and sorry for the undoubted head scratching it's likley to generate. I'm about 2/3rds the way thorugh the next post which is the real meaty stuff re: traction circle analysis etc. but have run out of time tonight so hoipefully get that finished tomorrow.

Maxx

[m3Chris]

Christ - the above stuff is pretty meaty!

[Stephen]

Fantastic writing Malcolm. We'll be putting a DL1 section on our site shortly under a banner of resources to help you get more out of track days. Would you like to be the first instructor contributor with a version of the stuff you are putting up here?

[Chris_w]

Thanks Maxx, all good stuff.

Chris, which unit are you thinking of going for, I'm thinking I might raid the piggy bank before next season and get the Performance Box.

[m3Chris]

I'm going to go for the DL1.