- When you're ready to start looking at performance, using the time variance plot
relative to your reference lap is going to be your best tool to start with.
Here I'm going to go through a couple of examples looking at a professional vs
an amateur driver in the same car on the same day and there's quite a big difference
in performance which makes it a really good data set to look at to start with because
it'll show lots of clear differences.
I'll take a look at the data a couple of different ways.
FIrst just assuming you've only got basic channels available with engine speed,
vehicle speed, lateral and longitudinal G.
Then I'll look at exactly the same data set with a few more advanced channels
added in as well.
Here on my laptop screen I've got the data loaded up, we've got the reference
lap which is the fastest lap we have for this car in white and we have the latest lap
which is from the amateur and the slower driver which is shown in the colour channels.
The points I want to concentrate on first are the areas where we've got the biggest
dips in the variance channel.
Looking at the variance I've got a really big dip here at turn 1, I've got another one
at turn 9 and I've got another one later in the lap around turn 10.
So these are the points I want to start with first and now we're going to dig into the
actual log data and look at the reasons for why those dips are there.
When I look down through my detailed log data here, I've got engine speed at the top,
then I've got my vehicle speed shown here, my longitudinal G force in red and my
lateral G force in green.
These are the bare minimum log channels I'd expect you to have if you're logging
data and these are what we're going to start doing this example with.
So if I just zoom into the first part of the lap, I'm looking here at this turn one section.
The first thing that's immediately obvious is the big difference in the speed trace.
So this is obviously a big part of where this time difference is coming from.
I also want to mention here in the reference data there's this big dip which is just a wheel
lock up in this case which is giving us a dip in the speed trace.
I just want to ignore that, that's not something that's really too relevant to our analysis
right now.
Looking through here the first thing if I look at the longitudinal G force, we can see here
that the amateur driver is braking much quicker 'cause we can see that this dotted line here
is the reference zero line.
So that's zero longitudinal G force.
So we can see it's dropping off a lot earlier, while the pro is still accelerating, the
amateur is dropping off here and starting to brake much earlier.
So this initial lift here is just them lifting off the throttle and it's not until we get
down this piece here, this lowest piece which is where the brake application's
actually coming in.
So even just dropping off the throttle here, we're dropping below the zero longitudinal
G force line because that's just the aerodynamic drag which is starting to retard the car at
that point.
So that makes it really clear, this loss in the first place but the really strong part of
the loss is actually happening much later in the corner, we can see the gradient really
drops over here in the variance channel.
We can see that the longitudinal force, the peak longitudinal force for the pro is
much higher here, that means they'll be using much more brake pressure than
the amateur at this point in the braking zone so that's one important point to
look at.
First there being the point where they're starting to do their braking, the second
being the magnitude of the braking so this is a really good example of the difference,
what you'll often see between a pro and an amateur, both in terms of braking point
and in terms of the braking strength, how hard they're actually braking.
Later in the turn, the longitudinal force is actually quite similar but because the
amateur has started braking so much earlier, we can see how much lower it sits in the
line here.
There's quite a big difference in speed trace.
Really obvious thing here looking at the lateral G is how much combined lateral
and longitudinal force the pro is holding compared to the amateur.
So we can see here that the amateur is driving the car much straighter.
So the lateral G force here is quite constant and then right as they approach
the corner entry they turn in quite sharply whereas the pro is able to hold a lot more
combined force so they're holding longitudinal and lateral at the same time.
So I'm just going to zoom back out and just look at the next point in the lap where I
wanted to discuss which was the turn 9 section.
So I'll just zoom to this section here.
Again looking at the speed trace we can see that the amateur is losing the majority
of their time in this second part of the braking phase.
So this is what I would generally refer to as the first part of the braking phase and then
this later section here is what we'd call the late brake when you tend to be
trailing into the turn.
And we can see that's where the gradient is strongest there in the variance.
It pretty clearly lines up with the difference in the speed traces there.
We can see that the pro is going a little bit later on the brakes when they start
their braking but that's not the most prominent part here, it's really the speed
at which they're able to build up the maximum braking force, so this line here
is much much more aggressive whereas for the amateur, taking them much more
time to get to that constant brake force.
We can see the pro here is much more aggressive with getting to the peak brake
force which is why this line is much closer to vertical, the white line.
Whereas the amateur is taking a lot more time to reach peak brake force which
doesn't happen until down here.
So that's the start of the braking zone.
Then you can see this diversion here in the longitudinal G there the pro is
beginning to already lift off the brake pedal and that's really where you see this
difference here where the longitudinal force drops off, there's a constant bleed
off of the pressure here in the white line and that's really where this divergence
happens in the speed trace at the same time.
And once that happens, it really just continues all the way to the apex
of the corner.
So if we just zoom back out again I just want to go to the final portion of the lap
and look at this.
And what we actually see here in this case is the amateur braking with more pressure
than the pro.
So this is a case where the amateur is over slowing the car where you don't need
to be over slowing the car as much and as a result, we can see how much more speed
the pro is carrying into this section of corners here.
We can see we've got a bit of a section of corners quite close together here with
these two dips in the speed trace and this little ramp in between.
So this is obviously coming up to a little complex of corners and we can see even
though the braking point and even the approximate ramp time to get to full
brake pressure is pretty similar, definitely a little more, a little quicker for the pro but
it's more similar than the previous example we looked at.
In this case of the way the brake is being bled off, you can see that the pro
is relatively consistent once they get to peak brake pressure, it's pretty constant
bleed off, the pressure.
Whereas the amateur is using more pressure and they've realised that they're going too
slow and that's why we see this kink here in the speed trace so they've overslowed
the car, realised they've overslowed it, all of a sudden jumped off the brake
pedal and then tried to pick up that speed again.
This style of braking is something you don't want to be doing because it can
often upset the car.
You don't want to be having the car nose dropping and then coming up and
dropping.
You want to have the car sitting down on the nose and it to be pretty consistently
down until you get to the apex and as you lift on the throttle and come out,
that's when the nose comes up.
You don't want to have any porpoising of the front, it's bad for grip, it's bad
for aerodynamics, it's really something you want to avoid.
That's an example of analysing the points of maximum loss just looking at those
4 channels of engine speed, car speed, longitudinal and lateral G.
Now I just want to add a XY plot and a track map just to show you how you can
exploit those to understand what's going on with the car as well.
So moving across to a slightly different view.
I've got the exact same log data shown here, the only addition is I've got my lat/long G
plot shown here and a track map for a little bit of context.
So if we just zoom back in to the initial point, I'm just going to turn the delta
back on, the variance channel so that we can see where we're looking again.
Going to go back to turn one and have a look.
So the point I was making initially about both this peak in brake pressure,
so you can see here we're on the XY plot where the white part of the cursor is
on the traction circle, versus where it is on the amateur parts of the track and
traction circle, we're getting much more braking, peak braking force on the reference
lap, on the pro lap.
But the point I really want to make using this traction circle here is if we bring
the cursor along to the point where we've got a lot of combined load.
So we can see the pro is starting to ramp up their lateral load while they've still got
quite a lot of longitudinal load, that becomes really clear in this difference in the traction
circle here.
One of the things about a traction circle is it can be quite overwhelming if you're
looking at it over an entire lap.
It often becomes a lot clearer what's going on if you zoom into a specific section of
track, maybe one left, one right hand corner.
Otherwise it's just too many points to overlap with each other and it tends to be much more
difficult to see the trends.
So in the same way that we can see with the log data produced on this time/distance
plot here, if we look at it on the traction circle, it's really clear that the pro is able
to ride that edge of the traction circle much closer so you can see from the
point of maximum lateral acceleration to maximum braking, it's a much more pronounced
outward line whereas the amateur is much more of a straight line and they're using
much less of the envelope of the car.
Looking at the example in that late section of the lap we can see something really
similar here on the traction circle where the pro is able to exploit much wider in the
traction circle than the amateur.
So the amateur's really sitting on this line here and the pro is using much more of
this combined area.
So being able to exploit that traction circle at the edges or getting much closer to
something that ideally runs a curve between the maximum lateral and the maximum
longitudinal, that's what we're aiming for.
One of the things I did want to emphasise is that even though it's great having those
extra channels, even just with the lat/long G, speed and the engine speed, you can already
see quite a lot about how the car's been driven, how it's been differently and I think
you can already start to do quite a lot just with those lat/long G channels.
That was just one of the modules taken out of our Data Analysis Fundamentals course.
If you want to become a better driver, get faster lap times and constantly progress your
driving skills, you'll need to know how to use a data logger and understand the information it
gives you.
In this course you'll learn the different types of logging systems and what will work for both
your needs and your budget.
You'll learn the fundamental cornerstones of data logging and analysis that'll form a
strong base that you'll be able to build on for the rest of the course.
Next you'll learn all about the bare minimum sensors needed to start analysing your driving.
And after that, you'll learn about your logging setup's more complex functionality which
you'll be able to make use of as your skills and experience increase.
To ensure you're able to put the theory of what you've learned into action,
there's a detailed practical skills section that shows the concepts explained in the course
being applied in the real world.
Finally you'll learn the 6 step data analysis process that'll give you a clear and structured
template to work from as you embark on your own data logging projects.
If you want to find out more, click the link in the description.