Over team radio, throughout a race and in all the technical after-talk, we hear about
engine maps and modes that drivers often change and fiddle with either independently or at
the behest of their engineers. So what is engine mapping and how does it
affect the way the cars perform?
Let’s start with the basics. In the way back when - and I mean way back when - the
accelerator pedal was directly, physically connected to the engine via a mechanical cable.
The more you pushed your foot to the pedal, the more the throttle opened, letting more
air and fuel into the engine cylinders, which drove more power from the engine via increased
combustion. It was simple, but limited. Now the amount of travel in the accelerator
pedal is measured electronically and read by the Electronic Control Unit or ECU
The ECU then takes in lots of other inputs from the car and works out exactly how to
manage the combustion part of the engine and ultimately the power output.
It works all this out via engine maps. Engine maps are essentially a bunch of data
tables in which the ECU looks up what’s going on with the car and driver inputs and
finds out what it’s supposed to do with the engine.
To get a feel for this, let’s start with the Engine Torque Map, which is really more
of lay of the land than a series of instruction, but it all fits into the wider picture, you’ll
see. The Engine Torque Map just describes how much
torque the engine delivers as standard at a given RPM and and amount of throttle.
The RPM (the rotational speed of the engine) and throttle level (basically, how much fuel
mixture you’re pumping into the engine) are your inputs.
The torque, (which is strictly how much turning force the engine is producing) is an output.
So if you know your RPM and throttle level, the map will tell you the engine torque.
Let’s imagine a very simple, scaled down version of this engine map. We can model it
to see what would happen at slow, medium and fast RPMs. And we can also look at narrow,
medium and full throttle levels. This gives us a nice table with 9 possible
scenarios - our outputs. So if the engine is running at low RPM and we’re only squeezing
the throttle a little, the map tells us the engine will be producing a small amount of
torque. Full throttle at high RPM produces a large
amount of torque. And so on. We just draw from the two inputs to find our output torque.
You get the idea Now, obviously, the engine map used in real
life is a lot more granular than that, using more than just our 3 gradations of input but
this one looks a lot more daunting at first glance.
So, really, this engine torque map just describes the engine as it normally behaves - we gather
this data but running the engine on a testing dyno and logging its torque levels under different
scenarios. But what if we wanted to create a map that did make it behave differently
to normal? This is where all the custom, various engine
mappings come in. We can create our own versions of this map so that, when a driver pushes
the accelerator pedal at a certain engine speed, the torques outputted will be different
under different maps. We might want to lower the torque at lower
revs, like this. Or we might want to make the jump from low to high torque more dramatic.
The idea behind these maps is that we’re going to demand from the engine a certain
amount of torque or power given certain scenarios. We’re going to tell the engine - if I’m
pushing the throttle half way and you’re revving at 8000 RPM then you better give me
180 Nm of torque, or whatever. This engine map is sometimes referred to,
aptly, as the Driver Demand Torque Map as the driver demands a specific output from
the engine by applying the throttle pedal. Let’s just simplify this again by taking
engine speed out of the equation for a second so we can think about what engine maps might
mean to the driver. So, instead, let’s think about the relationship
between the accelerator pedal and the torque out of the engine. So, you’re the driver
and when you adjust the pedal with your foot you’ll have an expectation of what the engine
does - what kind of power gets delivered to the rear wheels.
Let’s do a little graph showing how far the accelerator pedal is pushed down along
the bottom and how much torque the engine is giving you up the side.
Now, the rules state that 0% and 100% throttle must translate to 0% and 100% of the available
torque respectively, so that’s here and here.
We could draw a straight line between these points to create a linear relationship. That
would mean 50% throttle produces 50% torque. 27% throttle produces 27% torque and so on.
And you might think - cool, that makes sense. If I’m a driver that would be incredibly
intuitive to me; I’d know exactly where I am with that.
But consider this - if you’re accelerating out of a slow corner you’ve really got to
be careful of wheelspin: it slows you down and wears the tyre. This happens if you whack
too much torque into the tyres. So you might want the pedal to be more delicate
at first - each cm of travel in the pedal producing a smaller change in torque so you
can manage more finely a smooth increase in torque at lower speeds.
So the engine map would have a shallower graph with maybe the first 30% of the pedal travel
giving you just 10% of the engine torque. This is one of many scenarios that feed into
the Driver Demand torque map. You’ll probably have one more suited for wet weather, where
again wheel spin is a big problem - even at high speeds. You might have ones that are
more or less power intensive depending on whether you’re going full beans in qualifying
or pacing yourself in the middle of a race. Your maps will even vary from track to track,
with a slow, tight track like Monaco requiring a very different feel to, say, a high-speed
circuit like Spa Francorchamps that requires far less fiddling about in slow corners and
much more control at high speeds and high revs.
A big part of this is about driver feel. What mapping helps the driver deliver just the
power they need in the way they like to use the accelerator? Two drivers in the same team
on the same track might finesse their engine maps in different ways through practice.
If you, the viewer, are a driver you should understand this - though it may have become
subconsciously intuitive by now. When you use the accelerator pedal you have a sense
of how the car is going to behave - you know how it feels at different RPM and pedal travel.
Incidentally, there are limitations on how you can build your engine maps. You need to
submit them to the FIA who check you aren’t veering too close to traction control or launch
control - you can see how the art of managing errant wheel spin through a computer is a
little bit traction-controlly. So - the Driver Demand torque map takes in
the inputs from the pedal and the engine to deliver torque as requested in whichever map
is selected. All the different maps needed will be available to the driver via the knob
on the steering wheel. But how does the ECU then get the engine to
deliver the torque demanded by the driver? Well it uses a number of other maps to deliver
inputs into the actual mechanics of the engine to deliver the demanded torque - particularly
the Ignition Timing Map the Injector Timing map.
These two maps are essentially just tables that tell the engine when to fire the spark
plug and how much fuel to deliver into the cylinder by looking at the engine speed, or
RPM and the amount of torque currently on the engine.
We’re not going into the whole mechanics of a combustion engine here but essentially,
engine power comes from a mixture of air and fuel being injected into the cylinders and
a spark plug igniting to flash-combust that fuel mix into driving the pistons.
In the piston’s cycle of injection, compression, combustion and exhaustion the exact timing
of firing the spark plug - the ignition - the the amount of fuel delivered - the injection
- can have quite the effect on the torque output of engine.
So via the ignition and injection maps, the ECU looks at the Driver Demand map, it looks
at the current state of the engine, it looks at other inputting factors like temperature
and fuel mix and works out the exact combustion settings to meet the torque demands.
It sounds complicated but it all happens incredibly smoothly.
The driver sets an engine mapping they desire. They demand torque from the engine by pushing
the throttle pedal a certain amount. The ECU sees this demand and takes a look at the engine,
making note of its current speed, its loads, all the inputs it needs. It then takes these
inputs and looks them up on the engine map, which tells the ECU what it needs to do mechanically
to the engine to get the result it wants. Bear in mind, this is a different mechanism
to the fuel mix settings, which you may know from the Codemaster’s game for its Lean,
Standard and Rich mix settings. While you can map engines to work with fuel mixtures
and lean into the trade-offs of efficiency, power and wear, that kettle of fish is for
another time.
Let’s check in on a few of your questions “Was the liveries video finished before
Ferrari’s cheeky Philip Morris branding?” - actually, yeah! Well I was in the middle
of making it when Ferrari announced a ‘change in livery’. I was so disappointed that they
just stuck a rubbish new logo on the engine cover and that was that. I assume Mission
Winnow is a bottling facility. What’s my favourite livery this year? My
favourite liveries tend to be ones that are a change on the previous year executed really
well. The Sauber livery is really smart, and I’m really in love with what Toro Rosso
have been doing. But I think Renault have done something really nice this year.
And Gianluca asks what would happen is Toro Rosso didn’t actually get a second driver.
Well, if they only turned up with one car the F1 would class them as having not properly
turned up to a race. If the FIA deems you don’t have the means to take part in the
competition your team is disqualified. So they’ll shove Maldonado in there if they
have to. Til next time!