Going Critical... the first 10 seconds of a sprint at Goodwood

I though it might be interesting to analyze exactly what goes on in the mind of a driver at the start of a sprint. The recent Going Critical program that used a timeline to describe exactly what occurs before an incident has fascinated me. So armed with the data logs from my car, here is my "Going Critical" description of what I go through on just the first 10 seconds of a Sprint at Goodwood. The description is based around the data log taken from the car on its run.

Time -5.0 seconds

The red light is on. The green light will start within a few seconds. At this point the car is in first gear with the clutch depressed. The engine revs are increased to around 2500 to 3000 rpm. The instruments are checked to make sure there is no problem such as low oil pressure or overheating. It is tempting to look at the car ahead and see what he is doing and if you can get any inclination of what the conditions are going to be like. The best thing is to focus and concentrate on what you need to do and to get the sequence right in your head. If you have to think about it, it will be slow, such is the timing involved.

Time 0.0 seconds

The green light is on and it is time to go. The engine revs are raised to around 3400 which gives about 300 bhp and 300 ft/lb from the engine. The clutch pedal is raised to start delivering the power to the rear wheels. At clutch bite, the rear wheels start to move. This does not mean that both front and rear wheels will normally move together. The data log shows that the rear wheels start moving some 0.03 seconds after the front wheels and the car has started to accelerate. This is due to the characteristics of the data logging system and nothing more magical. What is important is that this has been a good start with both front and rear wheels moving together, virtually from the beginning. Getting this wrong can result in the rear wheels registering 20-30 mph while the car is stationary and a very slow getaway. It is impressive and slow and unfortunately you don't get prizes for style!

The clutch position is held and the throttle pressed further increasing the engine revs and the car's acceleration. With the car moving, the clutch can be fully engaged and the throttle pushed hard to the floor. The ECU detects this and increases the fuelling to the engine to improve the response. The engine is now on full throttle with the butterfly fully open. The fuel pumps behind the driver stir into action and deliver up to 1 litre of fuel every 10s to maintain the fuel pressure and demands from the engine at this point.

Time +0.6 seconds

The car has now reached 13.6 mph. At this point the car is accelerating at around 0.8 G

The rear wheels start to accelerate faster than the front and rear wheel spin has started. In 0.1 of a second, the rear wheels spin up to some 10-15 mph faster than the front wheels. This exceeds the threshold defined in the traction control system and this intervenes by switching off some fuel injectors to reduce the engine revs and power. The engine revs drop from 4250 to 3500 and the rear wheel speed matches the front again. The small bump in the data log shows that the traction control initiated a level 3 intervention to bring this under control. This took less than 0.6 of a second to complete without the driver having to lift off at all.

Time +1.0 second

The car is now accelerating rapidly and is already at 20 mph. The next critical point is the gear change from first to second gear. At 2.06 seconds the engine reaches 6000 rpm and the ECU lights a high intensity red LED in front of the driver. It is probably less time than most people take to read the last sentence. The red disco lighting inside the car is the unmistakable signal that the engine rev limit is approaching and that a gear change is needed. This coincides with peak power but not the rev limit. With a normal V8 engine with hydraulic lifters, these levels of revs are a no go area because the engine was not designed to rev to these limits and the gear change should have been made a lot earlier. With this engine capable of 7000+ rpm, the higher revs means that when a normal V8 starts to run out of steam, the engine is just reaching its stride. At this point, the engine is providing over 150 bhp more that a 5 litre Griffith or Chimaera at these revs.

As soon as the red light comes on, the drivers reaction time comes into play. 0.3 seconds after seeing the red light, the driver lifts off the throttle, depresses the clutch, selects 2nd gear, engages the clutch and floors the throttle. At the throttle lift off, the engine is just approaching the ECU controlled rev limit of 6250 rpm but never reaches it and thus does not experience the rev limiter coming in and reducing power and acceleration. With the butterfly closed, the ECU attempts to shut off the fuel supply to maintain the mixture but it cannot quite manage this. The excess neat fuel goes through the engine and out into the exhaust where it ignites and produces a jet of flame from the rear exhaust on some occasions. When the clutch is engaged and the throttle applied, the rear wheels will spin as some 300+ bhp is again pushed through the clutch. This wheel spin is detected by the traction control system that then intercepts the signals from the ECU to the fuel injectors and cuts the fuelling to reduce the power from the engine. This brings the wheel spin under control within 0.3 seconds and the car continues to accelerate. This is felt by the driver as a violent wiggle as the rear of the car tries to overtake the front due to the wheel spin. It requires an instinctive slight application of opposite lock or simple grin and bear it. It is heard as the tyres chirrup with the sudden stress that the experience. Again the foot is firmly planted to the floor. The gear change took less than 0.7 seconds and the car is now doing 41.5 mph. It is only 3.2 seconds since the car left the line.

Time +4.3 seconds

At this point, the magical 60 mph figure is reached while in second gear.

The car continues to accelerate and will spend less than 3 seconds in 2nd gear. The revs will increase until the 6000 limit triggers the gear change LED and the second gear change is started. This takes the same time as the first and again the rear wheels spin when the clutch is engaged but the traction control takes care of this and the throttle remains firmly planted to the floor.

The car continues to accelerate and up to now the main concern has been with gear changes and keeping the car in a straight line when it wheelspins. This is by and large automatic and doesn't require too much thinking. What does require some thought is what to do with the car when the straight bit ends. At this point, the driver has to start analyzing the situation to work out what he needs to do to get round the Madgewick hairpin. This is a double apex bend with a high entry speed and an even higher exit speed. The first reference point is where the change from 2nd to 3rd gear took place. If it was later than normal then there may not be enough time to get into fourth gear before the corner. If this is true then the entry speed may be low enough to simply lift off the throttle to reduce the speed for the corner. If the brakes are used, the speed reduction may be too much and a slower entry taken. This results in a slower exit on the back straight and the loss of a couple of miles per hour in speed has a big knock on effect.

If the change took place earlier, there may be time to change into fourth gear and gain more speed and a quicker time down the straight. This will require a firm application of the brakes to reduce the speed to that needed to get round the corner while staying on the track. With a double apex corner, the turn in is for the second apex and the first one is ignored. It is also important to get the car positioned so that there is enough space to brake before turning in. At this point, the driver is now working out the options, making a decision and steering the car. Part of these equations is an estimate of how much grip is there? This is the first time out and is the track in one of its magical states where there is plenty of grip to help you or is it in one of those "I'm going to catch you out!" states? The only way is to use the feel of the car and the track conditions and experience to gauge how far you can go. How does the car feel? Does it feel right to push it to its limit? Unlike a track day, there are no cones, markers or other traffic to help guide you. Unlike a race where you can recover some time on later laps when the tyres have got to temperature, the car is running on cold tyres and it has to be right.

Time: +7.5 seconds

The car is now doing nearly 90 mph and still accelerating. The decision point is fast approaching as the rev limit in third gear is now only 0.3 seconds away. The decision has to be taken just before the 6000 rpm limit is reached. If the decision is to stay in third and feather the throttle using the rev limiter, then a late decision has little impact. If the decision is to go for fourth gear, then the change must be fast enough to get some drive and restore the car's balance. It may be worth changing up slightly earlier to ensure this can be achieved. The driver has to work out whether to change gear and when, how much braking if any is needed and how to position the car to get the space to do this. It is only some 7.5 seconds since the car has left the line. The position of the car is established by visual clues such as changes in the tarmac colour and surface, different signs and objects on the side of the track and how much of the scene is in the driver's vision. This is done automatically without conscious effort from the driver: With the car travelling at over 100 feet per second, just taking a split second could mean the difference between braking corrrectly or 10 or 20 feet later and not making it round Madgewick. It's make your mind up time.

Time: +7.8 seconds

The decision is taken to change gear, immediately despite the fact that the engine has only reached 5600 rpm. This short shift is a slightly conservative strategy in that it will ensure that 4th gear can be used to accelerate the car further by changing up earlier and giving the car space before braking. The disadvantage is that this will take 2 to 3 tenths off the 0-100 time but does ensure that the car will get round the corner. Holding onto the rev limit in third is faster but needs the both time and distance to ensure that the gear change can be completed before the car enters the braking zone and corner. The combination of no drive and a car that is out of balance is not a pleasant one.

The car is now in fourth gear and still accelerating. This is where a game of chicken comes into play. How late can the braking be left? How long can the throttle be left flat on the floor? How much braking is needed to reduce the current speed to that needed for the corner entry. How hot are the tyres and how much grip will they provide?

Time: +9.2 seconds

The car has now passed the magical 100 mph mark and is still accelerating hard. The short shift into fourth has cost just over two tenths and in hindsight there is enough time to have stayed that touch longer in third. The driver now starts to experience onrush where the corner starts to rush up as if time is increasing. This can often trigger a panic reaction, especially if the driver has not decided what to do. With the car doing well over 100 mph, a panic reaction is not a good idea. At this point, the self preservation side of the brain starts reminding you of the laws of physics. It starts with a gentle reminder and then starts screaming for you to do something. All this is going on while you are trying to calculate what to do. The last thing you want is part of your brain screaming commands that are pretty well obvious that something has to be done. Now. Not later but NOW. Before it is too lateÉ Keeping a clear mind at these times is essential and requires preparation and practice. However, the turn into the corner is still approaching rapidly.

In a practice run, a less risky option of braking a bit earlier is usually adopted. This will ensure that the car will get round the corner but will sacrifice a little speed. Practice times don't win prizes. On a timed run, the braking can be left later by straight lining the first part of the corner and using this to get the speed down. This is a risky option as it requires fine control to prevent the rear of the car breaking away and causing the car to go spinning into the gravel trap. Straight lining describes the intention rather than the end result as left to its latest point requires braking while turning in which goes against everything most TVR drivers are quite rightly taught of break in a straight line. In addition there are some bumps on the later part of the corner that makes the car go light and can cause it to start moving. Applying the power too early on these bumps can cause the car to spin. Applying the power too late and the exit speed will be slow.

Is this the first or second apex at Madgewick? Decisions... Decisions...

Time: +10.2 seconds

"At last," screams the self-preservation side of the brain, "you are doing something!"

A slight lift on the throttle is used to get the car better balanced before the brakes are gently applied. With last year's car, no braking was required because it was slower and arrived at about the right speed. This year is different and positive action is needed.

Time: +10.7 seconds

The brakes are gently applied for 2 seconds and take some 15 mph off the car's speed. The braking area is not quite straight and is slightly curved. This means that the braking is not an on-off but is carefully applied so that when the car starts to turn in, the car will not spin off despite the fact that the braking is not completed. It is like steering with the brake pedal. Too much and the car will start to break away. Too little and the car will understeer and go off-roading. The key is all about balancing the car, while matching the car's speed to that needed to make the corner apex. This technique uses the weight transfer to the front under braking to increase the front tyre grip and get the car turning in. The car is travelling at around 90 mph at this point And yes, this is the entry speed into the Madgewick hairpin and not the speed down the straight.

With the car now starting to corner, the driver has to sense exactly what the car is doing from the physical feedback. The term of driving with the seat of your pants is very accurate. The physical forces that are pushing the driver into the side of the competition seat and against the seat belt. The car's movement can tell the driver how much power can be applied. Get it right and the car can be on full power before the exit and the car will have accelerated out of the corner and will be doing around 100-110 mph at the start of the main straight.

So are we competition drivers Hogwarts alumni? I'll leave you to make up your own mind!