Oulton Park, 19th July 2005
This was a day spent with Tim Harmer trying to drive faster around Oulton Park. Outline write-up is here. What follows is a corner-by-corner discussion of the data logs. In each case I will just use the DL1 quick graphs as they're easier to sort out. In all cases, the colours are: black Tim Harmer's fastest sector time red My fastest time from the first, and dog slow, session of the day. green My fastest sector time. Each sector discussion has a thumbnail of the main graph; click on this for a larger version in a separate window. This graph includes some of these traces: GPS derived corner radius Longitudinal acceleration Time slip, which will always be in comparison with one of the other traces, the one that's flat on this part of the graph. (In some cases this trace is taken by the understeer/oversteer balance trace derived from the yaw rate gyro.) Throttle position; this seems to be a good measure of how the car is being controlled. GPS derived speed. Understeer/oversteer balance. This, usually very wiggly, line shows you something about how the car's yawing. I'm not really very good at interpreting it although it is usually clear when the car is getting close to its limit when you can really see it big yaw angles building up. Steering angle. There are also graphs of the appropriate g-circle. In this case just the black and green traces are shown. Corners The following corners appear below: Old Hall Cascades Island/Shell Oils Hairpin Britten's Knickerbrook Druids Lodge Conclusions There's some of these at the end too.
Old Hall	top
This is the right hander after the start/finish straight and leads onto the fast downhill track down to Cascades. Times Tim Harmer: 15.59 (fastest) Me, first session: 16.00 secs Me, third session: 15.68 secs
Observations I start braking an age before Tim does, although we actually get back on the gas at about the same point. I manage to make a less sharp corner of it (minimum radius for me is 97m, for Tim it's 87m). However, as my minimum speed is actually lower than Tim's, by about 2mph, I must have slowed down too much. I'm on full power a bit before Tim, possibly as the end result of taking a wider radius, so actually I'm about 2mph faster on the run down towards Cascades. This effect is maintained even though I suffer an attack of the magical lifting right foot at the end of the sector. The g-circle shows that Tim braked much harder than me (0.8 rather than 0.6g). Apart from that the g-circles are much the same, although Tim seems to have managed a spike up to about 1.4 lateral which is fairly clever. The time slip graph shows that Tim made up time in the braking part of the corner and then progressively lost out as I was quicker out of the corner and away from it. Tim is less smoothly on the power than me, probably as a result of not knowing the car. This might be the reason for him not being on full power until a few metres after me. I was really rubbish in the first session, before Tim started shouting at me.
Conclusions So, I need to: Brake later and harder, although I could probably have got away with it if I'd just not slowed down as much. Don't lift off. Tim pointed out to me that that probably unsettles the car more anyway.
Cascades	top
A fast left handed sweep onto the Lakeside straight. Rather an odd downhill entry with the camber changing all over the place. Times Tim: 13.91 Me, first session: 14.32 Me, third session: 13.79 (fastest)
Observations All the same the issues are pretty much the same at this corner: I'm slightly ahead at the start but that soon disappears as I brake earlier, again. What's more, I seem to arrive on a bit of a trailing throttle anyway scoring just 80% on throttle position. Mind you, the red trace is really awful so I did get a lot better during the day. As expected really, the early braking makes surprisingly little difference. I actually slow down to about 1mph lower than Tim, although that's at a slightly later point on the track. It says in all the books (such as the Skip Barber book which is highly recommended, by the way) that you can brake early, especially if you modulate the braking a bit so that you don't end up going too slowly. Tim uses the throttle much more aggresively then me and gets into it earlier. However, he has to back out of it when the yaw angle climbs rather high and he's ultimately back onto full throttle about 10m further down the road than me. The bigggest problem that Tim had here, I think, is that he was in one gear lower than me as he went around the bend. Hence he has to change up about 2/3 of the way round the bend which costs him about 0.2sec off the throttle. As that's about the amount of the missing time that's probably what the problem was really. Astonishing performance when you consider that he'd only got into the car a couple of minutes beforehand. I seem to have slowed down right at the end, as can also be seen on the g-circles which, apart from that downwards green bit, are pretty much the same. One difference, though, is that in the horizontal part at the top of the traces, which corresponds to the corner exit as the steering input is removed as the car accelerates away from the corner, the green trace is consistently above the black trace. I think this is because the gearchange that Tim had to put in, which is the triangular segment at the top left of the chart, put him backwards which he could never recover from. This makes you realise why choosing the right gear is so important, even when changing gear takes so little time. I don't know why I got out of the throttle so extremely at the end of this sector. There may have been something in the way. All the same, I lost about a tenth as a consequence.
Conclusions Not really very surprising: Brake more firmly bit not too early. However, it isn't a big problem as long as the amount of deceleration is modulated into the trail-braking segment. Get on the power as firmly and as soon as possible.
Island/Shell Oils Hairpin	top
A sequence of corners. The first being a fast left hander on the way into the Shell Oils Hairpin which is a tight hairpin which has some effective banking allowing a really fast corner. You do, though, get spat out of the banking at the end of the corner which is a bit exciting. Times Tim: 25.27 Me, first session: 26.74 Me, third session: 24.63 (fastest)
Observations This time Tim is quickest into the sector. He brakes later but harder for Island and takes a much better line than me meaning that he makes up time down to the hairpin itself. Tim uses the throttle much harder between Island and Shell Oils although he doesn't seem to pull ahead much, although it's only a short sprint. Oddly, the US/OS trace here shows a sort of oscillation on Tim's trace, as if the car is oscillating in yaw with a frequency of about 0.8 second. Tim mentioned at the end of the day that he thought the car felt different at the front and back, although this might be due to the much larger weight than usual at the back. I wonder what this is? Again (!), he brakes later for the hairpin itself. Also, he again brakes harder but this time probably overdoes it as he ends up going slower round the corner itself. Tim's minimum speed is 46mph and mine is 48. Only a small difference but it does seem to matter. The g-circle clearly shows how much more Tim brakes. Both Tim and I get onto the power at about the same point but this is one of the laps where Tim has huge trouble changing up as he exited the hairpin and you can see that his speed trace goes sort of flat. I think it's clear that he would have been miles quicker than me here without this. As it is, I overhaul him here. Firstly as a result of just going round the apex very slightly quicker, but mainly because I actually manage to accelerate away from the corner. Comfortingly, we both score a similar number on the lateral g around the hairpin with a number of about 1.3g. The high number is probably a result of the banking as 1.2 is about all that's achievable normally.
Britten's	top
This is a little uphill left/right/left chicane on the run away from the hairpin. It's quite important to the lap times as the car needs to keep speed up for the run down to the Knickerbrook chicane. Britten's used to be called Foulston's but has changed for obvious reasons. Come to that the Knickerbrook chicane is properly called Hizzy's but I propose to ignore that. Times Tim: 15.75 Me, first session: 16.24 Me, third session: 15.42 (fastest)
Observations Yet again, I come in on a trailing throttle an Tim brakes hard at a sensible place. Tim puts in a little spurt on the throttle between the first and second apices but this almost seems to unsettle the car. Again, there's that oscillation Again he brakes harder tha me and ends up going around the second apex a good deal slower than me. I fact he's about 6mph slower than me. A good deal of this is probably because my corner radii are rather larger than his, as a result of me using much more of the kerbs. Tim kept telling me not to do this. However, I wonder as there are places where it seems sensible. The little blast he gives on the throttle between the first and second apices is what gives that diagonal line on the g-circle. We both seem to get on the power at about the same point although he's much aggressive about it, again. Again, though, the earlier version of me is much more circumspect. In this case the higher minimum speed seems to pay off and my trace is about 1mph faster than Tim's all the way up the hill on the way to Knickerbrook. Tim seems to get a better line on the third apex with it not even counting as a corner on this trace, which is limited to a maximum radius of 200m. However, this doesn't seem to make much difference, presumably because the 150m radius of my corner is still effectively flat.
Knickerbrook	top
This is another chicane, although one that's right/left/right and rather larger than the previous one. Times Tim: 19.45 Me, first session: 19.53 Me, third session: 19.23 (fastest)
Observations This is getting very familiar: Tim brakes later than me but rather deeper and therefore loses out in minimum speed terms. He's again much more aggresive on the throttle but again he seems to unsettle the car rather. This time there's an even larger blip on the US/OS trace. This time the steering angle trace, which isn't shown, shows a couple of opposite lock steering corrections. What you can see is the throttle modulation that he has to use to control the car. Again, I seem to have got an easier line as a result of using more kerb.
Druids	top
A very fast and rather daunting right hander at the top of the hill after the run up from Knickerbrook. There seems to be some dispute as to whether it should be treated as a single or double apex corner. Tim was pretty awesome through here. What's more, it's the one corner where I got slower through the day...:( Times Tim: 18.33 (fastest) Me, first session: 18.65 Me, third session: 18.71
Observations Basically, I'm rubbish at this corner. The main effect is that Tim has a much better line, which he tried to show me but I didn't really get the chance to try it properly. You can see from the radius trace that his line is more closely a double apex bend with both apices a larger radius than anything I managed. Ho hum. The g-circle shows dramatically how I got worse at this corner. I need to go to Oulton again and have a better go at this corner.
Lodge	top
This corner looks like it ought to be a fairly normal late-apex right hander. However, I seem to be capable of making a real rodent's posterior of it on every occation I went past. Something else I need to go back to... Having said that, I seem to have the fastest time, which is a bit alarming... Times Tim: 18.00 Me, first session: 17.44 Me, third session: 17.41 (fastest)
Observations All the things said up to now seem to apply to this corner. However, I don't know how I managed this as I seemed to be on a different bit of the track every time. What is interesting is the g-circle where I seem to have scored over 1.4g lateral!
Overall conclusions	top
The more I look at this the more obvious it is how useful the day was, pity it had to be short-cut due to the engine falling out. I need to concentrate on getting more consistent lines, and probably looking at these logs more carefully while at the circuit. I guess being more aggressive on the throttle on the way out of a corner is necessary too, and probably trying to build up more confidence in car control so that I can hang on to things when things get pear-shaped.
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