Three years in a Silvia

I was reading through some old posts recently and realised that my blog's been alive for one year today! I've also been driving a Silvia (of one kind or another) for three years. How the time flies (when you're having fun).

I'm really happy with how the blog is evolving - i've made 20 posts in the first year, discussed driving, modifications, and even managed to buy a new car! Over the next 12 months, the goal with the (still new) car will be to improve the lap times further, and hopefully post that 1:10 or better at Wakefield park. I think I can knock another few seconds off that Eastern Creek PB too. We shall see. I would also like to do a skidpan day and a hillclimb if the opportunity arises, and make some small but constructive modifications to improve the package I have.

Speaking of which, there will be a few updates for the car before my next track day at Eastern Creek on the 18th April. At my last outing, there were two key areas which I thought needed improving. The first was braking performance, the second was stability on corner-exit. A third thing that needed improving was me, but that's a given :)

To improve the car's braking performance, I have started with one of the simplest items - better brake pads. I have ordered another set of Project Mu HC+ - I was very happy with them on my Black Silvia and on paper, they are a superior pad to the QFM ones I am currently using. Along with a replacement of brake fluid, there should be a noticeable increase in stopping power next time out.

To improve traction on corner exit, I have bought some adjustable rear camber arms (see below) to allow a better wheel alignment. My car has been lowered on coilover suspension and as a result, the car has excessive camber at the rear which cannot be dialled out without the use of an adjustable suspension arm.

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The car also has excessive toe angle at the rear. An adjustable arm will again allow me to align the rear wheels at a more ideal setup for traction (see below).

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To complete the traction picture, I am also looking for a limited slip diff. This will allow the power to be applied more evenly to both rear wheels, again improving traction. Each of these suspension/drivetrain changes should allow me to apply more throttle sooner (and with more confidence), thus increasing acceleration out of each corner.

That's all for now. If you have been a regular reader, thank you for stopping by and I hope I have shared some useful information. If you feel like discussing the car or want some details on the events i've entered, feel free to email me: ljw8.au@gmail.com

Upping the grip: tyre pressures and temperatures

As I mentioned in my last post, I came across a great little device at my last supersprint which left me very impressed. A pyrometer (see pic) is a basically a temperature sensor, but it doesn't require contact with the object to take a reading. It measures thermal radiation, so you just point it at the object you wish to measure the temperature of and wait for the readout.

For the amateur track day goer, I think this is a great way to add a little "science" to my car setup - the idea being to take a little bit of the guesswork out, and make calculated changes to the car. So how would I use a pyrometer to help with my setup? By measuring tyre temperatures and drawing some basic conclusions from the data.

To maximise cornering grip, we want as much of the tyre touching the road as possible - how much of the tyre is touching the road is known as the contact patch. Wheel alignment plays an important role in maximising this patch, but so too does tyre pressure. If a tyre is over-inflated, it will "stand up" and not use the edges, and if too soft, it will flex - both detrimental to cornering grip.

Using a pyrometer, I can gather some useful information on how hard each section of the tyre is working and thus check if I have a good contact patch. After a session on the track, you can take three readings on each tyre - the outside section of the tyre, the middle of the tyre, and the inside section of the tyre. In this case, we are not particularly interested in the actual temeperature value, becuase it will vary a lot with the conditions. What is more important is uniformity - if the temperature across the three sections of tyre are similar, then the full tyre is touching the road the majority of the time, and thus being used to it's full potential. If, however, the edges of the tyre are cooler than the centre, it may suggest that the tyre is over-inflated. Conversely, hotter edges than the centre may suggest that the tyres are under-inflated. If the tyre is hotter on one edge than the other, it may indicate a handling bias which requires you to make a suspension change. This is pretty basic stuff, but as I said, it gives you an opportunity to inspect your car and take a more educated guess about making changes.

Given that it can read the temperature of anything you point it at, the pyrometer can also be used to monitor the temperature of brake rotors, your gearbox or diff, anything really! All these items have a safe operating temperature range, so I could check these periodically to make sure everything is in check.

So in summary, a great little device. I think that if I made the effort to do this at every track day, along with logging some basic weather information, and track temperature, it would help greatly in determining a suitable starting point for the conditions, and get me into that sweet spot sooner!

SSCC Supersprint: Wakefield, 14th March 2010

I spent yesterday at my second combined club Supersprint - this one organised by the WRX owner's club, and held at Wakefield Park.

I'm fairly familiar with Wakefield now, so I thought I'd have a good chance of improving my times significantly - but was brought back down to size early on. It was drizzly in the morning sessions, and my driving would probably be best described as "dog's breakfast". I was missing too many apexes and braking markers, leading to some off-road excursions and generally average times. In short, I didn't adjust too well to the conditions.

In the last session before lunch, I tried to change my mindset. My aim was to hit my braking markers, hit apexes, and build speed slowly. It was much more successful - I was more composed and the laps were more fluent.

After lunch, it cleared up nicely and I aimed to build a little speed with each session. I went from a best of 1:17 in the morning, to 1:14's, and by the end of the day, a 1:12.9. What pleased me more was that in my final session, I did four laps back to back within 0.2s of each other, suggesting i'd found some of that consistency I lacked in the morning sessions. On a side note, a pair of gloves was an excellent investment - no worries about sweaty hands; a nice bit of extra grip.

The Yokohama tyres were tough in the morning. They're a relatively hard tyre, and it was almost impossible to generate any heat in them. In the warmer conditions with a little less tyre pressure, they felt better but still lacked bite.

I also got some help from one of the SSCC regulars, Shane. He has a beautiful red Corvette which he's been taking to the track for ages, and he's pretty experienced. He commented that my rear wing angle was quite agressive, and might be hurting my straight line speed. By agressive, he means that the angle of the wing relative to the airflow is large. If you reduce the angle, less downforce is produced, but also less drag. And so there is a trade off - more straight line speed comes at the expense of some downforce. Shane reasoned that I probably had an adequate amount of rear grip, so the extra straight line speed may be more beneficial than the extra downforce.

And so in the last session of the day, I flattened out the wing angle. My top speed increased by around 5 km/h. Success? Maybe. The important thing to note is that there are several variables involved. It may just be that I was getting a better exit on to the straight, and so my top speed was naturally higher. This is why I value consistency in laps too - if you can lap consistently, it makes it easier to identify whether changes to the car have been valuable or detrimental.

Shane also game me some useful info about a little device called a pyrometer, which i'll make the subject of my next post.

I also took a bit of footage of the afternoon sessions: