Results from the PowerBox

You can see in the videos from the previous Motorkhana I had a small box mounted on the windscreen. This is a PerformanceBox, a GPS-enabled device that captures all sorts of real-time information on your driving. For example, it will record:

1. Speed
2. Direction
3. Rate of turn
4. Distance travelled
5. Radius of corner
6. ...and many more

The use is that I can objectively look at what I'm doing in the car in far more detail than my memory, or even the video, provides.

For example, in my last post, I was talking about how I needed to brake 15m before the corner, to scrub off 20kph to turn in at 80kph. But was I doing that? Not really....

From the data, I can see where I started to lose speed, where I started to turn, and the distance between the two. I can also see the speed at which I take the corners. What I can see is that I start slowing 40m before the turn instead of 15m, and I'm doing about 40kph through the turns....

Now you're probably thinking - what a clown, he doesn't even know what speed he's doing in a corner. To you I say - fair point, but there's a lot going on right then. All my limited brain power is focused on keeping it in the right direction.

Another interesting thing is I'm not braking hard enough. Looking at the rate of change in speed, I would expect to see a linear curve going upwards, which is the rate at which I can accelerate, which is a pretty straight line up to the 100kph max for the circuit. However, the brake profile is about the same pitch, just opposite. I would expect it to be much, much steeper, as I'd expect to be able to scrub off speed faster than I could pile it on. As they're the same, I might take a look into the brakes and how I'm using them.

You can also overlay results from one lap onto another, so you can see where I'm braking later, and the overall effect on speed, and where I'm coming out of corners faster. Once you get the hang of the software, it's actually quite interesting seeing what you're doing.

I get the feeling it would be a lot better on a closed loop like Barbagallo, where you cross a start finish line repeatedly, so you can get a number of contiguous laps.

March 8th Motorkhana

Ran another one of AEM's Motorkhana events last weekend. And with my best result yet - came 5th overall. About bloody time too. The car is too good to be running in the 20's. It's just a shame the driver isn't there yet.

I have to say, however, that 5th place was earnt mostly through not stuffing up, and the car basically behaving itself. All the other Birkin drivers had their dramas throughout the day. Frank's gearbox wasn't happy moving to second (leading to some interesting gearchanges), Conrad managed to go straight past a turn at full throttle in third, necessitating a rapid reverse back onto the course, and Tim had a shocking first round. He managed to hit a cone, then turn his engine off with his knee hitting the key, then overran the garage. Mind you, this was his first attempt at this event, and his final run was the 10th fastest of the round.

You also have to keep in mind that the timing is done by hand. I came ahead of Frank by 0.2 seconds, which is 0.05 seconds per run over four runs. Now you cannot tell me that someone with a stopwatch is that accurate.

Round 1 was the usual 'getting to know you' run. A bit of oversteer, which is becoming standard for my car at the moment, and needs some looking into. I also found the new tyres a bit glassy still, so the first run scrubbed them up well. The comment I got coming back in was that I was braking far too early - a few pointers of where I should be braking, a few 'you must be bloody joking' comments later, and I had a plan in mind.




Round 2 was where I implemented the plan. I think I did what I was supposed to. It all becomes a bit hard to follow, really. Unfortunately, my main evidence was going to be the video, but there's no sound this time around and therefore I'm not 100% sure of where my braking points were in reality. I know they were supposed to be around 15m before the turn, which when you're travelling at 100kph (my little Performance Box doing its thing), is half a second before the turn. In that time you have to brake, upshift to second, and begin the turn. Personally, I can't believe that's right, but I look at the video and it seems to be correct.

Mind you, I'm not stopping for the corner, so all I'm really doing is scrubbing off enough speed to make the corner. So for some of them it's probably just knocking off 20kph, as I can take some of these bends at 80kph.

The key difference was the time - I dropped 0.9 seconds from one run to the next, which is actually huge, and worth several places over four laps. Unfortunately, I forgot to set the video on this run.

Rounds 3 and 4 - well, pretty much the same, really. Just focusing in on braking points mainly.





Again, a lot of fun. Each time I get out of the car I'm shaking from the adrenaline, and I'm exhausted at the end of the day. I don't know how people do hours of racing.....

I'm going to have a look at the results from the Performance Box and see what my braking points are like - what speed to I drop to, where was I quicker etc. There may be some insights there, or perhaps just too much data for me to cope with.

Breaking stuff

It's always a good idea to go over the car the day before any sort of event, so that you can break all the things you would normally have broken when it really mattered.

Saturday was spent in the workshop, which is something I haven't done for a while. The idea originally was to just go over the car with a spanner and find anything that had worked it's way loose. It turned out to be a little more than that. Interestingly, whilst a lot got done on the car, very little of it was done by me....

First job of the day was the halfshafts - these are the bits that come out either side of the diff and go out to the wheels, and provide the drive to the rear. They weren't seated properly in the diff, which whilst wasn't a terrible thing, meant that the diff would throw a little oil out. This eventually would be a bad thing. So it was out with the tyre lever and a bit of leverage later, one was in. The other required removing the rear wheel, putting a long piece of wood against the CV joint, and whacking it as hard as possible with a hammer to get it seated in. Now both are clipped into the diff. This has also made the speedo a little more reliable - the speedo works off a hall sensor that 'reads' the number of bolt heads that go past it in a second. These are now closer to the sensor, so that it gets fewer false readings. So I no longer do 80kph sitting at a red light....

One of the characteristics of my car has always been a heavy clutch, heavy accelerator, and a sticky gearshift. I've always just taken this as part of the car, but apparently, these are bad things ;-) It got to the point where someone was testing out the accelerator pedal - and broke the pedal. Yes, you had to press hard enough to bend a 4mm ali plate. This probably indicated a problem.

It was at this point that my car became cause celibre for others for the day. I had at least three people working on it, with me sort of spectating, as the entire throttle cable was removed and replace (somehow the outer sleeve had been damaged), and the link to the throttle bodies themselves was re-engineered. I have to say the change is dramatic - the pedal throw is longer by about 30%, but there's a massive reduction in effort required. Not that it was hard work, it's just that you can't control things as well when the pedal movement isn't progressive.

The other area was the gearbox. Ever since I've had it in the car, the movement has been really, really heavy. We put a short-throw lever on it which probably just made it worse. So Frank re-worked the gear lever, making the throw a little longer, which has again made it a lot easier. It's still some way off what it should be, and perhaps the next time I have the engine out, we'll take the gearbox apart and see what's what. Perhaps a selector fork is bent, or something is causing excess friction somewhere.

There's a list of tasks for me to get on with over the coming weeks - I'm down to part time again at work, so I'll have a few days to spare to focus on the car.

The things to do are:
1. Pack the gear lever forks with grease - hopefully this will make the throw easier still
2. Redo the diff mounting plate - the mounting bolts keep working loose. These need an allen key to tighten - but the mounting plate covers the bolt head. These are coming out and are getting replaced with hex heads, but it does mean taking some of the back end out
3. Sort out the engine bay - put in the engine breather tank to take oil off the top of the engine

And, of course, what-ever else turns up, as it seems to do every time I look at it ;-)