March 31st, 2015
First let’s talk about how to use your Aim Solo. I have a suction mount for mine and I stick it to my windshield in a spot where I can see the lap times well, it doesn’t obstruct my view and I can reach the buttons while I’m belted in. If you are at a track that is already loaded into the system then all you need to do is turn it on and start doing laps. It will automatically start telling you lap times are you cross start/finish. If you are going to the Ridge make sure you set up that track first as I’ve detailed in a previous post. All other tracks should already be in the system.
When you first turn it on it searches for the GPS satellites. Once it has a good signal from enough of them it is ready to go. You should get something that looks like this:
Except for the “bitchen” part. I stole that image from the Aim site as you can see! Anyway it’s not quite what it looks like when you start. Above the the big lap time there should be text that says Static. This means that is is showing “static” lap times which I believe means that above the big lap time it shows your best lap time in smaller text. I’m not really sure. The reason is because I never use that mode. Instead I use what is called “predictive” mode. To change to that mode press the right-most button. Now the top text should say “PredT”.
Predictive mode can be a very useful mode for learning how to go fast. Basically what it does is predict what your next lap time is going to be. You can look at it at any point on the track and it will show you what it thinks your lap time is going to be. It does this by looking at previous laps and your current lap up to the point on the track you are currently at. So for example you could try a completely different line through a turn and after that turn look up and see whether your predicted lap time has gone down or not. Another really useful thing for predicted lap times is handy if you race and are qualifying. You can see if you are halfway through your lap and you are going faster then you know to keep pushing hard. But if predicted time tells you you’ve already blown it. Might as well cool your tires a bit and try again on the next lap. This is fun on track days as well. If you track a lot you know what your best lap time at track is. If predicted is showing you beating that, it gives you that little more incentive to push hard, not screw up and try to beat it. It’s always exciting when you beat your best time. Another interesting thing that it does is show you how even a small mistake trashes your lap time. Say you’ve been looking at it so you know what it thinks you’ll hit. Then you blow a braking zone and miss an apex and boom, 5/10ths goes out the window instantly. As greats as the good news it can give you is, the bad news can be a bummer as well.
On the right hand side of device is a little door you can open. This is where the USB connection is that we will use to download data to you PC.
There are two types of Aim Solo’s. The Aim Solo and Aim Solo DL. The DL version allows you to connect to the CAN bus in your car and collect extra data. The extra data available depends on your car. The DL is interesting, but I’m able to do everything I need using the cheaper version. The cheaper Aim Solo provides the following data in addition to the lap times which we will use to help us go faster:
- Longitudinal Acceleration - G force while braking
- Lateral Acceleration - G force while turning
It records these values many times a second for each lap. With just these three values we can do all sorts of interesting things to help you go faster. [Technical caveat since I know there are a lot of techies out there: It's not really recording G forces. It's just calculating them from GPS position data.]
Next time we’ll talk about how to download data from the device to your laptop and look at it.
March 30th, 2015
This post needs to be updated with the lastest education from Greg Fordahl. Simplest explanation is that center temps will only tell you if you are wildly off. Then you need to work harder from there.
This topic has come up at almost every track day I’ve been to this year. And just now I had someone in a corvette forum telling me I was wrong in my recommended hot tire pressures. So I’ve copied my post I put over there to here.
If you are running the stock tire that comes with the car, which I am. You will find that if you correctly determine hot track tire pressures using a pyrometer that the optimal pressure you get will be very close to the recommended OEM cold tire pressure. Why is that? Because the OEM tire pressure is generally set to put as much tire tread to the ground as possible. When the air in a tire heats up the tire expands slightly. That will cause the center of the tire to bow out slightly. If it the center bows out then you will not be using the outer portions of your tire to their maximum affect. You will also get uneven wear on the tire. During normal street driving a tire heats up very little. If you set to OEM cold 30 they may go up to 32 as a max. Hence you are still using the tire effectively even after they warm up.
When you take a car to the track and drive it hard. The air in the tires heats up high amount. For example if you start at cold 30. Do a 30 minute session and then come in and check your tire pressures. You will likely find that they are somewhere around 40+ on the Sport Cups. At that temperature you are riding around on the center portion of the tire.
How do you know that is happening? And how do you measure it? You use a pyrometer. A pyrometer measures heat in the tire. This is what one looks like: http://2.bp.blogspot.com/-eCo_YVSlkf…1600/50640.jpg. I prefer the needle kind for tire temps. I don’t think the infrared works as well. You take the pyrometer and measure tire temps in both outer portions of the tread and the center. So if you do that let’s say you get the following numbers: left-100 center-120 right-115. You can see that the center number is higher than both outer numbers. Than means you need to lower your tire pressure because the center is being overused. The optimal pressure will give you a center temperature which is the average if the two outer temps. If the center is lower than the average than your pressures are too low. These three temperatures can also tell you a lot about alignment but that is a whole other discussion.
The way to test this is to do a session and then come in after your last fast lap without any sort of cooldown. You don’t want the tires to cool down too much until you take the temps.
If you have a lot of track or race experience, on street tires you can feel the difference in handling of 1-2 pounds over. it is significant. On slicks you can start to feel things at even lower differences than that. Correct hot tire pressures are hugely important to going fast.
The amount that the air in your tires will heat up varies tire to tire. That means although it’s easy with a pyrometer to find the hot pressure, it takes some trial and error to find our how much air you should pull out of tire before your first session to hit your hot pressure. One way to get a goof starting point is if you’ve gotten the tire to their optimal hot pressures. Then drive the car home on that. Then next morning measure the pressures as it sits in your garage. They should have full cooled and that number gives you a good starting point. I would start out 3 pounds or so higher than that and work your way back down after each session.
March 29th, 2015
One of the reasons I’ve resurrected this blog is because I’ll be doing data support at all of the Cantrell Motorsports local track days this year. I’ll be using this blog to talk about the ways I use data to help a driver go faster. That way you can learn to do it yourself as well.
The current list of track days are:
- Friday May 8th Ridge Motorsports Park
- Wednesday May 20th Pacific Raceways 9am-9pm with twilight lapping.
- Friday July 3rd Ridge Motorsports Park
- Wednesday July 29th Pacific Raceways 9am to 9pm with twilight lapping.
- Friday August 28th Ridge Motorsports Park
- Saturday & Sunday October 3rd and 4th Ridge Motorsports Park
See you at the track, bring your Aim, CMS Lap Timer or whatever and we’ll figure out how to make you faster.
March 29th, 2015
For anyone other than the very experienced track driver it can be difficult to tell whether you can really go faster or not. It’s also difficult to tell whether you have a lot left to go as far as speed through a turn for example, or not. So the question is how do you learn to do that? Eventually you will be able to determine this through a “seat of the pants” feel by feeling what the car and tires are doing. But until then, how do you work your way up to that? Another question is that you may be timing your laps so you know your best time at a track. But for some reason on this day, you just can’t hit that time any more. How can you figure out what you did before that made you go faster.
For me the answer to both those questions is data acquisition. I’m not talking some fancy, expensive Motec system like in a race car. Most simple lap timers, if they have PC software that goes along with it can give you valuable information. I have a lot of experience with Aim systems since that is what I used when I was racing my Cup Car and the Aim Solo lap timers use the same data analysis software as the full-blown race setup does. With that timer and that software you can gain some valuable insights into how to improve your driving.
I’ve done a lot of data acquisition analysis for other people, including experienced drivers. Over a number of years I’ve developed a set of things that I look at with experienced driver that can tell whether you have things to work on or not and where on the track.
The first is whether you are using the capabilities of your tires to their maximum. If you are running something that is close to a sports car on the track (or in other words you don’t have ground effects downforce!) then your tires can give you only a certain level of grip while braking or turning. This is true whether they are street tires, DOT Hoosiers or Slicks. You’ve probably heard this a hundred times already, but if you are using all of that grip for braking, there is nothing left for turning. But that true statement also provides you with an interesting way to use data to determine if you are simply going way too slow through the turn.
I’ve found that for most people they know how to brake the car hard. They might not know where to brake, or how to transition off the brakes but they can brake the car pretty hard. That fact gives you an important piece of data that you can use for analyzing your mid-corner speed as well. If you can brake you car hard in a straight line you can measure the amount of G’s (in this case longitudinal G’s) that you are pulling when you do that. That amount of grip is close to the same amount of grip that is available to you in mid-corner when you are not braking at all but are in maintenance throttle. So if you measure your max G’s at mid-corner (these are longitudinal G’s) you can then check those two numbers against each other. If your mid-corner number is lower than your braking number then you can go faster.
Next I’ll show you exactly how to do this using an Aim Solo and the Aim Race Studio Analysis software.
Caveats: The track surface, track camber and so forth have an affect on all of this. So you need to take that into account to some extent. As does the car itself, front engine, rear engine and so forth. I’ll go into the details of that later.
March 29th, 2015
When using the Aim Solo most of the time the start/finish point for a track is already built into the system. So all you have to do is turn it on and drive. Unfortunately the start/finish for the Ridge Motorsports Park is not already included. So if you want to use your Aim Solo there you will need to set your own start/finish. You can certainly set your own by walking out to start/finish with the Aim and setting it. But instead if you follow the procedure I list below and use the start/finish that I created then we can all overlay and compare data against each other. You can’t do that unless the start/finish for a track is the same for all data captured.
The first thing you’ll need is that start/finish file which you can get from here. Next you need to start GPS Manager which is one of the Race Studio applications. Now plug in your Aim via USB. The list of tracks it already knows about should show up on the left of the screen. Now click the Import button and select the start/finish file you just downloaded. You should now see “Ridge Motorsports P” on the left side of the screen which means you have it installed to GPS Manager. Now you need to move it to the Aim. Select the Ridge from the left hand list, it should now show up checked. Now click the Arrow that points to the right to move the track to the Aim. If you scroll through your right hand list it should show up there now. That’s it. You can shut things down and disconnect.
March 29th, 2015
The C7 Z06 has a built in data acquisition system called the Performance Data Recorder (PDR). In order to capture lap times you must set the start/finish point for the track you are at manually. The systems does not automatically know these like say the Aim Solo does. Also it only remember one track start/finish at a time. If you erase your SD card it will even forget that one track start/finish.
This causes a number of problems:
- In order to compare laps times from one lap to a reference lap the start/finish must be the same.
- If you set a different start/finish on different days then you can’t compare across date from different days.
- Same problem if you want to compare one car to another. You can’t because the start/finish will differ between the two cars.
Luckily this can be fixed with some manual shuffling and renaming of files on the SD card. The start/finish for a track is stored on the SD card in a file named “.map.gpx”. If you just keep a version of this for each track that you go to and move the appropriate one onto the SD card you can have a consistent start/finish. You can also do the same thing across multiple cars.
If you go to my Lap Data Files page you’ll see that I have posted start/finish files for all the tracks I’ve been to. If you have a Z06 PDR then you can download these, rename them to “.map.gpx” and put them on your SD card and now we can all compare data against each other.