GPS Lap Timers - Anyone use them?

[radami]

I've been interested in a GPS lap timer in lieu of the beacon type, since my beacon type has not been reliable.

Does anyone use a GPS lap timer and can provide some feedback? I'm hoping they are reasonably easy to set up for first use, and then for keeping track of split times, downloadable to computer for future reference, save track maps, and reliable.

I've seen the Starlane Stealth II and the GET Athena MD60 as some good options at a somewhat reasonable price (although more than the cost for a set of tires). I don't have an iphone or anything similar to use.

RAdami

[Clarkie]

Been playing with an XT Racing GPX Pro, and did some testing in Phoenix with a test rider a few months ago, its pretty cool. You can wire in rpm, wheel speed (even though you have GPS speed), TPS, Gear position, and a few other sensors.

Pretty easy to use, you can even look at lines through a corner (early apex vs late apex kind of thing) but the best info for a racer is the effectiveness of a line. The TPS trace mid corner and the speed at the end of a straight from different line, gearing or just how soon and smooth you got on the gas 8)

It's kinda like physics, same terminal speed but 20ft earlier, is a faster sector (you plug in the start finsih and I think up to 3 or 4 sectors which is key). Crazy huh

Going 1 second a lap is cool, but knowing exactly where and why you were faster is even cooler :wink:

[rybo]

Randy,

I've been using the starlane for a couple of years and just purchased a GPX pro (like the one mentioned above) for 2011. The starlane was great, but offered limited functionality compared to the GPX. I'm really excited to try the GPX.

That being said, the Starlane was super easy to use. Turn it on, set the start finish line and a couple of sectors on the warm up lap and go. Had tach / RPM / sector time and complete lap time. It could piece together a theoretical best lap by putting together best sector times. On top of that it was well built and durable. I simply velcro'd mine to the top triple clamp.

Scott

[benfoxmra95]

The most important thing to look for on gps track mapping data loggers is gps sampling rate in HZ. High end professional gps loggers like Motec and pectel run 15Hz.

Hz rate is how many times per second the your location and speed are being measured as you travel around the track. Lower Hz spec on gps units opens the door for less accurate mapping of speed and location. The higher Hz gives you more accurate position and speed on the track because on bikes your traveling many feet per second, lower Hz loggers can give choppy/missed data. But in their software they'll have corrections to fudge this and make it look like smooth.

I think most gps enabled phones like the iPhone and android are around 1-2 Hz so although they are a nice little thing to experiment with, getting accurate data is not easy.

Here is another alternative to gps logging and data logging of channels:
http://www.getdata.it/categorie.php?...ia=36&lang=eng

Gps data is awesome I couldn't imagine racing without it now that I've used it.

[findgold]

I got a Qstarz Which is low budget. It is smaller then most cell phones and you need to have a laptop or other computer to down load the info. It is only a 5hz. I have only used it once so far and haven't figured out all the software yet. I got it from amazon for around 150 dollars. In other words you get what you pay for. I am heading down to ASR for the ASMA track day this weekend and will have a better idea as to how good it is.
I am running a 250 Ninjette which is kinda slow so the 5hz speed may not be too bad, I hope.

[oldtimer]

We both ran the GPX last year and it was hugely beneficial. Highly recommend it.

[jmaher]

What is the cost range of something like this?

Joe

[chris nami]

How much does one of these fancy shmancy GPX thing-a-Ma-jigs cost and where do I find one?

[Clarkie]

They retail for $679 but you can find them online for as low as $625 and I am sure Bart would hook you up. Here is the over view/webpage on them http://www.xtracing.com/en/gpxpro/index.php

They arent too bad to wire up, there are a few tricks to getting the actual Throttle TPS on the R6 and not the ECU controlled TPS but it's not too bad. The whole Fly-by-wire R6 thing, just have to tap into a different wire. You can either put the start finish in on the unit or change the start/finish and spilts on the laptop back in the pits, it also has your 'theoretical' best time when you use splits but that can also be depressing to know what you 'should' be able to do if you string a clean lap together

I was looking at a few systems in 2008 that did the same sort of thing and had the same capabilities, and they were over $2000 for the same sort of thing :shock:

[Clarkie]

A good Data Collection unit is basically a 'Lie dectector' and rather than someone telling you "It looks like you are doing this" you can look at the data and it is what it is, You cant just roll your eyes at them and say whatever

If you ask someone where they are getting on the gas for a particular corner (like leading onto the back straight at HPR), they will always 'think' they are feeding the throttle in earlier than they really are. I used to use a lot of visual markers, a rock or a mark on the track, but seeing the actual data on a screen is a lot better. Think about how if you feed in the gas 20 feet earlier, how much more speed you will carry down the straight.

Having the data is one thing, knowing what to do with it is another :wink:

[benfoxmra95]

data is fun, here's a test for you to have fun with, look at this pic, and then answer the question below:

http://www.facebook.com/photo.php?pi...=1530839803945



here's the question:
Can anyone see what the rider isn't used to here? what he over compensates for?


The pic is crappy, but there's more than enough viewable info on it to answer my question.

some info you'll need to figure out my question: the red cross on the track map is travelling in the ccw direction, if you can't read the header the pink trace line is front sus travel.






I love technology....

extra credit: what does this rider NOT do? if you've gotten the first question then you'll understand he did something pretty well (hint: what he didn't do is somethingthat could have turned it into a crash)

[KFinn]

Here is my analysis....

the rider reached roughly full throttle for a small gap of time (before the power band and then had a large amount of wheel spin (in the power band) which he sustained full throttle until the rider chopped the throttle, then jammed on the brakes because the suspension was compressed afterwords where as during spin it was uncompressed.

He got on the brakes good an hard afterwords and for awhile. So was he avoiding something in front of him?

Is the rider not used to the strong power band? and he chops off of the throttle instead of managing it?

I don't think I got the first one as I am not able to guess the extra credit.

[benfoxmra95]

No but don't be discouraged you are at least trying

Something to look at as well: at 40,350ft.... There's something happening there too, shows a pattern of how he rides. If the cursor line was lined up on that point it would be on the exit of the previous turn that's being discussed.

[spideyrdr]

Taking a stab at it being a rider who is not quick shifting / clutchless shifting.

[benfoxmra95]

Taking a stab at it being a rider who is not quick shifting / clutchless shifting.

no there's only one gear being held through this whole section

[KFinn]

Not looking far enough ahead and running wide?

[KFinn]

I got it!!! He is not use to having such awesome data collection!

:lol:

[benfoxmra95]

This particular guy is not used to traction control, he's compensating for rear wheel slip with throttle modulation, because he's hasn't found how much he can depend on it. He has however found his comfort limits with rear wheel slip as demonstrated at 40,300ft because he's consistently slipped the rear wheel to a point where no tc is engaged.



You have to zoom in close, but, you can see at 41850 ft, (before the cursor line) he has already started to drop the throttle down slightly, he's not holding 100%, he's been slipping the rear consistently all the way and knows thats he's coming to his comfort zone limits, so the rear wheel is spinning, then at 41925 ft, the rear tire lets go completely and tc is engaged to its max, he is slightly ahead of the tc because his throttle application was slightly dropping already down from 100% already beforehand , then he finally reduces throttle to 25%. the rear tire regains traction.



This is not a chop throttle, a chop throttle trace has a 90 degree drop off. It would look like a square edge and would drop down to 0%. Once traction was regained you see the rounded nose of the tps trace going back up to 100% showing he's gradually feeding throttle back in, not wacking it open.



If you look at 40300 ft, he exhibits the same type of throttle modulation, without breaking the rear loose, the tps trace has a rounded drop off down to 25% again and then a gradual rounded ramp back up to 100% once traction is gained(look at how the wheel slip trace follows the tps signal.)

if you watch the wheel slip as it climbs up when throttle is fed in, you can see he is slipping the rear consistently until he reaches 100% throttle, and searches possibly just a little too far when the rear tire breaks loose at the end of the chart.....or the real question is...had he not reduced throttle as much and trusted the tc would the ecu regain control of the tire????? This is the real mystery for me, where's the edge? do you have the dexterity and speed in your hands to find it? and here's the real question, can you even feel when the rear tire is going faster than the front? yeah most can feel when it steps out, but, as you can see there's alot of time on the track where the wheels slipping and you may not even know.



when he does modulate the throttle down you will see the front suspension change significantly, BUT, it does not change it attitude to anything more drastic than what the bike is at during normal acceleration, if the spike went off the chart, then that would be a chop, or a brake dive etc..



oh and if your wondering, the speeds listed are kph, not mph.



the shapes of the squiglly lines are important! when your looking at them, are you seeing ramps? rounded edges? square edges? convex shapes? concave shapes?

[Sol Performance]

Hey Ben.

So what do you make of the decrease in wheel slip that happens @ 41850? (Right before the tire starts spinning aggressively) The front gets loaded a bit when the spin line dips at that point. Almost like the bike was getting good (better) traction and the whole bike was loaded more. (Then the rear starts to let go...)
Do you know where this sample was taken? Was that at some sort of banking, on camber exit or possible a crest of a hill?

Also, do you know how the wheel slip is calculated? I was assuming it was the delta of GPS and wheel speed but that doesn't quite add up.

Thanks for posting the DAX. I can spend a ton of time just looking at this stuff!!

[Clarkie]

One of the coolest things with a TPS trace is to see how smooth the throttle is fed in. There are some corners like T1 at Pueblo (or T1 at Miller on the full/perimeter track, MMP actually has a lot of long critical corners that link together) where I used to be on and off the gas a lot, when I saw the data I changed the way I fed the gas in and it resulted in not only more speed but a more stable chassis mid corner 8)

Remember, 2mph mid corner can be 5mph half way down the straight, you just have to break your riding down a lot into segments. Every corner has at least 3 segments, entry, mid corner, exit and 0.03 seconds through each segment is around 0.1 per corner and with 10 corners that is around a second a lap and thats not counting the speed you gain in a straight line. More horsepower will get you down the straight faster, but the corners are where time is made up :wink:

It's a package deal. Motor, suspension, chassis and tire grip all work together to give the rider a good platform to go fast on. If one isnt right, the rider can still go fast but it is a lot more work and they end up overcompensating in another area. When you see a rider get off the bike after a 12 lap sprint race and they are exhausted, things arent working as good as they could be.

[benfoxmra95]

Do you know where this sample was taken? Was that at some sort of banking, on camber exit or possible a crest of a hill?

Also, do you know how the wheel slip is calculated? I was assuming it was the delta of GPS and wheel speed but that doesn't quite add up.

Thanks for posting the DAX. I can spend a ton of time just looking at this stuff!!

This is on the exit....remember I said it was going ccw. The bike is slightly leaned and moving towards upright position. Camber or banking or hills or are not present. The front suspension travel scaling can be deceiving. Those up and down spikes only really equate to small movements of the forks. It's magnified, so your looking too deeply at it.

The point of this is as clarkie is pointing out....throttle control....not really anything else.... Not suspension, not tc settings. Not speeds

Wheel slip is calculated by how much differential there is between the front and rear wheel. Both wheels have speeds sensors. Gps speed is only for reference it's not used n any calcs.

This data was taken from a rider I know very well and this section of track was the only area focused on during this experiment. There are two corners in a row where he could get a rythym and get very comfortable sliding the rear, so it tools several sessions to get this.

[Bartman]

Just like anything it takes time to learn how to use a new tool to its fullest extent, even a simple laptimer makes a differance but having real data rather than just what the rider says he feels is huge and the XT GPS is pretty damn good for the price. I will not violate Daves advertisement rules so no prices but if anybody wants a XT or Starlane call me and we will talk. After playing with both the XT is easier to use, while not a Motec for the average racer it is very good.
Ben how long did it take you to learn the ins and outs of your system?

[Clarkie]

Ben just looked up the instructions on Google

[Bartman]

Thats where all the worlds knowledge can be found, that and WIKI right. :lol:
If some jackass somewhere types it it must be true right.

[radami]

Thanks for you feedback,
I can understand the importance of the getting more information than lap & split times. I would really like to see throttle and brake inputs impacts the suspension and time lost or gain.
The question I have then is about affordability, is the first cost worth loosing out on a couple of races and track days, this season, to have the exceptional data we get from one of these?
Budgets are something we are all faced with each season, I'm just trying to balance the safety items with performance items.