Landracing Forum
Tech Information => Technical Discussion => Topic started by: Bryan Long on August 25, 2014, 09:10:50 PM
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It seems to me that there should be advantages to using GPS for vehicle speed, rather than speed calculated from a front wheel pickup - no issue of tire growth and no wheel slip. We are hoping to get to the 350 mph range. Is it usable at these speeds on the salt flats? Any experience that anyone can share?
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I use a RacePak IQ3 with integrated GPS and my times at the 2 1/4 and 3 were dead on the time slip from SCTA. No problem getting satellites on the salt I think I had 9 all the time. I think I heard the more satellites the more accurate the MPH. There are others on this sight that know far more than me and I am no expert. Just relaying my experience.
BR
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This has been discussed over the past couple of years, but record speeds are over a measured distance 1 mile or 1 kilo. Look in the archives. Thus the given GPS speed does not apply for records.
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Most Garmins will do speed very accurately up to about 600 MPH, but remember racing is average over a mile, not top speed you hit... unless you hold your speed for the mile. We started using one to help pull of the truck at the right speed as well as aiding in not exiting the track at too fast of a speed....
The exit speeds have matched the GPS speeds perfectly.
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... We started using one to help................ as well as aiding in not exiting the track at too fast of a speed..
I really don't see much need in needing it when on the course. I'd rather pay attention to the tach to hit shift points. The timing slip will tell you how fast you ran. At the speed you plan on running I'm not sure you will have much opportunity to look at a GPS speed.
I would of liked to of had one for what Stainless mentioned though. I had a very hard time figuring out how fast I was going slowing down and when to turn off. Came up just short of the return road twice and had to restart the motor to get there. Knowing the GPS mph slowing down I think I could of cleared the track faster and made it available sooner to the next one in line without the fear of spinning the car by pulling off too soon.
I'd like to have it for that in the future,
Sum
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can a GPS accurately show 350mph???
never been there :-D
But I did monitor GPS speed for licensing & turnoff purposes; got the idea from another bike guy, Ryan Ostergard.
On his advice, i bought a hiker's/ wrist mounted GPS, set display to BIG.
GARMIN 010-00776-00 Foretrex(R) 301 GPS Receiver, about $175.
(http://thumbs.ebaystatic.com/d/l140/m/m5gwbXXW-e660E-uXE2Zy9w.jpg)
The number fills the "screen" and is easily seen, even at speed & vibration, even for the "world's least observant person" = me.
Simply cut the wrist band off and velcroed it on my dash, worked great!
Thanks Ryan :cheers:
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Another advantage is maintaining the required speed on licensing passes.
I used to put a small sliver of tape on the lens of the GPS speedo
and it would keep me close to the the required speed.
Dave
# 3611
56 Corvette
Carlisle, Pa.
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we use a GPS for MPH mainly so our driver knows if your not over xxx MPH at the 3 you might as well click it because we can't pick up xx MPH in the next 2. So at least we don't put another 2 hard miles on the motor trying to catch a number we can't chase down.
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We use the IQ3 for GPS speed, before we had a Large digital GPS gauge from Nordskog (now closed) both useful as said before, push off speed, turn off speed, getting better idea of things. Our brains know MPH so its a great reference.
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I have an app for my Droid called EB GPS Speedometer that works great.
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my Droid app is Ulysses speedometer and it works perfectly up to 630mph, not sure over that, but that should be enough for most folks I'd think.
Rouse
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Aw gee only 630. :-D
That's what we'll be using one day.
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Check your GPS on your next airplane ride. I no....it's not supposed to be on but it will
certainly give you speeds above 400 MPH. A good tail wind will boggle your mind. It
will record in the Max speed section of the GPS and U can keep it as a Bar bet winner.
FREUD
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That what I did, but the Droid was in airplane mode so the flight attendant said it was OK.
545MPH on the way West, and 630 on the way East, the average then would be 587.5. Not bad for just over $300.00 per pass. :)
Rouse
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I've got my fingers crossed that the maximum speed number on my GPS gets changed at WoS... still sitting on 250 from last August, but it will be riding along with the Black Lightning... like to see it go faster.
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Our purpose would not be for using GPS speed on the course, but rather to record it along with other parameters so that we can determine slip after the run. Is there a GPS device that would output a signal that we can record? Such as 0-5 volts proportional to speed? Or a pulse output?
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Bryan, I was busy on a deal with a tracking company. Their system is obviously designed to allow fleet managers to monitor vehicle.
The system could relay 8 or 9 parameters to your laptop in real time.
If that's what you meant?.
Mike.
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Tauruck, thanks for your input. I will try to be a bit more clear in what I would like to do. We already have a data acquisition system on board the race car. Among other things, we record pulses from a front wheel. From that I calculate speed and compare that with speed calculated from engine RPM. The difference is interpreted as rear wheel slip. This works quite well, but there are some uncertainties. I know that that the speed from front wheel pulses is quite accurate because I can compare it with timing slip data. But that front tire diameter can increase with speed and there might be some slip of the front wheel; not likely very much, but who knows. My thinking is that we could eliminate those two unknowns if we had accurate GPS speed as one of the recorded parameters.
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Bryan, You are looking for something that is already available, no problem, all you have to do is ditch the data system you have and buy one with integrated GPS. You can buy standalone GPS recorders, but outputting something that will record on your data system is improbable. You could sync a time stamp between a GPS recorder and your data system that would help you compare data.
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Talk to the folks at Veracity Racing Data (veracitydata.com), they can fix you up. I run a GPS system on my AWD 'liner that they supplied and made it talk to the Motec for traction control and general speed ref. Works great.
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... But that front tire diameter can increase with speed and there might be some slip of the front wheel; not likely very much, but who knows. ...
Bryan,
I too am concerned with the "slip":
http://www.landracing.com/forum/index.php/topic,14323.0.html (http://www.landracing.com/forum/index.php/topic,14323.0.html)
At this point I'm looking for advice, not giving it.
But it sounds like we are doing something like what you are planning.
Our new lakester is set up with a Racepak system to record calculated mph from both the front (driven) & rear (passive) wheels as well as directly record GPS mph.
One of our priorities at WOS will be to calibrate F & R mph to GPS mph and from that data calculate and display % Slip of the front wheels.
I am 110% sure that I am way over the top on my obsession on logging mph & on our cool lil box, the % Slip Display.
But i got pretty successful at calculating gearing needs of my bikes, and found it satisfying to NOT be changing sprockets at the track.
Karl
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A Racepak G2X gives you a GPS speed on the dash and also records in on the data recorder along with any other thing you want to record. It will also draw a map of the course that you can then divide into how many sections that you want, for example you run a 5 mile course, you can break it up into 1 mile increments or how ever many you want. That way it is easy to see entry and exit speeds for each increment of the run. It has a built in G meter that along with engine RPM can help with gearing and tuning. It's a pretty nice recorder. JC
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So if you put a sensor on one corner of a roadster, will the GPS register rotational speed? :evil:
Doug :cheers: :cheers: :cheers:
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We use a garmin gps 18 to feed our logger an AEM AQ1
its good to reference events, but refresh rate at 1 hz is to little to get good wheelslip data
garmin do a 5 hz gps 18 , and if you want real accuracy look for a 10hz or better
The signal is probably not what you think , although 0-5v its relaying a 3 d position and needs a device configured to read such
nmea , if you want to google it
specs here may help
http://static.garmincdn.com/pumac/425_TechnicalSpecification.pdf
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"So if you put a sensor on one corner of a roadster, will the GPS register rotational speed? evil"
The GPS won't, but the RacePak system does measure and record lateral Gs .... :-D :evil:
vic