Home Forums Chassis & Handling Chassis Tuning with Tire Temp Sensors and Accelerometer

This topic contains 9 replies, has 9 voices, and was last updated by  Barry Hastings 3 years, 9 months ago.

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  • #52964

    Cal Kirley
    Participant

    Hi everyone,

    I just got into karting a few months ago and have been learning the ropes at the local track (Dousman, WI).  I’m currently going to school for Mechanical Engineering, so I decided to develop a data acquisition system that can help me understand chassis kinematics. I’ve gathered accelerometer data and tire temp data so far, but I still have to work out the bugs in my other sensors before I can get it fully functional.

    From the tire temp data, I can see that the right side of the kart is running very hot compared to the left (with equal cold tire pressures, temp sensors in the middle of the tire).  I know Dousman is mostly a left hand track, but I’m a little confused as to what direction I should proceed. Should I try to level the temps? Should I continue to favor the right side? There are points where the right rear is 100 degrees F hotter than the left rear,  and I know that this can quickly push the tires out of their optimal grip temperature (which I should be able to determine with the accelerometer).

    I can post some of the data I’ve gathered once I figure out how to post pictures if anyone is interested.

     

    Thanks,

     

    Cal Kirley

  • #52975

    Gary Lawson
    Participant

    although I’m sure it’s not what you want to hear tire temps are almost useless when it comes to tuning a kart. As you’ve already found, when a track is almost all one direction (like all tracks are) your temps simply won’t be even. You could try add a ridiculous amount of weight to the lefts to help them heat up more but you’ll go slower because the balance will be off. So what’s the point….
    My advice on tire temps is that is can be useful when comparing front to rear temps to determine balance. Also check 3 spots across the front tires to help with camber. Then again, if a bunch of negative camber is really fast even though it wears out the inside prematurely, then is it wrong?

  • #52977

    Gary Lawson
    Participant

    Basically your best bet would be to look for a correlation between a fast kart vs a slow kart in regard to tire temps. And even at that driving styles greatly affect tire temps, so you would be well served to use the same driver for testing.

  • #52981

    TJ Koyen
    Moderator

    Agreed on Gary’s posts.

    I’ve been racing at Dousman for 14 years and I would say that running even tire pressures across the kart has worked pretty well for me.

    You are never going to get them even on that track, though lots of guys will run a pound less on the right side tires.

    Also as a note, I’ve seen guys with really elaborate data systems and temp or steering angle sensors all over the kart, and they often get hung up on the numbers rather than actually watching their driving and feeling how the kart is handling and they have a hard time getting the kart dialed in for each session. Until you’re within .5 of the leaders, there’s still more to come from your driving.

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  • #52985

    Matt Dixon
    Participant

    Cal tune with the stop watch not a temp gouge as Gary said.

    Yes level your tire pressure hot when you come off the track. Then add or lower pressures for best results.

    94y

  • #53344

    JT TT
    Blocked

    Before I start, I will preface this by saying I’m an AiM dealer and data analysis is as deeply embedded into my post-session routine as lubing the kart’s chain.

     

    You should decide whether you want to spend your time becoming a better karter, or building a better data logger.  I’m not doubting your skills as an engineer, but AiM and other companies sell products which will fit your needs with analysis software that’s already built and should be wholly adequate to almost any karter out there.  You can buy a Mychron 4 and GPS unit for $650 retail, and find them here used for less.

     

    As far as tire temperatures go, karts aren’t like cars and formula cars.  You’re not going to follow the same rules setting up a kart as you would a formula car or tin top.

    The first sensor you need is a GPS unit.  While it doesn’t quantify your inputs as a driver, it identifies the product of your inputs.  You’ll be able to compare lap over lap,  corner over corner.

    Once you have the GPS and you have a couple bucks sitting around, buy the MyChron expansion, which allows you to connect 0-5v sensors to the MyChron.

    There are differing opinions on what analog sensors are necessary, but the following is my opinion, including the order.  I realize that budgets are finite which is why I order these in what I perceive to the most important first.

    1.) steering sensor

    2.) single axis accelerometer (used for lateral G)

    3.) <span style=”line-height: 1.5;”>throttle position</span>

    4.) Brake pressure

    5.) Front wheel speed (either side)

    Steering sensor is huge, as your input there has a large impact on your laptimes.  It will give you great insight into how you are steering.  You can also x-y plot the steering sensor against GPS lateral G to gain an understanding of the oversteer/understeer condition of the kart in any given corner, or an overall bias in one direction over the full lap.

    The single axis accelerometer gives you an extremely accurate way to identify oversteer understeer condition when aligned so values run in the same direction as the GPS lateral G data.  This is done with a math channel.

    Throttle pos and brake pressure give you more qualitative insight into how you are driving each corner.  Combined with steering input, this is how you will come to understand what is causing the time gain or loss through each corner that the GPS unit will uncover.

    Front wheel speed (only need 1, side doesn’t matter) lets you do some cool stuff after your race using math channels in race studio.

    For instance, you can use a complicated math channel which, using GPS lateral G, identifies the direction and radius of the corner your kart is in/leaving, then corrects the wheel speed sensor’s reading (which is only on one side) to reflect vehicle speed.  Once you have your vehicle speed, you can compare that to the speed you are driving the rear axle at (RPM/gear ratio * tire rollout / 60 * .6818) to observe wheelspin as you get back into the gas off the corner.  Rumor is that the upcoming logger will have the same capability of on-board math channels like the current automotive loggers do.

     

     

  • #53367

    Larry Hayashigawa
    Participant

    Carl,

    If you are serious about collecting good usable data don’t buy the GPS and buy the e-Box, a bit more but you can find them used.  The e-Box is more complicated to install and get operational but it’s worth it because the data is much more stable because the GPS data drifts too much.  I’ve found that the GPS unit is only good for comparing in-session data and have found it to be in error of .25 seconds at least on one track.  Because of this drift, the data between different days and even sessions has to be shifted by eye until it “lines” up but with the e-Box, there is no drift and I can compare data from a year ago to new data.

     

  • #54020

    Cory-Milne
    Participant

    depending on how accurate the tire temp sensors are you could possibly find out what certain adjustments do by adding a steering angle sensor and comparing tire temp to how much you move the steering wheel you can also find the optimal average tire temperature and rework the equation to find the optimal air pressure over a one lap run this of course is if your like a robot and can make identical laps every time, but with hundreds of laps and hundreds of trials im sure you can get really close…. thats just what i picked up in my short term with the Colorado State Formula Sae team… but i would also like to see how you did it i was interested in something like what your doing for a while

  • #54072

    Mark Horne
    Participant

    Tire temp across the rear tire should be used to set PSI. Even temps “generally” mean correct PSI. Changing track width could require different PSI.

    As Mr Lawson said, using temps to set front camber is a good strategy. The front end geometry will affect the handling and best handling may end up with uneven tire temps and quickly worn tires. I always try to get the front geometry correct first by looking at the handling. It takes more time and experience as someone said above, Karting requires different chassis tuning to be fast. It is even different from Sprints to Enduros.

     

    JT, a new model coming?? I need to get some training to expand my basic understanding of sorting through the data. I will look on line.

  • #55306

    Barry Hastings
    Participant

    Looking at as much as you can will open your eyes and cause you to question your sanity at the same time.

     

    First you need to define your test and what you want to accomplish.  Apply those tools and see where it points you.  But as Gary and others said, this wont help you find speed.  I  have a hard time, well extremely hard time, running and driving my own tests.  One reason, I’m paying too much attention to WHAT the kart is doing than driving it fast enough to find the problem.  PLUS if you are testing a theory, you are apt to judge it properly.  its your theory, you have a emotional attachment to if it works or not.

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