DIY ways to measure gains or losses on a budget
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  1. #1
    1000+ Posts jo proffi's Avatar
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    Default DIY ways to measure gains or losses on a budget

    As there seems to be a bit of a bun fight going on at the moment in regards to quantifying improvements mods may or may not bring, I thought i'd start a thread helping the less engineering educated among us to rise to the task of actually measuring these changes in a slightly scientific way, or at least with more detail than 'it looks good'.
    I'm sure there are people who can help out by offering practical suggestions of ways to measure aspects of performance.



    I'll get things rolling by asking, how is a good way (without spending heaps on a dyno) of measuring acceleration on the cheap without too many variables being introduced.
    Putting it on a dyno at $250 per hour is not in my budget.
    I dont think I'm needing absolute measurements, and relative measurements are fine for my needs. By that I mean I dont need to know that i'm pulling 67.4 kw at the wheels, just that the car is faster or slower with X mod.

    Is there any merit in buying a gtech type sensor???

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    I have my own 50m slightly uphill concrete drag strip on private property so the legalities of trials on the road can be ignored on that strip.

    or is it more accurate to whack the trailer on to keep speeds down and pick two fixed points on a hill like two sign posts, hit the first one at 30km/h in 3rd and boot it, recording the speed attained at the second landmark???

    Jo

  2. #2
    1000+ Posts dino's Avatar
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    Jo...you know how you ve got these guys/gals who can taste ten different glasses of wine...and then they can tell you what vintage each is...region...and the type of timber that stored the liquid...
    I certainly couldnt do it...well maybe with beer...

    An then there are guys/gals who can listen to a piano note and tell you the type of instrument used and what year it was played and possibly by whom...Again I couldnt do it..never ever never...

    But give me any vehicle and let me spend "sufficient time" (an hour or so) test driving it....do any mods you like and i ll be able to tell whether effect is positive or negative (given mod delivers .25% change)...




    Ok so "maybe" i am exaggerating just a little bit...what i m trying to say in a very round about way...is that I think if "YOU" know the car very well...then seat of pants should be enough...(isnt this what "test" drivers did in the early days)

    it is for me...

    otherwise point to point (where minimal other affects can impact- straight line, same temperature, cross winds & other climatic conditions etc, tyre pressure etc etc all else being equal- you understand)



    dino

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    Quote Originally Posted by jo proffi View Post
    Is there any merit in buying a gtech type sensor???
    There is probably an iPhone app. All the kiddies seem to have them.

    Tim

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    Quote Originally Posted by dino View Post
    seat of pants should be enough...(isnt this what "test" drivers did in the early days)

    it is for me...
    Sorry dino,

    you are as delusional as the rest, unfortunately.

    Tim

  5. #5
    1000+ Posts jo proffi's Avatar
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    One of my old time electrical engineer guru's , a frail old man who drinks too much these days, had a trophy with a speedway bike on it sitting on his shelf. I would be amazed if he could even ride a bike, so I asked about it one day.
    He told me the story of a mate in NZ who was winning speedway events, but needed a little input as to improvements.
    My mate, the fussy engineer, was amazed to find that like everyone else, their team was doing all the tests with a stop watch and a dirt track and getting driver impressions.
    He immediately set about building an engine dyno out of scrap industrial motors and parts, and the team went on to win the national even for the next 5 years or so, until the other teams worked out what their winning edge was.
    This was one of their constructers trophies the team gave him in honour of his scientific approach to winning races.

    Jo

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    Quote Originally Posted by tcusack View Post
    There is probably an iPhone app. All the kiddies seem to have them.

    Tim
    There is - Dynolicious - http://www.dynolicious.com/
    It uses the accelerometer in the iPhone so it's probably pretty accurate. $16

  7. #7
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    Quote Originally Posted by jo proffi View Post
    As there seems to be a bit of a bun fight going on at the moment in regards to quantifying improvements mods may or may not bring, I thought i'd start a thread helping the less engineering educated among us to rise to the task of actually measuring these changes in a slightly scientific way, or at least with more detail than 'it looks good'.
    I'm sure there are people who can help out by offering practical suggestions of ways to measure aspects of performance.



    I'll get things rolling by asking, how is a good way (without spending heaps on a dyno) of measuring acceleration on the cheap without too many variables being introduced.
    Putting it on a dyno at $250 per hour is not in my budget.
    I dont think I'm needing absolute measurements, and relative measurements are fine for my needs. By that I mean I dont need to know that i'm pulling 67.4 kw at the wheels, just that the car is faster or slower with X mod.

    Is there any merit in buying a gtech type sensor???

    I have my own 50m slightly uphill concrete drag strip on private property so the legalities of trials on the road can be ignored on that strip.

    or is it more accurate to whack the trailer on to keep speeds down and pick two fixed points on a hill like two sign posts, hit the first one at 30km/h in 3rd and boot it, recording the speed attained at the second landmark???

    Jo
    Jo,

    Good idea for a thread. Like some of the guys said you can get apps for many phones with accelerometers these day or a g-tech unit as you put it. You can also do what you said by driving over a known distance and recording the start and finish speed. Plug into into the following formula to get the average acceleration:

    Avg Accel = (Final speed)^2 - (Initial speed)^2
    ----------------------------------------------
    2 x (Distance travelled)

    Note make sure you use SI units such as metres for distance and speeds are converted to metres/sec before plugging the data into the formula. This is done by diving you speed that is in km/h by 3.6.

    You get your acceleration in meters/sec^2. You can use that to work out average power output too.

    But as a general rule you hit the nail on the head. By doing it in secnd or third, you avoid launch/grip issues and by doing it in different gears you can determine (all other things being equal) the benefit of the mod over various rev ranges for the respective gears, ie in 2nd gear you will get the top end of the rev range, in 3rd gear you will get the mid rev range and in 4 th and 5th so on. As the average acceleration speed is for the rev range you travelled, reducing the distance travelled will help narrow down the acceleration to provide a more finite value. Again at different gears and rev ranges and you could end up with acceleration curves for various gears and along with it, power curves too.

    It would be a pretty repeatable result. assuming you do a few runs and get some averages going. You could also get a freind to help out too for greater accuracy by reading out values (assuming there is no massive parallax error).

    Like you said, you will get a feel for what your power/ performance mod has done.
    Bad_Karma

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    mlb
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    Yep Dynolicious is pretty good. There is also a newer one called Zilla, which I haven't checked out yet.

    A G-Tech can be picked up pretty cheaply off eBay - just go for the old school type. Seeing as though you're only after measuring gains/losses and not concerned too much with the final figure, it's a good yardstick to use. Entering the same vehicle weight, and using it on the same piece of road can easily show the result of your efforts.

    And now I wait.....

    Matt
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    1000+ Posts dino's Avatar
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    Quote Originally Posted by tcusack View Post
    Sorry dino,

    you are as delusional as the rest, unfortunately.

    Tim
    sorry...but as a driver I m on a completely different level...hence why my judging ability is better 2...




    dino

  10. #10
    1000+ Posts robmac's Avatar
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    The actual accelerometers at component level are cheap as chips.

    http://www.oceancontrols.com.au/Sensors.html

    Don't we have a few programmers on AF who could write some software for a laptop to collect some really meaningful data?

    Shane ???

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    Quote Originally Posted by robmac View Post

    Don't we have a few programmers on AF who could write some software for a laptop to collect some really meaningful data?

    Shane ???
    Lol. Now I've seen it all. The words Shane and meaningful in the one post
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  12. #12
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    I have an old Gtech (the first version without the whizz bang screen). It is about the size of a match box and seems to work quite well. I don't know how accurate they are, but the numbers they output do appear fairly repeatable which is all you really need.

  13. #13
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    Quote Originally Posted by dino View Post
    sorry...but as a driver I m on a completely different level...hence why my judging ability is better 2...
    Hmmmmmmm, you AND Patrick? Perhaps this is an under-utilised resource. I'll see if I can organise a few laps in a Sprintcar - should sort things out.

    Tim

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    Test and tune days and your local drag strip?



    Chris

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    Quote Originally Posted by robmac View Post
    The actual accelerometers at component level are cheap as chips.

    http://www.oceancontrols.com.au/Sensors.html

    Don't we have a few programmers on AF who could write some software for a laptop to collect some really meaningful data?

    Shane ???
    Dont even seem to need to, as long as your laptop has a serial port.

    http://www.oceancontrols.com.au/ACC-010.html

    You can log that data and analyze it in anything.

  16. #16
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by spar View Post
    Dont even seem to need to, as long as your laptop has a serial port.

    http://www.oceancontrols.com.au/ACC-010.html

    You can log that data and analyze it in anything.
    That looks awesome.
    I need to find myself a pc computer guru to set up all this cheap computer gear.

    Jo

  17. #17
    Fellow Frogger! spar's Avatar
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    In case you dont have a serial port on your lappy (most modern ones dont) - usb to serial adaptor.

    http://cgi.ebay.com.au/OZ-USB-2-0-RS...item336596cd19

  18. #18
    1000+ Posts dino's Avatar
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    Quote Originally Posted by tcusack View Post
    Hmmmmmmm, you AND Patrick? Perhaps this is an under-utilised resource. I'll see if I can organise a few laps in a Sprintcar - should sort things out.

    Tim

    I m sure Pat is an "ok" driver... but he just lacks experience...I ve got what? close to 500 000 driving hours under my belt...and most of those being chased by cops...

    ohhhh...and pleeeeeeaaaaseee.....dont mention "sprintcars" around me....they are for girls...honestly, there are simpler ways to get out of the closet...Pat might be interested though.




    what




    dino

  19. #19
    XTC
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    Quote Originally Posted by dino View Post
    I m sure Pat is an "ok" driver... but he just lacks experience...I ve got what? close to 500 000 driving hours under my belt...and most of those being chased by cops...
    You've been taxi driving 24/7 for 57+ years ???

  20. #20
    1000+ Posts dino's Avatar
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    Quote Originally Posted by XTC View Post
    You've been taxi driving 24/7 for 57+ years ???

    No...you are confusing me with a practicing architect....




    dino

  21. #21
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    Default gtech

    Im with Mistareno - go the gtech. Even the older models still come up with some interesting figures.

    http://www.youtube.com/watch?v=mmfwg5eoAFs


    http://www.youtube.com/watch?v=ZCQnJ...eature=related
    Last edited by PugMonkey; 31st March 2011 at 03:24 PM.
    ....now watch a Peugeot turn into a corner!

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    Quote Originally Posted by spar View Post
    Dont even seem to need to, as long as your laptop has a serial port.

    http://www.oceancontrols.com.au/ACC-010.html

    You can log that data and analyze it in anything.
    You might be able to do this for free.

    If you have a newish Toshiba netbook/laptop, there's a good chance it has a software accessible accelerometer. It's used to detect freefalling and lock the disk to prevent damage resulting from a drop.

    See the video here:
    http://www.youtube.com/watch?v=-KVjjJnx-xk

    Can't find a link to the actual project, but you will if you search.

  23. #23
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    If you have a reasonable GPS with logging, the log may give you reasonable speed/time points to do the basic physics calcs.

    My Garmin will log at 1 second intervals so you can compare before and after runs. Other option along the same lines is a precision GPS logger (e.g. Performance Box).

    If you have an after market ECU with logging, then RPM/time logs can be turned into a speed vs time data source and hence be used for power calcs.

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