How to measure performance?

Schr-eng · #1 10-29-2003, 11:50 PM

I would like to see how modifications affect the car with real world numbers instead of a gut feeling of "it goes faster."

Anyone got ideas on how to measure performance?

What kind of dyno could i strap my AWD GTR to to get some horsepower figures?

How about top speed, how can i figure that out on the track?

And a timer relay system would be nice to get some acceleration vs top speed figures to tweak the gear ratios for max performance

any ideas?

slugbugg · #2 10-30-2003, 12:01 AM

I have thought about buying one of those microsizer lap counters and adding a second senser.If set up properly you could fool it into thinking you ran a lap when in fact you did a speed pass through two sensers.

Place a lap counter at one end all set to read the car as it goes by and at a presicly measured distance the second senser gets placed.Then just run the car flat out passed the sensers to accurately record the elapsed time.

The elapsed time, times the precise distance covered should give you accurate real world speeds.

OK I'm tired and going to bed now.

aperson · #3 10-30-2003, 02:51 PM

dunno if this will work but what about the timer from RS its supposed to snap onto the ZZ sidewall kit

slugbugg · #4 10-30-2003, 04:58 PM

Anything thing that can measure the speed accurately is good with me.
I thought about the microsizer lap counter when I seen one at a LHS that is closing, the price was $14.99 minus 30% I should have bought it, maybe tomorrow

Silent_NightR34 · #5 10-30-2003, 05:51 PM

use mirrors...heres a diagram showing how you would set it up...dont worry about that pic....i was bored

EDIT: sorry i didn't complete it before saving it..the arrows going left and right are ment to say 20ft...then you have to work out this whole big problem to find the mph...ill post the link later....and you satart from the left of the thing and go right...

fst blk supra · #6 10-30-2003, 06:36 PM

one thing is that u could test it on a treadmill ,if u have one, then test it stock and then test if modified and see which speed is equal to how fast ur xmod is and that should show u how much faster it is.

food123 · #7 10-30-2003, 10:01 PM

*the hard way* -time one minute of straight driving-measure distance driven in one minute-convert ft/min to mph straight

corysmith · #8 10-30-2003, 10:31 PM

a scale quarter mile is 47' 2" so spray paint a strip of street or sidewalk with the lines, and have someone else stopwatch

a scale Q for a zip zap is 20'7" i got mine up to a scale 294 mph

Rate = Distance / Time

Rate = .25 Miles / (X Seconds * 60 Seconds per minute * 60 minutes per hour)

Rate = .25 / X * 60 * 60 = ____ Scale MPH

Schr-eng · #9 10-30-2003, 11:00 PM

I'm not interested in scale speed because that kind of data is useless to me.

Who cares if it runs a scale speed? All that matters to me is the actual speed.

I've seen a lot of good ideas that you guys have posted and I thank you all for the good ideas

corysmith · #10 10-30-2003, 11:01 PM

Quote:

Originally posted by Schr-eng
I'm not interested in scale speed because that kind of data is useless to me.

Who cares if it runs a scale speed? All that matters to me is the actual speed.

I've seen a lot of good ideas that you guys have posted and I thank you all for the good ideas

I dont judge it by that either, its one of those useless stats, like slugging percentage

Micro S2000 · #11 10-31-2003, 12:01 AM

scale speed can be very important. if you know the scale speed and want to know the true speed jsut take the speed and divide by 28

X/28=accual speed

cyrc · #12 10-31-2003, 12:14 AM

i saw something on ebay it wasnt xmods brand i think it was for miniz but it looked like a mini dyno it could read speed on rc cars though .i cant find the link sorry

corysmith · #13 10-31-2003, 12:15 AM

stopwatch = cheaper

slugbugg · #14 10-31-2003, 06:18 AM

The dyno is good for some things like fine tuning it easily but I'd rather test the car in actuall operation.
I'm just going to have to go and buy one of those microsizer lap counters and see what I can do with it

SirPoonga · #15 11-09-2003, 05:21 PM

Quote:

Originally posted by Silent_NightR34
use mirrors...heres a diagram showing how you would set it up...dont worry about that pic....i was bored

EDIT: sorry i didn't complete it before saving it..the arrows going left and right are ment to say 20ft...then you have to work out this whole big problem to find the mph...ill post the link later....and you satart from the left of the thing and go right...

Good idea for light based system. BTW, if you get a one way mirror you don't need to have that one mirror offset like that.

What will happen is the light coming out of the lap counter will hit that mirror. Then reflect over to the lower right mirror which will reflect up to the upper right mirror. Then that will reflect over tot he upper lect mirror and that will reflect tot he lap counter THROUGH the first one way mirror.

But there is a simpler way, at least I think.

Build a setup like this:
http://www.kronosrobotics.com/pj_lap...apcounter1.htm

You'd setup two of those infrared systems say about 10 feet apart. The laser will trigger that same mechanism.
You can then wire it to the parallel port of a cheap/free 498 laptop (I have on running windows 95 per this site and grab the software off that site.
http://www.hoslotcarracing.com/LapCounter.html

The software will give you one lap and the time it took.

So take 10ft/Xs where X is the number of seconds the software told you. That's real speed. To convert it to real miles per hour multiply that result by (3600/5280) or the simplified fraction (15/22). (3600/5280) is convreting ft/s to mph. There are 3600 second in an hour and 5280ft in a mile.

So lets say it took 3 seconds to go 3 ft
10/3 = 3.3333ft/s
3.3333*(15/22) = 2.273mph

Now, if your scale is 1:28 I think all you need to do is multiply that by 28 to get scale speed.
So 63.644 mph scale

So to simplify the formula:
F = actual ft car travelled
S = actual second car travelled
X = 1:X where X is the scale

(F/S)*(3600/5280)*(X)
Simplified down (using algebra)
(15*F*X)/(22*S)

BTW, having a graphing calculator on hand is much easier to figure this. I have a TI-85 so I just need to use the conversion functions. I checked, my math is correct.

This will give you scale MPH.
Some may think this number doesn't mean anything. Well, there isn't much practical use of the number. However a car with 200mph scale is faster than a car with 190mph scale. Though you could just use real ft/s to compare

It would be cool to have a scale car go actual scale speeds. So if the car goes 200mph in real life would be 10.476ft/s for a 1:28 car. Then make a scale race track

As mentioned, if you do calculate make sure your car is going full speed when timing starts.