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Old 11-01-2004, 10:19 AM   #1
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Default Understanding Dyno Data

We have been playing around with some dynos recently, however it seems it is very important to know how to interpret the results, rather then checking maximum figures.

For example:
- What is the most current a modified motor can draw on acceleration?
- At max revs, what current will modified motors use?

I know motors vary, I just need an idea of what to expect

Thanks everyone for the help
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Old 11-01-2004, 10:35 AM   #2
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Have a look for example these two motors ...
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Old 11-01-2004, 10:36 AM   #3
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Motor 2
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Old 11-01-2004, 10:38 AM   #4
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We will be more than grateful if someone can explain to us the difference between the above 2 motors. Thanks a lot
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Old 11-01-2004, 10:57 AM   #5
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Those plots almost look like the same motor with different springs.

The first motor has more high RPM power than the second one so it should have more power at the end of the straight. The second motor has more power under a heavy load and should pull harder coming off the slower corners.

There's a whole bunch more that you need to think about when comparing two motors. What class, race length, and the number of cells all play a pretty big role when deciding what motor is better.
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Old 11-01-2004, 12:14 PM   #6
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you may try chaning the scale on the x axis too... try looking at actualy rpm or time based scales.... these may show things that % of max rpm dont show as clearly....
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Old 11-01-2004, 12:36 PM   #7
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The above motors are used on 1/10 touring cars in open modified class 5 mins races. To be more precise they are both 8 single motors. One with timing 4 deg and the other one with timing 5 deg.

How much current is normal for such motors to draw on acceleration and on top revs? Any other comparisions are more than welcome
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Old 11-01-2004, 03:34 PM   #8
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For the tight carpet track I run on and a 19T motor, I've measured current draw at over 70A from a standing start. The average amp draw for a 5 min. race for the same motor was aroun 25A, with currents just over 40A as the car accelerates out of the corner. If I remember right the amp draw dropped off to around 10A at the end of the longest straight before I got out of the throttle.
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Old 11-01-2004, 04:38 PM   #9
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Great input Steve R...any body has an idea of current draw figures from an 8 single ?
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Old 11-02-2004, 01:26 AM   #10
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So modified low wind motors draw more than 70 amps from a standing start
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Old 11-02-2004, 05:53 AM   #11
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oh yeah!
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Old 11-02-2004, 06:14 AM   #12
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The amount of time that the motor pulls really high current is actually pretty short. Most mod motors in sedan will average around 35 amps or so on the track.

The amount of current that the motor draws at the end of the longest straight depends on gearing. That's why you dump if you put too much gear on it.

It's pretty rare that we actually run an 8 turn on the dyno. There's more than enough power with an 8 so getting another 5 watts is no big deal.

5 deg of timing does sound a little low though. I seem to remember running 12-14 deg with the new Reedy stuff.
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