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Old 12-11-2003, 03:04 PM   #1
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Default reading dyno's

I am looking for info on how to set up the robitronics dyno and understanding the readings. i see people on here talking about the the spool up and how thay had to go down 3teeth and stuff like that. i would liek to know how to understand all of the readings better. so i can know when and why i am gearing down or up with a motor.


p.s. i have the robitronics dyno so any type of step by step instructiosn i can do right as i read them this would help out alot.
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Old 12-11-2003, 03:33 PM   #2
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Well,

What I can give you is my personal experience. We have our job easier in Europe because we are allowed to run only 12 turn motors.

From various tests I saw that a good 12 has a max rpm of aprox 38-40k rpm.

When I test a motor an compare the curves I can see that the power curve has it's max further ahead on the rev range, so I need to allow the motor to rev a little more and that's done going down in pinion.

When I got my first Kr I saw that it was able to do 45k rpm and comparing curves with a Ti for instance the max power was almost 5000 rpm ahead the Ti power curve. The conclusion I took from that was that instead of using a high 5.0 ratio or a low 6 would melt the motor because at the same point of rpm it had much less power and torque than the Ti. And if a motor is too loaded has the bad habit of heating and melting.
I had to allow the motor to rev more. I used a pinion 2 teeth lower and while my Kr is still in my box, 4 new Kr's melted in that race coz the guys were using the exact same ratio that they used with the Ti. They had no idea of the differences when they installed the motor on their cars.
6-7K rpm more is a lot. Too much to use the same ratio. Only a dyno will tell you this, unless you're gifted
The exact same pointers I got with a D5 and now with a Pt. I'm not a dyno god and I only use it to get some ideas that I need to prove on the track. If they are sucessful more than once then I may be doing something right.

I've beaten my personal track record (on my usual track) with my Kr while all the others had a hard time making it run decently.

The dyno just pointed me in the right direction, but the track testing proved I made the right assumptions.
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Old 12-11-2003, 03:55 PM   #3
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Are you a robitronics user antoniop? What do you think of it?
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Old 12-11-2003, 04:49 PM   #4
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I love it.

I had a CS Power Checker but I sold it o get the Robi.

It comes with a DOS software that's not bad but you can get a Windows version (paying extra).

They give the same info, but the W version is much easier to use. However when making motor readings the curves come out strange... with spikes and not very smooth. The DOS version doesn't have this problem.

So.. I make the readings with the DOS version and make my comparisons with the Windows version.

I learned to "read" dyno info with the CS and applied that info to my track testing. It made me go from the lower B's to the top A finals with the same exact motors, but tuned according to what the dyno was telling me.
Springs, brushes aligment, even a bad capacitor can be found with a dyno. You just have to test and test.
By now I have more than 200 tests on my motors and I can see some trends...

The power for the dyno comes from a 44Ah car battery . I can do tests all night, test my friends motors and still with plenty of capacity left. The CS had the problem of needing a 6 cell pack that went down very fast...
With this one the results are "more" repeatable.

It helps a lot.
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Old 12-11-2003, 06:17 PM   #5
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Well thanks for the input so far but what i was looking for wasnt that a higher reving motor needs to be geared down . i under stand that. what i wanted to know was about the readings and mainly the set up . there is a lot you can set up before you dyno the motor. like voltage,the amps i seen in there crap like that i want ot know how people do it . and what all reading mean , like it has a ton of numbers on the tourqe page. is the graph the only thing people look at?
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Old 12-11-2003, 08:33 PM   #6
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snopro - I tend to set a power range and look at the power numbers in that range for a good idication of power, which I feel is better than just looking at max power. For a stock motor, I would set the amp draw to look at to be between 20 and 25 amps, and for a mod, depending on the wind, maybe 25-30 for a milder wind, and 30-35 for hot winds.

I also look at the torque reading at max power. I'm still not sure if the numbers on the right of the screen, in their own box are calculated numbers based off the curve, or actual measured numbers. For instance, I ignore the friction number because it seems the way it measures friction is by measuring the time it takes a motor to spin down after a test, and I imagine it throws that in with max RPM in some equation to come up with friction, BUT the magnets are going to play a huge role in how much time it takes a motor to wind down, so a motor has, so a motor with stronger magnets may appear to have more friction.

Spin up time to max power is also a good number to look at, like antinop was saying, this could give you a very good indication of how to gear your motor.

I have been unable to get the DOS software to work on the newer laptop I'm using. I have experienced the same as antinop has - that the newer Windows software to produce curves that are not nearly as smooth. I don't know if the spikes it shows are an accurate representation, but they seem to me like they would throw off the readings. For example, if you have a spike after the peak of the curve, but rising higher than the peak of the curve, the software is going to interpret that as the max power figure, when in reality it isn't. This also would throw off the spin up time to max power reading because the spike is later in the curve than the max power really is, so the spinup time would appear slower.
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Old 12-11-2003, 08:58 PM   #7
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Hi thanks alot were do i set the amps? my dyno only goes down to a 50 amp
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Old 12-11-2003, 11:02 PM   #8
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You should be able to find the screen to set the specific amp draw to look at fairly easily. I don't remember exactly where it is, it may be under settings or utilities or something along those lines.
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