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Old 07-15-2011, 07:06 PM   #1
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Default How much more speed are we talking?

I have a HPI Sprint with a Tacon 3500kv motor and on 2s it does 34 mph. Im going to try and post a pic but Im on my phone and not sure how. Anyway, what kind of speed can I expect to see changing ONLY the motor to 4420kv? Same gears same battery. Thanks!


http://m1093.photobucket.com/albumvi...1hoUS%2BRzA%3D
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Old 07-15-2011, 08:55 PM   #2
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Changing motors without changing gearing is a bad idea, you will most likely overheat the new motor and either damage or destroy it. Your adding another 7,000 rpm approx. (1,000 rpms per volt)
Assuming your geared correctly now your going to ask the new motor to spin beyond what it should. If you start by monitoring temperatures you can see how it goes.
You can use this site to figure out approximate mph for your setup with different gear ratios. http://gearchart.com/
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Old 07-15-2011, 09:31 PM   #3
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Changing motors without changing gearing is a bad idea, you will most likely overheat the new motor and either damage or destroy it. Your adding another 7,000 rpm approx. (1,000 rpms per volt)
Assuming your geared correctly now your going to ask the new motor to spin beyond what it should. If you start by monitoring temperatures you can see how it goes.
You can use this site to figure out approximate mph for your setup with different gear ratios. http://gearchart.com/
Yeah I realize that doing this would create more heat but I just wanted a ballpark so I knew whether it was worth replacing a perfectly good motor with another one. Thanks for that link though, I'll try and input my stuff and see what happens! Thanks!
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Old 07-16-2011, 05:58 AM   #4
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speed estimator here.

http://scriptasylum.com/rc_speed/top_speed.html
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Old 07-16-2011, 08:28 AM   #5
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I don't know everything to make this one work. I use this one for my trucks!
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Old 07-16-2011, 12:00 PM   #6
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Originally Posted by Syxxstring View Post
Changing motors without changing gearing is a bad idea, you will most likely overheat the new motor and either damage or destroy it. Your adding another 7,000 rpm approx. (1,000 rpms per volt)
Assuming your geared correctly now your going to ask the new motor to spin beyond what it should. If you start by monitoring temperatures you can see how it goes.
You can use this site to figure out approximate mph for your setup with different gear ratios. http://gearchart.com/
Quick question about this. When using temps to find good gearing, how long should I run the kit before taking the temp? And should I run it as hard as I can to get the temps as high as possible to know whether to gear it down more? Also, is there a general rule that 1 tooth is worth x amount of degrees or something like that? I can't afford to spend a bunch on gears I'll only use to figure out gearing and won't use again. Thanks! I bought the 4420kv btw.
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Old 07-16-2011, 03:15 PM   #7
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Quote:
Originally Posted by jrowles91 View Post
Quick question about this. When using temps to find good gearing, how long should I run the kit before taking the temp? And should I run it as hard as I can to get the temps as high as possible to know whether to gear it down more? Also, is there a general rule that 1 tooth is worth x amount of degrees or something like that? I can't afford to spend a bunch on gears I'll only use to figure out gearing and won't use again. Thanks! I bought the 4420kv btw.
what speedcontrol are you using... Run the car for 1 minute at your track or your street/ parking lot. Then take a temp. If reaches 140f degrees then you are overgeared. Run the car 1 minute at a time until you reach 5 minutes. Then you can run it 5 minutes completely Motors can run safely at 165f degrees. A 4420kv motor is equivalent to a 10.5 motor. With proper gearing, timing and boost ( if your speed control has it ) you can get it up to 60mph. Start a 8.0 fdr with timing and boost. No timing and boost 7.0 fdr.
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Old 07-16-2011, 05:54 PM   #8
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what speedcontrol are you using... Run the car for 1 minute at your track or your street/ parking lot. Then take a temp. If reaches 140f degrees then you are overgeared. Run the car 1 minute at a time until you reach 5 minutes. Then you can run it 5 minutes completely Motors can run safely at 165f degrees. A 4420kv motor is equivalent to a 10.5 motor. With proper gearing, timing and boost ( if your speed control has it ) you can get it up to 60mph. Start a 8.0 fdr with timing and boost. No timing and boost 7.0 fdr.
I'm using the Ezrun 60a esc. Ok so when I get the new motor I'll play with it. I don't have a temp gun though. Is there a touch measurement like they use with nitros (using spit, yes spit on the head of the motor)?
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Old 07-16-2011, 10:21 PM   #9
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http://www.harborfreight.com/non-con...ter-93983.html
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Old 07-16-2011, 11:01 PM   #10
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you should be able to hold your fingers on the motor, if it burns your fingers its too hot.
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Old 07-17-2011, 01:33 AM   #11
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Old 07-17-2011, 01:47 AM   #12
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you should be able to hold your fingers on the motor, if it burns your fingers its too hot.


For me though that's only about 130 degrees. Oh well, guess I'll just have to get a temp gun.

Thanks everyone for your input.
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Old 07-18-2011, 12:15 PM   #13
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For me though that's only about 130 degrees. Oh well, guess I'll just have to get a temp gun.

Thanks everyone for your input.
You can buy a decent temp gun for about $20. With an ez run 60a you are not gonna get blistering speeds. I believe that esc only has motor timing. I would not put any motor higher than 4420kv motor you have. That esc is meant for stock racing. eg; 17.5, 13.5 and maybe 10.5
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Old 07-18-2011, 02:16 PM   #14
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You can buy a decent temp gun for about $20. With an ez run 60a you are not gonna get blistering speeds. I believe that esc only has motor timing. I would not put any motor higher than 4420kv motor you have. That esc is meant for stock racing. eg; 17.5, 13.5 and maybe 10.5
Yeah I figured that. I actually bought that esc for my kids Evader. Worked well on that, but then I got this car and wanted to hop it up.
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Old 07-18-2011, 04:02 PM   #15
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If you can touch your motor without burning your fingers after a run you are not working it hard enough.
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