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Old 06-14-2013, 05:26 PM   #1
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Default Stock vs. modified motors

I was wondering what the noticeable differences are between a stock and modified motor. I am using a reedy 17.5 turn, would I have just more top end if I used a 7.5 turn motor? And, would it be very noticeable? Thanks for the help, I am new to brushless motors.
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Old 06-14-2013, 05:31 PM   #2
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Yes, it would be very noticeable. More of everything. Be sure to adjust gearing, needs a considerably smaller pinion. Modifieds have less tolerance for incorrect gearing, they can heat up quickly. Many limit run time to help avoid excessive heat build up.
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Old 06-14-2013, 05:37 PM   #3
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Originally Posted by This-Guy View Post
I was wondering what the noticeable differences are between a stock and modified motor. I am using a reedy 17.5 turn, would I have just more top end if I used a 7.5 turn motor? And, would it be very noticeable? Thanks for the help, I am new to brushless motors.
I'm guessing you aren't racing at a track as they normally have rules as far as what motor you are allowed to enter with in a certain class, and if you got to see the races between mod and stock/spec class you would definitely know what the difference is. The 7.5 is quite a jump from a 17.5, would be heaps faster. The 17.5 would run cooler and give longer runtimes due to lower current draw and higher efficiency, but the 7.5 yields lots more revs. You do have to gear differently for a lower turn motor (smaller pinion gear) but the speed will still be very noticeable.
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Old 06-14-2013, 05:47 PM   #4
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Thanks for the replys. I run at a track but don't race. It's a small track so when I am running next to a modified cars it didn't seem to be too much difference. At a larger track I'm sure it would be a bigger difference.
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Old 06-14-2013, 05:49 PM   #5
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If you just want a bit more speed, try upping the timing a bit (unless you're already running 40) and just keep an eye on temps.
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Old 06-14-2013, 05:55 PM   #6
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Having the power and being able to use it are 2 different things, likely why the difference doesn't seem so obvious on track.

Perhaps start with a 10.5, it's a nice step up in power, more controllable, less heat and run time reduction issues. A lot of mortal club guys use a 10.5 for modified classes (edit: assuming offroad based on your signature).

Another thing to consider, look for a motor line that's rebuildable, with interchangeable stators. That way you could start with any wind, 7.5, 10.5, whatever, and for around half cost pick up a different stator, then have both (with a little careful pit work of course).

Either way, good luck!

Last edited by Dave H; 06-14-2013 at 06:08 PM.
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Old 06-16-2013, 08:40 AM   #7
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Here is my take on 17.5 vs mod motors....


17.5's are fast enough to do good fast laps. When racing, most the time a stock class(17.5) buggy will run the same or very close lap times as a mod motor buggy. 17.5 is way more controllable. In a stadium or short course truck I think a mod motor is an advantage.Trucks require more power. With a mod motor, driver skill is required more, "Tame the beast"or"Harness the power" thinking here. I run faster laps running my 17.5 car but prefer to drive and race my 7.5 buggy and 6.5 stadium truck do to fun factor. If I am in the mood to do well, I race my 17.5. If I am in the mood to have alot of fun and throw some sweet whips off the big triple, I run my mod stuff. Honestly, most rc tracks are not big enough to "need" the extra power of a mod motor unless you need to clear larger obstacles easier. At my local track, the stock buggy classwinner's fast lap and averages are only off the mod winner's by less than a second for fastlap and a few seconds for a top ten.

So 17.5= fast.......Mod= fun...... and more broken parts.LOL!
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Old 06-16-2013, 05:28 PM   #8
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If you were to race the standard class breakdowns in most areas is 17.5, 13.5, 10.5, open. So for now I'd suggest a 13.5, you won't be as overwhelmed by the power and on a smaller/medium track can turn competitive lap times. Also easing your way into mod is a step by step learning experience. Learn how to gear it, drive it, maintain it. And yea, learn how many more parts you break when driving out of control.
Heck Iv'e been doing this for 20 years and rarely run anything under 10.5, it's just easier to drive in general and if racing creates less margin for error and hence better results. It is my tendency to run less motor than most people, but I don't finish behind most of them so I'm ok with that. I remember one race in oh 1991? and this wicked fast guy passed me at least 6 times during a race, I'd just pass him back has he was getting marshalled.
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