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Old 09-21-2007, 02:39 PM   #1
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Default Stock Racing tips?

1. When preparing for a stock race is it better to charge the batteries at a lower amps to get the most power for the longest duration?

This stock race is going to be 6 minutes so I need as much power for the longest period, not just the first few minutes...

2. I am running a monster horsepower motor and though it's fast, I notice a bit of fade near the 5 minute mark... I am geared 21/78 on a Kyosho RB5 (sweet!) but the motor gets fairly hot. Should I toss this motor and go for a CO27?
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Old 09-21-2007, 02:44 PM   #2
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it depends what cells you are running. I run the EP 4200's and they are good batt. I charge mine at 5 amp. Also try gearing up and see what happens.
Let me know how it goes.
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Old 09-21-2007, 02:46 PM   #3
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When you lower amperage you lose power overall, what you need to do is experiment with your amperage setting until the battery makes good power only as long as it needs to (in your case, 6 minutes). So yeah, you got it right. Although, most of the bigger batteries on the market nowadays will do 6 or 7 minutes in a Stock car no sweat, even when charged as high as 6, 6.5amp.

The motor issue could be a number of things, not just gearing but the motor's condition, how free-spinning you've got the transmission, etc. etc. Go over everything and make sure it's all 100% up to snuff before you think about spending any money. It's not hard to compete in Stock, but to win you've got to put in the effort to find those little things that might be hindering your powertrain's performance.
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Old 09-21-2007, 02:48 PM   #4
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i run 4200 charged at 7
and the monster stock motor 88/18 in a Losi MF1 ( your gearing sounds good)

i dont really notice any drop in power

how hot is the motor after the race

charging your batteries at a higher voltage will keep the voltage higher longer

and run E brushes and red red springs in the motor you will notice a diference

and add some comm drops for a killer start (if your track can handle it )
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Old 09-21-2007, 02:57 PM   #5
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One of my packs is a 3 year old 3300
The other is a 4200 that's just under a year old
Both get charged at a little under 6.5amp, I say that because my el-cheapo charger uses a dial and not some fancy LCD display output (I keep things simple )

Strangely enough I like the 3300 more, but they both have a "peak" that lasts for 2 or 3 laps (roughly a minute) before settling into a good strong run.

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geared usually around 18/87, I've got an 84 spur if I feel like it
after a run the motor's hot enough to cook soup on, but MVP's are just funny that way

Track is a very short, hard, blue-grooving clay high traction indoor course.
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Old 09-21-2007, 03:02 PM   #6
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try to get ahold of a comm lathe to cut your motor at least once every two weeks.
also try messing with different spring rates for the brushes and i personally like the silver compound brushes.
also another thing would be to try a p2k2 pro motor. that is one of the best stock motors for truck period.
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Old 09-21-2007, 03:07 PM   #7
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Thanks for the quick responses

The motor is getting to around 165 timed at 7 minutes. (Originally the stock race was to be 7 minutes but may be dropped to 6)

I am running Pro Match 3600's usually always charged at 6 amps.

I'm using the 4499 brushes (E) but the stock springs Green on (-) Red on (+)
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Old 09-21-2007, 03:08 PM   #8
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Quote:
Originally Posted by action135 View Post
also try messing with different spring rates
I was brought up under the impression that generally you put a stiff spring on the positive side. The spring on the negative side only needs to be strong enough for it to keep contact with the commutator.

honestly I never understood it myself, the motor's only going to run when the brushes touch the comm so what difference would a spring make, but I'll be darned if they aren't right.
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Old 09-21-2007, 03:10 PM   #9
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From what I recall by putting a softer on the (-) you can effectively get higher RPMS because there is less friction. But you sacrifice some torque.. Balancing act. Now does higher RPM mean higher temps or does more torque cause higher temp?
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Old 09-21-2007, 03:14 PM   #10
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Thats one question i cant remember lol.
but im pretty sure higher rpms means higher temps.
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Old 09-21-2007, 03:15 PM   #11
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Resistance causes higher temps, in theory a motor with no load could run all day happy as a clam. But stick something to it and now it has to work.

I was told that the positive spring is where the tuning's done. The negative just has to hang along for the ride. So you put a flimsy spring on it to reduce friction
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Old 09-21-2007, 03:17 PM   #12
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i was just about to change my post to that.
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Old 09-21-2007, 03:18 PM   #13
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Quote:
Originally Posted by action135 View Post
but im pretty sure higher rpms means higher temps.
That is true, but maybe not for the reason you think. A high RPM motor has to lose torque, so the motor has to work harder to push the car up to top speed.

That's the scientific reason, what you posted was more of a rule of thumb. Just FYI
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Old 09-21-2007, 03:24 PM   #14
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Torque has a higher amp draw, causing for heat. As long as you have your busshings oiled, rpm won't have much of an effect on heat. It will still be present, but not like torque will.
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Old 09-21-2007, 03:29 PM   #15
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21/78 on a truck? I run on a small blue grouve track also. I run 21/90 in a buggy. We also run a 6 minute race. P2K2 motor, it comes off at 190 degrees, a little hot I know but I like the feel. As for charging, I charge at 2amps. I like the car to feel the same at 30 seconds as 6 minutes, 2 amps will keep the feel the same throught the entire run. Several people at the track have swapped to 2 amp charging. Some in here will think I'm crazy, but I rearly finish off the podium. I mean rearly... Also, my two stock motors are P2K2 and not pro's. They are almost 2 years old. I swap them every two weeks wile the other one I give to a local motor tuner. He zappes the magnets for me. So much that he says the lights in his house dim. Plus he zappes them for a longer time than any other person that he tunes motors for.(I request so) If you can find a local tuner that would zap magnets I'd give that a shot. I would also change youre spur to a bigger one.
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