How about some of you motor guru's help explain what to look for in a motor.
Which number is the most important????

I know when I look at the different labels I think:

WOW Killer RPM or

AWESOME TORQUE or

EFFICIENCY Hmmmm.

Ultimately I flip a coin and make my pick. Than I hear "Well, you have to rebuild it anyway before you use it...so what's the difference!"

Any thoughts?
Is it all mystique, voodoo, bs, or maybe just luck(that you get a good one)?

The numbers you see on the sticker are only god for 1-2 runs.. The higher the numbers you see the chances are that is a better motor.. When i use to buy over the counter i looked for a mix of good numbers accros the board.. Ie the higher each number is the better.. Im not sold on rpm's tho.. I like power numbers more.. Efficiency is a number i rarely look at.. That number can be tweaked when i rebuild..

The RPM's while important, aren't as important as torque can sometimes be. Depends on the track. Most tracks are really small ie: under 200' per lap. In that case it would be better to have a motor that produces more torque. Efficiency is the percentage of how much of the energy put in is turned into roatating energy versus how much is dissipated in the form of heat etc. I know for stock motors the efficiency should be at least 60%. The torque and rpm's vary with the kind of motor it is. Stock motors are very different from 19T and Mod motors.
Rick<><

Efficiency is the percentage of how much of the energy put in is turned into roatating energy versus how much is dissipated in the form of heat etc. I know for stock motors the efficiency should be at least 60%. Rick<><

With the batteries that are being used to day, I'm not so sure
that having a motor that is 60% efficient is a 'must have'..
You need the motor that has the most rip coming off the corners.
If that's 56% eff, then so be it.
Dragsters aren't very efficient, but they are the fastest cars on the planet.
If your power supply can last the duration of the run, that is the
most important thing..
I'm not suggesting that you shouldn't 'try' to gain efficiency, I am saying
that it would be a lot more important if you were running 10 minute races...
(as you mentioned, this is for mostly short track racing) imo....

I think Watts (HP) is the key in determining which motor will be faster, as long as rpm, torque, efficiency are within certain perimenters of each other. A motor that produces really high rpms, but watts, torque, efficiency are way below normal output doesn't run strong very long. But the motor that produces .108watts vs one that only makes .95 while the other power is relatively close the .108 motor is almost always faster.

Power is everything. Power is determined by RPM & torque together, so it's more of a package deal. Having really low numbers in either catagory hurts the whole thing. Efficiency doesn't matter, MORE POWER !!!

efficiency matters, especially with the new cells. a motor that is inefficient makes a ton of heat. with the voltage that we have now, the heat from an inefficient motor will lay down faster, and the lap times suffer from 2 minutes out JMHO

Well we,ve had six replies and six different answers,LOL shall we go for seven.

usally trq. and eff. will be higher if rpm is lower vice versa,. unless you are running on a very big track rpm isnt the key,. you need trq. to pull you off the turn the faster out of the turn the faster down the straight. old cells, new cells it dosent matter. eff.is always good to.

just my 2 cents
there's #7 pepe
fp racing

LOL! Frank,it's just funny to see these things I stay confused a lot reading these boards.

lol,./ i know it makes your head spin,

efficiency matters, especially with the new cells. a motor that is inefficient makes a ton of heat. with the voltage that we have now, the heat from an inefficient motor will lay down faster, and the lap times suffer from 2 minutes out JMHO

When I said it was not important to have a motor with over 60% efficiency,
I did not imply that it was okay to have one at 45%!!!
Nor did I suggest that you melt the comm off it either...

Yes, it's important, but as with everything else, there is a point of
diminishing returns... You have to consider that it is going to take
"X" amount of power to move an object (the car) a given amount of distance.
That's just the definition of 'work'.
If your motor is too efficient, you will not be able to extract the amount
of power needed to move that object in the given time the same distance...

Efficiency is better related to time than anything.
We don't care about time. We care about getting the object to move
the farthest distance, in the least time.

Do you want a big block racing engine in your car that runs 65% efficient,
or a Honda that runs 80% in a drag race?

I'll take the one that gets hotter, and puts out more power, because I
know the race is set to a specific time, to move the object.
And I can make the time.
What I need to have control over, is the heat.

just my opinion, as well.
But I do know, that the fastest my car goes,
is NOT with the most efficient motor I have..... :rolleyes:

Here's # 8
I run alot of 4 cell stk and my experience has been Torque, Efficiency, and watts are all key, RPM's are secondary as in most every race situation the motor will not see much more than 15,000 rpm's. A high amp draw stock motor or one that is not efficient will fall of in that last 2 mins.
Shall we go for #9

Doug P

Doug,
I will chime in with #9, lol

My theory is the lower I can roll out the better..Therefore I shoot for high RPM.
I have always been quicker on high rpm motors geared lower than high torque motors geared higher.

The way I see it is if Torque and Watts were key we would all be running P2K's because by far they have the most torque and most watts of any stock motor made.
But I see more Monsters and Roar Epic stocks in more cars than anything else....why? because they have higher RPM.

95% of Monsters I have spun up have always had better power and torque numbers than an Epic Stock. But I will take a Properly geared lower power Epic Stock over a higher powered Monster any day....why? once again more RPM...which means lower rollout, which means motor ends cooler typically....which results in stronger finishing times.
Same reason everybody started running the Monster and gave up on the GM3...MORE RPM--->lower rollout.

give that man a cigar.....

What about when you have a motor that EVEN ON THE LABEL is outside of the norm... I have a 19T KC motor that has INSANE RPMS.. I mean on the label it was 4000 rpms higher then the other 3 that I have>>>On a turbodyno it is 4200 rpms higeher than any other ive ever had, on a fantom same deal... YET I can not find a sweet spot gearing wise with the thing... Seems like the motor falls on its face 2 min in every run...Im down to where Im about 4 points lower in rollout and still a slug.. the POWER and eff are all good as well BUT the rpms seems to be freakish... And before you ask YES they were all set to the same timing etc etc...just for whatever reason this one spins like no tomorrow.. However all its good for is spinning on the dyno to impress people with numbers..

looks like a stock shootout coming soon,.lol ,..i'll take a GM3 anyday to be honest ,.. do they still make them?

Man! there are so many variables,so far seems like the short tracks need the grunt IE TQ, while the larger tracks like the RPMS? but then again it probably depends on driving style ETC ETC.Erock,your driving is so smooth, that's why you like RPMS,you never get the car bound up and RPM's work well for you,but if you aren't quite so smooth IE: ME, LOL I need the TQ to get the car back up to speed.

I will chime in with #9, lol

95% of Monsters I have spun up have always had better power and torque numbers than an Epic Stock. But I will take a Properly geared lower power Epic Stock over a higher powered Monster any day....why? once again more RPM...which means lower rollout, which means motor ends cooler typically....which results in stronger finishing times.


I tend to agree with you that the Epic certainly has a lot more
potential, but yikes... they seem to be so...persnickety...
I just don't have a lot of luck finding that 'sweet spot' with them..
I think the monsters are a little more forgiving.
For a duffer like me, that's fairly important! :drunk:

I agree that more RPM = a faster motor. It is a mathmatic fact. The downside is that higher RPMs are more sensative to gearing that most people don't have the patience to find the sweet spot. Also, just because a motor is turning alot of Rs, doen't mean it will be fast. If you don't have torque, then you can't pull the car out of the corners. Just think off a motor with weak magnets. A motor that still turns high RPM under a heavy load is a great motor. The Monster has the best combination of Torque and RPM.

With Monsters I have gone the same lap times with about 20 - 25 points difference in rollout. With the Epics you have about within 3-5 points of the right rollout.

Track time is of the essence with them to make em fast. I bought 2 brand new Epics this summer, played with only those 2 motors. Even though they dyno'd similar the one always took a gear one tooth higher than the other.
Then when our big race rolled around and the track got better I was able to go up a tooth with them.

I'll take Erock's word for it... While I've never run a EPIC stock... and for a long time argued that any RPM motor with good power could run fast... I have seen some evidence that higher RPM motors do tend to work better on the track... But even that can be misleading...

One theory I've had is that higher RPM motors often actualy run cooler... Not sure I could ever prove that... but anyway my experiance has been that any motor with good power can and will run just as fast regardless of the RPM, at least for a short period of time... However it seems to me that higher RPM motors (with their fewer laminations and sometimes with big holes in the cans...) can run fast longer then a lower RPM motor... Now if you have a 1 minute race... I still think RPM doesn't matter... and well in the end, I think it's not really the high RPM that matters, it's something else that really makes it work... (like better cooling, if my theory is correct)...

Effciency... well you can't really make power without having effciency... After all, power out devided by power in equals effciency... Now where the peak effeciency is and where the peak power is... can also effect things...

but anyway... depending on where your getting your numbers from... none of it may matter... Or said anohter way... I wouldn't trust any numbers that come stuck to the side of a motor... and even if they are accurate they'll only be accurate for one run or so... For sure the next time you change brushes, you could have a whole differnt experiance, depending on many factors.

Oh... and I should mention... If you've not got your chasis dialed in as best you can... your motor won't mean squat anyway...

Oh... and I should mention... If you've not got your chasis dialed in as best you can... your motor won't mean squat anyway...

Amen !!!
To quote Putnam: "You Can't fire a cannon from a canoe..."
My quote: "But it is nice to fire a cannon from a Cruise Ship once in a while"
LOL Todd liked that one