Mike D

The question that started this thread asked how to use the CE Turbodyno to tune a 12th scale motor. I don't completely agree with anybody that posted on here. Why does everybody insist on setting up their CE dyno to use AMP loads? Has anybody really geared their car for amp draw in the last 2-3 years? If not, then why gauge how good a motor is by its power at a given amp draw? I would gladly give up 15% efficiency to gain 10% power in a stock motor. AMP loads on a CE Dyno can hide the better motor. Today's stock racing is HORSEPOWER limited not EFFICIENCY limited. Trust me, if you are dumping in stock a dyno won't help you.

Let me give an example on the two motors listed in the original post. Fortunately the posted dyno sheets can be used in this comparison. Ignore the amp draw for now and just look at similar torque values.

Motor 1
RPM Torque Watt EF AMPS
17372 3.3 43 58 15 <-----
15905 4.8 57 64 18
15077 5.7 64 64 20
14265 6.5 68 61 22 <-----
13145 7.6 74 59 25 <-----
12194 8.5 77 55 28

Motor 2
RPM Torque Watt EF AMPS
21507 2.1 33 44 15
19467 3.4 48 53 18 <-----
17327 4.4 56 56 20
16470 5.1 62 56 22
14953 6.3 70 56 25 <-----
13672 7.7 78 56 28 <-----

The highlighted dyno load steps are fairly close in torque, so for arguments sake assume the dyno was set to TORQUE load steps. This means the RPM and AMPS would be measured values and the torque would be fixed values. Ignore Watt(Power) and EF(efficiency) for now - those are just calculated numbers from true measured values. Who cares about Watt and efficiency numbers when a TRUE comparison on RPM will tell how much faster a motor will go down the straight and a TRUE comparison on AMP draw will tell how much battery is being used.

Compared to Motor 1, Motor 2 draws 3 amps more (about 10%) but makes 500-700 more RPM (about 5%) at those same higher torque loads. At the lower torque load, Motor 2 draws 3 more amps (about 17%) but has 2100 more RPM (about 11%).

Without knowing racing conditions, classes, etc, I would take that trade off on a stock motor and pick Motor 2.

Remember, using torque loads are all about making apple-to-apple comparisons with motors. Think of Torque as the force a motor puts out. A certain about of force is needed to push a car out of a turn and a certain amount of force is needed to push a car down the straight away. A higher rpm motor at equal torque loads will almost always be faster at equal gear ratios. Most of the time that same motor will have higher amp draw and will overheat and slow down sooner too. Dynoing the motors 5-10 times in a row will prove that.

The trick is to gear Motor 2 at a lower rollout so it struggles less in the infield then Motor 1 and won't heat up as quick. Motor 2 still needs to be geared high enough that it can keep up with Motor 1 on the straight.

Usually there will be a larger RPM spread between two motors at lower torque loads versus higher torque loads. For example, lower torque loads (3.3/3.4 on the examples) will have larger rpm spreads between motors and therefore tell you to run a larger difference in rollouts between motors. Higher torque loads (7.6/7.7 on the examples) will have smaller rpm spreads between motors and therefore tell you to run a smaller difference in rollouts between motors. Trial and error with gear ratios on the track will show which torque loads best represent the racing conditions.

Try it and let me know what you think. I had a lot of success building motors this way. Its fairly easy to tell which motors are good and I usually came very close to the right gear on a new motor from the start.

Mike Dunnigan

Hyper1

Mike can you give us an example of how you've got your dyno set up? I'm not a TC driver but a 4 cell stock oval driver, your theory is interesting to say the least.

Todd Putnam

Mike and I have our dynos set up the same way when testing in torque steps, (unless he's changed his recently, not sure)
Torque Steps @ 5 volts:
3
4.5
6
7
8
9


-Todd

erock1331

Interesting concepts, I like this kinda thread !!!

I have always been a fan of big RPM...I am an oval guy, and in oval everybody says you need torque. But I have always been quicker on RPM geared a tooth or 2 lower than a big torque motor geared higher.

I had a robi dyno but grew frustrated and sold it.
I thought I had the thing figured out until I was able to run alot faster with EPIC Roar stocks (lower on power and Torque but higher RPM, than my Monster motors. I mean these motors had no business being faster. I ran my robi at 7.5 volts and They were roughly 8 to 10 points lower wattage wise. 8 points or so lower on torque, but had on average about 800-1100 more RPM. I would gear them about 15 points lower on rollout and they were money.

Here is my question.
Say you use one of those Integy Dyno's or Much Motor motor checkers, Orion checker etc...Would free standing RPM tell you anything ?
I know its not under load but think about it.. at a fixed input say 5volts, if a Motor pulls 20,000 and another motor pulls 21,500 wouldnt the 21,500 rpm motor be quicker on the track if geared properly ?

Hyper1

MAN! Erock your the man,I have been wondering the same thing,I have a TD45 at the house but bought a Much more motor master for use at the track,and have yet to figure out the best way to use it,because of the no load thing,being that no load amp draw means nothing! OH! I love RPM'S also.

erock1331

Hyper
do this for me if you get a chance.

Take 2 motors, call them Motor x and motor y.

spin them up on your Turbo dyno...write down the RPM value at 22 amps.
then let them sit about half hour, then put them on the Much More tester.

Write down the RPM. I am curious to see if it relates or differs between machines.

Mike D

Hyper1 - I still do the same loads that Todd listed. I would just use that as a guideline and tune the Torque loads in to the size and style of your track. After a while you will see which motors work way better on the track and which Torque loads show it the best on the dyno.

For 1/12 scale onroad, I found the RPM at the 8.0-9.0 torque loads gave a good indication on how hard the motor would pull off the turns. The RPM at 3.0-4.5 torque loads showed what the motor would do at the end of the straights. I looked at the amp draw on all the loads to get an idea how quickly the motor would heat up and fade.

My guess for oval is that you would look just at a tigher spread of loads in the middle to high torque range. TP could answer how to look at the motor numbers for oval better then me. I stopped oval racing 6-7 years ago.

burgboyz

iTrader: (70)

I hope someone is able to answer the question about
checking "no load rpm's" with the "motor checkers" or "toy dynos".
I own a toy dyno and need some valid info relating to other questions on this thread.....i.e.-basic 1/12th gearing with rpms/// comparing amp draw
What use is any of the info that the motor checkers give us?????
I use the APS and I can view high amp draw & high rpm. That is about it.
Please HELP!!!!

burgboyz

iTrader: (70)

anybody?

teamgp

I have an Orion "little" dyno and have found it very useful to dial in the sweetspot spring combination. Playing with the springs (using an Integy spring dyno to move up/down 5 points at a time), I'm able to dial in the correct springs where the rpm @2v will jump up several hundred points.

On a "big" dyno and on the track, the results are always confirmed as well. After playing with gearing between two motors, the motor that gave more rpm @2v with no load, always seems faster overall.

Recently I bought the Integy "little" dyno in an effort to "upgrade" without spending too much money. But its readings were inconsistent when compared to the Orion and I wasn't able to use it the same way to dial in the spring combination.

I'll be receiving my first "big" dyno tomorrow though and I plan on seeing how its results compare to the Orion over time.

burgboyz

iTrader: (70)

Thanks!!!
Look forward to your next report

outlandr91

Hi Yankey, Um, how did you arrive at a 1.73 roll-out? Thanks

kerry

iTrader: (1)

whats the differance in tuning in torque steps and amp steps?

theisgroup

iTrader: (10)

torque would be your control parameter. you would step the dyno in torque units and rpm and amp would just be measured.

kerry

iTrader: (1)

what torque steps should be used for stocks and what are the advantages