1515 vs 1518
 

I currently run a 1515 1Y in my Losi 2.0 Truggy E conversion with 4 cell and I am mostly happy. The truggy is using a bit more battery than I want (5400mA in 10 min) and I'd like to get a longer run time.

Can somebody tell me how well the 1518 works in truggy and will I get a longer run time without loosing too much top end.

X

I used the 1518 on 5s in a 8ight2.0 and loved it. I could definitely last longer than the 2200 guys but never had to as our races were only 6,8, or 10 minutes. I had no problems completing 10 minute heats.

Power and speed were definitely more than the 2200kv truggies.

You can use the 1518 at the same voltage of your 2200Kv, to keep the same top end you just need to increase the pinion size. You will gain a little runtime because the 1518 will run a little more efficient than the 2200Kv.

I have to disagree.

The 1518 will make more power, to get more power you use more amps, that decreasing the runtime. Lower gearing with your current setup will increase runtime, or going up in voltage, and then lowering gearing. Batteries are cheaper than motors, so go to 5s lipo, and gear down.

Plus the 1518 will be a bit slow on 4s, IMO. More of a 5s motor.

If you are happy with the performance of the 1515 stick with it. Higher voltage and lower gearing will equal less load.

Higher voltage setups are more efficient than lower voltage setups. Even if you keep the same overall battery weight (meaning your 4s pack will have more capacity than the 5s you switch to) you will notice an increase in run time. This figures that your driving style and top speed are the same, which if you retain the same kv motor will require you to run a smaller pinion as the motor will spin faster.

lincpimp, you didn't understand what i meant, here is my opinion :
Keep in mind that the motor produce the power the setup requires, the motor doesn't force its power to the setup.
Geared for the same speed, the 1518 motor will draw the same amp of his current 2200Kv 1515 setup ;) even a little less amp because it will run more efficient, and even on 4S (same power in a bigger motor which has same winding width and type).
Volt up and gear down is not always the best solution to gain some efficiency, because there is bigger amp spikes at higher voltage.
However, trying with 5S and low gearing (if the motor mount allows it) is a good idea, but don't forget to increase the punch control, in order to avoid the amp spikes which are responsible of heat and unefficiency...

Nuz, I have to disagree as well. While the motor is large and more powerful, in order to reach the same level of performance when dropping voltage, you have to increase amperage.

You don't drop the voltage, you keep it same, 4S for both 1515 and 1518.
Feel free to do the test, I have done it between 1515 and 1520, both on 4S. You just need a bigger pinion with the 1520 to have the same top speed, both motor operate at the same voltage and draw the same current, both motor provide same performance and consume the same power, the 1520 is just a little more efficient because it handle the same amp in a bigger space.
And the 1520 does not produce more power than the 1515, the 1520 "CAN HANDLE" more power if it "HAS TO", there is a difference.
It's not a Kv comparison like 1515/1Y 2200Kv and 1515/1.5Y 1500Kv, in this case, like you said, the 1.5Y windings need 1.5 more voltage to have the same performance. See the castle description for 1512 motor, max amp rating is 80A for 1512/1.5Y and 120A for 1512/1Y.

But you're talking about a larger motor, with a lower kv, being geared up to achieve the same speed on the same voltage- I'd doubt it would pull exactly the same current as the 1515 motor somehow- you have no way of knowing how much current each setup would pull without putting them both on a dyno to get exact numbers. Gearing up a low kv motor will place more strain on the system- higher mechanical load so a higher current draw. Using a higher voltage with a lower kv motor & lower gearing though will produce the same speed at a reduced load, so better efficiency in principle.

You'd really need to increase the voltage to 5s & adjust the gearing to match the original setup- I wager you'd get your longer runtimes & better efficiency then for sure. Gearing up a lower kv motor, when its larger and capable of a higher total power output is gonna cause it to draw more current vs the slightly smaller motor with a higher kv motor that has a lower gear ratio ( relatively speaking )..

Thereoretically nuz69 is right. The setup only draws as much power as it needs for a certain speed. If the output power required to go 40Mph is 2500W, then for the same vehice it will ALWAYS be 2500W to go 40Mph. What changes however is the input power from the battery based on the efficiency of the system.

nuz69's theory is based on the assumption that the efficiency of the 1518 will be the same as that of the 1515, with a 4S lipo pack. This is incorrect as the 1515 will have the most efficient top RPM of 32,560 whilst the 1518 will have a max RPM of 26,640. At 26,640 the motor is in a lower portion of its power curve, and is not as efficient compared to an RPM of around 30,000. The 1518 motor is more efficient when run on higher voltage, in the right RPM range, compared to the 1515 on a lower voltage - as it is high current that increases the power loss in the system.

As a result, the lower efficiency of the motor will demand more INPUT power from the batteries. More Input power for the same voltage means a Higher current draw. Therefore, running the 1518 on 4s will draw more current from the battery resulting in shorter run times. Not to mention higher temperatures.

Xsmoker, I think there are only two options for you. higher capacity 4S batteries for longer run times or a 5S setup with a 1518 and lower gearing. Cheapest would be the larger 4S batteries, since the other option requires you to buy a whole set of new 5S batteries and a 1518 motor.

No I am damn sorry, this statement is correct for two motors of same weight and different Kv due to different windings, BUT we are talking about two motors wich have same windings and different weight.
"lower portion of its power curve", This is not a nitro motor, the efficiency of a brushless motor is not measured by varying the voltage, but the LOAD or the AMP going through the motor, while the motor is under a given voltage.
The 1518 motor, with its longer rotor, produce more torque at the same amp, so puting an higher pinion on it will compensate the lack of RPM and will result of the same working point in terms of current, however the shaft of the motor will be strain of an higher torque. Moreover, the 1518 will have to handle the same power in a larger can and on a longer rotor, so the temperature will necessarly drop a little, and efficiency will go up.
That's exactly the reason why here in europe in our large tracks we use the 1515 2200Kv on 4S instead using 1512 2650Kv on 4S because it always overheats, too small motor...
On the other part, in our practical application, a lower Kv motor will produce lower amp spikes during acceleration, and amp spikes are responsible too of the heat and bad efficiency, that's where the 1518 win the efficiency test too.
I have done the test between a 1515 and a 1520 on 4S geared for the same speed in my mbx5T, I always had lower temp and longer runtimes with the 1520. I suggest you to do the test.
Anyway I race my truggy on 6S with the 1600Kv but with adapted ESC parameters to avoid as possible the amp spikes...

==> Xsmoker you can begin by increasing the punch control, and maybe drop one pinion tooth, I know by experience that most of the pilots have a too large gearing for the track they race.
After that if you have some dollars to spend, don't buy larger 4S batteries, it will add more weight, not good for the driving behavior and strain on the system. Buy some 5S 4000mAh and reduce the pinion of 4/5 x actual number.

I have to agree with Nuz69 as well -- geared for the same speed, the 1518 will run a little more efficiently than the 1515. It will run at lower RPM, which will result in lower magnetic losses. Copper losses will be a wash between the two motors (because current will be very similar.)

In most cases, when geared to give equal speeds, the longer, lower Kv motor will usually be a little more efficient.

This assumes that the two motors have the same winding and construction (like the 1515 and 1518).

Thanx!

Patrick

ahhh so thats what I was missing, the fact that the 1518 is a longer motor and hence can provide more torque at lower RPM, with a roughly equal efficiency. I stand corrected.

As it sits now, I turn down my EPA about 20% so the 1800kv motor should be fine where I'm geared at now. If it will generate some more runtime, that would be great. To be honest, I'm a little heave on the throttle so there is a lot of tire rotation waste in my driving. Taking away some of that might help improve my driving and get my battery run times where they should be. I'm burning 5400mah in 10 min with about 1 lap warmup, that's too much. Sometimes when I run with nitro's they run 15minute mains and that forces my driving to tune down so I can make the main. Other E truggies finish with plenty of batteries left. I have nothing binding or anything like that, my truggy is tuned so that is not the cause. I was thinking the 1800kv motor would be more efficient than the 2200kv and therefore I'd have a longer run time.

X

The EPA does not necessary cancel the amp spikes, especially if you are heavy on the throttle. Try the punch control at 80%.

EPA should never be adjusted more or less than 100%. It is the incorrect way to accomplish your goal and actually can cause more strain on the system.

Adjusting start power, punch control, and throttle curves is the correct way.