which would draw more amps?

feigao 540c-9L (3345kv)
neu 1515 2.5d (1700kv)

in a 1/10 4wd stadium truck, on 5s1p lipo, both geared for the same speed (~75mph)?

the neu says 700-3000watts, so on 20v, that's 35-150amps.. should i expect peaks as high as 150 amps?
the feigao is 88amps (the 540-7L is 3500kv, which is similar to mine). the feigao would also be around 67k rpm. while the neu would only be 34000rpm.

i guess what im looking for is which would draw the least ammount of amps?

[sleebus.jones]

First off, spinning a feigao that high isn't that good of an idea. They like to run around 35K, so 67K is a bit much.

If you are running the same voltage and getting both motors to do the same amount of work, the amp draw will be the same. If you went with 6S on the neu, and regeared accordingly, that combination would have a lower amp draw, because of the higher voltage. The watts output (assuming you are going for the same speed) would be the same as the 5S, since again, you are doing the same amount of work.

Sleeb

[BrianG]

^ +1.

While a good idea to keep amp draw in mind, a lot of people seem to get too hung up on it, but it's not as big deal as you'd think. For one thing, cars are "peaky"; they pull large currents for a short time, but the average is usually between 5-7x lower than the peak draw.

Any system will require X amount of power to get the speed you want in Y amount of time. Increase the weight, increase the speed, and/or lower the time to get that speed = more power. Power is volts X amps. Higher voltage means less amps for a given power.

That said, any similarly sized motor is capable of approximately the same power output. However, higher currents are not as efficient, so there are more voltage drop losses, not to mention requiring beefier batteries, wire, and ESC.

[glassdoctor]

the neu says 700-3000watts, so on 20v, that's 35-150amps.. should i expect peaks as high as 150 amps?

You can't look at it backwards like that. The watt ratings given for each motor are simply what they can "handle". It doesn't mean that they can't/won't draw more amps... or that they WILL draw that amount. It's simply a "duty rating".

It will take X amount of watts to get to a specific speed... no matter what motor/battery setup is used. Watts=horsepower.

Except that one motor is more efficient... so that means the less efficient motor will have more watts wasted as heat, so really it does take more watts to make that motor do the job.

If my ramblings make no sense... no worries... ha ha

thanks guys.. but then which motor should I go with? I know 60k is a bit high, but i've pushed hacker S cans to 80k, and feel 60k in a lighter 1/10 with a L can won't be that bad. my goal is to make a very fast, and very light truck, primarily used for jumping. my lsp-r's just too heavy to try and hit a jump WOT.. i can't find any heavier springs for it either.
so the plan's to put the lsp-r's shocks on the mt2.. run just one of my 5s1p 5Ah true-rc packs, and hopefully it doesn't over-tax the battery pack..
i've ran my LSP-R with just one battery pack, and it didn't harm the pack at all, so I'm sure i'm being over precautious.
what would you guys do if you were in this situation? the feigao would make gearing alot easier, as I have pinions 16 through 22. i'm not sure what the diff ratio on the mt2 is, but i dont think 34k w/ a 22t pinion will be fast enough..

[cart213]

Also, the 540c 9L is not 3345kv. The 9L is around 2700kv.

Btw, why are you trying to go 75mph in a MT2? I used to own a brushless MT2 (see my avatar), and I used a 540c 9L in it with 4s li-ion cells. I think my pinion was 15t, but I'm not sure. That combo was good for 60 mph, and I can't imagine anyone trying to squeeze another 15 mph out of that truck, especially for jumping. IMO, unless you upgraded everything for extra durability, that truck is not tough enough to withstand 75 mph bashing. Although, if you can keep from crashing it, then the toughness won't matter, right?

That's why I upgraded to the ST-1 truggy (also in my avatar). It's MUCH tougher than the MT2, but it is about 4 pounds heavier.

With that said, I think you should use the Neu in the MT2. My 9L got really hot on 4s and 5s will make it even hotter.

that really is a cake or death decision really if i have ever seen one.

The neu should run nicely on 5s but that feigao motor would as been suggested be running at 60k rpm that would probably make the motor about 50 percent efficient and quickly become a blob of fused aluminium and copper.

[sleebus.jones]

Yup, I agree, neu over feigao. 60K rpm is not a good idea.

you really think it'd melt the motor chilled? when i first got into brushless, i was anything but on the conservative side.. hacker b50 8s on 16 cells, lehner basic 5300 on 12 cells.. 2x basic 5300's on 24 cells.. lol another option is simply limiting the epa.. and the parts are cheap to replace, as long as i protect the batt, controller and motor, i'll be happy. i figure its time i start getting video that people will enjoy watching again :) i think of it as a sub-hobby lol.

oh, and cart, my motor's 3345kv. it's written in pen on a label on the endbell. i forget where i bought it from, but i remember being told it wasn't a "regular" 540c-9l.

[sleebus.jones]

It's simply not efficient. You don't need to rev it high like a nitro engine. The more RPM you make, the more drag you have in bearings, etc. Let the gearing provide the advantage.

the problem is with feigao motors is they accumulate heat if you want to do short drag races then i am sure it would be fine but after you have been driving for 30mins i would not like to see the temp of that fegao.

at least you can go upto 660 celcius before it melts.

I really don't know that you can push a 1/10 scale truck to much over 60 and retain any sort of control. The tires and suspension actually become your enemy at those speeds. In fact, doing 75+ with an on road on anything other than a prepared track was dicey.

We were able to attain 94+ mph with an 1/8 scale Kyosho on road car with a 1900kv motor on 5S lipo. It was all in the gearing and not the sheer rpms.

[Patrick]

I wouldn't count on the neu doing 34 000rpm, I think it would be more like 30 000 or a bit less, depending on what voltage those batteries can hold in 1p when geared that high.