I'm using a Neu 1515 2Y (smooth can) since almost 1.5 years paired with 9-11s1p A123 (27-33V avg) and a Jazz 55-10-32 Esc. It has powered my
truggy,
buggy,
buggy/truggy mix,
Rally game Buggy,
Trophy truck and now a
custom 1:5 Baja.
Due to its low kv (1100kv) it needs more volt than your average MMM setup with max 6s. Feed it with around 30V (8s lipo or 10s A123) and you will have a good rpm range to power any 1:8 buggy or truggy. Power it with up to 10s lipo (or 12s A123) and this motor just becomes plain silly from a torque point of view. Due to its higher resistance you want to keep amps low. Temperature remains very reasonable as long as your Amps hover between 10-70A with an average of 10-20A.
Don't expect a big jump in runtime when switching from say a Neu 1515/1Y fed by 4s 5000mAh to a Neu 1515/2Y fed by 8s 2500mAh. Both motors can output the same amount of power.
Example:
. Neu 1515 1Y: 3.5V x 4s x 100A = 1400W -> 100A^2 x 0.006ohm = 60W lost in heat (only windings)
. Neu 1515 2Y: 3.5V x 8s x 50A = 1400W -> 50A^2 x 0.019ohm = 47,5W lost in heat (only windings)
Theoretically and practically there is a small gain in efficiency when switching from a 1Y to 2y when doubling the voltage. Heat build up of the motor is somewhat lesser. Same goes for cables, connections, Esc.
Now if you feed a 1515/2Y with 100A -> 100^2 x 0.019ohm = 190W lost in heat (windings only) opposed to 60W with a 1Y motor. Explaining why you don't want a 1515/2Y hitting 100A to often otherwise it will heat up quickly. On the other hand 3.5Vx8sx100A = 2800W (minus atleast 190W -> 2610W). That's some serious power for a truggy which you won't need at your track anyway. My truggy (CD with 30000k oil) started to wheel with power levels above 1700W.
This is one of the last videos of my truggy powered by a Neu 1515/2y fed by 9s1p A123 (27V avg) with integrated eagletree inserts. Amp levels were on the safe side, no heat issues. Power was good (still somewhat to agressive).
If you already have a good working 4s setup and only expect a huge advantage in runtime i'm sorry to say a step up to a 8s setup might give you a runtime advantage of only a few seconds (maybe half a minute) when you run both setups at the same power level with the same energy amount on board. A friend of mine switched from a Neu 1515/1Y 6s2p A123 setup to a Neu 1515/2Y 11s1p A123 setup (1 cell less than his LV setup). We couldn't compare them under the absolute same track and setup conditions but power felt almost same, no runtime upgrade (Ok, 1 cell less) ... motor may have run slightly cooler.
At the end: Your car will require the same amount of power to move around a track at the same velocity, no matter which motor you use. Neu motors are efficient no matter what winding you choose. When properly geared and fed (voltage) a Neu 1515 should run happily for a long time in a truggy. As already mentioned: you will see the biggest improvement in runtime with an adjustment to a "rounder" driving style or by adding a bigger (more mah) battery pack.