1/8 bl gearing?
 

running a losi8T,neu15152.5d,mm esc ,4s4000 lipo and 13 pinion&46 spur!truggy seeems kind of slow though. maybe change gearing?or maybe a 5s lipo with a new esc? i know how to change my throttle and acceleration curves on the mm esc, but the higher i run the mm esc the more cogging i get!

probably going to need more voltage with the 1515 2.5d. Try gearing up, but the MM may not like it.

The reason why it is so slow is because the 2.5d is 1700KV. Try a 5s lipo, or even better 6s lipo... you will probably need a new ESC for running this voltage though.

I would think you should be geared around a 16t. when I run my 1521 (1577kv) I run a 18t or 19t. If you go to a higher voltage you will need another esc.

The 1515 2.5D (1700kv) doesn't rev that high on 4s, so you need to gear up a bit to get your speed, but then too much gearing might coarse more cogging with the mm, not sure.
Are you racing? Not sure what sort of speeds you want, but 35mph is a good area for racing I think. You'll want about a 16t pinion to get ~35mph.
Try BrianG's calculator if you haven't seen it before. http://www.scriptasylum.com/rc_speed/_top_speed.html

I use the 1515 2.5D (1700kv) geared 46/13 in my truggy too, but I use it on 5s to get around 35mph. Seems pretty good how it is, but once I get the handling, and my driving sorted out I'll probably go to a 14t pinion for little bit more top end.

i found that a 16 tooth pinion works good in mine but it just depends on the track size. im also running a four cell an my motor is a little over 1800kvs.

I don't reccomend 6s on that motor. I am running 5s at 12/51 and it is faster than any V-spec truggy on the track. 6s and you will be running a 9T pinion with more torque than you (or anyone) can handle on a track. my 2 cents.

Correction...I am running 5s on 13T/51 on the 1515 2.5d, not 12/51. Screams like hell. :diablo: