It's a 4 cell motor for our use.  If you try a five cell, it would have way too much RPM for stunt use.

It's a 4 cell motor for our use.  If you try a five cell, it would have way too much RPM for stunt use.

I know I'm disagreeing with Robert, here, but as long as your ESC or timer holds the RPM steady, the only really significant thing that's going to happen if you go from four cells to five is that your ESC will get a bit warmer from increased switching losses.  So your system overall will be slightly less efficient, but unless you're already on the ragged edge with your ESC everything else should be fine.

There's quite a few people who have gone from four cells to five (or five to six) just because they can get a slightly lighter pack, or a slightly taller, shorter pack.

Thanks Robert  I should of made myself more clearer sorry about that. Yes I was looking for just a tad more power for the pattern.    Thanks again. Steve

Come again?  What's lacking in the current setup?  I'm an engineer, so it's kind of obligatory that I beat the terminology drum here: do you really mean power, as in the motor's ability to pull the airplane through the pattern at any given instant, or do you mean energy, as in the system's ability to run just as well in the hourglass and cloverleaf as it did in the wingover and the loops?

If it's a matter of just power, then you may need to extract the available power from the system better, or you may have a woefully undersized motor.  If the system is running out of poop at the end of the flight, then you're talking energy, and that can be cured either with bigger cells in a 4S pack (more mAh), or with a 5S pack (possibly with smaller cells).

Hey Steve:

OK, first the grain-o-salt: I fly slime CL.  None of the CL-specific stuff I say comes from direct personal experience.  But I'm an electrical engineer and I fly electric RC, so I think I know some of this stuff.

Second, if you're putting back 2400mAh into a 3300mAh pack, then you're currently doing fine as far as energy use goes.  We may be able to change that, however.

Third, I think you need to increase the launch RPM a bit.  You should have enough voltage overhead to push the launch RPM up to nearly 10,000 RPM, which is probably way too fast.  I vote for nudging the speed up a bit and seeing if it fixes the verticals and overheads without speeding up your level flight and rounds too much.  If you're feeling it run out of grunt as loss of line tension, then make sure that you've done a Really Good Job trimming it after the make over, perhaps after you bump up the RPM, at least temporarily.

After you get the RPM up, if it flies nice, pay attention to how much is going back into the pack, just to make sure that you're not overtaxing your batteries.

Steve:

Be careful with the higher rpm. You are using a KR Governor so remember that it has the variable gain feature. This increases the rpm when the prop comes under increased load in the maneuvers. With a 4 cell battery you only have approximately 10,300 usable rpm available with that motor. (870 kv X 14.8 X 80%). If your lap time with your current rpm is around the 5-2 to 5-4 second level I would leave the rpm where it is and try increasing the gain (you can go all the way up to 7). That should give you the extra Umph you want in the maneuvers yet still leave you sufficient head room in the rpm available for use. If you increase the rpm to the 10000 that Tim suggested it would not leave you very much head room for the gain to work. If increasing the gain  does not work certainly going to the 5 cell would increase the total usable rpm (870 x 18.5 X 80% gives you approximately 12,800 usable rpm)

FYI, Mike Haverly tried the Eflight 25 on his profile ( somewhere around 600 inchs ish),, he said,, nix, nada no go,, just was not happy,,

just more info for your fires,,