17.5 Motor Question
 

I have been running a mod motor in 2 wheel buggy on carpet. I want to get into 17.5 racing so I went out and got a Orion ultimate stock 17.5 and took some laps last week. I could not get enough power to clear this double at our track. Checking motor temps I could not get the temp over 100. So I kept going up on the pinion trying to get some heat out of the motor. I ended up with a 36P & 69S after that I gave up still with not enough power to clear the double with ease. Again motor never above 110. So I went out and bought a Revtech 24K certified and a Gforce Analyzer to play with timing. My numbers on the Orion from the track were as follows
KV 2783
rpm 20600
u 7.4V
I 2.2 amp
Timing 36
32 37 38
After bumping up the timing way up from before I am at
KV 3455
rpm 27299
u 7.9V
I 6.7 amp
Timing 50
48 50 53
My Revtech 24k certified out of the box is
KV3238
rpm 23639
u 7.8v
I 6.2 amp
timing
52
50 54 52
So which motor is better by these numbers? And with the differences in the Orion numbers, should that motor be much better then before with the timing moved up?

They are close, but I am leaning towards the orion. If you never ran it with the timing at 50, you are in for a surprise.
Are you running a stock class where you have to run in blinky mode?

It's very hard to compare motors with different numbers, looking at the battery voltage would make me ask if the battery was fully charged, and of quality, not some cheap pack, so generally I have seen a lot of motors set at 6 amps, and if your running longer mains I would imagine 5 amps, but won't know for a month on that number, as last year my motor was set at 4.0 amps and ran a 15 minute main, my certified motor was at 9 amps, but would fade at 5 minutes.
So what I have been doing is keeping a note book with motors and their numbers, first being timing and what it actually was on the motor can, then amp draw, and RPM's along with voltage, then at the track temps, personally I would keep it under 6.5 amps, seemed that the amp draw was more than the RPM's, also making sure to keep the battery charged makes a huge difference, but I will say I am no expert on tuning, just reading and trial and error.

Yes, I will running in blinky mode. Mod seemed easier with just setting the esc and letting it do the work.

Thanks for the info. Looks like I have a lot of testing to do at the track. I have been keeping a log as well on the motors and will be also logging track results. Can you use the Motor Analyzer while the motor is connected to the esc?

that's fine as long as you take out the sensor wire from the esc . you have to take out the pinion too.

Didn't see how low you tried gearing. On my Fantom v2, anything above 69/29 I was not clearing long jumps. Have you tried gearing DOWN to 69/28 or 29? May wake the motor up. Looks like you already have good rpm and could gear down for torque. Also don't know if that's a short stack but would think 30 would be max if it was

When converting to stock racing, I've found motor selection to be relatively negligible, provided you have already optimized each respective motor by adjusting the timing on a motor analyzer. In order to clear jumps better and get faster acceleration, I've found it far more important to shed as much weight as possible, particularly any rotating mass, I try to get within a couple grams of the min weight. Things I've done to shed weight include, lightened aluminum axles/outdrives (MIP Pucks), Slipper eliminator, plastic pinion gear, cut spur gear... I first started with a sub-shorty for a cheap method to reduce weight, but found it better to go with a lightened chassis, lightweight body and shorten wires with motor tabs on bottom of chassis, then went with a standard shorty to get more punch.

https://www.youtube.com/watch?v=0t3m_Fl0rxU

Now that I bumped up the timing I going to start with a 69/30 and see what my temp will do. It's a tight carpet track with a lot of big jumps that need to be cleared.

I went out and bought a new XB2 just for stock as my mod XB2 had some brass up front. For stock I am running a plastic pinion with a slipper eliminator. Aluminum bulkhead & steering. My total weight right now is 1485 just under the minimum. One difference I did do from my mod was using a 3200mah Orion instead of the 5000mah Orion I use in the mod. Would using the smaller battery have a effect for power? Both batteries are fairly new Orion batteries that are 110c. I haven't found a option that lets XB2 users the option to use a Mip pucks yet without giving up the gear diff.

the difference between a sub shorty and standard is negligible at the beginning of a run, but the sub shorties might not be able to clear some of the larger jumps toward an end of a run... I see a lot of XB2's at my local club and they're all very competitive, though not exactly sure what mods they're doing. I'm currently running a 22-3.0 so can only speak for the improvements I've made to this platform and basically, 1 single change doesn't make any measurable difference, but a collection of all the changes together will really add up and then you start to see tenth's of seconds drop off the lap times ;)

Oh and another tip for stock is I like to run AVID Ceramic Revolution bearings (less rotating mass than traditional bearings) .... I remove the rubber shield completely (significantly less friction) and place the exposed end to the inside of each hub, I also flush the grease from the bearing with brake cleaner and use a dry Teflon based bike chain fluid for lubrication of bearings and metal rollers on my Pucks. When I free spin a front wheel, it tends to continue rolling indefinitely, ha!

Sounds like the gearing was your issue. Had no real issues with the xb2 when i owned it. I will say it does fly a little lower and nose high compared to all the other brands. Don't know exactly why. If you're lower grip, I found the long rod ends on the rear shocks helped with this. Buggy has very little droop anyhow.

I got to the track for a couple of days of testing. I found the power I needed to clear the jumps just not 6 minutes of that power. Right around 5 minutes and then I lose the power to clear those jumps. I am going to continue the quest to be able to hold that power for at least 6 minutes for the main. I was thinking going back to a 6 amp draw and playing with gearing. I am also using 5000 mah Orion batteries.