Why faster lap times driving my SC10 17.5 than my SC10 3300kv???
 

I have 2 Team Associated SC10's that are set up almost identical. The first is a SC10 RTR with the original ESC and Brushless 3300kv motor (uncensored). The other one is a SC10 Factory Team with a LRP SXX "Modiefied" Competition Brushless ESC and a Speed Passion V3.0 17.5 Brushless "sensored" motor. Both trucks have the same tires and ball diff trannies, same batteries. I have the slippers and ball diff adjusted the same also. The 3300kv has 16/87 gearing and the 17.5 has 25/78 gearing. The 3300kv seems to have a faster top end, but that doesn't seem to matter as you'll see below.

Here's my question? why do I consistently run 2 second faster lap times at my indoor short course track (clay, hard, low to medium traction, pretty tight course, you might get to top speed on one straight away for a split second) with my 17.5? It seems like no matter what gearing I run on the 3300kv, I can never get enough torque/hook up out of the corners to jump anything, hence to slower lap times. It almost feels like I have too much top end and not enough bottom end, so I can't jump anything compared to the 17.5. It feels like it doesn't "spool up" fast enough out of the corners, like it lacks torque. Could this be a ESC and/or motor itself issue, meaning, does this motor not "spool up" fast enough on tighter courses, that it's more of a top end motor? I heard that the stock Team Associated ESC's aren't the best. Could it be becasue it's not a sensored motor, compared to my other sensored motor? Somenoe mentioned that since the 3300kv motor is "unsensored", that I'm probably not getting the bottom end/instantaneous acceleration offered by a sensored motor to get the bottom end out of corners to make the jumps.

Any ideas? My thoughts are that shouldn't a mod class truck be turning faster lap times than a stock class truck?

Do I need to by an aftermarket ESC and sensored motor?

Thanks!

Basic motor physics. A ROAR 17.5 is about 2200kv. The lower the KV the higher the torque and acceleration but the lower the high end. They can also be geared to basically anything. The 3300kv will obviously have more top end but lower torque and acceleration.

Also chances are the 17.5 gives a more "handle-able" driving experience therefore you spend less time correcting yourself then with the 3300kv.

Precisely. Consistency. I've been considering installing my 17.5, but may look to get a 13.5.

With the short course trucks, sometimes slower is faster due to wheel spin. The 3300 could be too much motor for the track. The track I run at, the top drivers in Stock are within .5 seconds of the top drivers in Mod. Most the mod motors are 8.5 systems.

Understood! I really don't think it is due to wheel spin though. What are your thoughts on the whole sensored/unsensored thing, and/or a stock ESC versus a competition ESC?

I'm thinking it may be the trucks, swap both engine/esc combo's over and go from there, a local went from fast to pwning by going from the original kit to the FT with the same setup

I suspect the ESC is a big part of it. The timing of something like a SXX can make a huge difference, depending on settings. A 17.5 can darn near run with modifieds with a jacked up ESC.

But how much have you played with gearing on the RTR, what kind of motor and temps are you experiencing? Oddly enough if the motor is not too hot, say 110~120F or lower, and especially if the ESC is hotter than the motor, you might be able to get more punch out of it with a bigger pinion. Assuming enough battery current capability. Just be careful and keep tabs on temps, don’t overdo it. Perhaps no more than 150F to be safe.

For a 3300 kv motor you are undergeared. Weird as it may sound, gearing lower does not necessarily give you more torque. If you feel that the 3300 has less "pop" than the 17.5 (and is running under 140 degrees) gear up. I would imagine gearing a 3300 closer to 22/87.

I've got the 3300 setup inmy SC10. 16/87 is WAY too low. They come from the factory at 18/87 and that's really conservative. I ran on a roughly 30x60track at 22/87 last weekend and I was almost able to keep up with the guys running 10.5s. I was running 3000mah each session and it was hot to the touch, but not so hot I couldn't keep my finger on it. Try going to 20/87 and see what the temps are. If that's too cool setup up one tooth at a time and check your temps every 5 minutes.

I've had experiences with sensored and non sensored systems (Tekin). The difference is the more precise acceleration from a dead stop with sensored.

The biggest drop in lap times for me when going sensored was the faster response from the motor after the occasional spin out and roll back. The sensorless systems tended to hesitate in such a situation, whereas the sensored system was able to move right away.

Try it for yourself. Take the SC10 with the stock 3300 system, power it up, drive it for several feet. Next, roll it backwards by hand about two feet, and notice the hesitation when accelerating from a stop . Now do the same with the SC10 and the 17.5 system and see the difference.

Ok, you guys have me interested in the gearing issue. I'll try a 22'ish pinion on Wednesday and see how it does with bottom end/torque out of the hole. I'll let you know!

I think it's the sensorless system. The Velineon by Traxxas acts the same way and is hard to race with because of it. You pull the trigger to clear a jump and it doesn't go.

I totally agree. Once I learned about sensored and sensorless I tested them out as well. Sensored systems are definitely the way to go. Once moving at a good pace you won't notice a huge difference between the two but from a standing start or very slow moving will be very different. Definitely try the gearing change as suggested to see how that makes a difference as well. It's good to get the gearing experience.

The one time I ran a 17.5 in anything, it was in my T4, and my gearing was at like 34/78

Good to hear that some people think it may be the sensor/less issue. Either way, I'm going to try the gearing changes, and compare that back to back with a Tekin 9.5 and 10.5 ESC and motor system. They should be here Wednesday.