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17.5T vs. 13.5T in 2wd buggy

17.5T vs. 13.5T in 2wd buggy

Old 12-13-2015, 05:56 PM
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Default 17.5T vs. 13.5T in 2wd buggy

Need help with this. I have a 17.5t trinity short stack motor that I ran yesterday in my serpent srx2. It was my first time with 2wd and a higher turn motor. I had trouble making the first jump on the double double. It is right after a 180 deg turn so I was hitting it at low speed and gunning it at the bottom of the jump. I had the motor timing around 50 (how it came stock) and the esc timing at 25. I can bump that to 40 max. But what I want to know is would a 13.5T motor help me out with more instant power in that situation? I have the opportunity to trade for a schuur speed 13.5 but I don't want to make a mistake. I hear the short stack is fast but I am mainly looking for control and consistency. This is not a big track so too speed Isnt a big deal. But maybe if I bump the esc timing to 40 it would give me the instant torque I need. But would the 13.5 Do a little better or atleast be about the same? I just don't want it to be worse.
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Old 12-13-2015, 06:29 PM
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If you have a 17.5, doesn't that mean you are running in a 17.5/stock class and have to use a 17.5 motor even if you're otherwise in the (rare) situation of being allowed ESC boost? Otherwise, if you're running a 17.5 in a 13.5 class, then yes, you should get a 13.5. If you're running a 17.5 in an open 2w buggy class, skip the 13.5 and get a real mod like an 8.5.
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Old 12-13-2015, 06:59 PM
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Originally Posted by MarkA View Post
If you have a 17.5, doesn't that mean you are running in a 17.5/stock class and have to use a 17.5 motor even if you're otherwise in the (rare) situation of being allowed ESC boost? Otherwise, if you're running a 17.5 in a 13.5 class, then yes, you should get a 13.5. If you're running a 17.5 in an open 2w buggy class, skip the 13.5 and get a real mod like an 8.5.
It just felt like the 17.5 wasn't enough, so I am mainly wondering if 13.5 will be a good step up in torquey power. It is an open 2wd buggy class. You can run whatever you want. I have a 8.5 in my 4wd and I think it will be too much for me in the 2wd. Like I said it was my first time in that class yesterday and it feels a lot different than anything else I've run. It also seems like I have not a lot of steering. It pushes like crazy (on power and off throttle). In 4wd there is a lot more ateering and I can whip around a corner. If I try that in 2wd I just spin out. If I just let off throttle and turn I'm like making very wide turns. Guess I'll have to learn how to brake in the corner.
And this is not a big track. I don't need a lot of speed I need torque mostly I would say. Maybe 10.5 would be te way to go. Kinda in the middle. Mayb I'll do the 13.5 til I can buy at 10.5. Just seemed like the 17.5 wasn't enough
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Old 12-13-2015, 07:08 PM
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If it's an open 2wd class get the 13.5. More timing won't help with the short run-up to the jump. The 13.5 will make it easy to clear without making the car much harder to drive.
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Old 12-13-2015, 07:26 PM
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Try dropping the timing down some as well. More timing gives you more top end speed but you do sacrifice low end torque. Also, how is your gearing? Again, if top end speed is not an issue, drop a tooth or two on the pinion. This will give you more torque as well an help with the short run up to the jump. Also, you may want to tighten the slipper a bit, you may be loosing some acceleration if you're getting to much slip.
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Old 12-13-2015, 07:27 PM
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Originally Posted by Davidka View Post
If it's an open 2wd class get the 13.5. More timing won't help with the short run-up to the jump. The 13.5 will make it easy to clear without making the car much harder to drive.
Ok thAnk you... So what is the timing going to do? More top end? Are there any settings I should be using to help me?
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Old 12-13-2015, 08:00 PM
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Originally Posted by Slapjack View Post
Need help with this. I have a 17.5t trinity short stack motor that I ran yesterday in my serpent srx2. It was my first time with 2wd and a higher turn motor. I had trouble making the first jump on the double double. It is right after a 180 deg turn so I was hitting it at low speed and gunning it at the bottom of the jump. I had the motor timing around 50 (how it came stock) and the esc timing at 25. I can bump that to 40 max. But what I want to know is would a 13.5T motor help me out with more instant power in that situation? I have the opportunity to trade for a schuur speed 13.5 but I don't want to make a mistake. I hear the short stack is fast but I am mainly looking for control and consistency. This is not a big track so too speed Isnt a big deal. But maybe if I bump the esc timing to 40 it would give me the instant torque I need. But would the 13.5 Do a little better or atleast be about the same? I just don't want it to be worse.
What ESC, Batteries, and gearing are you running?
But like said below if your running a 17.5 in a mod class, definitely get more motor! 13.5 is a nice step up but a 10.5 would be a better choice IMHO!
BUT that being said if 17.5 is fast enough for you maybe better gearing might be something to look into?
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Old 12-13-2015, 08:59 PM
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open 2wd? 8.5 will work well. large or small, you will want the quick acceleration for the corner exit to double, etc.. as you mentioned. you can always turn down your throttle epa.
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Old 12-13-2015, 09:04 PM
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I just dealt with this same issue. I was running a 17.5 zero timing car in an open class. The 17.5 demanded that I line up perfectly and get an early run up to clear certain doubles. Near the end of 10 minute mains, with certain batteries I would destroy a perfectly clean run by bouncing off the apex of certain doubles. I finally decided to install a 13.5. Jumps are no problem now, top speed is real close but everything runs cooler and with less timing. I was running 34/75 @ 40 degrees with my Reedy Mach 3 17.5. The 13.5 is at 26/81 @ 15 degrees. Nice upgrade and achieved what I wanted. The 13.5 is a good choice on my opinion. AR
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Old 12-13-2015, 10:09 PM
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Originally Posted by Alan_r View Post
I just dealt with this same issue. I was running a 17.5 zero timing car in an open class. The 17.5 demanded that I line up perfectly and get an early run up to clear certain doubles. Near the end of 10 minute mains, with certain batteries I would destroy a perfectly clean run by bouncing off the apex of certain doubles. I finally decided to install a 13.5. Jumps are no problem now, top speed is real close but everything runs cooler and with less timing. I was running 34/75 @ 40 degrees with my Reedy Mach 3 17.5. The 13.5 is at 26/81 @ 15 degrees. Nice upgrade and achieved what I wanted. The 13.5 is a good choice on my opinion. AR
Awesome, thank you. this is the response I was hoping to get (someone that did what I wanted to do). I am going thru with the trade for the 13.5. . I currently have a 78 spur. What FDR should I be between with the 13.5? With the 17.5 buggy the manual said 5.5-6.5.
But I am running an orca vx3 with trakpower 6000mah/80c saddles or smc 5600/70c saddles.
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Old 12-14-2015, 08:29 AM
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My apologies with a mistyped number on my phone. I started out with a 28T pinion and 81T spur with my 2.25:1 IR. FDR was 6.509. I ended up going to a 29T pinion for 6.284 as I was able to carry more momentum throughout the track than I originally thought I could. I may start playing with the timing curves in my esc to maximize this FDR but the car was pretty good for that days conditions. I usually start with the recommended ratios in the manual and then gear up or down depending on the track I'm running at. I.E gear down on tighter, tech tracks where acceleration is more important and traction is high, or gear up when the track is fast and allows me to carry lots of momentum throughout the layout. In the end, the only cars that end up way off the manual settings are my SPEC setup cars. Hope that helps. AR
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