Proper Gearing
03-04-2011, 06:28 PM
#1
Proper Gearing
Ok, I practiced the other night at my LHS. It's an indoor technical off road course. I was trying to find the right gearing for the motor I installed. I ran for 3 minutes and barely 100 deg. I then left it cool and added another tooth on the pinion and went out again and again only around 100 deg. I tried this several times and could not get the temp any hotter than 123 deg. 
I then changed the timing on the motor from 0 deg to 10 deg. to still no avail. My question is I have seen Associated states FDR 6.96 for the 17.5 class that I am running. My FDR was 7.81 and the truck did not have the torque I like for the jumps but it was easier to drive since the rear was more planted with less wheel spin. Should I have lowered the FDR more or am I going in the wrong direction? I did notice I was having less and less runtime during the process as well. Anyone have any suggestions or similar problems? Also, if this is right how many teeth do I have to add to the pinion if I run a 10minute main?
I then changed the timing on the motor from 0 deg to 10 deg. to still no avail. My question is I have seen Associated states FDR 6.96 for the 17.5 class that I am running. My FDR was 7.81 and the truck did not have the torque I like for the jumps but it was easier to drive since the rear was more planted with less wheel spin. Should I have lowered the FDR more or am I going in the wrong direction? I did notice I was having less and less runtime during the process as well. Anyone have any suggestions or similar problems? Also, if this is right how many teeth do I have to add to the pinion if I run a 10minute main?
03-04-2011, 08:34 PM
#5
with the smaller spur u wont have the bottom end...i run an 81 spur on my sc10...its got more torque than the 78 especially on a tech track...wont have to go as wide in the corners to get ur speed up to clear obstacles
03-05-2011, 01:13 AM
#7
Im running on an indoor tight clay track, med-high bite. It is all acceleration. Not much room for any kind of real top end.
17.5 class i am using a 81/24, similar to another guy running a 78/23
Max boost timing (55 degrees) from 5k-20k rpm
5 degrees turbo 2.0 ramp
Came off the track tonight after A-main at 147 degrees.
To some it is all in how you want your truck to feel. I am to the point that changing 1 tooth pinion, or 3 teeth on spur, i can totally tell a difference on this track. The 17.5 is torquey enough that small changes in gear seem to change your torque curve to the ground. It is possible to get better acceleration with a smaller fdr too. It all depends on exactly what you are running. This is pretty dam evident in 2wd buggy, especially when using a 17.5.
A higher FDR will most definitely blast off the line quicker, no doubt there, but going smaller can put your powerband in a different spot. Just as an example, rolling starts at certain speeds, a smaller fdr can find its own advantages upon acceleration.
Maybe a little long winded there. Almost a sure-fire way is to ask around at your track and try some of the more popular combos. Everyone is different so it is going to vary. You dont always have to gear to temp, gear to what feels good, temp the motor every few minutes to be sure and make adjustments from there.
17.5 class i am using a 81/24, similar to another guy running a 78/23
Max boost timing (55 degrees) from 5k-20k rpm
5 degrees turbo 2.0 ramp
Came off the track tonight after A-main at 147 degrees.
To some it is all in how you want your truck to feel. I am to the point that changing 1 tooth pinion, or 3 teeth on spur, i can totally tell a difference on this track. The 17.5 is torquey enough that small changes in gear seem to change your torque curve to the ground. It is possible to get better acceleration with a smaller fdr too. It all depends on exactly what you are running. This is pretty dam evident in 2wd buggy, especially when using a 17.5.
A higher FDR will most definitely blast off the line quicker, no doubt there, but going smaller can put your powerband in a different spot. Just as an example, rolling starts at certain speeds, a smaller fdr can find its own advantages upon acceleration.
Maybe a little long winded there. Almost a sure-fire way is to ask around at your track and try some of the more popular combos. Everyone is different so it is going to vary. You dont always have to gear to temp, gear to what feels good, temp the motor every few minutes to be sure and make adjustments from there.
03-05-2011, 05:44 AM
#8
Im running on an indoor tight clay track, med-high bite. It is all acceleration. Not much room for any kind of real top end.
17.5 class i am using a 81/24, similar to another guy running a 78/23
Max boost timing (55 degrees) from 5k-20k rpm
5 degrees turbo 2.0 ramp
Came off the track tonight after A-main at 147 degrees.
To some it is all in how you want your truck to feel. I am to the point that changing 1 tooth pinion, or 3 teeth on spur, i can totally tell a difference on this track. The 17.5 is torquey enough that small changes in gear seem to change your torque curve to the ground. It is possible to get better acceleration with a smaller fdr too. It all depends on exactly what you are running. This is pretty dam evident in 2wd buggy, especially when using a 17.5.
A higher FDR will most definitely blast off the line quicker, no doubt there, but going smaller can put your powerband in a different spot. Just as an example, rolling starts at certain speeds, a smaller fdr can find its own advantages upon acceleration.
Maybe a little long winded there. Almost a sure-fire way is to ask around at your track and try some of the more popular combos. Everyone is different so it is going to vary. You dont always have to gear to temp, gear to what feels good, temp the motor every few minutes to be sure and make adjustments from there.
17.5 class i am using a 81/24, similar to another guy running a 78/23
Max boost timing (55 degrees) from 5k-20k rpm
5 degrees turbo 2.0 ramp
Came off the track tonight after A-main at 147 degrees.
To some it is all in how you want your truck to feel. I am to the point that changing 1 tooth pinion, or 3 teeth on spur, i can totally tell a difference on this track. The 17.5 is torquey enough that small changes in gear seem to change your torque curve to the ground. It is possible to get better acceleration with a smaller fdr too. It all depends on exactly what you are running. This is pretty dam evident in 2wd buggy, especially when using a 17.5.
A higher FDR will most definitely blast off the line quicker, no doubt there, but going smaller can put your powerband in a different spot. Just as an example, rolling starts at certain speeds, a smaller fdr can find its own advantages upon acceleration.
Maybe a little long winded there. Almost a sure-fire way is to ask around at your track and try some of the more popular combos. Everyone is different so it is going to vary. You dont always have to gear to temp, gear to what feels good, temp the motor every few minutes to be sure and make adjustments from there.
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