muggzy Posted May 20, 2011 Report Posted May 20, 2011 Ok, i'd been running with a 13t front and stock rear (got it that way) and recently changed to a 14t front. I rode it for litterally 2 min and liked how it felt: surprisingly no noticable loss in low end torque. So I went ahead and changed my domes from 22cc to 21cc and the compression went from 145ea to 158ea. I'm still running 93 oct. The bottom end is awesome and the power band "hit" smoothed out completely which is exactly what I was looking to do. My top speed is only about 4mph faster. I thought with the bigger front sprocket and more torque, I would've got a little more top speed than that.??? Quote
LS3 Machine Posted May 20, 2011 Report Posted May 20, 2011 Ok, i'd been running with a 13t front and stock rear (got it that way) and recently changed to a 14t front. I rode it for litterally 2 min and liked how it felt: surprisingly no noticable loss in low end torque. So I went ahead and changed my domes from 22cc to 21cc and the compression went from 145ea to 158ea. I'm still running 93 oct. The bottom end is awesome and the power band "hit" smoothed out completely which is exactly what I was looking to do. My top speed is only about 4mph faster. I thought with the bigger front sprocket and more torque, I would've got a little more top speed than that.??? Thats actually a very good increase in speed for relatively little in terms of mods: At higher speeds aerodynamic forces become important, increasing as the square of the airspeed. A flat plate of one square foot area and perpendicular to the relative wind will produce drag force of zero at zero miles per hour, 33 pounds at 100 mph, 133 pounds at 200 mph and 299 pounds at 300 mph. The corresponding horsepower required to overcome the aerodynamic drag is zero, 9 hp at 100 mph, 71 hp at 200 mph, and 239 hp at 300 mph. A drag racer may have drag equivalent to a flat plate 12 feet in area and acting several feet above the ground, requiring 2,868 hp to overcome the aerodynamic drag at 300 mph. Going faster is expensive, how fast do you want to go? Quote
robert.b.west Posted May 20, 2011 Report Posted May 20, 2011 Changing one tooth on the front sprocket is usually about a 5 mph change. If you have enough power to turn the gear ratio to overcome drag. Here is just something that compares hp req'd to go a certain mph to over come drag. This is not exact. I dont know the frontal area of a banshee or the drag coef. I estimated to my best ability. It just shows if you gear correctly if you machine as (x) hp you should be able to do (y) speed. 10 0.074 20 0.594 30 2.004 40 4.751 50 9.279 60 16.033 70 25.460 80 38.005 90 54.113 100 74.228 110 98.798 120 128.267 Quote
muggzy Posted May 21, 2011 Author Report Posted May 21, 2011 (edited) Going faster is expensive, how fast do you want to go? I'm going fast enough. I generally ride woods and trails. I really wasn't looking for or need more top end, just surprised it wasn't a little more .... see below well more compression kills overrev. I knew there would be hit from the laws of diminishing returns as far as higher RPMs and therefore overall top end speed but I'd read somewhere that it happened at higher compression than I added. Changing one tooth on the front sprocket is usually about a 5 mph change. If you have enough power to turn the gear ratio to overcome drag. Yeah, that's why I thought there'd be more. I figured another 5 or so and I added some power with the compression ... Here is just something that compares hp req'd to go a certain mph to over come drag. This is not exact. I dont know the frontal area of a banshee or the drag coef. I estimated to my best ability. It just shows if you gear correctly if you machine as (x) hp you should be able to do (y) speed. 10 0.074 20 0.594 30 2.004 40 4.751 50 9.279 60 16.033 70 25.460 80 38.005 90 54.113 100 74.228 110 98.798 120 128.267 According to this (if I'm reading you correctly), I'm putting out just over 100hp. No offense, but I doubt it. Overall, I'm thrilled with the improved throttle response. The only thing I wasn't totally happy about with my Banshee was the sort of unpredictable way the power band would hit when I just wanted a little more not necessarily A LOT more. Like at the or near the crest of a steep hill climb Edited May 21, 2011 by muggzy Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.