hello after seeing alot of dyno results of the CRF250L ive noticed that the average number at the wheel is about 18-19hp and 14-15ftlb. would this average be considered correct? i noticed that most of the dyno results were done at 500m or less, so close to sea level. my question really would be how altitude effects these results? i know in cars one will see about 5-10% power loss per 3000ft/1000m. i ride my bike in the mountains alot in BC and i regularly ride 2000-3000m.
Those numbers match what I've seen as well. Bikes see the same performance hits at high altitude as cars; the common factor is normally-aspirated engines. The only ways to avoid altitude (thinner air) from affecting power, are pressurizing that air with turbocharging / supercharging. Or run an electric motor, like the one that has been kicking butt at Pikes Peak.
ok, that makes sense then. because ive got a BB-305cc, bazzaz fuel tuner, dual exhaust, air box mod, polished ports, base gasket reduction for more compression, and head porting. all work done custom by me. i was getting abit worried that i fucked up something because my dyno run gave me 20.5hp and 17.7ft-lb. now ive seen that the BB305 is suppose to be getting around 23hp with 19ft-lb. but i guess since i live at 1200m that would explain the drop in power. also, ive been running this setup for about 25,000km, so that might have something to do with the drop in power too. so stock at my elevation i should be seeing like 17hp@13ft-lb. it pulls alot harder, power wheelies in 1st and 2nd, before it could not power wheelie in any gear, and 0-60mph in 7sec instead of 9.5sec, so the mods defiantly worked. i am no stranger to building/modding engines, i do alot of garage work on cars/bikes, my 2007R1 was putting 210hp down. it just seems that these single piston engine are much more susceptible to factors such as elevation, temp, humidity, ect,ect even tho its got FI.
Yep. I'm not sure they are affected any more or less from a percentage basis, but when we're starting with such lower power, it's much more noticeable.
exactly, @20 hp you would notice it, while with 200hp, you wouldn't notice it too much i also noticed that the power curve on my bike is much lower in the rpm range. stock is peak hp @8600rpm, while mine peak HP is @6500rpm same with torque, stock peak is @ 5800rpm, while my torque peaks @ 5300rpm.
