have been working on the next version of wheelcalc....
but i need some help..... if you have a dyno graph of your car could you scan it in and email it to me
ike849@hotmail.com
In the next version of wheelcalc it estimates your torque curve (based on your pear torque and pear power values) using parabola and linear functions to get the correct shift points for each gear.
I just want to check how close the estimate is to real world examples so the more dyno graphs i have the better!!!!!
2nd point of help needed for those that are maths/physics orientated (or just know the answer).
basically i want to take into account the wheel size when calculating 'road torque' (at the moment it doesn't account to wheel size), as the wheel size is actually part of the gearing.
using this forumla;
road torque = engine torque x diff ratio x gear ratio x wheel size
A dyno graph is typically taken in 4th gear as that has a ratio of 1:1 (or close to it), say my diff ratio was 4.35:1 you end up with;
RT = ET x 4.35 x 1 x wheel size
now to my understanding a dyno graph should show you 'road torque' as it is measured at the wheels WITHOUT the diff ratio accounted for (gear ratio ignored as it is 1:1). so in my example dyno 68nM @ 4500rpm would make the forumla look like this;
68 = ET x 1 x 4.35 x wheel size
68/4.35 = ET x 1 x wheelsize
15.6 = ET x wheelsize
now if you believe dyno guys that say manual cars have a 15% loss of POWER through the transmission (gears + diff + friction on tyre), you can then convert that percentage loss of power at 4500rpm to a torque loss. (I by the way don't like this as the weight of the transmission internals, speed at which they are turning and actual design of the gears needs to be taken into account for an accurate power loss figure, but since the whole shift point is an estimate 15% is easy and will 'probably' put us in the right area)
so 68nM @ 4500rpm = 32kW @ 4500rpm
15% loss equals 27.2kW @ 4500rpm = 57.7nM @ 4500rpm
so i have (57.7 / 4.35 to bring the diff ratio back in)
15.6 = 13.27 x wheelsize
wheelsize = 1.175
now this actually (well quite dodgy really) gives me a ratio for the wheel size for the car when dyno'd (145/70/R12).
How would i get this ratio without being dodgy, ie. is there a way of having a wheel circumference and converting that into a ratio so that it can be factored into the 'road torque'????
once i have these things sorted i will email brayden the new wheelcalc....