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Summary of change:
It is very easy to calculate dRPM / dt, which is proportionate to torque. However, when doing tuning runs, you want to be able to compare the result after changes (like changes in ignadv). Analyzing the logged runs, in RPM-bins, in a similar way as lambda, VE and ignadvn is tuned is very helpful. Something like this (except for real data, and colored nicely): ||'''RPM'''||'''3000'''||'''3500'''||'''4000'''|| || MAP || 110 || 140 || 170 || ||ignadv || 24|| 25 || 27 || ||EGT(C)|| 552 || 603 || 612 || ||lambda || 0.82||0.81 || 0.8 || ||torque dRPM/dt || 1600 || 3100 || 3900 || ---- '''RPM => power calculation''' is very simple Some of the input parameters are often estimated though (a well known such parameter: m=mass, you can measure that too, of course) * P=F*v * F=m* (dv/dt + anull) + Fnull ** where anull = g*slopepercent (like g*0.04 for a 4% slope to keep the car climbing without deceleration) ** Fnull = some force to keep the car running without decel even on a 0 slope. Fnull=500N means that 500N * 20m/s = 10kW sounds reasonable below 100km/h (at high speed this climbs as v**2, due to air drag) * so P=v* (m* (dv/dt+anull) + Fnull) * v = RPM * const ** where, with audi in gear2: const = 1/2.13/4.11 * wheel_circumference ** wheel_circumference=1.87m (if you measure diameter and calculate 0.6m * pi, you get 1.885m, but remember the tyre is somewhat pressed in) ** so the '''audi wheelspeed at 7000 RPM and gear2''': 7000 / 60 /2.13/4.11 * 1.87 = 24.9 m/s = '''89.7 km/h''' [http://all-car-parts.net/specifications/specifications.htm gear ratios] ---- '''dRPM/dt => Nm (torque) calculation''' So (with the 1600kg audi in gear2) what is the const in the ''torque=const * dRPM/dt'' to get the result in Nm ? * dRPM / dt is given * as in the upper formula, force on the wheels: F=m* (dv/dt + anull) + Fnull * wheel torque Mwheel = F * wheelradius * motor torque Mengine = Mwheel / drivetrain = Mwheel / 2.13/4.11 ** v (in m/s) = RPM/60 / 2.13/4.11 * wheel_circumference ** m=1600kg (1400kg + spare tyre + fuel + 2 persons) ** wheelradius = 0.3m ** Fnull = 500N ** the uphill we use for tuning: anull = 0.03 * 9.81 m/ss *** this contributes to less than 10% of the power, at dRPM/dt = 1000 RPM/sec it is like 3 + 0.29 for the accel and the climb components octave snippet: <code> drivetrain1=3.6 drivetrain2=2.13 drivetrain3=1.36 drivetrain4=0.97 drivetrain5=0.73 drivetrainfinal=4.11 drivetraintotal2=drivetrain2 * drivetrainfinal g=9.81 Fnull = 500 wheel_radius=0.3 wheel_circumference=2*pi*wheel_radius rpmtov=1/60/ drivetraintotal2 * wheel_circumference # the best so far, for the untuned audi was 1000 RPM / sec in gear2 dRPMdt=1000 F=m* (dRPMdt*rpmtov + anull) + Fnull Mwheel=F*wheel_radius Mengine = Mwheel / drivetraintotal2 result: with the given mass, on given uphill in gear2 at 1000 RPM/sec is 230 Nm engine torque (measured on the wheels) </code>
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