Diesel engines up to 35% in best point, gasoline engine up to 30% in best point. In real life use, averaged about 25% for drivetrains with Diesel and about 20% for those with gasoline engines.

Kind regards, 

Mario

I agree with Dr. Hirtz in all what he has mentioned, but I confirm here that the fuel type plays an important role in determining Dr. Hertz mentioned ratios. The achieve these efficiencies you have to use high octane number in gasoline engines, and diesel with ultralow sulfur and high cetane number. When lower octane number gasoline or lower cetane number diesel are used the resulted efficiency is quietly differs from these ratios.

Regards

Diesel Engine ... 34- 36%

Gasoline .... 29- 32 %

The engine efficiency depends on the engine rpm and load. Car engines rarely operate at their peak efficiency, so peak efficiency and rated power are of limited relevancy to the reality. In urban driving with a typical gasoline car, more fuel is used to keep the engine running than to deliver the energy to propel the car.

The above-mentioned efficiency are basically measure from tank to crankshaft (thermal efficiency). In reality, there are more lost along the way; in flywheel, transmission, axle etc before power reaches the wheels. So effectively, the tank-to-wheel efficiency is in the order of about 10% or much less (quoted from Prof. John Heywood's article some years back). Or course the number may have improved over the years with the advancement of tribology, lighter chassis, improved engines and fuels etc.

Tank-to-wheel efficiency includes the entire efficiency chain from the energy storage (e.g. fuel in the tank), the energy conversion in the engine (e.g. combustion engine), plus the mentioned losses of transmission and drive train components. Thus, it includes the efficiency of the engine.

Lightweight design of chassis is not involved. This component influences the vehicle mass, which influences the driving resistances (and thus the energy demand of the car for driving), but it does not influence the tank-to-wheel efficiency.

Kind regards, 

Mario

kg = 1; m = 1; N = 1; sec = 1; W = 1; % [kg], [meter], [Newton], [sec], [Watt]

eta = 0.60; % Efficiency of the modern electric cars is about 59..62%

M = 300*kg; % Car mass

g = 9.81*m/sec^2; % Gravitational acceleration

V = 40/3.6*m/sec; % Speed

Omega = 4000*2*pi/60*sec; % Engine rotations

P = 1200*W; % Engine power

RL = .40*m; % Wheel radius

Tau_e = P/Omega*N/m; % Engine torque (ideal)

Tau_a = Tau_e*eta; % Actual

Omega_wheel = V/RL*1/sec; % Angular velocity

Ratio = Omega/Omega_wheel; % Gear/Transmission Ratio

muR = .0125; % Rolling resistance coefficient: 0.01...0.015 Car tires on asphalt

Frr = muR*M*g; % Rolling resistance force [N]

Tau_e = P/Omega*N/m;

Tau_a = Tau_e*eta;

Omega_wheel = V/RL*1/sec;

Ratio = Omega/Omega_wheel;

F_traction = Tau_a*Ratio/RL - Frr;

Tau_wheels_effective = F_traction*RL;

fprintf('Electric car making %3.2f m/s (40kmph) with E-motor of %3.0f W \n', V, P)

fprintf('Generates %3.0f Nm torque in the engine \n', Tau_a)

fprintf('Actual effective torgue is %3.1f Nm on the wheels \n', Tau_wheels_effective)

fprintf('In order to make %3.2f m/s (40kmph), the Gear Ratio has to be %3.0f \n', V, Ratio)

ANSWER: 15

Fuel to wheel efficiency of a modern hybrid vehicle is about 36% (sourced by Toyota). At the other hand, research with gas-optimized engine (pre-chamber and main combustion chamber modified design) has reached to 45% as peak record (sourced by Volkswagen Group, The GasOn Project, with data from Swiss Federal Laboratories for Materials Science and Technology). Diesel engines will be gradually reduced to heavy vehicles operations, as combustion and turbo losses at lower loads cannot be significantly optimized throughout time.

Electric cars have a lousy efficiency:

Motor efficiency: 85..90%

Battery load efficiency: 80..90 %

Battery discharge efficiency: 80..90 %

Power generation efficiency at powerplant: 30..40 %

Transfer efficiency from powerplant to reloading station: 90..95 %

Energy conversion efficiency AC to DC: 90..95 %

Energy conversion efficiency DC to AC: 90..95 %

Now lets take the product of all this with the maximal values:

0.9 * 0.9 * 0.9 * 0.4 * 0.95 * 0.95 * 0.95 = 0.25 == 25 %

Note: the 25 % is the upper limit. The lower limit is 12 %.

So, an electric car is no better than a gasoline powered one, rather worse.

Go for diesel. These start at 30 % and reach up to 45 %.

ArNO2