>city bus should be able to operate at or near optimum stoichiometric conditions at all times Diesel motors operate quite differently than gasoline engines in

>city bus should be able to operate at or near optimum stoichiometric conditions at all times Diesel motors operate quite differently than gasoline engines in this regard, actually. A diesel motor is only operating at the correct stoichiometric ratio at full throttle and is running lean for the rest of the time because there is no throttle plate to modulate air intake and power is only modulated by the quantity of fuel injected into the cylinders.