This report investigates methods to reduce fuel consumption in SAAB's prototype hybrid car. It is primarily concerned with changes in the final drive ratio (FDR) of the gearbox. Reducing the FDR lowers the engine speed, allowing the engine to run at a more efficient operating point. However, this has a negative impact on engine power and vehicle performance. It was thought that the hybrid's eXWD (electric cross wheel drive) system could make up for this loss of performance. Computer simulations showed significant improvements in fuel economy when the FDR was reduced. This was confirmed by real world tests on a chassis dynamometer, although the number of tests were too low to establish the precise fuel consumption reduction. The effects on performance were evaluated by creating a quasi static model of the drivetrain and calculating which combinations of speed and acceleration corresponded to the engine's torque limits. The loss of acceleration was found to be lower than the increase in acceleration made possible by eXWD for most choices of FDR. It is therefore possible to reduce the FDR in the hybrid version of the car and still maintain a performance advantage compared to the front wheel drive version. No other major disadvantageous effects were found. The conclusion was therefore that a reduction of the final drive ratio is a feasible method to improve the fuel economy of the prototype car, given that maximizing performance is deemed less important than increasing fuel economy.

I Sverige används det idag cirka 5,4% förnybara drivmedel inom transportsektorn, att jämföra med under 0,5% år 2000. Av de ickefossila drivmedlen är el något som ofta benämns som en permanent och realistisk framtida lösning. Visionen ”Stockholm – Elbilsstad 2030” drivs av Stockholms Stad i samarbete med Fortum AB i syfte att ersätta den fossilbränsleslukande fordonsflottan. I den här studien undersöks de tekniska förutsättningarna och de eventuella vinsterna av ett storskaligt införande av elbilar. Studien har gjorts genom en modellering där parametrar som elbilens prestanda, elpris, bilens inköpspris och totala utsläpp använts. Resultatet skall presentera ett mikro- och ett makroresultat. Vinsterna beräknas dels för den enskilde individen, men också för samhället i stort. Vinsterna beräknas med en känslighetsanalys baserad på reella framtida scenarier. Resultaten visar tydligt att för den genomsnittlige Stockholmaren är elbilen det mest ekonomiskt lönsamma valet på sikt. På tio års sikt beräknas bensinbilen kosta individen 65,93% mer än elbilen om bensinpriset fortsätter med samma utveckling. En känslighetsanalys visar att även om bensinpriset skulle sjunka med 5% årligen in i framtiden skulle bensinbilen ändå vara 31,3% dyrare på tio års sikt. Resultaten visar också att samhällets kostnader för bilflottans utsläpp förväntas sjunka med 98% eller 92% beroende på om den svenska elproduktionen är tillräcklig eller om man måste importera el från övriga Norden. Samtidigt som kostnaderna för utsläppen sjunker för samhället, sjunker även skatteintäkterna till följd av minskad bensinanvändning. Om elpriset på sikt skulle stiga till följd av en ökad användning skulle detta dock kunna leda till att förlusten reduceras. Klart är att storskaligt införande av elbilar kräver ett engagemang från staten där den ekonomiska förlusten får ses som en investering i miljön och framtiden. / In Sweden there are currently about 5.4% renewable fuel vehicles within the transport sector, compared to less than 0.5% in 2000. Amongst the non-fossil fuel alternatives electricity is something which has often been referred to as a permanent and realistic future solution. The vision “Stockholm – A City of Electric Cars in 2030" is run by the City of Stockholm in cooperation with Fortum AB in order to replace the fossil-fuel-guzzling fleet. This report examines the technical conditions and possible gains of a large scale introduction of electric cars. The study was conducted through a modelling in which parameters such as electric car performance, tariff and total emissions are used. The conclusion will reveal a micro- and macro result. Economic gains are calculated both for the individual, but also for society at large. The profits are calculated by a sensitivity analysis based on realistic future scenarios. The results clearly show that for the average Stockholm resident, the electric car is the most economical choice. In ten years time the gasoline car is expected to cost the individual 65.93% more than the electrical car based on that the price of gasoline continues its current growth. A sensitivity analysis shows that even if gasoline prices were to drop by 5% annually into the future, gasoline car would still be 31.3% more expensive than the electric car in ten years time. The results also show that the societal costs of the car fleet’s emissions are expected to fall by 98% or 92% depending on whether the Swedish electricity production is sufficient, or whether imported electricity from other Nordic countries is necessary. While the cost of emissions decreases for the society, so are tax revenues due to reduced gasoline use. However, if the electricity price in the long run would rise due to increased use, this could however lead to a reduction of the loss. It is clear that for a large-scale introduction of electric cars to be successful it requires a committed government which will have to see the economic loss as a means to investment in the future and the environment.