No, it is not your imagination. What once seemed impossible is now happening with a great many cars. One of the “for certains” in the automobile industry is no longer for certain.
What are we talking about?
For years…..for decades….it was a given fact that a manual transmission would provide better gas mileage than an automatic transmission. You would see the EPA ratings on cars and without an exception, the same model with a manual transmission had better fuel efficiency than the model with an automatic transmission.
Well welcome to the year 2014, and one of the truths of the industry has been shattered. Today we have finally reached the point where the automatic transmission is virtually equal to the manual transmission in gas mileage. How did it happen you ask?
To answer that question you need to understand a bit about transmissions. With automatic transmission, rather than use a mechanical clutch they use fluid couplings between the engine and the gear-sets to transmit torque. Unless a mechanical clutch is slipping, it is able to transfer 100% of the torque that goes in; not so with an automatic transmission. There is always slippage with an automatic transmission, and this slippage, this loss of torque, is what lowers the fuel efficiency. Less slippage, better gas mileage; more slippage, less gas mileage.
To correct this problem, engineers have made three major advancements in the design of the automatic transmission. First, they have increased gear ratios. Second, they designed lock-up torque converters. And third, they introduced electronic controls to the transmission.
Increasing gear ratios simply means that there is a more efficient use of torque; to put it another way, less torque is lost. Lock-up torque converters have a mechanical clutch that couples the pump and turbine so that there is no transmission shifting while cruising. Thus the torque converter achieves almost 100% efficiency. Lastly, the electronic controls increase the proportion of time that the torque converter is locked, again increasing efficiency.
All of this adds up to the fact that an automatic transmission can now equal the manual transmission for efficiency. We now see six, seven and even eight gear automatic transmissions, and most likely that will be the practical ceiling. What the engineers will do now is seek the perfect balance and operating efficiency in the torque converter.
We at PDQ transmission parts hope that helps in understanding why automatic transmissions have now become so efficient.
