Re: Automatic Transmission?
Fri, 06 Sep 2002 12:42:49 -0700
Patchem, Eric EM2 wrote:
> I had read that an automatic transmission is less efficient than a
The efficiency of a manual and automatic transmission are essentially
the same; both well above 90%. The problem with the automatic is
entirely in the torque converter, which goes between the engine and
transmission. It is basically a big slipping clutch.
Some newer cars have torque converters that "lock up" under certain
conditions or above a certain speed. If your Fiesta has such a locking
torque converter, you can probably use the automatic as-is with no loss
If you do NOT have a locking torque converter, then you're going to
suffer a 10% or so loss in range due to the slipping torque converter.
Automatic transmissions need oil pressure to shift. The pressure comes
from an oil pump on the front of the transmission that is turned by the
torque converter. So you have to "idle" the electric motor when the car
is stopped to maintain oil pressure for the transmission to work.
Or, you can keep the automatic transmission but leave out the torque
converter. This will require some machinist work to connect the motor,
and seal up the oil flow that normally goes between transmission and
torque converter. You will also want to add an external oil pump or
motor to operate the transmission's internal oil pump to maintain
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