The FEV cost teardown study (EPA/FEV 2010) had the following issues: (1) the baseline was not a four-speed automatic transmission but was a five-speed transmission, and (2) the six-speed transmission had a Ravigneaux gear set, whereas the five-speed transmission has three planetary gear sets, which is more complex than the Ravigneaux gear set. The three planetary gear sets require nine control elements (four disc clutches, three disc brakes, and two sprag clutches), whereas the six-speed transmission with the Ravigneaux gear set only requires six control elements (two disc clutches, three disc brakes and one sprag clutch). FEV recognized these issues by providing the following statement in their study:
In regard to the 5-speed automatic transmission, many of innovative ideas implemented into the 6-speed automatic could have been incorporated into a new 5-speed if it were to be redesigned. The most obvious NTA (New Technology Advances) would be adopting a similar Ravigneaux geartrain design, which could conceivably have the same financial benefit recognized by the 6-speed automatic.
This was an unusual teardown cost analysis since the five-speed transmission contained more hardware (i.e., approximately 150 more parts), and was generally more complex, than the six-speed transmission. As a result, the six-speed transmission established a zero-cost baseline from which an incremental cost for the five-speed was established. The majority of the incremental cost increase of the five-speed over the six-speed was associated with the two additional clutch packs, the need for a counter shaft assembly, and some additional gearing.
Neutral control is when the transmission control moduleTCM disengages the
forward clutch, (C1), at a stop with the brake applied. This reduces the load
on the engine, therefore reducing engine vibration and improving fuel economy.
When the brake is released the forward clutch engages. The following conditions
must be met before the neutral control function will be allowed:
• Manual shifter must be in D, 4 or 3. Neutral control will not work in winter
• Transmission oil temperature must be above 10°C.
• Throttle position must be less than 3%.
• Brake pedal must be depressed.
• Vehicle speed must be zero Km/h.
• Engine speed must be less than 1500 RPM.
• There is a 2 second delay once the vehicle has stopped in the D position and
a 5 second delay when shifted from N to D.
Aceasta facilitate este automata. Nu
trebuie sa selectezi nimic. TCM-ul (calculatorul cutiei) face asta automat. Pur
si simplu se simte ca, in conditiile in care masina s-a oprit si mentii
piciorul apasat pe frana, tractiunea de la roti se decupleaza. Si poti s-o tii
asa in D cu frana apasata cat vrei tu.
Calculatorul cutiei are o multitudine de
programe si strategii (unele de care nici nu ne dam seama in timpul mersului).
In functie de programul selectat de calculator (TCM) schimbarile treptelor sunt
diferite, de aceea ni se pare ca uneori cutia schimba vitezele altfel decat
eram noi obisnuiti. Asta pe langa facilitatea de "autoadaptare" adica
invatarea modului personal in care fiecare conduce masina.
Fara a avea pretentia ca programele
urmatoare se aplica oricarei CVA, redau un extras din manualul masinii mele
referitor la programele cutiei de viteza:
Economy Mode – This mode is used by TCM under normal
acceleration. The TCM provides the earliest possible upshifts and lockup for
best economy. The TCM adjusts oil pressure to provide smooth shifts and
Sport Mode – The TCM changes from economy to sport mode if the
accelerator pedal is pressed down quickly and the vehicle exceeds 50 km/h. In
sports mode the shift points are raised to provide the best performance and
down shifting occurs at lower engine RPM. When the accelerator pedal is moved
less quickly, the TCM resumes economy mode automatically.
Kick down – When maximum acceleration is required (e.g. during
overtaking), if the accelerator is rapidly and fully depressed, lower gears are
automatically engaged, provided the engine rpm enable this operation. Later,
when the accelerator pedal is released, the gear engaged is selected according
to the type of driving and the position of the accelerator. Kick-down can be
engaged only when the gear lever is at D.
Downhill Mode – When the throttle angle is less than 3% and the
vehicle speed is increasing, the computer will command higher shift speeds to
provide more engine braking.
Uphill Mode – When engine load is high and vehicle speed is
decreasing, the computer will command higher shift speeds.
Traffic Jam Mode – When the vehicle stops and starts with less than
10% throttle angle, the computer commands 2nd gear starts to increase fuel economy
and reduce shift busyness. Normal mode resumes when the throttle angle is
greater than 30% or vehicle speed is greater than 30 km/h.
Curve - TCM is able to recognize particular situations like a
curve, detected as a different speed of front wheel instant rotation through
the ABS active sensors, thus preventing shifting to the higher gear until the
engine revolution limit is reached. Only with this condition or at the end of
the curve will it be possible to shift gear. This strategy is useful to improve
the car balance and to guarantee a prompt acceleration when coming out of the
curve, since the car has already the right gear engaged. Likely, during sudden
braking, the lower gear is engaged to exploit the engine braking action at
best. In case of a curve, the new gear will be engaged during slowing down
before the curve, therefore when coming out of the curve it will not be
necessary to shift gear to accelerate.
Winter Mode –When starting to drive with a reduced road grip
(snow-covered, icy road, etc.), the shift control unit automatically engage the
“ICE” programme. This programme allows starting with the 2nd gear engaged, in
order to improve the gear shift efficiency according to grip conditions.
Catalytic Converter Start – This function helps the engine to reach
operating temperature by preventing converter lockup and delaying the 1-2 and
2-3 upshifts when the engine is cold. This is a normal function.
Cold Mode – When the engine coolant temperature is less than 50°C,
the shifts will occur at a higher speed.
Hot Mode – When the transmission oil temperature reaches 140°C, the
computer applies the converter clutch at lower than normal speeds and raises
the shift points to a high speed. When the transmission oil temperature drops
below 132°C, normal mode will resume.
High Altitude Mode – When the barometric pressure is less than
12.76, the computer will command higher shift speeds.
Protection Mode – This mode is like failsafe or limp-in mode in
other vehicles. When the protection mode is tripped by a code you will have 5th
gear in drive and intermediate. When in manual low you will have 2nd gear.
Cycling the ignition will give you normal mode again until the code is set