I know the tranny on a RDX is not like an DSG tranny but is it similar to a BMW SMG? How do our 5 speed sequential shift tranny work?

 

I believe, though I could be wrong, that BMWs SMG is different than a normal planetary based automatic transmission.

Mike

 

Normal auto transmissions are not planetary.

The RDX automatic is best described as a manumatic -- merely an auto transmission with some level of manual control. Instead of letting a computer/controller decide when to shift, it can let the driver do it. Everything else about it is the same as a traditional auto trans. It is still a fluid-based (ie, torque converter) auto trans.

 

Normal auto transmissions are planetary.


Mike

 

Oops, you are right. I call them epicyclic gears, but you are correct.

 

Do you know if their has ever been a car with a true manual transmission that could also be controlled automatically? I'm not talking about a DSG or any of that stuff, but rather a "normal" single clutch based system in which a computer or the user could control the clutch pedal and shifter?

Mike

 

Ah wouldn't that be a dream. The closest available to consumers are the electronically controlled single clutches manual transmissions (no torque converter). Similar systems are BMW's SMG, Honda's i-Shift, etc.

Also Honda automatic transmissions are not planetary gear based with exception of the current RL's rear overdrive mechanism.

 

Huh, your right. Just did some quick research. Any visual brakedowns of the setup?

Mike

 

There are a couple of applications found on some top end exotic cars that have a true manual tanmission controlled automatically ie. porsche 911, some ferrari's. But today you can find it most commonly on Mercedes-Benz little smart fortwo car. This car has a typical auto trans look PRND, but it has a actual clutch as a trans. (without a peddal). It really is an interesting concept but it is no where near as smooth as your present day auto trans.

 

so you want a fully automatic manual? You're 18, so I'll forgive you.

Manual transmission cars are great. My biggest disappointment in the RDX is that a manual isn't available.

DSG and SMG, btw, are the same thing. Semi-Automatic manual transmissions. Obviously VW has theirs in the GTI, Mitsubishi is introducing one in the Evo X, and BMW has theirs (along with some others). They're really all the same thing. Manual transmission with a computer-controlled clutch and paddle shifters.

Our RDX is a weeny automatic with a lame torque converter (auto-skirt transmission, I like to call them).

 

The acura has an auto tranny that can me shifted manualy, whereas the BMW has a manual tranny that can be set to shift automatically.

SMG (sequencial manual gearbox)

 

The RDX has an ordinary auto trans with a torque converter connecting engine output to the drivetrain. The Powertrain Control Module utilizes sensors throughout the vehicle to determine and electronically select the correct gear. Using the paddle shifters overrides the PCM shift logic and sends an electronic signal to change gears.

The PCM still will not allow a damaging gear selection or excessive rpm. When the PCM prevents a paddle gear selection the gear indicator will flash. When the PCM prevents excessive rpm the fuel cutoff causes engine stutter and power loss. This will get your attention if you are trying to pass by downshifting in Sport mode.

RDX paddle gear selection is mostly useful in pre-selecting a corner exit gear which will keep the turbo engine in it's peak power band.

Because power goes through a torque converter there is minimal on-off-on shift shock.

The BMW SMG is much more closely related to a manual gearbox. There is no torque converter. The engine output is connected to the drivetrain by a single clutch, but there is no manual clutch operation. When the vehicle stops the clutch is electronically disengaged. When a paddle shifter (or lever shifter) signal is sent the clutch is electronically disengaged and the next gear is electronically selected.

Because power goes through a clutch it feels much more like a manual with on-off-on shift shock.

The SMG can be placed on full auto control, and operated like an auto trans.

Volkswagen's DSG operates much like SMG but with two clutches. Clutch A is used for 1st, 3rd and 5th, and clutch B is used for 2nd, 4th and 6th. During acceleration, when 2nd gear is engaged through clutch A, third gear is preselected and clutch B is on standby. At gear change clutch A disengages and simultaneously clutch B engages. There is no momentary on-off-on power loss and shift shock is almost imperceptable. With 3rd gear engaged through clutch B, 4th gear is now preselected and clutch A is on standby. Clutch alternation and instant changeover takes place throughout the up and down range.

Like SMG the DSG can be placed on full auto control.

Hope this helps.

 

good info! I wasn't aware of that dual-clutch setup in the VWs.