sequential just means a transmission that cannot skip gears.
like downshift from 4th to 2cnd.
you have to go thru each gear, although you could do it in quick succession, 4th, 3rd, 2cnd.
this doesnt have much to do w/ my questions?
the manual sequentials do have a clutch pedal.

ikeya in the link above has seq. shftrs for porsches as well.

 

Some reading on dual clutch: http://auto.howstuffworks.com/dual-c...ansmission.htm

 

I finally know what the Porsche acronym PDK stands for now.

 

its the other way around...back for upshift, forward for downshift

 

jeff that's right but that is becuase of the layout/design being sequential

hope this helps any confusion you or others might have

 

So for Sabine's purposes, what are the advantages for this sequential manual transmission?
Other than hands closer to the wheel?

Can this be done to a street car (easily)?

 

no offense but you didnt address my questions.

i guess it boils down to why do motorcycles have inexpensive reliable manual sequential shifters but cars do not?
and what makes the current manual sequentials shifters something you wouldnt want to use on the street?
i understand now jcm's post about it not being 100% durable after carrerarings post of the dog type trans needing a rebuild every 10k miles or so.
but again . . . they don't have to do that on motorcycles!?
also don't understand why the transmission would cost so much and a company like ikeya can sell them for a couple thousand usd.
i used the smg on a 2006 m5 and liked it OK!
but on bmw's new 3 series tt they didnt use smg?
i've heard also the new f-car 599 f1 shifts extremely fast.
i guess the transmission market is just in a period of transition!?

 

Jeff,

When you shift these things, they don't like to be short shifted and really like to sync up at very high rpms > 8-8500 and at times they sound like you're hitting an anvil with a sledge hammer....I keep looking in the rear view mirror to see if anything fell off!! It can be really loud. Some mechanics call them Crash Boxes (very appropriately)....( I know; not the same as the old Saturday night "crash box" you used to date back in college, but entirely synonymous with Cash Box; as in bring one to your mechanic if you F it up.)

 

I might be able to support previous answers on this thread.

The sequential gearbox is very loud, and very unfriendly for daily usage. They are very expensive, and the reason being the amount of torque, stress and heat they have to sustain during racing.
It is not true that they have to be rebuilt every 10k miles, it depends who built it and how it is being used, could be every race, or if used on the street and some track events with no racing, many thousand miles. You need cooling on these gearboxes.

The motorcycle gearboxes are not designed to sustain so much torque, they can therefore be much cheaper. Holinger Engineering arguably makes the best sequential gearboxes, with Ricardo in the UK being on a different standard all together.

Often when I shift especially from neutral to 1st or second, I feel like the suspension frame came off the chassis of the car. I agree with Leif997, they like to be shifted at very high RPMs.

My car is in the workshop removing my 6spd. sequential gearbox right now, back to stock G64/51 so that I can enjoy my car all over again on the street. It will be going for sale soon.

BTW you can add paddle shifting to your sequential gearbox, it costs about $5k if I recall correctly.

 

Motorcycles have inexpensive reliable sequential gearboxes for a number of reasons- 1) Shift pattern (clicking up and down) is simple enough to operate with your foot. 2) Motorcycles produce very low torque outputs allowing the use of relatively small gears and dog rings, which are compact in size, lightweight, and don't make that much noise. (For the most part, torque kills gearboxes, not HP) Because these items have relatively low inertia when spinning about in the gearbox they are less prone to wear. Furthermore, dogs deal better with the higher rpm differentials seen in bikes than do syncros.

In an automotive gearbox, dog rings, as opposed to syncros, are much noisier in operation and don't work well when shifted slowly. They are designed to engage gears very quickly and if shifted slowly tend to bind and wear badly. Additionally, dogs are usually mated to straight cut gears with large teeth (for strength) and these attributes compound the noise issue. Another disadvantage as you mentioned is the inability to skip gears in a seq box.

As far as clutches being involved in shifting a sequential dog gear box- for the most part they are not requiered. A simple spark cut would suffice in breaking the torque flow on upshift. On downshift, usually under braking, there is obviously limited torque flow, and clutch is used typically to smooth the gearchange and mimimize back torque locking the rear wheels. However, in say the last 10 years, more purpose built seq. dog boxes utilize electrohydraulic clutch actuation, in very minimal amounts to momenterally break the torque flow and thus make the shift easier on the dogs.

Finally, I don't know of any 4 wheeled vehicle authorized for road use in the US that uses a sequentially arranged gearbox, despite the term's popularity in the marketplace.

 

As far as I know, Cup and RSR cars run all steel syncro rings, but the gears are straigth cut for strength (hence the deafening whine.)

 

porsche's site just says "dog type" w/ no mention of all steel synchro rings for both cup and rsr!?

thanks for the responses, i have a little better understanding now.

 

Well, I can't even spell "straight;" so what do I know?

If it's a dog box, you'll never drive it on the street, not without going mad ... and having to shovel metal out of the box every day.

As for sequential shifters, there must be a Web site explaining it all somewhere.

 

The Radical has a motorcycle drive-train and a sequential shifter. It's SB100, not really an every day car as such.

 

The biggest issues are torque, smooth shifting (or lack thereof, particularly when just cruising around town) and comfort...

Again when the car/engine is being pushed hard then the SMG/F1/DSG/PDK's work very well enough, the aforementioned issues are encountered when doing "normal city driving."