Z-man

Just a side note:
There seems to be a misconception that slamming gears and shifting fast makes a car actually go faster. This simply is not the case.

The method of up shifting I've learned is this: clutch in, shift out of gear, move the shift lever through the neutral plane, and then into the next gear, release clutch, and then back on gas. The actual shifting is a three-part process. (Out of gear, through neutral plane, into next gear).

I've taped myself on the track, and this method of shifting literally takes 1-2 seconds max. AND: it causes much less wear on your car than the "SLAM! BAM!" method.

Regarding powershifting: if you have unlimited disposable income, go ahead and powershift. The claims of not hurting the tranny are only valid if you get the shift perfectly. IMHO, it isn't worth power-shifting any car.

-Z.

TheJonesBoy

Why are automatics slower? Its not necessarily because of the viscous coupling. Most (all?) automatics lock the coupling over a certian engine RPM to prevent loss. If you let your tranny fluid go low, this point is really obvious whack.

Automatics use a planetary gear setup. This is where you have a gear in the middle, several small gears that spin around it, and a big gear around the outside with the teeth on the inside. There is a lot of meshing going on, and therefore a lot of driveline loss. You also have more inertia spinning all that fluid, metal, and clutches.

Manual trannys use standard, side by side gears with little between. Less inertia, less friction less loss.

Triptronics are just automatics with switches for up/downshift. OK, they are a lot more complex than that, but they are very similar.

You also have the BMW/Ferrari systems which use hydraulic/electronic controlled manual trannys. These systems are also used in World Rally Championship cars. They shift fast and smooth. WRC cars can easily shift in turns while holding constant skids. That takes a lot of technology and money.

VW and Dana just came up with a new tranny system. It is like a manual trans, but has 1 input shaft, and 2 connected output shafts. It also has a funky 2 way clutch (engaged 1 way, engaged another, and disengaged). The whole idea is that shifting will alternate between 2 different output shafts, enabling the car to have 2 gears engaged, one supplying power, and the other ready for the shift. All the car does during a shift is throw 1 clutch (selecting shaft A or B). Gear selection changes can be done at the car's leisure. This cuts down shift time (as you never go through neutral), feels like a standard auto, has really low drivetrain loss, is small, light.... I know I screwed up some of the details, but that is the jist of how it works.

As for power shifting, that is shifting without a clutch. It is bad because our cars were designed for shifting WITH a clutch. The difference lies in the splines in the gear selectors. Cars have dozens of small, arrow pointed splines which will mesh (usually) even when the engine is off. Things like motorcycles are designed for clutchless shifts. They ususally have 3 large "dog" teeth which won't shear off when you bang gears. Our tiny teeth will break apart, leaving little bits of metal flying around a high tolerance gear mesh. Thats bad. There is no "sweet spot" for banging gears. Someone said at one speed the engine and trans are synched for the next gear. Bull****. You are only synched for the gear you are in. Thats why you are in it. The only time 2 gears running off the same shaft (at different ratios) are synched is at 0 rpm.

Double clutching is for when you want to DOWNSHIFT. Never upshift. On an upshift, you want the engine to slow down to match the speed your engine should be at if you were in the next gear. It does that naturally when you move through the neutral portion of the shift tree. When you downshift, you want the engine to speed up to the speed of the lower gear. There are little things called synchros in your trans that do this for you. They are little, conical brass bushings that act as brake clutches to match the speed of the input shaft to the gearset you are putting the car into. Its tough to explain without a diagram. If you are going down 2 or more gears rapidly, these weak little guys may not do the job, and the gear bangs into place. Its times like these you want to double clutch. To double clutch, you do a regular shift into neutral, rev the engine to a little above what it would be to go the speed you are going in the gear you want to be in, and while holding that high RPM, shift into that gear and go.

You always want to use the clutch between shifts, even when double clutching. Remember those little fingers in the gear shift selector? They are tapered! This is done so that if you do not fully enage a gear, the taper will cause the gear to fully engage ITSELF under power! Neat, huh? Unfortunately, if you shift under power without the clutch you wear them down and actually REVERSE the taper. That means under power, the gear will want to disengage. Thats bad. I know someone who went through an entire performance rally where the co-driver had to hold the car in second gear. He shaved a lot of metal off the splines during shifts. When we rebuilt the trans, it was full of something I can only describe as metal paste. Everything was trashed. The ring and pinion were both missing teeth, and the metal shavings ruined all the bearings. It was a VW tranny, which is pretty weak, but any trans will wear with clutchless beatings.

hope this cleared some stuff up!

Scootin159

You can shift without the clutch, or without wearing out the transmission. It's just not easy, and not practical.

As you're going along, let off the throttle until you're neither accelorating or decelorating (may not work as well going up hill)

Push the gear selector into neutral without the clutch (alright, this may cause a little wear because, as you said, the dogteeth are designed to pull the gears together. I would think though that under minimal load this wouldn't be any worse than when you do it with the clutch).

With the transmission in neutral, raise/lower RPM's to EXACTLY what they need to be for the next gear. This should match the engine RPM and input shaft RPM with the output shaft/wheel rpm.

Push gear selector into the correct gear. There should be no wear if you do it at exactly the right speed and without much engine load. The input shaft and output shaft will be at the same speed, so there will be no wear on the syncro (it's not so much the RPM that matters as it is the relative speed diference between the input and output shaft).

Once the next gear is fully engaged continue driving as normal.

I've done this a couple times in my car (pretty much just to show off, and only when just coasting along trying to be as smooth as possible). If you do it right there will be no noise and you won't feel any "jump" in the drivetrain.

Zporsche944

I had a 94 saturn SC2 and I always powershifted that thing its so easy... I have powershifted the 944 too but its not as easy

Catfood

the new 911 turbos with tips are faster 0-60 than a manual because they keep the boost up while idling, ferrari is also making some impressive automanual cars which can shift faster by computer than a human can.

Stien

Not to sound stupid but I still don't get why double clutching is necessary. I downshift 5->3 or 4->2 in my piece of **** camry and there is no grinding, no noises at all. Obviously I rev match. Bring on the replies lol.

Zporsche944

ur camry has syncro's that do the work for you... we are talking pre war vehicals or 80's or older, gas large trucks not sure about newer ones every one I have seen that is newer is auto... and in the diesels you have to powershift or you will lose to much boost cuz double clutching takes time ( in most 70's and 80's grain trucks you have to double clutch its how I learnt to drive a standard)... but I am a farm boy :P

cyinisis

You could always use a rock-crusher transmission...like a lot of middle-aged guys will remember from their muscle car drag days.

...that is if you enjoy rebuilding a transmission every 10-15 shifts.

PSUice944

TheJonesBoy that transmission is called the DSG or Direct Shift Gearbox. Audi and VW toy, I have played with them when I was selling/financing at that store in my auto group. Very cool stuff, the "downside" is that though it's uber quick, it doesn't quite have the MFer Race mode the SMGs do which many like at the track. Where it excels is that it does regular street driving really well AND there is virtually NO lag between shifts as it simply switches output shafts and keeps going. It's Faster from a dig too now with launch control.

This will be my next daily driver tranny, best of all worlds with virtually no comprimises, I'm sure there is a "how it works" out there that is a really neat write-up to look into.

Legoland951

I can't believe someone dug up such an old thread. Power shifting is when you shift without lifting the throttle. Speed shifting is when you shift without a clutch. Double clutching is absolutely not necessary in our cars. Its mostly used in heavy duty diesels like a semi where you really need to double clutch in order to get it to downshift.

sandwood

i got a ride once in a car with a dog box transmission. the driver's shift technique, when he wanted to accelerate and shift as fast as possible, was to accelerate until the motor bounced off the rev-limiter and then, with just a gentle touch on the shifter, the tranny wd drop into the next gear (especially for the 1-2, 3-4 shifts, of course). no clutch required, no liftnig off the gas. a dog box can stand that kind of abuse, and the rev-limiter automatically dropped the revs to a range appropriate for the next gear. by far the fastest shifts I have ever seen/heard (but I've never experienced an f1 type gearbox).

Gremlin85

Usually, as stated, manuals are faster. There are some exceptions in higher end modern cars. One of my FAVORITE examples is the 2004-2006 Pontiac GTO's... there is only a .1 second difference 0-60 between the auto and manual and that is in favor of the AUTOMATIC! Go figure.

V2Rocket

Automatic cars are also slower slightly because of the extra weight that slushboxes have; the power inefficiency is the main reason though.

The 997TT is faster by .4 seocnds to 62MPH with the Tiptronic because the automatic keeps the engine RPM high for the turbos to keep boosting.

Ferrari paddle-shifters can go much faster than any human; the ones on the Enzo and 599GTB can do it in 1/10th of a second or less.

Mamooguy

My 944 auto accelerates like a whale trying to crawl onto dry land, but once it's going it kicks butt with the best of them. I of course haven't compared it to anything, don't have any numbers ... but give me an open road and my baby wants to fly.