LaxTSX

Hi all,
I know this may be stupid question, but I'm by no means a car girl. I was wonder why a MT is faster or more powerful than an AT ?

gocubsgo55

manuals allow you to shift at the best time during acceleration. in past years autos havent been able to shift as well as a person. autos are computerized and take a little longer to shift into the next gear. recently, autos have been improving, but it still remains inferior to manual in terms of getting all the acceleration out of your engine. a manual can give you a second or even in some cases two seconds off your 0-60 time. someone correct me if im wrong, but this is what i was told a long, long time ago.

fdl

More importantly, with an automatic transmission there is more drivetrain loss. So you will get more HP to the wheels in a MT car. Also , an AT is heavier than a MT, so there is a weight advantage. And lastly, in some cars such as the TSX .. the gearing on the MT is more aggressive.


We've discussed this quite a bit before, so if you do a search you will find some real good discussions we've had on the topic.

trolldrengi

The automatic transmission's Torque Converter is what makes the biggest difference versus the locking clutch in a manual tranny.

This article does a fine job of explaining how torque converters work (without being too technical or boring).

http://auto.howstuffworks.com/torque-converter.htm

outersquare

get a high stall TC and a shift kit

LaxTSX

hi ,
whats a high stall TC and a shift kit for and whats the benefit? Also when I orginally posted I had the SportShifter vs Manual in mind, but I' guessing its the all the same issues except for the one thread " gocubsgo55" mentioned shifting at the right time.

TSXhopefull

with the average driver, automatic is probably faster. The people at car and driver, and motor trend, and other car mags are trained professionals. They use several attempts in their zero to 60 runs, implimenting several tactics to get the best times. With auto, or sportshift auto, they usually just toss it in drive and hold onto the gas.

trolldrengi

Um... no.

Traditional and sportshift autos are never going to be faster than even the average manual driver. Autos tend to have less gears, taller gearing, and are heavier than manual transmissions. Then there's the issue of slushboxes robbing drivetrain power through torque converters. Even an average driver can shift faster than an automatic transmission, and with a little practice can learn to 'launch' a car properly.

In everyday driving, MTs are definitely faster than any auto (sportshift or not). They enable a driver to maximize use of the cars power at will... there's no computer to fight with, and power to the wheels is direct, without the extra drain of the TC.

xizor

Bass Mechanic

i think your all giving this girl the wrong advise..
the reasons an auto is slower than a manual transmission is this

1. all automatic transmissions have a hydrolic pump that is driven off the engine just inside the front end of the transmission. this pump is needed to provide hydrolic pressure to engage the various clutch packs so that gear changes are possible.

2. automatic transmissions also use planetary gearsets, there is more moving parts in an automatic transmission and because there are more gears to turn there is more friction.

3. the Auto transmission had 5 gears rather than 6. this means that the gear selection is a larger step between each gear and will cause the engine to have to drop a little lower in the RPM range than a manual will each time you upshift. since hondas make most of their power at the top end you want to stay away from low RPM's when changing from 1 gear to the next.

4 Automatic transmissions weigh more than manuels do because of all the added parts and the automatic transmission also usually takes more fluid than an aotomatic as well as the fluid that has to go through the transcooler section in the radiator.

the good thing about an auto is if you run at the track your times will be within a few 10ths of a second because basically the car accelerates and shifts exactly the same way every time.

fdl

Absolutely not. As I said earlier, an MT car is lighter, has more aggressive gearing (sometimes) and has less drivetrain loss. Even with an "average" driver the MT will be noticablly quicker.

Bass Mechanic

actually that is wrong torque convertors dont loose any power they actually enhance it, the reason a torque convertor is called what it's called is because it can take an engine's horsepower and convert it into torque. it does this by allowing the engine to spin faster than the drivetrain on a launch.
in simple terms you can reach peak torque of the engine say at 4000 rpm but the input side of the transmission is is turning at only 2500 rpm. this is known similar to stall speed. the difference is that stall speed is the maximum rpm you can get the engine to rev to while your foot is on the brake.
as the engine and input shaft of the transmission begin to turn the centrifigual force applied to the fluid in the torque convertor will cause the difference in RPM between the engine and input shaft of the transmission to become less and less different. eventually as in most modern transmissions the torque convertor has a lockup feature that works just like a manuel clutch. it locks the engine and input shaft together to result in better fuel economey.

Bass Mechanic

a high stall convertor will allow the engine to reach a more optimal RPM for launching say 4K RPM rather than stock. a shift kit is a modification you can do to the clutch packs to give them more surface area. this will cause it to shift faster and more solid and withstand more power.
however in todays electronically controlled transmissions many of these bennifits can be achieved with the reprogramming of the transmission ECU (usually part of the engine computer management) since the computer is in charge of gear changes it would be easy to reprogram and adjust the shift points.

Bass Mechanic

ill challenge this also,

you will find most of the big competition use auto transmissions for racing. especially when your running in the 11-12 seconds range. most imports are manuels at the track for the reasons you stated, however people running in the sub 11 second range would usually bennifit from an auto because quite simple there just isnt enough time to change 4 gears along the 1/4 and drive at the same time.
ill give an example, about 2 years ago i saw a neon run a 9 second pass.
it had a 2.4L boosted quite a bit. i can tell you that when his trap speeds are well over 100 MPH there is no time. this car could power brake the auto transmission and come oput of the hole with authority and to watch it run down the 1/4 the gear changes are instant and precise. if it were a manuel transmission the gears go by way too fast to hit the shift perfectly and compleatly. to shift that fast and do it perfect is out of human control and ability.

also somthing to consider about an auto verses a manuel is that unlike a manuel an auto transmission has all its gears engaged all the time, the difference is that it needs only to release 1 clutch and engage another to make the gear changes. in fact all automatic transmissions engage both clutches from 1 gear to the next at the same time, this provides smoother shifts and shifts that can be done under full throttle.

a manuel can be in only 1 gear at a time and has to be disengaged from the engine to make the gear change possible

also somthing interesting to note, all manuel transmissions have all their gears already meshed and turning all the time. when you use a particular gear you are in fact locking that gear to the output shaft, your not exactly engaging the gear itself. so your not grinding teeth from the gear when you grind one your grinding the teeth on the cog that attaches it to the shaft.

trolldrengi

Yes, at low speeds it is true that TCs enhance power - at speeds over ~40mph this is not the case. For highway passing, and merging onto roads like NJ's Garden State Pkwy, MTs will be faster.

Most current autos do not have a locking tc... not even recent model corvettes have this (at least they didn't the last time I checked around 4yrs ago).

My comments are directed only at traditional autos with or without 'sportshift' manual gear selection. Which is exactly what the TSX has. The SMG and F1 style trannies of BMW & Ferrari are far more advanced and are much faster shifting than any human with a clutch pedal (and they actually have a clutch which the computer controls).

Gearing and so forth play equal roles, but other folks have covered that adequately... I thought the effects of a Torque Converter were worth mentioning. It still astounds me that people will go out of their way by spending thousands of dollars to make their car faster, and still have a slushbox automatic.

Bass Mechanic

some interesting pictures and in depth explanation of what i just posted above. can be found here. there is an interactive diagram where you can change through 5 gears and reverse on the 2nd or 3rd page and you can see how the reansmission behaves
http://auto.howstuffworks.com/transmission1.htm

Bass Mechanic

actually you would be hard pressed to find an auto without a locking TC i dont know about the vette.
my 96 accord, 2001 TL, the RSX, the TSX, and the toyotas i have owned all had one.
even my 89 pontiac grand am had one

here i found a good explanation here
http://auto.howstuffworks.com/torque-converter3.htm
go to page 1 if you want to read the whole lesson.

trolldrengi

Um... right, whatever. I don't follow econo-car drag racing, and I find it hilarious that people do this to their cars and still try to drive them on the street.

Top-fuel dragsters DO have manual transmissions (just specialized ones), and they cover the 1/4 mile in what, 3-4secs?

Real race cars, from Formula 1, WRC, and NASCAR all run manuals. Different kinds, Paddle Shift, SMG, old fashioned 4-spd with a clutch pedal...

In everyday driving, in the real world, in unmodified, bone-stock TSXs, a manual trans will be faster than an automatic...

trolldrengi

Uh, yeah, if you go back to the first page of this thread, you'll see that I'm the one who posted that link in the first place.

Yes, these vehicles have a basic 'overdrive' torque converter clutch, but this only locks when the vehicle is driving at a steady speed above about 48mph. This is NOT the same as a true locking clutch in a manual transmission.

Bass Mechanic

actually top fuel dragsters make over 3000 horsepower and as a result only have 1 gear. for the exact same reason i already explained it takes too long to shift gears at that speed and in a 6-7 second run. Top fuel dragsters run a single gear and a clutch that through a series of 5-6 (i think) clutch disks and pressure plates all squished together with hydrolics during the launch is what propels the car down the strip. in fact the clutch is slipping much like a torque convertor does about 3/4 the way down the track. the tires also expand due to the speed they are rolling down the track from launch to the end of the drag strip. this expansion of the tires not only raises the rear end of the drag car up off the gorund but also effectivly becomes a gear that gets larger with speed.

so the fact is top fuel dragstrers are manuel but i wouldnt call it a transmission exactly since there are no gears to change
secondly the gear ration is continusly variable because the tires change size down the track.

edit, i forgot to mention that after a run they replace the clutch, it usually welds itself together from the heat generated by dumping 3000+ horsepower into it and alloing it to slip of r3/4 of the run. it makes a lot of heat and welds itself together.
the key is that they have to very carefully adjust the amount of pressure they engage it with and how long it takes for that to happen to get consistant runs.

Bass Mechanic

read the whole page at the bottom it says and i quote

"To counter this effect, some cars have a torque converter with a lockup clutch. When the two halves of the torque converter get up to speed, this clutch locks them together, eliminating the slippage and improving efficiency. "

this is in fact a locking TC

trolldrengi

Exactly... whereas a manual transmission is locked during all but the duration of the shift... the driver has absolute control over the clutch.

The locking effect your referring to is only in effect at steady speeds, it doesn't occur during heavy acceeleration... the two halves of the tc aren't working at the same speed.

This is different from upgraded locking TCs I've read about as available on 'Vettes, where the shift action is much harsher as the aggressive profile of the locking TC causes locking immediately after each shift.

Thanks for the info on the dragster stuff, I've never looked into it that closely. I did always wonder how those trannies functioned.