Also remember, if you have to go thru 7 shifts from 0 - 100, it doesn't necessarily mean it will be fasters than 5 shifts from 0 - 100 because everytime you shift, the engine is disengaged from the tranny
not necessary; 6th and 7th gears are overdrive gears and on there for fuel economy purposes. i can't speak for the mercedes one, but i know te SMGIII on the BMW M5 can hit top speed (155mph) with 5th, 6th, and 7th. yet that car has some pretty insane elasticility numbers.
It's all about tuning too--A transmission that keeps the engine in the powerband in each gear is going to get good acceleration.
First of all if you read my post over again you will hit the words "doesn't necessarily mean"
and second, lower RPMs on a higher gear does not necessarily mean the car will have better fuel economy. And 6th and 7th gears are not only there for fuel economy purposes. They are there to suit the higher horsepower cars that are appropriate. You made it sound like its only there for fuel economy purposes. Having too many gears on a vehicle with lower horsepower will be a waste of a gear because the car will not be able to keep up RPMs in that gear without having to inject too much fuel.
For many many years, pro dragster rails used 2 speed automatic transmissions, which were bullet proofed and manuals couldn't come close to their ET's. Simply, a lot of their hydraulic efficiency loss was overcome.
Manual and auto cars should have different axel ratios also. It's not as straightforward as it may seem.
Manual and auto cars should have different axel ratios also. It's not as straightforward as it may seem.
First of all, reading through your quote, you seem to think that a 7 speed auto will HAVE to shift through 7 gears to get to 100mph. My post is saying that it doesn't.
And if a car's top speed is already reached by 5th gear, then why else would 6th and 7th gears be there except to improve fuel economy (and marketing maybe
)makken, you retard, do u know what the words "doesn't necessarily" mean?
And if a top speed of a car is only reached by 5th gear, the 6th and 7th gear, when shifted to those gears, will only slow it down and decrease fuel economy.
And if a top speed of a car is only reached by 5th gear, the 6th and 7th gear, when shifted to those gears, will only slow it down and decrease fuel economy.
Well, the number one, bottom line, fundamental reason is that with a clutch and a manual transmission you control the amount of torque that is applied to the wheels over a given period of time. You can run the revs up and then engage the clutch and pop off the mark, which is something no automatic will let you do (unless you are willing to attempt what is known as a "neutral drop," and with modern transmissions not even then.)
I know what "doesn't necessarily" mean, and my post didn't have anything to do with that. Here's the point my post was about:
I'm saying it usually doesn't have to shift through 7 gears.
You're saying that it has to shift through 7 gears.
Secondly, If you run top speed at 5th gear at the 8250RPM redline vs 7th at say 5000RPM, you will be using a lot more gas.
ok, read my post again and it says the words "doesn't necessarily" right after "if you have to go thru 7 shifts from 0 - 100"
and besides, that statement was going towards those people who think more gears and gear ratios being closer together will make a car accelerate faster.
and if you top out in 5th, you won't top out in 7th. Therefore however much gas you save you will also go slower. Nor will it necessarily mean you will save more gas just by going at a lower RPM. Cars are NOT as straightforward as you think they are.
and besides, that statement was going towards those people who think more gears and gear ratios being closer together will make a car accelerate faster.
and if you top out in 5th, you won't top out in 7th. Therefore however much gas you save you will also go slower. Nor will it necessarily mean you will save more gas just by going at a lower RPM. Cars are NOT as straightforward as you think they are.
Just for kicks:
To me, that's saying:
A 7spd auto will shift 7 times going from zero to 100. Shifting 7 times may or may not be faster than a 5 spd auto that only shifts 5 times because of the lag between shifts. If i'm reading that wrong, please let me know.
I agree with you that shifting 7 times while accelerating to a predetermined speed may or may not be faster than shifting 5 times, it depends on the car and transmission, therefore I have no problem with that statement. I don't, however, agree with the first part: 'A 7spd auto will shift 7 times going from zero to 100.' that was what my post was about.
And I think we mean different max speeds. The max speed i was refering to is the governed max speed of the car--either by computer (cuts off fuel after a certain speed), or some other factor (tires for example). Virtually all cars, minus the exotics, have computered governed max speeds these days (I know the ford tarus is limited to 120mph--yah ask how I know
) while the majority of german cars (Mercedes, Audi, BMW) have a 'gentlement's agreement' stating that they will not exceed 155mph on their cars.The max speed you're refering to (commonly called Vmax), is the absolute maximum--where engine output power = drag force. If that is what you're refering to, then you're right, a higher gear ratio will mean a lower Vmax.
no prob. happens to the best of us
Manual transmissions have less power loss than an auto. All else being equal a manual can out accelerate an auto, but there is more to drag racing than just the amount of power at the wheels; weight transfer, tractions, how the power hits the tires.
My 2001 Cobra with a manual,. It will have a higher MPH in the traps but will have a slow ET than an auto car with the same power, due to an auto can power brake off the line, shift quicker and more consistant. An auto applies the power easier to the tires. A manual clutch is nearly like a light switch, unless you want to ride the clutch and burn it out in 20 passes. But going down the track, by just pressing the loud peddle isn't too much fun. I like the twisty tracks more anyway.
gsellis
Diamond Member
- Dec 4, 2003
- 6,061
- 0
- 0
Standard manuals are faster than current torque converted automatics because of loss and different gearing.
BUT, the king of automatics is faster than any manual. That would be the F1 automatic gearbox that was preprogrammed for each circuit. It was outlawed as a driver's aid by the FIA. Gear changes were below .1 second and it had minimal loss. In conjunction with the traction control, it could do perfect launches with near perfect wheel spin. Not sure I could find linkage as they went away at least 10 years ago. The F1 paddle shifted tranny is its heir.
BUT, the king of automatics is faster than any manual. That would be the F1 automatic gearbox that was preprogrammed for each circuit. It was outlawed as a driver's aid by the FIA. Gear changes were below .1 second and it had minimal loss. In conjunction with the traction control, it could do perfect launches with near perfect wheel spin. Not sure I could find linkage as they went away at least 10 years ago. The F1 paddle shifted tranny is its heir.
Originally posted by: makken
Just for kicks:
To me, that's saying:
A 7spd auto will shift 7 times going from zero to 100. Shifting 7 times may or may not be faster than a 5 spd auto that only shifts 5 times because of the lag between shifts. If i'm reading that wrong, please let me know.
I agree with you that shifting 7 times while accelerating to a predetermined speed may or may not be faster than shifting 5 times, it depends on the car and transmission, therefore I have no problem with that statement. I don't, however, agree with the first part: 'A 7spd auto will shift 7 times going from zero to 100.' that was what my post was about.
And I think we mean different max speeds. The max speed i was refering to is the governed max speed of the car--either by computer (cuts off fuel after a certain speed), or some other factor (tires for example). Virtually all cars, minus the exotics, have computered governed max speeds these days (I know the ford tarus is limited to 120mph--yah ask how I know
The max speed you're refering to (commonly called Vmax), is the absolute maximum--where engine output power = drag force. If that is what you're refering to, then you're right, a higher gear ratio will mean a lower Vmax.
no prob. happens to the best of us
I would like to add, most manual transmissions are 1:1 in 4th gear. Any gear above 4th is an overdrive or less than 1:1. In my 2001 Cobra 0-100 is done through 1st-3rd gears. 3rd gear (1.33:1) tops out at about 125mph with my 3.27 rear end gears.
..wow. steep gearing you got there. My third tops out at 88mph (6500rpm) and I think I have either a 2.73 or a 2.86 diff, can't remember.
It sounds like you have 4.10s.
Ihave stock gears again. I use to have 4.10s, which were nice with the DOHC V8 engine that doesn't make peak torque until 4,000-5,000. I put the 3.27 back in with a Eaton LSD, which really doesn't slip at all, for a turbo setup that I haven't finished. I blew the engine last year and had it rebuilt with 9.1:1 CR from 9.85:1. N/A I have it tuned up to use 87 octane gas. HAHAHAhttp://www.angelfire.com/fl/procrastination/rear.html
The Boston Dangler
Lifer
- Mar 10, 2005
- 14,647
- 2
- 0
Most of those German rocket sedans have multiple speed limiters. Tuner shops find them in every nook and cranny.
if you read carefully there is also an "IF" before all of that. Basically that statement doesn't mean you have to shift 7 times to end all this gibberish.
Basically, to sum it all up and reword it, what it meant was that closer gears in a car doesnt necessarily mean the car will accelerate faster, unlike what people said in the first page or so of this thread
And there are many ECUs that can take out speed limiters.
Basically, to sum it all up and reword it, what it meant was that closer gears in a car doesnt necessarily mean the car will accelerate faster, unlike what people said in the first page or so of this thread
And there are many ECUs that can take out speed limiters.
The Boston Dangler
Lifer
- Mar 10, 2005
- 14,647
- 2
- 0
I'm referring to speed limiters found in the fuel system, ABS, stability control, odometer, differential, transmission, impact sensors, traction control, the list goes on and on. These limiters cannot be defeated with a chip swap, more extensive methods are used.
TRENDING THREADS
-
Discussion Zen 5 Speculation (EPYC Turin and Strix Point/Granite Ridge - Ryzen 9000)- Started by DisEnchantment
- Replies: 25K
-
Discussion Intel Meteor, Arrow, Lunar & Panther Lakes Discussion Threads
- Started by Tigerick
- Replies: 21K
-
Discussion Intel current and future Lakes & Rapids thread- Started by TheF34RChannel
- Replies: 23K
-
-
Facebook
Twitter