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Old 10-18-2005, 03:57 AM   #1
Pythias
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Question Automatic and Manual Transmissions...

Hello everyone I was wondering if someone could explain to me how power is wasted through automatics(torque convertor?). From everything I know manuals are faster, I would just like someone to explain what are all the disadvantages of an automatic. When I buy a mustang I was lenaing way more automatic because I am not great with manual yet, driveable but not great. So if someone could lend me some assistance that would be great, thanks in advance.
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Old 10-18-2005, 04:09 AM   #2
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The disadvantages of an automatic is that you have to wait for the transmission to shift itself. With a manual, you control exactly when you want it to shift, what gear to shift into, and how fast it shifts.
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Old 10-18-2005, 04:19 AM   #3
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Quote:
Originally Posted by Oomba
The disadvantages of an automatic is that you have to wait for the transmission to shift itself. With a manual, you control exactly when you want it to shift, what gear to shift into, and how fast it shifts.

What about torque convertors, other then that do you loose any torque or horsepower? I was thinking about getting a 95 GT as automatic and modding it. Eventually to around 300HP stock would that be so much harder than if it were manual?
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Old 10-18-2005, 04:25 AM   #4
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Automatics get worse mileage, and with a Mustang, even the manuals don't do too well...
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Old 10-18-2005, 04:30 AM   #5
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I will attempt to explain torque converters:

Notice how in a manual car, you cannot be in gear, and stopped at the same time, unless you depress the clutch pedal. Otherwise you would simply stall the car. When the clutch is engaged, the engine, transmission, and wheels are all turning together. So if one stops, the other has to stop as well.

Notice in an automatic car, you can stop and go at free will, yet never have to "disconnect" any of the drive line parts to keep the car from stalling. This is achieved through a torque converter.

This is the easy way I was taught. Imagine two fans facing each other. If you turn one fan on, it will start going and slowly speed up until it reaches its maximum speed. The other fan will start to turn, and slowly pick up speed, but not as fast as the first. Now imagine the switched on fan is your engine flywheel. Imagine the other fan is the input shaft of your transmission. This is the reason for the power loss. The fans are not connected, therefor, not 100% of the power is transmitted from the engine to the transmission. Also, if you were to grab the unpowered fan with your hand, you would be able to stop it, even though the powered fan is still turning. This is like when holding the brake at a stop light. The engine is still turning, but the brake is holding the wheels, which stops the unpowered "fan" from moving. When you let go of the brake, the unpowered fan begins to move again, and the car drifts forward slowly.

This is the concept behind the torque converter. A torque converter is actually more like one fan inside another fan, in a housing filled with fluid. It still accomplishes the same thing though. This is also known as a fluid coupling.
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Old 10-18-2005, 08:35 AM   #6
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Quote:
Originally Posted by Mathew
I will attempt to explain torque converters:

Notice how in a manual car, you cannot be in gear, and stopped at the same time, unless you depress the clutch pedal. Otherwise you would simply stall the car. When the clutch is engaged, the engine, transmission, and wheels are all turning together. So if one stops, the other has to stop as well.

Notice in an automatic car, you can stop and go at free will, yet never have to "disconnect" any of the drive line parts to keep the car from stalling. This is achieved through a torque converter.

This is the easy way I was taught. Imagine two fans facing each other. If you turn one fan on, it will start going and slowly speed up until it reaches its maximum speed. The other fan will start to turn, and slowly pick up speed, but not as fast as the first. Now imagine the switched on fan is your engine flywheel. Imagine the other fan is the input shaft of your transmission. This is the reason for the power loss. The fans are not connected, therefor, not 100% of the power is transmitted from the engine to the transmission. Also, if you were to grab the unpowered fan with your hand, you would be able to stop it, even though the powered fan is still turning. This is like when holding the brake at a stop light. The engine is still turning, but the brake is holding the wheels, which stops the unpowered "fan" from moving. When you let go of the brake, the unpowered fan begins to move again, and the car drifts forward slowly.

This is the concept behind the torque converter. A torque converter is actually more like one fan inside another fan, in a housing filled with fluid. It still accomplishes the same thing though. This is also known as a fluid coupling.
nicely explained!

you're using a fluid to transfer the torque, not friction like in a clutch.... so there's no direct contact. Bound to be losses.
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Old 10-18-2005, 08:27 PM   #7
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Post

Quote:
Originally Posted by Mathew
I will attempt to explain torque converters:

Notice how in a manual car, you cannot be in gear, and stopped at the same time, unless you depress the clutch pedal. Otherwise you would simply stall the car. When the clutch is engaged, the engine, transmission, and wheels are all turning together. So if one stops, the other has to stop as well.

Notice in an automatic car, you can stop and go at free will, yet never have to "disconnect" any of the drive line parts to keep the car from stalling. This is achieved through a torque converter.

This is the easy way I was taught. Imagine two fans facing each other. If you turn one fan on, it will start going and slowly speed up until it reaches its maximum speed. The other fan will start to turn, and slowly pick up speed, but not as fast as the first. Now imagine the switched on fan is your engine flywheel. Imagine the other fan is the input shaft of your transmission. This is the reason for the power loss. The fans are not connected, therefor, not 100% of the power is transmitted from the engine to the transmission. Also, if you were to grab the unpowered fan with your hand, you would be able to stop it, even though the powered fan is still turning. This is like when holding the brake at a stop light. The engine is still turning, but the brake is holding the wheels, which stops the unpowered "fan" from moving. When you let go of the brake, the unpowered fan begins to move again, and the car drifts forward slowly.

This is the concept behind the torque converter. A torque converter is actually more like one fan inside another fan, in a housing filled with fluid. It still accomplishes the same thing though. This is also known as a fluid coupling.

Thank you very much I understood this greatly. Now my next question i am planning to save money through the winter until about January or Febuary to buy my mustang. So far at this point in time I was a 1995 GT automatic, Convertible, with leather interior. I plan on using ONLY bolt-ons to reach the power (250-300RWHP) Would it be a great deal harder to achieve this goal in an automatic? Another reason I want automatic is because a majority of sports cars like this are manuals, I'd like to be able to pull some good numbers through an automatic transmission. And no I do not plan on changing the transmission soon after I get this car to a C4 or somethin.
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Old 10-19-2005, 09:41 PM   #8
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Actually, something like 80% of Mustangs are sold with auto trans. I have one myself with an auto, V6 though. I'm not sure about the '95 GT but Ford claims with the '05 GT that it does 0-60m in 5.2 sec with either transmission, meaning that the auto will match the manual in this case.
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Old 10-19-2005, 10:57 PM   #9
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Yes, there are losses with a torque converter, just like there are losses when you slip the clutch to take off. (most people forget that part. if you aren't using full power to accellerate with in a manual trans car, such as at part throttle or while in teh process of slipping the clutch to take off from a stop, then you are losing equal amounts of power there...) Most torque converters have a "stall speed" which is the point where they are direct drive (and lock up torque converters physically lock together at a certain rpm, just as if you had fully engaged the clutch). So it's not as bas as most people think.

Also, a torque converter does something else most people don't understand, it multiplies torque by providing nearly infinite gear ratios from idle to stall.

The main issue of losses is during shifts, where most automatics are tuned to be smooth. This results in excess slippage between gears and waiting around for the gearchange to happen. This is why most stock automatics are slower than manual transmissions for accelleration.

But that can be changed. And in fact, as many drag racers know, an auomatic with a mdified valve body and high stall converter can end up beng quicker than a manual transmission in accelleration, and shift exactly when the driver wants. On older domestic cars and musclecars, the modifications are cheap and simple, and will make the shifts much faster than you can do it manually. The shifts can either be done automatically OR manually by simply moving the lever. The engine never slows down DURING the shift, so it never loses power (good for turbo cars that keep the turbo spooled up) and the shifts are done accurately with no missed shifts. A trans set up like this can be VERY quick, and very fun on the street as well as on the track.
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Old 10-19-2005, 11:15 PM   #10
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Quote:
Originally Posted by Pythias
So far at this point in time I was a 1995 GT automatic, Convertible, with leather interior. I plan on using ONLY bolt-ons to reach the power (250-300RWHP) Would it be a great deal harder to achieve this goal in an automatic?

The trans cares not how much power you make. Well, at these levels.


Quote:
Another reason I want automatic is because a majority of sports cars like this are manuals, I'd like to be able to pull some good numbers through an automatic transmission. And no I do not plan on changing the transmission soon after I get this car to a C4 or somethin.

Just put a $50 B&M shift improver kit into the stock EAOD. Basically the same trans I had in my V8 RX7. When not on the throttle, the car could be driven like a stock automatic (though with quicker shifts) but give it the gas, and it could bark the tires into every gear including overdrive. And if you wanted, just moving the lever instantly put the car into that gear unless the revs were too high (e.g., if you were at the top of third, it would NOT shift down to second, so you couldn't pull a maneuver like shift from third to first and blow the engine, as some people have been known to do witha manual).
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Old 10-20-2005, 02:59 AM   #11
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Quote:
Originally Posted by ChrisV
Most torque converters have a "stall speed" which is the point where they are direct drive (and lock up torque converters physically lock together at a certain rpm, just as if you had fully engaged the clutch). So it's not as bas as most people think.


I typed so much there, I forgot to mention that one part. Once the torque converter locks up, there is no loss of power.
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Old 10-21-2005, 02:22 AM   #12
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Why go for the 5.0 though? Why not bump it up a year to the 4.6?

You'll already be pushing 290 horses, and there are equal as many performance mods.
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Old 10-21-2005, 05:02 PM   #13
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The 4.6 in '96 was rediculously underpowered...'96-'98 were the dark years for the 4.6. The 5.0 is a good way to go. I noticed a lot of good information posted here about automatics so, you have a good starting point. The only thing that was left out, was that a decent AODE will be obscenely consistent(through the quarter mile).

If you've got some money to drop, get a quality rebuilt tranmission and install a Lentech Strip Terminator valve body and for that power level, a torque convertor with a stall speed anywhere from 2400-3200 depending on how aggressive you want to get. The Lentech valve body will allow full manual shifts of all gears(like a manual w/o a clutch) as well as a trans brake feature. The OD is controlled by a switch instead of a gear position. While Lentech is quite expensive, you get what you pay for. You could go with a B&M shift kit, that's what I run, but you won't have good control over your gear selection. Also, install the largest trans cooler you can, that will prolong the life of the transmission greatly and make the trans run more consistently.

ChrisV...that sounds like fun in that little RX-7. Too bad the hogs we call mustangs aren't that light.
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Old 10-23-2005, 06:58 PM   #14
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Quote:
Originally Posted by Godlaus
Why go for the 5.0 though? Why not bump it up a year to the 4.6?

You'll already be pushing 290 horses, and there are equal as many performance mods.

290 horses? Correct me if I am wrong anybody but 215 was the stock rated power for the 96' GT. I believe it's specs were 215 horses and 285 torque meanwhile the 95 was 225 and 300 torque. Could be wrong but I know it right around there. And I love the 5.0 engines.
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Old 10-25-2005, 12:22 AM   #15
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Quote:
Originally Posted by Pythias
290 horses? Correct me if I am wrong anybody but 215 was the stock rated power for the 96' GT. I believe it's specs were 215 horses and 285 torque meanwhile the 95 was 225 and 300 torque. Could be wrong but I know it right around there. And I love the 5.0 engines.

The 5.0 was rated at 225hp and 300lb-ft until '92, then from '93-'95, it was rated at 215hp. The 4.6 never produced the torque that Ford made with the 5.0.
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