just few simple questions
WindsorMan
10-27-2005, 05:07 PM
Hi everybody, I´m kinda new at the whole muscle car department, I have some questions for you that I know you guys can answer quickly, I have been watching drag racing for a while and want to know a little more about transmissions.
1. What is a converter, what does it do and what is a 2600-3500 stall converter, what is the difference between a 8" converter and a 9.5"
2. Manual valve box, what is that and how does it work?
3. Transbrake, am I right when I say that it, well as the name says, brakes the trans, how does it works?
best regards
Dave
1. What is a converter, what does it do and what is a 2600-3500 stall converter, what is the difference between a 8" converter and a 9.5"
2. Manual valve box, what is that and how does it work?
3. Transbrake, am I right when I say that it, well as the name says, brakes the trans, how does it works?
best regards
Dave
MrPbody
10-28-2005, 09:42 AM
A torque converter is the fluid coupling between the engine and transmission. A catalytic converter is the item in the exhaust system, usually containing platinum, that "reacts" with the unburned fuel coming out of the engine, "cleaning" the emmisions. Based on your further questions, I must assume you're speaking of the torque converter.
A torque converter is most easily described by example. Take two table fans. Place them opposing each other. Turn one on. As air is a fluid, it will begin moving in the same rotation as the running fan. It will eventually get the other fan turnng the same direction. While this is a simplification, it is the best simple demonstration.
Insde the converter, there are several components. One is a "rotor". Another is "impeller". The third (and most complex in purpose) is the "stator".
See the impeller as the running fan. The rotor is the fan that is forced to turn by the moving fluid. Transmission fluid is "flung" at a high rate of speed by the impeller against the rotor. That in turn, makes the rotor turn. The impeller is mechanically linked to the engine, while the rotor is mechanically linked to the input shaft of the transmission.
The stator's role is to "direct" the fluid toward the rotor in the most efficient manner to achieve "lockup" (the point where both the impeller and rotor are moving at approximately the same speed).
Stall speed is controlled by the size and aggressiveness of the "blades" on the impeller and rotor. Stall speed is also the point where, once reached, unless something "gives", the engine will not rev any higher. Something "giving" would be the car begins to move, the tires turn over, or the internals of the transmission "slip".
A 2,600 RPM "stall" means locup occurs at approximately 2,600 RPM, with a given amount of torque. Converters are usually "rated" using a "base line" of a given engine. In today's market, 350 Chevy is the most common measuring stick. The higher the torque output of the engine, the higher the RPM will be at "lockup".
More is made of converter diameter than necessary. Stall speed is more important for most applications. In general, a larger diameter would be a better chice for a street application. A converter designer can achieve the desired results more easily by using various diameters. For the most part, the smaller the diameter, the higher the stall speed. Except for some small engine applications, an 8" converter would be strictly a very high stall speed, for drag racing only.
A manual valve body (not "box") is a modification to an automatic transmission, where the driver must physically shift the gears, not unlike a manual transmission, without the need for a clutch. These are generally reserved for racing applications, but it's not unusual to see it in high performance street cars.
There's a variatioin on that theme, a "reverse" manual valve body. That;s wehre the shifter osition is altered, and 1st gear is at the top of the gate (the first in line) and high ("Drive") is at the bottom of the line. This allows one to shift the transmission without worrying about missing the shift and shoving the trans into nuetral at the most inopportune time.
A trans brake is a hydralically controlled "brake" inside the transmission, to control the launch in drag racing. It involves some electronics as well.
When staging the car, the driver "sets" the trans brake. Once activated, it uses an internal timer (in the "box", a small computer) to release the brake. The driver releases the button controlling it, when they see the first amber light. It has the internal timer set to release at the same instant the green light goes on (if all things are correct).
It works by applying reverse and low gear at the same time. A transmission will "lock" (not allow any movement) while two gears are engaged at the same time. When "released", it simply "unapplies" reverse, putting all the pwer through low gear.
This is basic, but fundemetally accurate. Some of it may be an over-simplification, but it should get you on the right path.
Jim
A torque converter is most easily described by example. Take two table fans. Place them opposing each other. Turn one on. As air is a fluid, it will begin moving in the same rotation as the running fan. It will eventually get the other fan turnng the same direction. While this is a simplification, it is the best simple demonstration.
Insde the converter, there are several components. One is a "rotor". Another is "impeller". The third (and most complex in purpose) is the "stator".
See the impeller as the running fan. The rotor is the fan that is forced to turn by the moving fluid. Transmission fluid is "flung" at a high rate of speed by the impeller against the rotor. That in turn, makes the rotor turn. The impeller is mechanically linked to the engine, while the rotor is mechanically linked to the input shaft of the transmission.
The stator's role is to "direct" the fluid toward the rotor in the most efficient manner to achieve "lockup" (the point where both the impeller and rotor are moving at approximately the same speed).
Stall speed is controlled by the size and aggressiveness of the "blades" on the impeller and rotor. Stall speed is also the point where, once reached, unless something "gives", the engine will not rev any higher. Something "giving" would be the car begins to move, the tires turn over, or the internals of the transmission "slip".
A 2,600 RPM "stall" means locup occurs at approximately 2,600 RPM, with a given amount of torque. Converters are usually "rated" using a "base line" of a given engine. In today's market, 350 Chevy is the most common measuring stick. The higher the torque output of the engine, the higher the RPM will be at "lockup".
More is made of converter diameter than necessary. Stall speed is more important for most applications. In general, a larger diameter would be a better chice for a street application. A converter designer can achieve the desired results more easily by using various diameters. For the most part, the smaller the diameter, the higher the stall speed. Except for some small engine applications, an 8" converter would be strictly a very high stall speed, for drag racing only.
A manual valve body (not "box") is a modification to an automatic transmission, where the driver must physically shift the gears, not unlike a manual transmission, without the need for a clutch. These are generally reserved for racing applications, but it's not unusual to see it in high performance street cars.
There's a variatioin on that theme, a "reverse" manual valve body. That;s wehre the shifter osition is altered, and 1st gear is at the top of the gate (the first in line) and high ("Drive") is at the bottom of the line. This allows one to shift the transmission without worrying about missing the shift and shoving the trans into nuetral at the most inopportune time.
A trans brake is a hydralically controlled "brake" inside the transmission, to control the launch in drag racing. It involves some electronics as well.
When staging the car, the driver "sets" the trans brake. Once activated, it uses an internal timer (in the "box", a small computer) to release the brake. The driver releases the button controlling it, when they see the first amber light. It has the internal timer set to release at the same instant the green light goes on (if all things are correct).
It works by applying reverse and low gear at the same time. A transmission will "lock" (not allow any movement) while two gears are engaged at the same time. When "released", it simply "unapplies" reverse, putting all the pwer through low gear.
This is basic, but fundemetally accurate. Some of it may be an over-simplification, but it should get you on the right path.
Jim
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