Tuning za avtomatik vozila
Objavljeno: Sr avg 23, 2006 10:20 am
Brez posega v sam motor lahko izboljšamo performanse vozila z posegom v menjalnik.
Celoten tekst je v angleščini - enjoy!
Old-style ('50s-'70s) torque converters rarely failed so car owners gave them little thought. Failures were usually caused by rocking a car from drive to reverse trying to get unstuck in the snow, or overheating the trans by towing thereby wiping out the phenolic bushings and washers found in stock torque converters. Another cause of torque converter failure is when the engine's horsepower is increased without installing a performance torque converter that has been fortified for the extra power. Lock-up torque converters introduced in the '80s and used in virtually every automatic transmission today were prone to clutch failure early on, but most of those problems have been resolved.
When to Replace
How can you tell if your torque converter needs replacing? Some sure signs are metal contamination in the transmission fluid. A loss of power or a loss of stall speed (the rpm at which a converter slips when you step on the gas). A torque converter may make a grinding noise from internal metal-to-metal contact when clearances go away. Basically, if your transmission fluid has been cooked several times or the transmission has failed sending debris into the converter, then it's time for a rebuilt converter. Expect to fork out $150-$250 for a standard rebuilt replacement converter.
For an additional $200-$400 you can replace your present torque converter with a modern performance converter and gain the performance benefits plus durability that is unavailable in OE replacements. And it's the perfect resto modification. It can't be detected by any show judge and the vehicle can always be returned to original by installing the OE converter (not that anyone would want to).
What to Expect
Okay, what do you get for your $450-$650 dollars? Depending who you purchase the torque converter from, this is what you should get. A modern converter core (virtually all torque converters are rebuilt from existing OE cores). Early torque converters from the '60s typically had a 1.7- 1.9-torque multiplication factor. What this means is that if your engine produced 200 lb.-ft. of torque at the converter's stall speed, it would multiply it by 1.7 providing 340 lb.-ft. of torque to the driveshaft. A typical modern torque converter has a torque multiplication factor of 2.5, so just changing to a modern design with the same stall speed would bump the torque from 340 lb.-ft. at the driveshaft to 500 lb.-ft. without touching the engine.
The second area of potential gains with a performance torque converter is increased stall speed. Racers have known this speed secret for years. Install a smaller-diameter torque converter, one with more stall speed (slip), and the engine will launch the car in its power band. Racers try to match torque converter stall speed with the engine's peak torque. Street driven cars can benefit by just increasing stall speed enough to get into the "fat" part of the torque curve. Let's say our hypothetical engine makes its 200 lb.-ft. of torque at 1800 rpm (a typical stock stall speed converter). However, at 2500 rpm it produces 300 lb.-ft. of torque. That means this same engine could now put 750 lb.-ft. of torque to the driveshaft for take-off compared to the stock 340 lb.-ft. produced with the OE torque converter. By changing the torque converter you've more than doubled the output torque of the engine!
Additional Mods
Other modifications that should be included in any high performance torque converter are furnace brazed fins, Torrington-style thrust washers and a heavy-duty sprag. Many companies sell "high-stall speed" torque converters that are just modified low torque multiplication converters. They will get the engine up into its torque band, but you loose the efficiency of the new converter designs. For instance, most race style converters have been and are still being built out of '60s Opel torque converter cores. Much more efficient race converters are being constructed with Dodge Neon cores.
A final word of caution: Any time you increase torque converter stall speed (slip), you increase heat. Make sure that you install an auxiliary transmission cooler when you go to a high performance torque converter.
Torque Converter Tips
> Select a torque converter stall speed by matching it to a rpm where your engine is producing at least 80 percent of peak torque.
> Make sure that the torque converter you are purchasing has been modified from a modern, high torque multiplication core.
> Most companies can determine the correct converter for your vehicle if you provide engine peak torque figure and rpm, vehicle weight, transmission type, rear gear ratio and tire diameter.
> Deal only with companies that warranty their products.
> Install a transmission cooler to eliminate the increased heat caused by a high performance torque converter.
Celoten tekst je v angleščini - enjoy!
Old-style ('50s-'70s) torque converters rarely failed so car owners gave them little thought. Failures were usually caused by rocking a car from drive to reverse trying to get unstuck in the snow, or overheating the trans by towing thereby wiping out the phenolic bushings and washers found in stock torque converters. Another cause of torque converter failure is when the engine's horsepower is increased without installing a performance torque converter that has been fortified for the extra power. Lock-up torque converters introduced in the '80s and used in virtually every automatic transmission today were prone to clutch failure early on, but most of those problems have been resolved.
When to Replace
How can you tell if your torque converter needs replacing? Some sure signs are metal contamination in the transmission fluid. A loss of power or a loss of stall speed (the rpm at which a converter slips when you step on the gas). A torque converter may make a grinding noise from internal metal-to-metal contact when clearances go away. Basically, if your transmission fluid has been cooked several times or the transmission has failed sending debris into the converter, then it's time for a rebuilt converter. Expect to fork out $150-$250 for a standard rebuilt replacement converter.
For an additional $200-$400 you can replace your present torque converter with a modern performance converter and gain the performance benefits plus durability that is unavailable in OE replacements. And it's the perfect resto modification. It can't be detected by any show judge and the vehicle can always be returned to original by installing the OE converter (not that anyone would want to).
What to Expect
Okay, what do you get for your $450-$650 dollars? Depending who you purchase the torque converter from, this is what you should get. A modern converter core (virtually all torque converters are rebuilt from existing OE cores). Early torque converters from the '60s typically had a 1.7- 1.9-torque multiplication factor. What this means is that if your engine produced 200 lb.-ft. of torque at the converter's stall speed, it would multiply it by 1.7 providing 340 lb.-ft. of torque to the driveshaft. A typical modern torque converter has a torque multiplication factor of 2.5, so just changing to a modern design with the same stall speed would bump the torque from 340 lb.-ft. at the driveshaft to 500 lb.-ft. without touching the engine.
The second area of potential gains with a performance torque converter is increased stall speed. Racers have known this speed secret for years. Install a smaller-diameter torque converter, one with more stall speed (slip), and the engine will launch the car in its power band. Racers try to match torque converter stall speed with the engine's peak torque. Street driven cars can benefit by just increasing stall speed enough to get into the "fat" part of the torque curve. Let's say our hypothetical engine makes its 200 lb.-ft. of torque at 1800 rpm (a typical stock stall speed converter). However, at 2500 rpm it produces 300 lb.-ft. of torque. That means this same engine could now put 750 lb.-ft. of torque to the driveshaft for take-off compared to the stock 340 lb.-ft. produced with the OE torque converter. By changing the torque converter you've more than doubled the output torque of the engine!
Additional Mods
Other modifications that should be included in any high performance torque converter are furnace brazed fins, Torrington-style thrust washers and a heavy-duty sprag. Many companies sell "high-stall speed" torque converters that are just modified low torque multiplication converters. They will get the engine up into its torque band, but you loose the efficiency of the new converter designs. For instance, most race style converters have been and are still being built out of '60s Opel torque converter cores. Much more efficient race converters are being constructed with Dodge Neon cores.
A final word of caution: Any time you increase torque converter stall speed (slip), you increase heat. Make sure that you install an auxiliary transmission cooler when you go to a high performance torque converter.
Torque Converter Tips
> Select a torque converter stall speed by matching it to a rpm where your engine is producing at least 80 percent of peak torque.
> Make sure that the torque converter you are purchasing has been modified from a modern, high torque multiplication core.
> Most companies can determine the correct converter for your vehicle if you provide engine peak torque figure and rpm, vehicle weight, transmission type, rear gear ratio and tire diameter.
> Deal only with companies that warranty their products.
> Install a transmission cooler to eliminate the increased heat caused by a high performance torque converter.