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Torque Converters
All torque converters have a stall speed. however 99.9% of stock torque converters will never be spoken of as a "stall converter". there is no difference in the way a stock converter works and a "stall converter" honestly, a "stall converter" is an oxymoron. all torque converters stall, thats how they work.

Lets start at the beginning of torque converters. The torque converter is nothing more than a fluid coupler that connects the engine crankshaft to the drive shaft using hydraulic fluid (transmission fluid). There is no direct mechanical connection between the crankshaft and the drive shaft in an automatic transmission. This fluid coupling method allows the transmission to shift gears automatically and without breaking any mechanical connection. It does this by monitoring transmission fluid pressures and/or engine vacuum (depending on the transmission). The rpm that the converter stalls at can be varied by any number of methods. Chief among them is the diameter of the converter or the pitch of the stator vanes. A converter that stalls at a higher rpm than the typical "stock" unit could be called a high stall converter. Stall speed varies with engine torque, so a 4000 RPM converter behind a 502 might provide a 1700 RPM stall behind a 283 (which is one thing people dont take into account when they purchase a stall, a "universal" 3000rpm stall will not stall at that speed for every motor).

things to look at:
True Stall: The rpm the engine cannot exceed when the driveline is locked. The most accurate way to determine true stall is by locking First gear and Reverse with a transbrake and observing engine rpm at WOT. (however, most of us dont have a reverse manual valve body and a transbrake to practice this, so we have to rely on the manufacturer's recomendation).

Flash Stall: The rpm the engine “flashes” to when launched from rest at WOT. A converter will often briefly flash to a higher rpm than its true stall speed. This is due to the fact that when you go to WOT, the transmission builds pressure faster than when you gradually "stall up". and basically "overstalls" the converter before you launch.

Brake Stall: The rpm the engine cannot exceed with the brakes locked and the driveshaft not spinning. Brake stall isn’t usually an accurate measuring tool since the engine often overpowers the wheels before the true stall speed is reached.

now, those are all things about how converters why would you want one that stalls higher than stock?

Advantages of a higher stall converter include: More torque multiplication which means better acceleration. An engine that is set up with a high rpm cam produces poor low speed torque and usually idles at a higher than normal speed. A higher stall converter slips more at idle speeds and eliminates idle creep along with allowing the engine to wind up into its power band when launching. A high stall converter is usually smaller and lighter, producing less flywheel effect and faster rpm gain. In short, your engine will idle easier and rev quicker.

Disadvantages include heat. High stall converters are less efficient at transmitting power and the wasted energy turns up as heat. You can expect your fuel mileage to go down especially in town.

Another factor that gets confusing is converter slip. Slip is basically a measure of converter efficiency. Due to the difference in rotating speeds between the impeller and the turbine, there is usually a five to 10 percent efficiency loss at cruising speeds for non-lockup converters. Because a converter gradually slips, or creeps up, to full stall/lockup rpm, the higher the stall speed, the more slippage you get. On a street-driven vehicle, that can lead to poor idle and low end performance, worse gas mileage, and most importantly, greater heat buildup-the number one killer of converters and transmissions. If you do run a high stall converter, a good transmission cooler is a must.

Unless you have years of experience in the field, it’s nearly impossible to predict precisely how an individual torque converter will behave in your own car. Things like upgraded Torrington bearings and furnace-brazed fins come to play, an 11-inch 3,000 converter vs a 10-inch converter and which is better for your application.

and cus im lazy, here's a link with more info on how converters work, inside and out

If you run an oddball combination of parts, don’t be surprised if a tech guy recommends a custom-built converter. Although companies like TCI and B&M believe an off-the-shelf converter will suit 90 percent of their customers, remember that even these ready-to-ship converters have been designed for common yet specific engine/vehicle applications. But while a mild 350 in a ’78 Camaro is an easy application to match up, there’s probably no converter ready to install behind a twin-turbo 400ci ’68 Caprice.

most manufacturers dont usually recommend anything less than a mid-level Heavy Duty Super Torque converter. the best philosophy is, “You get what you pay for. Why back a $16,000 engine with a cheap converter?”

i've used off-the-shelf converters in a myriad of cars; sometimes they work wonderfully, and sometimes they’re less than great. Custom converters built for specific cars have always been dynamite. although the $900 list price hurts a little, its worth paying to know that what you are putting into the car is going to last thru the abuse.

Anti-balloon plates.

These are primarily used with nitrous setups as the more horsepower you have, the more cover pump pressure there is. With enough pressure your converter will balloon. Pump pressure drives the impeller hub into your transmission pump causing the pump to fail. It also creates bearing endplay creating premature converter failure. When the converter balloons, it loses the dynamic flow through your converter, resulting in loss of efficiency and horsepower. Anti Ballooning flanged hubs keep the converter from expanding outward. The converter will actually become longer from front to rear when it balloons.

Created by Milk 1027, 08-12-2009 at 06:31 PM
Last edited by Milk 1027, 08-12-2009 at 06:33 PM
0 Comments, 10,925 Views

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