stall speed
Thread Starter
Burning Brakes
Joined: Mar 2003
Posts: 1,030
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From: Pittsburgh PA
stall speed
For all you auto experts. Bare with me here. I don't have a good understanding of torque converters. What is 'stall speed'? What happens when the converter reaches stall? Is this when it locks -up? Why do higher stalls work better for drag racing? Why wouldn't I want a 4000 stall on the street?
Thanks in advance
Thanks in advance
Race Director
Joined: Oct 2004
Posts: 10,089
Likes: 14
Originally Posted by aaaaa
For all you auto experts. Bare with me here. I don't have a good understanding of torque converters. What is 'stall speed'? What happens when the converter reaches stall? Is this when it locks -up? Why do higher stalls work better for drag racing? Why wouldn't I want a 4000 stall on the street?
Thanks in advance
Thanks in advance
When the torque converter reaches stall, it no longer slips like a clutch, and torque multiplication falls to 1x. (Note that there is still some slip due to fluid shear, and modern transmissions employ a mechanical lockup at this point to eliminate slippage completely. This improves fuel economy, and reduces heat buildup in the transmission.)
Now if we raise the stall speed, we allow the engine to rev higher into its power band before being fully loaded. This gives a stronger launch. This is great for drag racing. But on the street we cruise at 1500 to 2000 RPM, and a 4000 RPM torque converter would still be acting as a fluid clutch, slipping and wasting gas, and generating excess heat in the transmission. That would be bad. So torque converters for street cars have stall speeds in the 1200 to 1600 RPM range.
Former Vendor
Joined: Mar 2003
Posts: 18,666
Likes: 395
From: Tampa FL
St. Jude Donor '07-'08-'09-'10-'11-'12'-'13-'14-'15
Originally Posted by shopdog
A torque converter serves two purposes. It acts as a fluid clutch, and it actually multiplies torque. Both are necessary in an automatic transmission. At idle, and when starting off, we want it to slip like a clutch. This prevents stalling the engine. As RPMs rise and we load the torque converter, it uses the stator to multiply torque (up to 2x in our transmssions). This effectively gives us a lower gear to launch the car.
When the torque converter reaches stall, it no longer slips like a clutch, and torque multiplication falls to 1x. (Note that there is still some slip due to fluid shear, and modern transmissions employ a mechanical lockup at this point to eliminate slippage completely. This improves fuel economy, and reduces heat buildup in the transmission.)
Now if we raise the stall speed, we allow the engine to rev higher into its power band before being fully loaded. This gives a stronger launch. This is great for drag racing. But on the street we cruise at 1500 to 2000 RPM, and a 4000 RPM torque converter would still be acting as a fluid clutch, slipping and wasting gas, and generating excess heat in the transmission. That would be bad. So torque converters for street cars have stall speeds in the 1200 to 1600 RPM range.
When the torque converter reaches stall, it no longer slips like a clutch, and torque multiplication falls to 1x. (Note that there is still some slip due to fluid shear, and modern transmissions employ a mechanical lockup at this point to eliminate slippage completely. This improves fuel economy, and reduces heat buildup in the transmission.)
Now if we raise the stall speed, we allow the engine to rev higher into its power band before being fully loaded. This gives a stronger launch. This is great for drag racing. But on the street we cruise at 1500 to 2000 RPM, and a 4000 RPM torque converter would still be acting as a fluid clutch, slipping and wasting gas, and generating excess heat in the transmission. That would be bad. So torque converters for street cars have stall speeds in the 1200 to 1600 RPM range.
Talk to the experts here are the links
http://www.protorque.com/prodln/pl_po.htm
http://www.prodyno.com/Product/Produ...x?id=43&cid=17
http://www.prodyno.com/Product/Produ...id=17#overview
Cajun
Last edited by Cajun @ Edgyvette; Oct 17, 2005 at 09:38 PM.
Thread Starter
Burning Brakes
Joined: Mar 2003
Posts: 1,030
Likes: 0
From: Pittsburgh PA
Originally Posted by ccajun4real
Very well put. I recommend the Yank or PT 3200 for stock gears and 3600-3800 for 3:42 or 3:73 gears.
Talk to the experts here are the links
http://www.protorque.com/prodln/pl_po.htm
http://www.prodyno.com/Product/Produ...x?id=43&cid=17
http://www.prodyno.com/Product/Produ...id=17#overview
Cajun
Talk to the experts here are the links
http://www.protorque.com/prodln/pl_po.htm
http://www.prodyno.com/Product/Produ...x?id=43&cid=17
http://www.prodyno.com/Product/Produ...id=17#overview
Cajun
