School me on torque convertors

[DartGTDan]

Why does the factory use low stall speed torque convertors (say 1600 rpm)?

And why do performance applications require/desire the use of a higher stall convertor (say 2600 rpm)?

Does the stall speed rpm indicate when the vehicle begins to move? If yes, then the performance application (say the 2600 rpm stall speed) makes the vehicle move closer to the engine's performance peak?

How would you calculate what stall speed rpm your engine needs/desires?

Please school me!

Thanks

 

[duster340]

the factory low stall converters are more fueleficient and makes alot less heat, most stock engines makes enough torque at low rpm to work well with the lower stall.

first of you may need a looser converter just to be able to idle a big camed engine in gear second you want the converter to flash to about the rpm where engine makes peak torque for maximum acceleration,this may or may not be doable in a streetcar since a 5000rpm stall converter may slip alitle to much in normal driving.

a for example 3500rpm stall converter does not mean thats where your car startsrolling,thats where its suposed to be locked up,it will always slip alitle when drag from the car moving thru air is acounted for.

there is a big diference betwen a good and a cheap converter when you start to make some power a cheap converter may flash to a set rpm but will slip alot above that range and will slip alot during normal driving while a real good converter will feel almost like driving with a stock converter i have a custom made converter that flashes to about 3500rpms and it drives almost like a stock unit except its alitle looser at idle. a friend of mine has a cheap **** converter that stalls about the same and his car hardly moves under 2000rpms and has horrible slip at the top end at the track something like 14%

also a converter that says its a 2600rpm stall unit may stall just that behind a stock 318 try that same converter behind a mean 500+cube engine and it may never lock up.

it depends on alot of factors wish converter to chose for max perfomance you want a stall´speed close to peak torque,if you drive it around on the street and have a nice torquey engine you may apreciate a lower stall unit for efficensy and a all around nicer driving car.

just my two cents and im not an expert i have just learnt that i like well made converters and i dont care if they cost me more

 

[demon seed]

Quote: How would you calculate what stall speed rpm your engine needs/desires?

Any good converter builder will have a questionare you need to fill out, honestly, that will include almost everything about your car. Two of the most important items are the camshaft specs and rear end ratio with cam being number one. Also being that a torque converter is just that, whether the engine is a SB or BB matters because of different torque characteristics each engine will have. Each engine is different and as far as the power train goes IMO the most important component is the converter and if it ain't doing its job ya end up chasing your tail, bin there done that.:read2:

http://www.ultimateconverter.com/home.html

 

[RustyRatRod]

First off, Mopar does not use low stall speed converters in comparison to all other makes. The stock "low stall" converters are a good bit higher rated than the equivilant phord or chebbie. whereas the phord or chebbie will have a stock stall rating of generally around a grand, the stock "low stall" Mopar will be around 1600 as you described. The factory high stall Mopar converters were typically around 1K more than the low stall and in some cases, a little more. It's not impossible to see a factory high stall converter from Mopar flash to 3200 RPM give or take in the right application. My guess as to the why would be that most passenger Chrysler products had pretty high gearsets on the order of 2.76 and the extra flash speed helped to get the car moving. Just a guess. Of course in a factory performance application, the reason was obvious.