What effect does a larger or smaller diamter have?
Good write DJV
Disclaimer: the following is based primarily on my own deranged reasoning
I believe the diameter to mostly influence inertia. A smaller diameter presents a lower moment of inertia (rev quicker, less torque) while a larger diameter presents a greater moment of inertia (rev slower, more torque). The speed at which a given converter stalls is a function of input power and the angle/shape of the stator elements as they interact with the thing** that I can't think of the name of at present.
** turbine, perhaps
Inertia and the amount of fluid it use's and force's out of the converter into the tranny to operate.
how dynamic explained it to me was the smaller diameter gives it the higher stahl, and the positive pitch on the veins makes it lock up and be efficient.
I beileve that is also due to the converter being a custom make/design for the application. Of course, having less fluid for power transfer is adding to the combo and action of this all.
Valvebounce, I think the above is on the right track. I don't have much to add since I'm really a manual trans owner and have not been down the road with high stalll auto trans cars. Though, I have been in several high and very high stall set ups, alot depends on the build of the engine and how and where it is making power and how you want to use it.
High stall converters do not automaticly mean you can not drive it on the street due to having nothing below the advertised stall speed. There just less efficent and sometimes terribly so below the stall speed. Alot depends on design of the inside of the converter as well as size and intended purpose for it.
From what I am told, (*In general since there are alot of variables to contend with) that a stall converter of approx. 2600 - 2800 will still act reasonable if not close to a stock converter unless you hit the gas pedal hard.
Having a converter stall @ 3200 - 3600 will have a soft feeling down low and etc... and on up the RPM range for each converter stalling higher and higher. The above recomendation for Dynamic is about the best you can do since if I was to list the top 5 converter makers for performance applications, they would be in it.
You can also contact PTC (Performance Torque Converters)
They come with a very good rep as well Do a search on this for more info and the forum members favorites on this topic. I'm sure you'll find some very very good info on it.
It can't be easy living across the Pacific ocean and getting these parts. I can see why you wuld be very careful and slow to get anything. Theres a few areas of building a car that some will jump up and shout, this is an area where you just do not skimp. This would be one of them if your getting serious about racing the car. Purchasing a "Econo" C-verter could be OK for a dual purpose machine or a lightly raced car where the racer isn't so serious about chasing the money with victories.