FormulaNHRA

iTrader: (1)

Alright I'm a little new to cams and converters but I've read tons of posts and the sticky plenty of times trying to decide which setup I would want. I have an 2000 a4 formula with pacesetter headers, y pipe, and slp loudmouth, and soon to come an ls6. My main questions are why is it necessary to have a higher stall with a cam, and is it necessary?? I've heard if too high of a STR you'll burn rubber out the whazzoo and my tires wouldn't be able to handle it (eagle f1's) But I also heard that a cam helps to lower torque at the low end. So how necessary is it to get a TC with a cam, and second what exactly will a higher stall do for me?? Any info on the topic is appreciated I searched but couldn't find many topics relating the two, if you know of some please post. One big mess over here, THANKS!

schultzsj

iTrader: (1)

A higher stall torque converter allows you engine to rev higher before transfering the torque to your transmission & tires. This allows your engine to be in it's power band from the very start rather than having to wait for the car to speed up first. This equals better acceleration and generally a bigger improvement in 1/4 mile times than a cam alone will give (depending on many variables such as traction, gear ratio, cam selection, Etc.). As such, a TC is generally recommended before a cam (but you need to know what cam you are going to install to pick the right TC).

Whether you NEED a TC or not is dependent on what cam you are planning to get. In general, higher duration cams trade low RPM torque for high RPM torque and peak horsepower. As such, the higher the cam duration, the more you will need to "skip" the lower RPM's. Cam durations below 220 or so don't need one (use 2500-3000 RPM stall if you get TC). In the 220's it is a good idea (use 3000-3500). In the 230's or above it is basically required due the loss of low-end torque and the extension of the powerband (use 3500 plus).

Regarding Stall Torque Ratio's (STR), there are more in-depth discussions available but, generally, the higher the STR the more torque you get off the line and the "tighter" or less rev-happy the converter feels on the street (requires more traction to take advantage of and is usually less efficient on the high end). The higher the STR the less torque off the line and the "looser" or more rev-happy the converter feels on street (requires less traction so it is easier to control tire spin and is usually more efficient at the high end).

All that said, you SHOULD have a higher stall TC period, even without a cam. Some the the converter manufacturers have good selection info online or you can talk to them or our sponsors to help pick the right one. You can see my sig for a cam/TC combo that I am happy with.

Steve

PREDATOR-Z

Well said, also:

You need to match your TC shift extentions to the cam's powerband, otherwise if you extensions are too high; you loose valuable usable power, if they are too low; then you have to wait till you reach power making range and you are waisting valuable time.

So the balance falls in the cam power range amongst other things.

FormulaNHRA

iTrader: (1)

will my tires have enough traction to withstand the extra torque, say for instance i had the same converter as you? (tires are eagle f1's) Because i would rather not have to go out and buy new tires again, so i would need to look at my coverter accordingly

SVT THIS

iTrader: (27)

It is a dumb idea to get a smaller converter so you don't have to go out and buy new tires because sooner or later you WILL have to buy new tires. Browse the "for sale" section. I got a set of Mickey Thompson ET Streets for 220 shipped to my door with only 3 track passes on them!

I would get nothing less than a 3500 stall on a STOCK motor. That will work awesome for the stock motor, and, it will give you some good room to play with if you do decide to get a cam. Any of the "big" cams (MS3, MS4, G5X4, TRex, F14) will need a 4000 or higher.