Need help understanding torque converters

[Jeasen]

I have installed a new Neal Chance torque converter in my car. When the motor was out (due to a needed head gasket change) I noticed that my cam was going flat. I selected a cam that would move some of the low end power to the upper RPM range. Now my new Neal Chance converter that was order to stall at 3000 RPMs+ will either spin the tires at 2400 RPMs or push the front tires. Marty the owner of Neal Chance is blamming the cam shaft change for the low stall number. I say if I cannot hold the car back when it is making 100 HP at 2400 RPMs then it makes no difference if it is making 400 HP it still would not go above 2400 without breaking the tires loose. Any thoughts on this? Am I wrong? Is blaming the cam change a cop out by Neal Chance? All comment and opinions are welcome. BTW the car is down on power in the lower RPM range but pulls much harder on the top end. I say if the torque was looser then some of the low end power would come back and I would not have this problem. The torque converter will not allow more than 2400 RPMs at no boost or if I hit it at 5 lbs of boost. What do you guys think?
Jim Armbrust

 

[WE4]

I would listen to Neal Chance...... Just me....

 

[Jeasen]

Bruce thanks for the advice, I will, but first I need to understand how a torque converter works. I know it is a fluid clutch and it allows a certain amount of slippage until it will not allow any more and locks up. Here is where I am confused. I am told that the torque converter acts like a dyno. The more power a motor makes at a constant RPM the higher the lockup point will be. If a motor is making 200 HP and the converter is locking up at 2400 RPMs then the converter would lock up at say 2000 RPMs if the motor only makes 100 HP at the 2000 RPM mark. However, if the motor made 300 HP at 2400 RPMs then the converter would not lockup until say 2800 or 3000 RPMs. This moving lockup target is what I do not understand. I am confused. I do not profess to know anything about torque converters, but I am able to reason. Seems like lockup is lockup, and it does not matter how much power the motor is making as long as it makes enough power to get to the lockup point. If the motor is not making enough power to get to the lockup point then I should be able to hold the lesser power without spinning the tires or pushing the front tires because I have not reached the lockup point of the converter. Once the lockup point is reached then what is the difference if the motor is making 200 or 500 HP? Can someone explain this moving lockup target to me? If not, then can you point me to an article or web site explaning this? I really need to understand this so I don't make the same mistake again and I am sure that it will also help many others in the future.
Jim Armbrust

 

[WE4]

Get ahold of a Principals of operation book. GM makes them. This would be very very interesting reading for you. I may even still have one at work and I know I can get them. If you feel this would help call shop during work hours and we will get one to you. It is a VERY good publication and will help you immensly to understand.

BT