Weight and the converter

[Todd Boyer]

Originally Posted by Billy Nees

Yes, but even though the flash rpm would stay the same, once the car is moving the converter would "act" tighter in the lighter car.

Is this because the weight of the car affects the 'force' the converter 'sees'? Or that if the car is heavier, the converter is 'forced' to work harder and will therefore be looser?

[Billy Nees]

Originally Posted by Todd Boyer

Is this because the weight of the car affects the 'force' the converter 'sees'? Or that if the car is heavier, the converter is 'forced' to work harder and will therefore be looser?

The converter would be loaded for a slightly longer period of time in the heavier car. (200 lbs heavier, same car)

[Mark Yacavone]

Originally Posted by Todd Boyer

Is this because the weight of the car affects the 'force' the converter 'sees'? Or that if the car is heavier, the converter is 'forced' to work harder and will therefore be looser?

If I understand what you're asking, the answer is > both.
A good running Powerglide car does so, in spite of having such a high 1st gear ratio, because the converter is forced to "work harder".

As another example pertaining to weight; A street and strip car with a high stall converter,cruising along on the freeway, comes to a hill or rise in the road.
The effect of the hill is that the car thinks it's "heavier" and the RPMs will rise, while maintaining the same MPH.
You've got to remember,unless it's got a lock up clutch it it, it is a fluid coupling

[Chris Hill]

Originally Posted by Mark Yacavone

You've got to remember,unless it's got a lock up clutch it it, it is a fluid coupling

This is something that has always made me wonder. What are the actual physics involved to cause a converter's stall?

At least in our cars, the engine goes past the torque peak then settles down at a lower torque value for flash/stall. And keeping everything equal with gearing and weight, in good air it will flash at a higher rpm with increased torque.

[63corvette]

Originally Posted by Chris Hill

This is something that has always made me wonder. What are the actual physics involved to cause a converter's stall?

At least in our cars, the engine goes past the torque peak then settles down at a lower torque value for flash/stall. And keeping everything equal with gearing and weight, in good air it will flash at a higher rpm with increased torque.

Chris remember in good air the engine is making more HP and Torque which explains the higher rpm flash.
My 2 Cents
Rick Cates

[Chris Hill]

I agree with the higher hp and torque with better air.

But does XYZ converter stall at say 500 ft lbs no matter what? When you have better air, lets say the torque curve shifts up 10 ft*lbs. What is the phyiscs that sets stall speed? Or is it actually a stall torque that fits particular engines differently due to the engines torque curve?

So in better air, you have to increase rpm more until the torque drops off to the 500 ft*lb value, hence higher stall speed.

[danny waters sr]

Here is an experience and example of good and bad air vs rpm.
We had a 8.90 car on a throttle-stop and when it went on the stop we had it set at 3800.
Each morning we would check and set it to the same rpm and a lot of times it would be diff due to air quality. We would even check it during the day and sometimes it would be diff due to air change. A lot of people could not figure why their cars would not run the same on day as it did the next (although they would just change the time in the timer to compensate)... tere is a diff in most cases.My little 283 will change quicker than most combos due to little carb and such....

[Mark Yacavone]

Originally Posted by Chris Hill

I agree with the higher hp and torque with better air.

But does XYZ converter stall at say 500 ft lbs no matter what? When you have better air, lets say the torque curve shifts up 10 ft*lbs. What is the phyiscs that sets stall speed? Or is it actually a stall torque that fits particular engines differently due to the engines torque curve?

So in better air, you have to increase rpm more until the torque drops off to the 500 ft*lb value, hence higher stall speed.

Chris , I could give you an answer ,but I don't know how to explain it in technical terms.
It's kinda like, I know that Christina Hendricks works for me, but I can't put that in words either. LOL
It has to do with hydraulic pressure, generated centrifugally and the shear, or over -ride point.
Maybe we need an engineer to explain it. Rusty 3011?

[Joe DeMarzo]

Lenny from Ultimate where are you when we need you. This is good stuff.