Weight and the converter
 

Does the weight of a car change the stall of the converter? For example if a converter stallls at 4800 in a 3400 lbs car and you remove 200lbs does it change or stay the same?

Re: Weight and the converter
 

The stall of the converter has to do with the horsepower supplied by the engine to the converter and nothing to do with the weight of the car until the car is launched when the converter starts to do its work.
My 2 Cents
Rick Cates

Re: Weight and the converter
 

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.

Re: Weight and the converter
 

Sho 'nuff!

Re: Weight and the converter
 

x2

Re: Weight and the converter
 

Billy, Well said!
It will also change the way it works if you change gear ratios. A deeper low gear will make it act like it is tighter.

Re: Weight and the converter
 

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?

Re: Weight and the converter
 

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

Re: Weight and the converter
 

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

Re: Weight and the converter
 

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.

Re: Weight and the converter
 

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

Re: Weight and the converter
 

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.

Re: Weight and the converter
 

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....

Re: Weight and the converter
 

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?

Re: Weight and the converter
 

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

Re: Weight and the converter
 

Yes Mark,
It is all explained in Fluid Dynamics. Anyone beside me still have their College books? Chris?
A good converter guy that understands it can do all kinds of nice things to a converter. It is just like with a camshaft: There is more to it than lift and duration. Same thing for converters: more to it than slip, stall and flash.

Re: Weight and the converter
 

Fluid coupling is also known as a turbine, brain fart at my end. My fluid dynamics book has maybe 10 pages if that. I'll review it tommorow and see if it makes more sense then.

Thanks for jogging my memory Adger.

Re: Weight and the converter
 

Chris,
I knew you would remember it!
Pay close attention to fluid velocity. I bet there are a few interesting refrences to it.
When I was working with Jet boats and racing them I kept my old books on my headboard. Wrong wife #2 couldn't understand what/why I was reading in the middle of the night making notes. :~)

Re: Weight and the converter
 

Rermember, a torque converter is a fluid coupling, where a fluid coupling is not always a torque converter.
A fluid coupling doesn't necessarily multiply anything.

Re: Weight and the converter
 

That is why a torque converter has a section called a "Pump".. :~)
Most fluid couplings (simple explanation) operate like similar fans blowing air on another.
AH! Weedhopper, what happens when we change the size and pitch of the blades on one of the fans? :~)

Re: Weight and the converter
 

Let me dive in for a question again after reading all of this as far as application...... added 200 lbs to change classes...car was running well in lighter class.....do I need to get the converter adjusted to accomodate the heavier class ???? ( 3200 to 3400 lbs ) Also changed the rear gear from 4.88 to 5.00.....rpms at stripe did not change if that means anything...any comments ????

Re: Weight and the converter
 

Well I hope that I don't get raked over the coals for over simplifying this but by adding 200 lbs. you would make the converter "act" looser but by adding the gear you would make it "act" tighter. Clear as mud.

Re: Weight and the converter
 

Are you saying the gear change should have put the converter in the same operating mode as the lighter class with the shorter gear ???

Re: Weight and the converter
 

Yes, that is what he is saying and your finish line RPM is telling you. Didn't you see where I said if you change the low gear, rear gear too, the way the converter works will change? Your gear change was 2.4% so the steeper gear made the converter work tight enough to overcome the weight and the extra rpm the gear ratio should give you at the finish line.