Torque converter stall speed question...

[shone190]

Hi guys,


I read so many articles regarding torque converter stall speed but I still have some concerns.


My main question is, what is the difference between, for the example, 1200rmp and 2800rpm stall speed converters?


As I understood, first converter will be fully engaged after 1200rpm, and the other after 2800rpm. So, if I never have a need to race with the car with left foot on brake pedal and right on the gas pedal, I will only see difference in fuel consumption between two of them?


Also, if I started from stop light "normally" with using only right foot (depress brake pedal and press gas pedal), the car will be quicker with 1200rpm stall converter because it will be sooner fully engaged?


Am I right or I missed something?


Thanks to all in advance.

 

[Greg Ducato]

There are so many variables I think you might want to do a web search on the subject, there are many articles on the subject that will help you understand the theory and principles of stall speed and converter operation

 

[khryslerkid]

That has a lot to do with your engine build.

Is it stock? Is it a mild build or a heavy hitter?

 

[shone190]

My engine is 493 stroker, 525HP/590lbs, why is this important for the question?

 

[khryslerkid]

I'm not into the high tech answers that other people on here would know. You are correct in the way the torque converter "flashes" at different rpm ratings.

There are many setups that work better than others. Knowing what you have and what you want out of your build will be more rewarding in the end. The right combination of components (parts), will get you your best gas mileage, if that's what your looking for. It will get you your best performance, if that's what your looking for. Or something in the middle.

There are members on here useing stroked engines as yours that can give you the right information.

 

[67 B-body]

Higher engine torque values can result in higher RPM (stall) when the foot hits the floor, compared to a lower torque engines.
You have some specs on HP and Torque,,,,, were those derived from a dyno session? If so, look at where your power curve begins in RPM.... If you want to use some of the torque being generated from a stand still throttle punch,,, then your converter will need to work with that given RPM...
Keep in mind that the numbers advertised are a ball park figure! The only way to dial in a converter is to try one and have it tuned based on the results given... There are plenty of good converter manufactures that build them based on your input (typically values from Dyno's and car weight vs. your driving habits)....

Good luck!

 

[shone190]

I know that, but imagine that with my engine one converter has 1200rmp stall and the other 2800rpm stall. My question is still the same, so, if I never have a need to race with the car with left foot on brake pedal and right on the gas pedal, I will only see difference in fuel consumption between two of them plus the car will be quicker from stop light with 1200rpm stall converter, because it will be sooner fully engaged?

 

[krowbar]

It might start off a little sooner, but that doesn't mean it will be faster. it depends where your car makes power ( rpm range). That will effect how fast you come off the line.

 

[67 B-body]

I know that, but imagine that with my engine one converter has 1200rmp stall and the other 2800rpm stall. My question is still the same, so, if I never have a need to race with the car with left foot on brake pedal and right on the gas pedal, I will only see difference in fuel consumption between two of them plus the car will be quicker from stop light with 1200rpm stall converter, because it will be sooner fully engaged?

No,,,
When you want to impress your buddies and stuff your foot into the thing with a 1200 rpm converter then you just hear Boooooooooooog,,,, until it hits 2000 rpm you'll understand.
You could literately build a combo that wont even turn the tires for the first 10 feet or MORE with a stock RPM converter and a modified engine....
no one can help you pick it out with information provided BTW... Perhaps a scanned image of your dyno sheet posted would give some good recommendations...

 

[coloradodave]

I'll try a different approach. A stock type torque converter will 'hook-up' your motor to the driveline at a low engine speed (your 1200 rpm example). A 'performance' torque converter will allow the engine to rev to a higher rpm before it 'hooks-up' your engine to the drivetrain (your 2800 rpm example). This is why it is important to know at what rpm your engine starts making a good amount of torque. Let's say your engine starts making good torque at 2800 rpm. If you use a 1200 rpm converter, the car will not accelerate very quickly because the engine isn't making good torque. In this example, a 2800 rpm torque converter will allow the engine to rev to the point that it has good torque and the car will accelerate quickly. Theoretically, the higher the converter rating, the looser it is, and the mileage will suffer some. As was said, the actual rpm that a converter locks-up at (flashes) will vary depending on YOUR combination. All the engine specs, the car's weight, tire type and size, rear end gear ratio, traction devices and intended use will all figure in to picking the right converter for YOUR car. I highly recommend that you contact a few companies that build converters and get their recommendations. I would be happy to provide you with some names if it will help. Hope this gets you started.

 

[furyus]

And drivable type will suffer with the stock convertor. It will try to pull the car or stall when in gear and foot on the brake. A performance car is a complete package. The convertor needs to be matched to the rest of the combination. As was said before, contact quality convertor manufacturers and get their recommendations.

 

[Ron Ward]

This is why I drive a 4-speed.

 

[shone190]

And also this is why I will buy TKO600

 

[furyus]

And drivable type will suffer with the stock convertor. It will try to pull the car or stall when in gear and foot on the brake. A performance car is a complete package. The convertor needs to be matched to the rest of the combination. As was said before, contact quality convertor manufacturers and get their recommendations.

 

[coloradodave]

And also this is why I will buy TKO600

Torque converters aren't voodoo science for a street car. Get all the appropriate information together and contact a reputable converter MANUFACTURER. Don't go by what the order desk guy says at the mail order giants. I like my 4 speed but would have no problem running a 727 with the right converter and gearing. Your choice...

 

[sleepar]

The difference is one is stalls to low one to high and one just right... just because it may say it's a 2400rpm stall that particular one may flash at 25 or 2200... the smallest detail on engine and drive train and vehicle weight someone can recommend one ... usually it takes a few to get the right one.... Or you live with the one you have... 2400 is good on the street all around...

Cams... converter... carbs.... gear ratio tire size... etc... the colour of the car doesn't matter but everything else does... because it's you're clutch....

 

[coloradodave]

Torque converters aren't voodoo science for a street car. Get all the appropriate information together and contact a reputable converter MANUFACTURER. Don't go by what the order desk guy says at the mail order giants. I like my 4 speed but would have no problem running a 727 with the right converter and gearing. Your choice...

shone190: Did you get your question answered to your satisfaction?

 

[shone190]

No I didn't off course. I will buy TKO600, that's the answer

 

[HT413]

Hi guys,


I read so many articles regarding torque converter stall speed but I still have some concerns.


My main question is, what is the difference between, for the example, 1200rmp and 2800rpm stall speed converters?

1200 rpm converter, when you get to 1200 rpm, the converter is fully engaged. A 2800 rpm converter fully engages at 2800 rpm. It is a little more complex than that, as some feel nice and engaged at its stall rating, but if youre stopped and nail it, it will 'flash' a bit higher. For example, i had a 4000 stall converter that would flash to 4500. It was an older race converter so it was a pig at 1800 rpm (as you might imagine) but was great at about 3000 rpm and up.

As I understood, first converter will be fully engaged after 1200rpm, and the other after 2800rpm. So, if I never have a need to race with the car with left foot on brake pedal and right on the gas pedal, I will only see difference in fuel consumption between two of them?

Depends on the your cruising rpm. If you like to cruise at 1800 rpm, the 1200 converter will give the best economy and when you hit it, it will just go like a normal car. At 1800 it is giving great fuel economy. The 2800 stall will be slipping at 1800 rpm and generate heat. This wastes fuel. However, you nail it, the converter will flash to 2800 rpm and the car will launch much more powerfully because the engine is much closer to its peak torque.

Also, if I started from stop light "normally" with using only right foot (depress brake pedal and press gas pedal), the car will be quicker with 1200rpm stall converter because it will be sooner fully engaged?


Am I right or I missed something?


Thanks to all in advance.

As stated above, technically, the converter with a stall that is matched to your combo will give you the faster launch. The 1200 rpm converter will be the all around slowest because it engages at such a low rpm, the engine is no where near its peak torque and is forced to fight its way all the way through the powerband.

Importantly, modern converters (not junk) will act so much more subtly than that. A modern 2800 rpm converter will launch at 2800, but cruise nice and tight at maybe 1800 and under light acceleration, feel like its pretty engaged at that rpm, generate very little heat. But nail it and BAM, it flashes to 2800 and the car is off like a rocket.

I've talked to a few converter houses (dynamic, coan, and a few others) and they all say the same thing - they can build a converter to your combination and your driving habits. Just be honest with yourself and build it for the 99% of your driving, not the 1%.

 

[shone190]

Great answer, that's what I was looking for So, for the fuel economy, especially in city, 1200rpm stall is a lot better as I thought. As I see, with A727 there must be some compromise because there is no lockup converter and there will always be slippage, except above 3000rpm
As I see, much better option is TKO600, but much more expensive too