Converter stall Speed

Transmission to Rear-end

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F-BIRD'88
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Re: Converter stall Speed

Post by F-BIRD'88 » Wed Oct 18, 2017 1:41 pm

Geoff2 wrote:
Wed Oct 18, 2017 5:16 am
The vehicle weight has to affect stall speed & flash stall. Extreme example, but imagine if the car weight was 10,000 lb; more tq will be needed to move it from rest, & that is going to result in more c'ter slippage to get the needed tq....& higher stall speeds.

That is a function of engine torque input.. Yes more engine torque will result in a higher stall speed.

Give it more or less throttle and you get more or less stall speed.
The car weight is irrelevant. It is souley about how much (engine) torque is applied.
(assuming the tires do not spin)

You can test this on any or many auto trans car. Test the launch stall speed at WOT. Now do it again but limit the throttle. The stall changes.
Now add weight to the car and repeat 200lbs 500 lbs 1000 lbs. The stall speed will be the same.
The only thing that changes it is engine torque input.
Start in 1st gear or 2nd or 3rd gear ( manual valve body)
the max WOT launch stall speed will be the same.

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Re: Converter stall Speed

Post by F-BIRD'88 » Wed Oct 18, 2017 1:49 pm

tenxal wrote:
Wed Oct 18, 2017 6:12 am
Gear ratio also influences convertor 'flash'.

If you take a set of 4.56's out and change to 5.38's (for example), the convertor 'flash' will be lower as the car moves easier with the 5.38's. Same with transmissions...a change from a 2.08 low gear to a 2.75 will result in a lower 'flash' rpm.
This is false and you can test it for your self and see. Try launching at WOT but in a different gear
say 2nd gar or 3rd gear. As long as engine torque input is the same input the max WOT launch stall will be the same.

Change engine torque input even a little +/- and the stall speed will change.
Once you have 3 test samples of known real measured engine torque input and resulting stalls from that.

You can write a math formula for it to predict converter stall speed.
this is the "K factor" formula.
Car weight is not a factor for launch stall speed. But engine torque is.

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Re: Converter stall Speed

Post by lefty o » Wed Oct 18, 2017 3:16 pm

#-o

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Re: Converter stall Speed

Post by F-BIRD'88 » Wed Oct 18, 2017 4:55 pm

The only time you will see any real variation in launch stall rpm is if the trans clutches are slipping or the trans fluid is real thin (way too hot) or the pump is on the way out (converter starved for oil flow)
or the fluid has air in it from pump or converter cavitation. Or the converter is flexing (ballooning) or the stator sprag is failing to hold on launch These can ALL effect the stall +/-.
So can tire slip. This assumes the engine torque has not changed.

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Re: Converter stall Speed

Post by Geoff2 » Thu Oct 19, 2017 5:14 am

So exactly as I said, a heavier car will require more stall rpm because more tq is reqd to move a heavier car.

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Re: Converter stall Speed

Post by tenxal » Thu Oct 19, 2017 6:16 am

F-BIRD '88: As you are seemingly unable (or unwilling) to process what those of use that actually work with this stuff offer, I'll offer some exceprts from well known torque convertor builder, Hughes:

"A torque converter will provide a range of stall speeds based on the amount of load that is placed on the torque converter. Many factors influence torque converter stall speed including; output torque of the engine, vehicle weight, rear axle ratio, rear tire height, torque converter diameter, impeller fin angle design, stator design, impeller-to-turbine clearance, stator-to-impeller clearance, stator-to-turbine clearance, and brake bias."

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Re: Converter stall Speed

Post by tenxal » Thu Oct 19, 2017 8:10 am

tenxal wrote:
Thu Oct 19, 2017 6:16 am
F-BIRD '88: As you are seemingly unable (or unwilling) to process what those of use that actually work with this stuff offer, I'll offer some excerpts from well known torque convertor builder, Hughes:

"A torque converter will provide a range of stall speeds based on the amount of load that is placed on the torque converter. Many factors influence torque converter stall speed including; output torque of the engine, vehicle weight, rear axle ratio, rear tire height, torque converter diameter, impeller fin angle design, stator design, impeller-to-turbine clearance, stator-to-impeller clearance, stator-to-turbine clearance, and brake bias."

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Re: Converter stall Speed

Post by lefty o » Thu Oct 19, 2017 2:05 pm

tenxal wrote:
Thu Oct 19, 2017 6:16 am
F-BIRD '88: As you are seemingly unable (or unwilling) to process what those of use that actually work with this stuff offer, I'll offer some exceprts from well known torque convertor builder, Hughes:

"A torque converter will provide a range of stall speeds based on the amount of load that is placed on the torque converter. Many factors influence torque converter stall speed including; output torque of the engine, vehicle weight, rear axle ratio, rear tire height, torque converter diameter, impeller fin angle design, stator design, impeller-to-turbine clearance, stator-to-impeller clearance, stator-to-turbine clearance, and brake bias."
are you saying that hughes knows something about converters that our in house expert doesnt? :lol:

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Re: Converter stall Speed

Post by tenxal » Thu Oct 19, 2017 8:58 pm

lefty o wrote:
Thu Oct 19, 2017 2:05 pm
are you saying that hughes knows something about converters that our in house expert doesnt? :lol:
As I mentioned, there are those of us here that actually work with this stuff in the Real World. :wink:

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Re: Converter stall Speed

Post by AMXstocker1 » Fri Oct 20, 2017 4:31 pm

Weight and gear will make a converter act differently less weight it will stall lower and slip less more gear has the same effect. Call ATI or Ultimate converters they can explain this, and hook you up with the right converter for your car. also if your car is down on estimated hp say you tell the converter company your car makes 600hp and it makes 450 than its not going to act right at all either it will lock up way too early and you'll have big drops inbetween shifts.

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Re: Converter stall Speed

Post by F-BIRD'88 » Fri Oct 20, 2017 10:54 pm

All those factors will effect the real LAUNCH flash stall speed you get.. EXCEPT the WEIGHT of the car.

WHY...because the car has no even started to MOVE yet. The converter at this point is loaded as much as it is going to get loaded. and at this point it is all about engine torque input.

The weight and wind resistance and drive friction of the car at high speed does effect how the converter
functions down track ("lock up") But again at LAUNCH the weight of the car has nothing to do with the converter stall speed.

I have been doing this some 40+ years. All those factors effect things and a converter builder can tweek all that for you. +/-.
But at car launch the weight of the car has no effect on the stall speed.

Try launching in 1st gear , then second or drive (3rd) (1:1) gear for your self.

You can do this simple test yourself easily on any auto trans car with a manual valve body)

The flash stall speed at launch will be the same. ( unless the tires spin)
Try adding weight to the car. 400 LBS of sewing caps or cement blocks in the trunk or 5-10 buddies what ever and test. It will be the same stall speed at launch.
Cause it is all a function of engine torque INPUT. Not car wEIGHT.

Try it yourself... It is a easy test. Try it on any car.

If after you get the gear ratio and cam right the converter is still slipping too much in the top end
You can get the converter tweeked by anybody that builds converters.
impeller fin angle design, stator design, impeller-to-turbine clearance, stator-to-impeller clearance, stator-to-turbine clearance,
Yes this is what they will tweek inside the converter +/- to get it right.

But you got to get the gear ratio right first...

Right now you gear ratio is too low, you are crossing the finish line at a rpm that is way too close to the stall speed. (under 6000 rpm) That is why it seems it has too much slip. You are riding the converter stall all the way down the track.
When you correct the gear the converter will "lock up" (7% +/- slip at high speed)

Correct the car's gearing so the car 1/4 mile traps 2000 rpm higher than the flash stall speed.
(about 7000 rpm in your case with a 5000 stall)..

You can read all the advertizing you want... you can buy 10 more converters. you won't get it right until you do this.

Does your power glide trans have a manual valve body?
If so you cab test the launch stall by starting in first gear then second ( high) gear.
You can see for yourself the real flash stall speed at initial launch.
Post your result....

Add a bunch of real weigh MEANINGFUL weight (300 400 -500 LBS) to the car... test again. Post your result.
you are testing the initial car launch...first 100 feet of car launch travel from start...
As long as the tires do not spin on launch at each test the stall speed will be the SAME.

If the tires do spin the test is not valid. Yup spinning tires effects what the tach rpm says.
No mystery.

Not down track performance. The performance down track is different.
Yup weight does effect this espcially when the axle gear ratio is way out of wack.
Last edited by F-BIRD'88 on Fri Oct 20, 2017 11:25 pm, edited 2 times in total.

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Re: Converter stall Speed

Post by F-BIRD'88 » Fri Oct 20, 2017 11:06 pm

if your car is down on estimated hp say you tell the converter company your car makes 600hp and it makes 450 than its not going to act right at all either it will lock up way too early and you'll have big drops inbetween shifts.

This is absolutely true and you do want to tell the converter guy the REAL engine power and torque.

This one tested at 306 chassis HP. It is not that powerfull. The car needs WAY more GEAR.

Look on your chassis dyno print out sheets. WHAT is the power CORRECTION factor from the sheets?

You want the Uncorrected power numbers. that is corrected power divided by correction factor.

This is the actual power on that day under those conditions. This the real power.
Not "corrected power" This what you would tell the converter guy.
This will also tell you real close what the cars 1/4 mile MPH will be
if you know the cars true weight with driver.

Go to the track and test it. The track MPH will be +/- 1.5 MPH of predicted.
Now you can gear the car correctly. You are way under geared for this engine in this car.

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Re: Converter stall Speed

Post by F-BIRD'88 » Fri Oct 20, 2017 11:37 pm

We just had it on a rolling road and established that we weren't getting locked in wheel speed until about 5,600 - 5,700 rpm when the cam is nearly done and we've missed it's peak torque, 306hp to the rear wheels.



This is Normal for a 5000 stall converter. The reason the cars seems to never "Lock up" is because the car does not have enough rear gar ratio. The engine rpm is NOT high enough at high speed.
it is "on the converter" all the time. Lack of gear ratio.

It bet the real tested on track LAUNCH flash stall speed behind your 327 is 5000-5200 rpm+/-.
There is nothing wrong with this converter that correct car gearing won't fix.

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Re: Converter stall Speed

Post by Brian P » Sat Oct 21, 2017 10:11 am

Or, if the engine won't rev that high or doesn't make power up that high (the original poster never stated!) ... the stall speed is too high.

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Re: Converter stall Speed

Post by 1972ho » Sat Oct 21, 2017 11:02 am

See how you guys are talking converters I have a question about a converter I plan to run on a different engine combo.I I’m running a C-4 behind a engine that the converter is already maximized on,But I want to run this set up behind a ford v-6 that makes hp and torque around the same rpm as the v-8 that it will replace.Now the amount of hp is about the same but v-8 makes around 100 more ft/# than the v-6.So do you all think that this converter will stall and function the same behind the v-6 as would behind the v-8,providing nothing else is changed except the weight the car will weight about 140 less with the v-6.Thanks

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