Horsepower & Converter Stall Question

kenewagner

Registered User
I am clear on some TQ converter facts like a nonlocking converter is going to cost you on the dyno but is a big plus on the track. My question is how does, if at all, the stall point affect HP on the dyno. Will a nonlocking TQ with a stall of 2400 dyno higher HP #s than a nonlocking TQ with a 3500 stall? Given same size converter and configuration? My thoughts are no, since hp is made at a higher RPM than either stall. Am I correct in thinking that?

Ken
 
Ken,

I'm expecting my new 3500 stall non locking converter to show less peak power on the dyno than my 2800 stall non locking did, because higher stall rpms generally results in a greater percentage of slip. This isn't always the case and I've read that some of high dollar race converters can stall at 4500 rpms and have almost no slippage at 7000 rpms.

I'd really like to hear from Alan on this topic.

David
 
Since when are you guys worried about dyno numbers, I thought the trend with the blower guys was to shoot for 10s at 85mph
 
Actually on the dyno the part you ignore goes through the roof with a high stall converter, that is torque and it works on the track.
The dyno means nothing, all points must be proved on the track.
Stall number means virtually nothing, that is just the end result of the combination in your application.
Alan
 
I don't have any definitive answer, but I will say that my car has never dyno'd higher than 365 rwhp and I'm running just as fast as guys with higher dyno numbers.
 
Well I am just looking for the answer to a question. Will the higher stall nonlocking converter loose HP on the top end vs a lower stall nonlocking TQ converter?

Ken
 
Well I am just looking for the answer to a question. Will the higher stall nonlocking converter loose HP on the top end vs a lower stall nonlocking TQ converter?

Ken

That's because you didn't catch what they were saying. How much slip a converter has and hence how much HP it costs you is a function of it's internal design. Some converters are just very loose and waste a lot of energy. This is one way of making a high stall converter, but it's not efficient. Then there is creating a higher stall speed by changing the pitch of the turbine to alter it's efficiency rpm. In doing so you can make a high stall converter that is very efficient at the same time. In most cases you get what you pay for.

That being said, most of the time a higher stall converter may be slightly looser on the top end where HP is measured so generally speaking yes, the high stall converters tend to transmit a little less HP. But there is no "rule" or guideline on how much. There are too many variables.

Oh, and BTW I just wanted to point out that a non-locking converter is NOT faster at the track than a properly designed locker. Chris Vining's converter locks up solid as soon as he hits 2nd gear and stays that way. As you may have noticed his car is quicker than others with significantly more dyno HP.
 
That being said, most of the time a higher stall converter may be slightly looser on the top end where HP is measured so generally speaking yes, the high stall converters tend to transmit a little less HP. But there is no "rule" or guideline on how much. There are too many variables.

Thats as close an answer as I was looking for given a lot of variables

Ken
 
Actually on the dyno the part you ignore goes through the roof with a high stall converter, that is torque and it works on the track.
Alan

So to beat a dead horse here:rolleyes: Are you talking nonlocking or locking in your above statement? For the track what do you prefer?? and why???

Ken
 
Isn't Zimmerly's transmission a locking transmission (in 3rd and 4th)?

Did Vining lock his trans during the dyno competition?
 
Chris Vining's converter locks up solid as soon as he hits 2nd gear and stays that way. As you may have noticed his car is quicker than others with significantly more dyno HP.
Isn't that an apples to oranges comparison? AOD vs. 4r70w
 
So to beat a dead horse here:rolleyes: Are you talking nonlocking or locking in your above statement? For the track what do you prefer?? and why???

Ken

Nonlocking or unlocked. The dyno values for wheel speed below a certain MPH will not linearly correspond to an engine RPM until you reach your stall speed, thus, you can't accurately interpret that part of the dyno.

I.E. 1-40mph in 2nd is 4000rpms for me unless I lock my converter. Load changes during this time period as well, thus you can't consider numbers below stall RPM accurate.

A locking converter with the propper stall is best on the track. You retain the same advantage from the high stall, and you gain more mechanical efficiency by having a direct drive when the converter is locked. Similarly to a manual transmission.
 
Nonlocking or unlocked. The dyno values for wheel speed below a certain MPH will not linearly correspond to an engine RPM until you reach your stall speed, thus, you can't accurately interpret that part of the dyno.

I.E. 1-40mph in 2nd is 4000rpms for me unless I lock my converter. Load changes during this time period as well, thus you can't consider numbers below stall RPM accurate.

A locking converter with the propper stall is best on the track. You retain the same advantage from the high stall, and you gain more mechanical efficiency by having a direct drive when the converter is locked. Similarly to a manual transmission.

My understanding is the nonlocking TQ converter multiples TQ all the way down the track while the locking converter reach its lockup than relies on only engine TQ to continue down the track once it locks up. That is the way it was explained to me. Going by that explanation the nonlocker should be better for the track. Seems to be some that agree with that and some like yourself disagree. Im am just looking for people to explain in a logical way for a layman like myself why one is better and why the other is not. I think a lot of guys on this club latch on to an idea and dont realize the other side has excellent points to be made.

Ken

Ken
 
My understanding is the nonlocking TQ converter multiples TQ all the way down the track while the locking converter reach its lockup than relies on only engine TQ to continue down the track once it locks up. That is the way it was explained to me. Going by that explanation the nonlocker should be better for the track. Seems to be some that agree with that and some like yourself disagree. Im am just looking for people to explain in a logical way for a layman like myself why one is better and why the other is not. I think a lot of guys on this club latch on to an idea and dont realize the other side has excellent points to be made.

Ken

Ken

The "Torque Multiplication" is due to the ability of the converter slipping and allowing you to stay at a constant **HIGHER** RPM. The torque comes from the motor the whole time, and isn't really "Multiplied" as it sounds....

Consider the torque converter as a slightly less efficient CVT, Or an infinitely variable ratio differential... Whatever makes more sense to you....

As you floor it off the line, the pressure in the converter builds, and the engine RPMs are able to spin the converter as fast as the pressure will allow up to some point (Stall speed). Your drive ratio also has changed at this point, since things are not 1:1... Your motor is now at 4000rpms (Stall speed) where it would be at 900rpms with a manual transmission. The added torque is because the drive ratio's mechanical advantage allowing you to put more force on the drivetrain. You're appling power 4000 times a second instead of 900.

Once you reach your stall speed, you have very minimal slip allowed in the converter due to the dynamics of it, and it is mostly a power loss to heat from the lack of direct drive. Using a fluid coupling to move a 4000lb car obviously has it's parasitic losses...

Above your stall speed, the converter's purpose has been fulfilled, and is more of a hinderance because of the parasitic loss. If you have the ability to lock the converter, you take that out of the equation, and have a full 1:1 drive ratio through the converter just as a manual transmission with a locked up clutch. You're able to plant more power to the ground rather than waste it in heat. This is shown by higher horsepower on a dyno with a (the same) converter locked as opposed to unlocked.
 
Last edited:
So to beat a dead horse here:rolleyes: Are you talking nonlocking or locking in your above statement? For the track what do you prefer?? and why???

Ken

I prefer lockup by all means, however aod transmissions do not have lockup, everyone just wants to call it that. The aod uses a direct drive shaft that still has a ratio loss from the other shaft. The setup is abusive and weak. I prefer no direct drive in all aod's 4r70w's the only reason to eliminate lockup is for a transbrake.
Alan
 
The "Torque Multiplication" is due to the ability of the converter slipping and allowing you to stay at a constant **HIGHER** RPM. The torque comes from the motor the whole time, and isn't really "Multiplied" as it sounds....

Consider the torque converter as a slightly less efficient CVT, Or an infinitely variable ratio differential... Whatever makes more sense to you....

As you floor it off the line, the pressure in the converter builds, and the engine RPMs are able to spin the converter as fast as the pressure will allow up to some point (Stall speed). Your drive ratio also has changed at this point, since things are not 1:1... Your motor is now at 4000rpms (Stall speed) where it would be at 900rpms with a manual transmission. The added torque is because the drive ratio's mechanical advantage allowing you to put more force on the drivetrain. You're appling power 4000 times a second instead of 900.

Once you reach your stall speed, you have very minimal slip allowed in the converter due to the dynamics of it, and it is mostly a power loss to heat from the lack of direct drive. Using a fluid coupling to move a 4000lb car obviously has it's parasitic losses...

Above your stall speed, the converter's purpose has been fulfilled, and is more of a hinderance because of the parasitic loss. If you have the ability to lock the converter, you take that out of the equation, and have a full 1:1 drive ratio through the converter just as a manual transmission with a locked up clutch. You're able to plant more power to the ground rather than waste it in heat. This is shown by higher horsepower on a dyno with a (the same) converter locked as opposed to unlocked.


That is a well written discription of the TQ converters purpose and for and against arguments on the two types of converters. Had I known more I might have got a lock up converter. I have gotten much good information from this thread. There are still some really fast guys out there running a nonlocking TQ converter like David Neibert but I dont know why the nonlocking was touted to be the best on the track unless someone has an argument for that side.

Ken
 
Back
Top