Let's talk Torque Converters

[merc]

Tq. Converter Stall Speed

Switching to a higher stall-speed torque converter can provide the benefit of increased launch RPM and better low-speed acceleration. Once your vehicle is up and moving, though, a different converter will have little effect. Like any other performance tuning variable, converter stall-speed should be closely matched to your vehicle and power-train requirements. Also, a torque converter may not necessarily deliver the advertised stall speed due to differences in engine torque output and vehicle chassis conditions. After-market torque converters vary greatly in their quality and coupling efficiency. However, no converter should have to reach its advertised stall RPM just to back out of your driveway or accelerate in city traffic, as is a common misconception about higher-stall-speed torque converters. In fact, a properly designed mild after-market converter (i.e. 2500 RPM stall-speed) should not feel much different than its OEM counterpart in everyday driving.

Stall speed should be selected so that the torque converter will reach its stall speed just before the engine starts it power-band (when torque output begins increasing sharply). Too much stall RPM will actually slow a car down by wasting part of the engine's useful power curve. A stock torque converter in an AOD equipped Mustang will produce a stall speed of about 1800RPM, while the stock 5.0L H.O. engine enters its power-producing stage slightly later. Therefore, a stall speed of 2500 RPM is best for most stock and mildly modified 5.0L HO applications. Stock 5.0L Mustang AOD-E torque converters stall at about 2400 RPM, and will provide significant improvements over an AOD converter. Vehicles with significantly altered valve events (i.e. large camshafts and/or huge valves) may benefit from stall speeds as high as 3000RPM or more depending upon configuration and torque curve. In such cases, it is best to consult your camshaft supplier or engine builder for best results.

For AOD transmissions (as well as C-4 and C-6 applications) there are a number of vendors providing high quality torque converters in many different configurations. As mentioned in the AOD section, Art Carr's converters require use of their special input shaft for the AOD and are available in a variety of stall speeds and sizes. Precision Industries also makes converters in both "lockup" and "non-lockup" varieties for the AOD with stall speeds to order. Baumann Engineering can also furnish high quality custom built converters for Ford transmissions at competitive prices. Before purchasing any torque converter, we suggest that you get objective recommendations from other performance enthusiasts and avoid using purchase price as the sole selection criteria.

As with the E4OD and A4LD transmissions, few vendors have yet to produce higher stall-speed torque converters for the AOD-E/4R70W transmission. However, Baumann Engineering can provide a custom-built torque converter for these and most other applications. In the case of converter clutch style transmissions, such as the AOD-E/4R70W, E4OD and A4LD, we rarely advocate removing the lockup clutch assembly from the torque converter. Therefore, they provide their converters with new heavy-duty lockup clutch assemblies. This allows you to selectively control converter lockup with the Baumannator TCS™ or even external switches if desired, thereby providing maximum efficiency and versatility with no adverse effect on vehicle performance.

How do I choose the right stall speed?
Under ideal circumstances you should select a converter that stalls approx 700 rpm below peak torque. This will set the converter and the transmission's gearing to do their job, until you reach peak hp or shift points.

For street use we never recommend a stall speed higher than 3000 to 3500 rpm depending on the rear end ratio and your normal driving rpm. If your normal 55 to 60 mph cruising rpm is at 2500 rpm, you don't want a convertor that is any higer. What you do want is the convertor to be highered up at that speed in order to avoid the heat buildup a converer generates when it is working.

It is a general misunderstanding that a vehicle will not move until the stall speed is reached. This is not the case. With a 3000 rpm stall this vehicle is drivable at any rpm, it may seem a bit sluggish or lazy until you reach 3000 rpm.

The SC makes peak torque somewhere from 2500-3000 rpm depending on what mods you have. This calls for a 1800-2300rpm stall for most applications. Unlike naturally aspirated motors, the SC makes all of it's power down low. By stalling the motor ABOVE IT'S EFFECTIVE POWER BAND, you are wasting most of it's effective power through slippage in the torque convertor.

I suggest 2,800 rpm stall converter in a SC only if you wish to drive at or above the peakTorque rmp of the engine. In other words I would not recommend a high stall converter in a SC if you intend to use it as a dailydriver. It is nearly impossible to keep the rear end from breaking loose. I am exchanging it for the 2,200 rpm converter. http://www.protorque.com, Precission Industries

Do you agree with the above statement. If not please tell me why.

[Zack]

I have a 3500 from Darrin, feels way grippier at the low rpm's compared to the PI.

[ImpalaSlayer]

thanks for the info. still very confusing though

[MarauderTJA]

I have a 3500 from Darrin, feels way grippier at the low rpm's compared to the PI.

I have found the exact same thing with mine. Absolutley no comparision to the 3000 PI I had previously in the car. I think due to the larger surface area of his converters.

[MarauderTJA]

BTW Merc, an excellent and informative thread. My new BC Auto 3500 stall converter is far superior than my previous PI 3000 Stallion, hands down.

[merc]

Since we are on the subject of converters lets use the illustration below to help us understand the parts involved.

[merc]

I have found the exact same thing with mine. Absolutley no comparision to the 3000 PI I had previously in the car. I think due to the larger surface area of his converters.

When towing or hauling a heavy load, the stock torque converter clutch can slip while in lockup mode, which causes excessive lockup clutch wear and transmission heat. Some aftermarket valve bodies overcome this problem by boosting transmission line pressure past the limit of the transmission seals, which can cause leaks. Some Torque Converter’s lockup surface are lined with a special carbon-ceramic material that withstands heat and resists slippage better than the stock cellulose-based paper material that is used in the PI convertor. Additionally, the clutch surface area is increased for truck applications, allowing a stronger lockup at safe line pressures.

[gonzo50]

Tq. Converter Stall Speed

The SC makes peak torque somewhere from 2500-3000 rpm depending on what mods you have. This calls for a 1800-2300rpm stall for most applications. Unlike naturally aspirated motors, the SC makes all of it's power down low. By stalling the motor ABOVE IT'S EFFECTIVE POWER BAND, you are wasting most of it's effective power through slippage in the torque convertor.

I suggest 2,800 rpm stall converter in a SC only if you wish to drive at or above the peakTorque rmp of the engine. In other words I would not recommend a high stall converter in a SC if you intend to use it as a dailydriver. It is nearly impossible to keep the rear end from breaking loose. I am exchanging it for the 2,200 rpm converter.
Do you agree with the above statement. If not please tell me why.

I have the 3000 rpm stall converter from PI, so what you're saying is when I decide to go S/C, I lose all streetabilty driving due to not being able to get any grip.

Will I have to also change out my converter ?

[merc]

Edited duplicate thread. Admin please delete.

[merc]

thanks for the info. still very confusing though

Torque converter 101

The basic function of the torque converter is to multiply the turning force of an engine while at the same time replacing the clutch found in manual transmissions. The engine is connected to the torque converter by means of the crankshaft. The crankshaft ends in the torque converter, which is also where the main input or transmission shaft ends as well. However, these two shafts are not connected to each other so there isn’t any physical connection between the engine and transmission in any way. The two shafts have the slightest gap between them and are immersed in transmission fluid.

The transmission shaft is turned by the crankshaft by means of a process called hydraulic coupling. As all fluids are not easily compressed, this property is utilized in the automatic transmission. The hydraulic fluid used is the automatic transmission fluid (ATF) which fills the entire transmission and torque converter. The one downside to utilizing hydraulic coupling is that is causes automatic transmissions to be slightly more inefficient than their manual counterparts. The fluid connection between the crankshaft and transmission shaft allows some slippage to occur. As a result, there is a two to eight percent loss in energy transferred from one shaft to the other. This is the reason why automatic cars generally get slightly worse fuel economy than the manual version of the same car model.

Inside the torque converter casing, there are three main components: the impeller (pump), stator (guide wheel) and turbine. Hydraulic coupling is also at work within the torque converter itself, and to improve the efficiency of energy transfer, both the impeller and turbine have blades which are designed to increase the surface area that the fluid can act on.

Inside the transmission fluid filled torque converter, the impeller is located on the engine side while the turbine is situated on the transmission side. When the impeller starts to spin, the turbine wheel spins in tandem with it through hydraulic coupling. As this happens, centrifugal forces cause the fluid to move towards the outer edges of the blades, where the stator redirects the fluid towards the turbine side of the torque converter. This continuous flow of transmission fluid is what causes the torque converter to multiply the turning power applied by the engine.

The majority of modern torque converters will also include a lock-up feature through the use of a torque converter clutch. The highly pressurized fluid flowing through the transmission is channeled through the transmission shaft as the speed of the vehicle nears forty miles an hour. When this happens, the torque converter clutch or a metal pin, physically ‘locks’ or connects the turbine to the impeller. The pin remains connected until either the vehicle slows down below forty miles an hour or a gear-shift occurs. This feature was developed and incorporated into the modern torque converter to improve the highway fuel economy.

[KillJoy]

Interesting.

Could it possibly be that you just need to relearn how to "drive" the car when you get a higher stall TC???



KillJoy

[merc]

I have the 3000 rpm stall converter from PI, so what you're saying is when I decide to go S/C, I lose all streetabilty driving due to not being able to get any grip.

Will I have to also change out my converter ?

Lidio wrote this back in 04-02-2003. In conversation with him he prefers the Marauder stock 04 converter over any high stall unit on the market. Lidio has since sold his Marauder but still provides aftermarket performance parts to our community.

I’d also like to note that at the end of the ¼ mile the rpms in 3d gear were only at about 4600rpm! This is not optimal for a drag racer when the engine shifts at 6000 ish. We would usually like to see a trap rpm of about 6000+ on this type of set up. This would probablly produce about a 2-3 tenth increase in ET but traction would become a much more serious problem with out a tire upgrade. This is why I’m suggesting leaving the 3.55’s in the rear for now if the Trilogy blower is in your Marauder’s future. Also the stock torque converter stall speed is perfect for the blower application. Once again a change here would only produce greater traction problems and if loosened up to much can cause a drivability concern around town when locking and unlocking.

[Dennis Reinhart]

Tq. Converter Stall Speed

Switching to a higher stall-speed torque converter can provide the benefit of increased launch RPM and better low-speed acceleration. Once your vehicle is up and moving, though, a different converter will have little effect. Like any other performance tuning variable, converter stall-speed should be closely matched to your vehicle and power-train requirements. Also, a torque converter may not necessarily deliver the advertised stall speed due to differences in engine torque output and vehicle chassis conditions. After-market torque converters vary greatly in their quality and coupling efficiency. However, no converter should have to reach its advertised stall RPM just to back out of your driveway or accelerate in city traffic, as is a common misconception about higher-stall-speed torque converters. In fact, a properly designed mild after-market converter (i.e. 2500 RPM stall-speed) should not feel much different than its OEM counterpart in everyday driving.

Stall speed should be selected so that the torque converter will reach its stall speed just before the engine starts it power-band (when torque output begins increasing sharply). Too much stall RPM will actually slow a car down by wasting part of the engine's useful power curve. A stock torque converter in an AOD equipped Mustang will produce a stall speed of about 1800RPM, while the stock 5.0L H.O. engine enters its power-producing stage slightly later. Therefore, a stall speed of 2500 RPM is best for most stock and mildly modified 5.0L HO applications. Stock 5.0L Mustang AOD-E torque converters stall at about 2400 RPM, and will provide significant improvements over an AOD converter. Vehicles with significantly altered valve events (i.e. large camshafts and/or huge valves) may benefit from stall speeds as high as 3000RPM or more depending upon configuration and torque curve. In such cases, it is best to consult your camshaft supplier or engine builder for best results.

For AOD transmissions (as well as C-4 and C-6 applications) there are a number of vendors providing high quality torque converters in many different configurations. As mentioned in the AOD section, Art Carr's converters require use of their special input shaft for the AOD and are available in a variety of stall speeds and sizes. Precision Industries also makes converters in both "lockup" and "non-lockup" varieties for the AOD with stall speeds to order. Baumann Engineering can also furnish high quality custom built converters for Ford transmissions at competitive prices. Before purchasing any torque converter, we suggest that you get objective recommendations from other performance enthusiasts and avoid using purchase price as the sole selection criteria.

As with the E4OD and A4LD transmissions, few vendors have yet to produce higher stall-speed torque converters for the AOD-E/4R70W transmission. However, Baumann Engineering can provide a custom-built torque converter for these and most other applications. In the case of converter clutch style transmissions, such as the AOD-E/4R70W, E4OD and A4LD, we rarely advocate removing the lockup clutch assembly from the torque converter. Therefore, they provide their converters with new heavy-duty lockup clutch assemblies. This allows you to selectively control converter lockup with the Baumannator TCS™ or even external switches if desired, thereby providing maximum efficiency and versatility with no adverse effect on vehicle performance.

How do I choose the right stall speed?
Under ideal circumstances you should select a converter that stalls approx 700 rpm below peak torque. This will set the converter and the transmission's gearing to do their job, until you reach peak hp or shift points.

For street use we never recommend a stall speed higher than 3000 to 3500 rpm depending on the rear end ratio and your normal driving rpm. If your normal 55 to 60 mph cruising rpm is at 2500 rpm, you don't want a convertor that is any higer. What you do want is the convertor to be highered up at that speed in order to avoid the heat buildup a converer generates when it is working.

It is a general misunderstanding that a vehicle will not move until the stall speed is reached. This is not the case. With a 3000 rpm stall this vehicle is drivable at any rpm, it may seem a bit sluggish or lazy until you reach 3000 rpm.

The SC makes peak torque somewhere from 2500-3000 rpm depending on what mods you have. This calls for a 1800-2300rpm stall for most applications. Unlike naturally aspirated motors, the SC makes all of it's power down low. By stalling the motor ABOVE IT'S EFFECTIVE POWER BAND, you are wasting most of it's effective power through slippage in the torque convertor.

I suggest 2,800 rpm stall converter in a SC only if you wish to drive at or above the peakTorque rmp of the engine. In other words I would not recommend a high stall converter in a SC if you intend to use it as a dailydriver. It is nearly impossible to keep the rear end from breaking loose. I am exchanging it for the 2,200 rpm converter. http://www.protorque.com, Precission Industries

Do you agree with the above statement. If not please tell me why.

for a 4000lb car on the street N/A or SC a 3000/3500 works out fine, I had a 4500 in my Mark 8 and yes that was a bit much to drive on the street, PI makes a very good converter

[merc]

Interesting.

Could it possibly be that you just need to relearn how to "drive" the car when you get a higher stall TC???



KillJoy

This is a good question Killjoy. Just dropping in a high stall converter with out optimizing the lockup schedules and shift points would cause some driver frustration. In my personal experience I have had 3 difference tunes that effected my transmission. I was happiest with Injected Engineering tune when I was N/A. They got my transmission singing a different song. Currently I have the stock Lidio tune for the basic 3.4 pulley setup. I find that I have to regulate my foot to have smooth highway shifts and I hate hearing the transmission lock and unlock between 60 and 70 miles per hour. I will be addressing that problem in the near future with a different tune.

[merc]

for a 4000lb car on the street N/A or SC a 3000/3500 works out fine, I had a 4500 in my Mark 8 and yes that was a bit much to drive on the street, PI makes a very good converter

Thanks Dennis for chiming in on this thread. You have a ton of real world experience that would be helpful to share. I don't intend for this conversation to be a debate. At the end of the day we can all learn and formulate better questions with the wisdom of understanding.