How can I tell if my converter is effecient as its rated at?
03-30-2004, 04:07 PM
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I will take a stab at it.
First you will need to know how the efficiency was originally measured and at what RPM.
If a torque converter is 95% efficient at 8000rpm on a dyno who cares. What matters is how efficient is a TC at your intended operating RPM and load conditions.
As far as I know there are 2 ways for the average person to measure the efficiency of their converter.
1 – On a dyno. Measure difference in HP with the converter locked vs unlocked. This seems to be that preferred method but it will show the converter to be more efficient than it really is. This is due in part to the fact that a DynoJet dyno does not load the TC as much as it would if it were on the street and therefore shows better efficiency numbers.
2 – On the street with the converter unlocked at WOT in 3rd gear. Using a scan tool record Transmission input shaft RPM and divide it by the Engine RPM. For example: TIS=3025 / EngRPM=5687 = 53%.
There are many factors that have an effect on the efficiency of a torque converter such as the following:
RPM the efficiency is measured at.
Gear ratio/tire size
Transmission gear ratio if measured in a gear other than 3rd (1:1)
Converter stall speed
“On The Street” method
It is not valid to measure the TC efficiency of a 4000 RPM stall at 3000 RPM because that is below the RPM speed that the TC becomes hydraulically coupled. The RPM must be at or above this point.
Gear ratio/tire size – A 4000 stall with 4.11 gears will be much more efficient than with 2.73 gears. This is because with the 4.11 gear the transmission from the input shaft towards the rear will be turning faster. This will allow the input shaft of the transmission to spin at a RPM closer to that of the engine. The 4.11 gears reduce the load on the converter. In other words you will not be riding the converter as much with the 4.11 gear as you will be with the 2.73 gears.
Transmission gear ratio if measured in a gear other than 3rd (1:1) – TC efficiency should always be measured in your 1:1 gear (usually 3rd gear). The reason is that the TC will be most efficient in 1st gear and then 2nd gear because of the positive effect of gear multiplication. 3rd gear will offer the most load to the converter.
Converter stall speed - TC efficiency should always be measured at a RPM that is equal to or greater than the RPM at which the converters become hydraulically coupled.
I think a good rule of thumb would be to add 1500 RPM to the rated TC stall RPM and measure efficiency at that point and higher while in 3rd gear at WOT.
Needless to say there is no reason to measure or care about TC efficiency at a RPM level that is above what you will be operating at.
For instance my Yank PT4000 which turned out to really be a 4800-5200 RPM stall never was more efficient than 80% at WOT at 6300rpm with 3.23 gears. If I measured the efficiency of the Yank PT converter at 6700+RPM it might have been in the 90% range. At a RPM below 4000 the Yank PT converter had efficiencies of 50% or lower. This is what makes the converter “loose”.
My Vig3200 is about 94% efficient at WOT at 6300rpm with 3.23 gears. At RPM below 2000 the Vig3200 probably has efficiencies of 50% or lower as well.
I hope this helps to answer your question.
John
First you will need to know how the efficiency was originally measured and at what RPM.
If a torque converter is 95% efficient at 8000rpm on a dyno who cares. What matters is how efficient is a TC at your intended operating RPM and load conditions.
As far as I know there are 2 ways for the average person to measure the efficiency of their converter.
1 – On a dyno. Measure difference in HP with the converter locked vs unlocked. This seems to be that preferred method but it will show the converter to be more efficient than it really is. This is due in part to the fact that a DynoJet dyno does not load the TC as much as it would if it were on the street and therefore shows better efficiency numbers.
2 – On the street with the converter unlocked at WOT in 3rd gear. Using a scan tool record Transmission input shaft RPM and divide it by the Engine RPM. For example: TIS=3025 / EngRPM=5687 = 53%.
There are many factors that have an effect on the efficiency of a torque converter such as the following:
RPM the efficiency is measured at.
Gear ratio/tire size
Transmission gear ratio if measured in a gear other than 3rd (1:1)
Converter stall speed
“On The Street” method
It is not valid to measure the TC efficiency of a 4000 RPM stall at 3000 RPM because that is below the RPM speed that the TC becomes hydraulically coupled. The RPM must be at or above this point.
Gear ratio/tire size – A 4000 stall with 4.11 gears will be much more efficient than with 2.73 gears. This is because with the 4.11 gear the transmission from the input shaft towards the rear will be turning faster. This will allow the input shaft of the transmission to spin at a RPM closer to that of the engine. The 4.11 gears reduce the load on the converter. In other words you will not be riding the converter as much with the 4.11 gear as you will be with the 2.73 gears.
Transmission gear ratio if measured in a gear other than 3rd (1:1) – TC efficiency should always be measured in your 1:1 gear (usually 3rd gear). The reason is that the TC will be most efficient in 1st gear and then 2nd gear because of the positive effect of gear multiplication. 3rd gear will offer the most load to the converter.
Converter stall speed - TC efficiency should always be measured at a RPM that is equal to or greater than the RPM at which the converters become hydraulically coupled.
I think a good rule of thumb would be to add 1500 RPM to the rated TC stall RPM and measure efficiency at that point and higher while in 3rd gear at WOT.
Needless to say there is no reason to measure or care about TC efficiency at a RPM level that is above what you will be operating at.
For instance my Yank PT4000 which turned out to really be a 4800-5200 RPM stall never was more efficient than 80% at WOT at 6300rpm with 3.23 gears. If I measured the efficiency of the Yank PT converter at 6700+RPM it might have been in the 90% range. At a RPM below 4000 the Yank PT converter had efficiencies of 50% or lower. This is what makes the converter “loose”.
My Vig3200 is about 94% efficient at WOT at 6300rpm with 3.23 gears. At RPM below 2000 the Vig3200 probably has efficiencies of 50% or lower as well.
I hope this helps to answer your question.
John
Last edited by JNorris; 04-06-2004 at 06:12 PM.