Just a question about torque multiplication
Thread Starter
Drifting
Joined: Sep 2014
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From: Trieste Italy
Just a question about torque multiplication
Just a question about torque converter, I know very well as it works, just I'm going crazy to get this point
Can torque converter produce more torque than engine torque peak?
1.Absolutely no
2.Usually no: can goes over torque with particular stall speed type converter
3.Usually yes
Can torque converter produce more torque than engine torque peak?
1.Absolutely no
2.Usually no: can goes over torque with particular stall speed type converter
3.Usually yes
Last edited by Christi@n; Mar 20, 2017 at 02:33 PM.
Melting Slicks
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From: Downers Grove Illinois
Thread Starter
Drifting
Joined: Sep 2014
Posts: 1,579
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From: Trieste Italy
Ok, obviously i've made a lot of search before to post this question...
And there are some few things that i'm not grabbing...
1.There are a lot of dyno chart around on web for c4 - c5 vette with auto trans, usually their max torque is 320-340 ft/lb or even less for stock cars. Why we cannot see the torque peak?
Also 4l60 is rated to handle max 360 ft/lb (if i'm right), well with a torque multiplication ratio of 1,5:1 or 2:1 should have from 450 ft/lb to 660 ft/lb as result... Thiscould rip the transmsission input shaft
And there are some few things that i'm not grabbing...
1.There are a lot of dyno chart around on web for c4 - c5 vette with auto trans, usually their max torque is 320-340 ft/lb or even less for stock cars. Why we cannot see the torque peak?
Also 4l60 is rated to handle max 360 ft/lb (if i'm right), well with a torque multiplication ratio of 1,5:1 or 2:1 should have from 450 ft/lb to 660 ft/lb as result... Thiscould rip the transmsission input shaft
Last edited by Christi@n; Mar 20, 2017 at 06:05 PM.
Safety Car
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From: Glenbeulah Wi
Ok, obviously i've made a lot of search before to post this question...
And there are some few things that i'm not grabbing...
1.There are a lot of dyno chart around on web for c4 - c5 vette with auto trans, usually their max torque is 320-340 ft/lb or even less for stock cars. Why we cannot see the torque peak?
Also 4l60 is rated to handle max 360 ft/lb (if i'm right), well with a torque multiplication ratio of 1,5:1 or 2:1 should have from 450 ft/lb to 660 ft/lb as result... Thiscould rip the transmsission input shaft
And there are some few things that i'm not grabbing...
1.There are a lot of dyno chart around on web for c4 - c5 vette with auto trans, usually their max torque is 320-340 ft/lb or even less for stock cars. Why we cannot see the torque peak?
Also 4l60 is rated to handle max 360 ft/lb (if i'm right), well with a torque multiplication ratio of 1,5:1 or 2:1 should have from 450 ft/lb to 660 ft/lb as result... Thiscould rip the transmsission input shaft
When GM rates the transmissions they do take this into account, and what GM rates is continuous torque and not the peak torque the transmissions can handle.
Last edited by bjankuski; Mar 20, 2017 at 09:50 PM.
Thread Starter
Drifting
Joined: Sep 2014
Posts: 1,579
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From: Trieste Italy
That is because a stock torque converter stalls at 1600 RPM and most dyno runs are started in third gear at an rpm higher than 1600 RPM so you will not see the added torque multiplication on the dyno chart. The added torque multiplication is the highest when the input shaft is at zero RPM and the torque converter is rotating at stall speed. In this condition the torque multiplication will be near 2 to 1. As the car accelerates the and the input shaft and torque converter RPM match each other the torque multiplication drops to zero. You can see the added torque converter multiplication on dyno charts when you have a high stall converter in a car on a dyno run. If the high stall converter stalls higher then the RPM that the dyno run is started at, it will show a torque spike that is higher then what the engine torque output is. You can tell this happened if you see a steadily declining peak torque curve.
When GM rates the transmissions they do take this into account, and what GM rates is continuous torque and not the peak torque the transmissions can handle.
When GM rates the transmissions they do take this into account, and what GM rates is continuous torque and not the peak torque the transmissions can handle.
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Not likely in first gear. The tires will loose traction long before there's 660ft lbs on the input shaft.
Now take the car to Bonneville and have everything right where you develop 660ft lbs of output at the speed that has equal aerodynamic drag and yes, the transmission is seeing 660ft lbs at the input shaft. But you probably won't get the 660ft lbs.
Now take the car to Bonneville and have everything right where you develop 660ft lbs of output at the speed that has equal aerodynamic drag and yes, the transmission is seeing 660ft lbs at the input shaft. But you probably won't get the 660ft lbs.
I agree with you that the tires will spin before you reach max tq output from the trans.
.
Last edited by Tom400CFI; Mar 21, 2017 at 10:46 AM.
Thread Starter
Drifting
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From: Trieste Italy
No. No 660 ft lbs (actually it should be >900 lb ft; 300 lbs of tq, * 1st gear ratio (3.07)= 921 ft lbs...*whatever multiplication you get in the converter) is going to be found at top speed. Engine can make a peak of 330 lbs, trans would be in 3rd gear (1:1) and tq converter should be locked up (also 1:1). 330 in , 330 minus parasitic draw of trans going out, minus tq fall off at whatever RPM car reaches top speed.
As input shaft speed increases. Doesn't matter what road speed is really; it's about the differential in converter housing RPM vs. impeller RPM. The greater the diff, the greater the tq multiplication. Stalling the converter at a stand still will provide the greatest Tq multiplication.
I agree with you that the tires will spin before you reach max tq output from the trans.
.
As input shaft speed increases. Doesn't matter what road speed is really; it's about the differential in converter housing RPM vs. impeller RPM. The greater the diff, the greater the tq multiplication. Stalling the converter at a stand still will provide the greatest Tq multiplication.
I agree with you that the tires will spin before you reach max tq output from the trans.
.
Converter would be stock or is it high stall?
Last edited by Christi@n; Mar 21, 2017 at 10:51 AM.
Thread Starter
Drifting
Joined: Sep 2014
Posts: 1,579
Likes: 59
From: Trieste Italy
So all that torque that is when there's big difference speed from impeller to turbine where goes it?
It goes not to trans input shaft cause it is spinning very slow
It just helps to spin better the engine to reach its torque/power band?
It goes not to trans input shaft cause it is spinning very slow
It just helps to spin better the engine to reach its torque/power band?
Last edited by Christi@n; Mar 21, 2017 at 10:58 AM.