auto versus 6 speed

[DPelletier]

Oh yeah,

FWIW I just took my truck out with the camper and when I shift, my RPM's drop to only 2200 RPM, not 1400 RPM - well within the powerband for the Cummins.



Dave

 

[HoofinSoot]

Just figure out how to shoe-horn this in, and it will be the best of BOTH worlds !!



Eaton AutoShift

 

[hasselbach]

1. Unfortunately, the higher the torque multiple, the more slippage in the converter, and the less mechanically efficient it is (thus, higher ATF temps with higher stall speeds).



2. What is stall speed, anyway? Stall speed is the torque-dependent maximum differential of rotational speeds between the input and outputs of a fluid coupling.



3. Slippage IS an evil outcome from the TC, because we want maximum efficiency and the heat generated is an indicator of inefficiency. This evil loss of efficiency does provide some nice benefits, like smoothness and torque multiplication. It depends on what you mean by "evil"-- since I favor pure efficiency, slippage IS evil.

1. Not true, slippage and torque multiplication are not direct relationships. You can build a very high output torque multiple converter with extremely low amounts of slippage. How? Increase the diameter of the TC. A 13 or 14 inch converter will make more torque than an equally "stalling" converter of say 10 or 11 inches.



2. stall speed is defined at the point that the stator becomes stationary and is producing max amount of torque at a given input.



3. You keep saying slippage is evil. Not so. Imagine your two fans facing each other, yet one fan (the input side) is smaller than the opposing fan. Thus it requires more revolutions to pump fluid to the larger fan (which has more leverage on the output shaft due to the larger blades). Thus the smaller fan must turn more revolutions than the driven fan, but a result is increased torque output. The stator's role is to redirect the fluid once the output fan begins to move (rotate), equalizing the driving fan (making the input fan think its bigger than it is). How is this evil? Sounds to me like a very efficient manner to distribute power flow, the converter is constantly adjusting the driving fan to the load required. When torque multiplication is not required, the converter moves toward a 1 to 1 ratio, (and gets there 100% once locked up). If you favor efficiency, how is banging gears, moving around the power curve, accelerating and decelerating mass, coupling and uncoupling the clutch an efficient form of power distribution?



edited for tact and friendly form :-laf

 

[HoofinSoot]

... . called "K" factor.

 

[RustyJC]

2. stall speed is defined at the point that the stator becomes stationary and is producing max amount of torque at a given input.

What is unsaid here is that the torque converter is also transmitting 0 BHP. Basically, the power coming into the torque converter from the engine (BHPin) is being dissipated as heat at the rate of 1 BHP = 42. 44498 BTU/minute, and the mechanical power coming out of the converter into the transmission (BHPout) is zero. Therefore, the mechanical efficiency of the converter at stall ([BHPout / BHPin] x 100) is 0%. Once the brake is released, mechanical efficiency will increase as turbine speed approaches pump speed, but until lockup is achieved, torque converter mechanical efficiency will be lower than the mechanical efficiency of an engaged clutch.



Rusty

 

[Archive]

Since a computer can shift either a "manual" or an "automatic" (technology is blurring the distinction, is it not?), the question is simplified. Is a friction coupling better based on fluid or dry design?



The fluid coupling can multiply torque whereas the friction coupling cannot.



Both generate heat.



The torque mulitplication advantage of the fluid coupling can be duplicated by adding one extra lower gear to the manual; a simpler and cheaper solution than adding the fluid coupling.



Fluid is easier to change than a friction disk.



The fluid coupling can be driven by near morons (don't laugh, this can be a very important consideration).



Bottom line: if cost is unimportant, there are a lot of possibilities in drivetrain design. Unfortunately, RAM owers have to choose between an automatic that, as this discussion has demonstrated, is clearly not an advanced piece of technology, and a relatively inconvenient, but well evolved, strong and dependable manual.

 

[hasselbach]

What is unsaid here is that the torque converter is also transmitting 0 BHP. Basically, the power coming into the torque converter from the engine (BHPin) is being dissipated as heat at the rate of 1 BHP = 42. 44498 BTU/minute, and the mechanical power coming out of the converter into the transmission (BHPout) is zero. Therefore, the mechanical efficiency of the converter at stall ([BHPout / BHPin] x 100) is 0%. Once the brake is released, mechanical efficiency will increase as turbine speed approaches pump speed, but until lockup is achieved, torque converter mechanical efficiency will be lower than the mechanical efficiency of an engaged clutch.



Rusty

Not true, you keep talking about the efficiency of a clutch, but the clutch is only one aspect of the power distribution equation.



quote ''but until lockup is achieved, torque converter mechanical efficiency will be lower than the mechanical efficiency of an engaged clutch. ''



How so? Once the converter is locked up, its a moot point, yet when in multiplication mode, it is by far superior that a slipping clutch, or better, when the manual transmission must shift 1 to 2 times to match the variable output of the TC. Yes, some heat is displaced, but again, so what? A manual clutch doesn't get hot? Automatics and manuals absorb almost an equal amount of parasitic power (and the auto wins this one when locked up due to a more efficient axial power flow route)



And how many BTU's are displaced on each gear change required for the manual (ie consumption of fuel)? Energy required for Increasing and decreasing the mass of the flywheel is free? And how efficient in operating the engine at various rpms? We all know that internal combustion motors have a small window where the power generated vs. the least amount of fuel consumed is very small. Wouldn't it make more sense to operate the engine at maximum volumetric efficiency, and allow the TC to adjust the torque output required? Again, we don't drive our trucks in a static state (flat ground, one speed continuously). We have stop signs, hills, variable loads and speeds. No matter how much you argue, the TC and auto is better suited than the inferior operation of the stick.



I'm curious, and don't take this as a slight and respond that I have ATTITUDE, but how much dyno time (engine and transmission), how many hands-on tests, how many converters, how much research have you done on this actual matter? I get the feeling that you are quoting text book rule vs. actual hands on research.

 

[RustyJC]

Not true... .

Saying something doesn't make it so. What, precisely, is untrue in what I said? Is the equation for mechanical efficiency ([BHPout / BHPin) x 100) incorrect? Is the fact that, at stall, the turbine is turning 0 RPM and, therefore, transmitting 0 BHP (BHP = [Q x N] / 5252, and N = 0) untrue? Is the fact that, since BHPout = 0 and BHPin > 0, mechanical efficiency is equal to 0% untrue? Is the statement that an unlocked torque converter has lower mechanical efficiency (again, [BHPout / BHPin] x 100) than an engaged clutch untrue? What specifically is untrue, Mr. Hasselbach?



Rusty

 

[Archive]

Shouldn't this efficiency argument really be about how to get the sytem locked up as quickly as possible?



If the TC can be locked up as soon as first gear, like a clutch, then there won't be much difference between either system. But right now, clutches spend less time slipping than fluid couplings. Particularly as related to the 48re which doesn't lock up in 1st or 2nd, and not all the time in 3rd.

 

[hasselbach]

Saying something doesn't make it so. What, precisely, is untrue in what I said? Is the equation for mechanical efficiency ([BHPout / BHPin) x 100) incorrect? Is the fact that, at stall, the turbine is turning 0 RPM and, therefore, transmitting 0 BHP (BHP = [Q x N] / 5252, and N = 0) untrue? Is the fact that, since BHPout = 0 and BHPin > 0, mechanical efficiency is equal to 0% untrue? Is the statement that an unlocked torque converter has lower mechanical efficiency (again, [BHPout / BHPin] x 100) than an engaged clutch untrue? What specifically is untrue, Mr. Hasselbach?



Rusty

Oh boy, this is getting to be ridiculous. You can twist mechanical efficiency equations around to make a point that is worthless at best. I can only answer such a rhetorical question with the following:



1. How much Torque is transmitted when the clutch is disengaged (ie Mechanical efficiency)? Answer: Zero

2. How much heat is generated with a mechanical clutch when the input is say 2000 rpm and the output is 0 rpms (ie, slippage). Answer: A lot.

3. You failed to answer my previous question, which was how much actual experience do you have in this field regarding actual research, hands on work, etc. ? Answer: None.

 

[RustyJC]

Therefore, there was nothing untrue in my statement, correct?



Rusty

 

[hasselbach]

Therefore, there was nothing untrue in my statement, correct?



Rusty

No, your statement ' a stalled converter has less efficiency than a locked clutch" makes no sense. Again, so what? How much torque is being transferred with a un locked clutch? Answer none.



''An unlocked converter is more efficient than a disengaged clutch''. Now That makes sense.



How you compare a stalled converter to a locked clutch doesn't make sense.



There, I answered your questions, now answer mine. Other than text books on various forms of engineering principles, how much experience have you had in this field? :--)

 

[RustyJC]

No, your statement ' a stalled converter has less efficiency than a locked clutch" makes no sense.

Sir, I made no such statement. What I specifically said was:

Once the brake is released, mechanical efficiency will increase as turbine speed approaches pump speed, but until lockup is achieved, torque converter mechanical efficiency will be lower than the mechanical efficiency of an engaged clutch.

Would you care to critique that statement?





Rusty

 

[hasselbach]

Sir, I made no such statement. What I specifically said was:

Would you care to critique that statement?





Rusty

Yeah, its real simple, a slipping clutch (under gradual engagement to move said load) is less efficient than a TC that is converting pressure to the driven impeller to torque multiplication, so yes, your statement is false.



Answer the question Rusty, how much actual hands on research have you done in this field? You keep avoiding this critical question...

 

[RustyJC]

Yeah, its real simple, a slipping clutch (under gradual engagement to move said load) is less efficient than a TC that is converting pressure to the driven impeller to torque multiplication, so yes, your statement is false.

Nonresponsive to my statement.



My experience is not the critical question - that's a red herring. The critical question is relative performance of the 48RE versus the 6 speed, and those factors that contribute to the overall performance of each.



Rusty

 

[hasselbach]

Nonresponsive to my statement.



My experience is not the critical question - that's a red herring. The critical question is relative performance of the 48RE versus the 6 speed, and those factors that contribute to the overall performance of each.



Rusty

Sure your experience is critical in this issue, because you are posting information and asking questions that makes no sense, you have no hands on testing, you've probably never been in a dyno room, conducted track testing under controlled conditions, plotted fuel curves to match HP, Torque curves, never performed an efficiency analysis, etc etc. heck, have you even seen the inside of a converter? Oo.



About 30 years ago, an associate of mine had a bright idea, remove the TC from a turbo 400, install a clutch and you'd have the best of both worlds "Clutch Turbo"(given, this was for a lighter car usage, not a truck). You'd have extremely fast shifting, yet the lock up of a clutch. Guess what happened, the unit was a pig and got worse mileage than without the converter. Hard to launch, broke parts and overall worse than a stock turbo 400.



Why? The efficiency of the TC being able to vary the output based on the load required was lost due to the inefficiency of the clutch (clutch is either on or off, and does not create torque). Even with more gears, it probably wouldn't have worked any better. I have one in my garage if someone wants it (free to good home)

 

[Lorenz]

Lock Up Switch

I need some advise on how to be smarter than my '03 transmission's electronics. A "mystery switch" will lock up a TQ on command but im not shure the ins-and-outs of when and when not to use it. Any advise guys?



heres a link to the mystery from tst web site



http://www.tstproducts.com/tranny_install.html

 

[RustyJC]

Sure your experience is critical in this issue, because you are posting information and asking questions that makes no sense, you have no hands on testing, you've probably never been in a dyno room, conducted track testing under controlled conditions, plotted fuel curves to match HP, Torque curves, never performed an efficiency analysis, etc etc. heck, have you even seen the inside of a converter? Oo.

You have yet to disprove any technical information I've presented. Therefore, I fail to see why you feel it necessary to question my engineering background. I have worked for a manufacturer of engines, gas turbines, reciprocating and centrifugal compressors and turbochargers for 31 years, 26 of those in technical and engineering management. So, yes, I'm familiar with dynamometer testing for product development as well as production testing, compressor open and closed loop as well as load bank and dynamometer production testing, turbocharger bootstrap testing, development and use of engine, turbine, turbocharger and compressor performance curves (not just BSFC), field testing (performance and vibration), etc.



Now, what does all the above have to do with the discussion at hand? Absolutely nothing.



Rusty

 

[DPelletier]

Hasselbach,



The amount of time my clutch is slipping is infinitismally small compared to the amount of time an auto TC is slipping. I don't use "gradual engagement to move a load", I choose the appropriate gear and let the clutch out. Process takes a fraction of a second. I think the amount of time that my clutch is slipping is only a very, very small percentage of my driving time and perhaps its importance is being overstated here. Just an observation.



Rusty is a smart guy with lots to contribute. I don't think that putting him down for his relative lack of experience is useful. The discussion has been interesting for the last couple of pages, hopefully it won't deteriorate at this point.



Dave

 

[hasselbach]

You have yet to disprove any technical information I've presented. Therefore, I fail to see why you feel it necessary to question my engineering background. I have worked for a manufacturer of engines, gas turbines, reciprocating and centrifugal compressors and turbochargers for 31 years, 26 of those in technical and engineering management. So, yes, I'm familiar with dynamometer testing for product development as well as production testing, compressor open and closed loop as well as load bank and dynamometer production testing, turbocharger bootstrap testing, development and use of engine, turbine, turbocharger and compressor performance curves (not just BSFC), field testing (performance and vibration), etc.



Now, what does all the above have to do with the discussion at hand? Absolutely nothing.



Rusty

ah, no actual transmission or torque converter testing though? Okay, that's all I needed to know, thank you.