The allison is supposed to be semi automatic. Unfortunately the average driver has below average aptitude when driving a powered vehicle. What can I say. Our hormones overcome our reasoning abilities. No manufacturer wants the masses to have complete control. They do not trust us to make wise decisions.

 

Lets clear this up first. The following are quotes from http://neptune.spacebears.com/opine/horsepwr.html:

I will tell you right right of the bat that is is not your accessories that are making the differnece. It is the exhaust system, stock intake and emission that make the big difference. I have Engine Analyzer 3.0 at home and it lets me sim almost any combo you can think of. 1960's era accessories take about 50hp to run. By the time you get to the 90's that has drop to 30. Biggest reason for this is electronic cooling fans.

The last thing to talk about is RWHP. THe following is again from my source quoted above.

Now not once in any of my post have I ever said that a auto is more effecient than a manual. The truth of the matter though is the TS is matched better to the PSD than the Cummins is to the NV5600. The Ford even having 30lbs less torque and and having a 5% less effecient drive train it still out tows the Dodge. We are not talking about what if's but what is.

 

LH, you really confused me here. I think you are mixing apples and oranges I'll try and respond. Efficiency has nothing to do with stall speed. What it has to do with is at speed how close does the TC get to 1:1 without lockup. The closer I get to 1:1 you cooler the tranny runs, i.e. no slipage from the TC. In todays world this does not really apply because we have lockup conveters.

But for most of my life I have not had the advantage of a lockup converter. Rock crawling, mudding, 4x4ing in general I love an auto. Not once have I had a problem with a tranny failure due to heat. The only time was with the 700R4 and that was at freeway speed.

 

We are talking about autos and towing. More heat is generated while towing. Or manuevering at low speeds. Ive burned the fluid in an auto more than once. Their effective lifespans are temp and fluid related. At 220 degrees an auto might last just a few thousand miles.

I make most of my comparisons as worst case scenario. What will happen at full load at 65mph.

Different efficiencies are present at different speeds for a tc. In multiplication obviously they are very innefficient. At stall. They are most efficient. Sorry for any confusion. At stall. One might expect 80-90% efficiency. 100% energy in, 90% out. 10% is lost to heat. Stall is also called fluid coupling. Nice way of saying this is as good as it gets before lockup. My phrasing may be incorrect but the intent is right on.

Torque converter efficiency is a rated efficiency that it comes with. It is not subjective. It would be like rated hp. They test for it and know how much it is. Less than 90% efficiency would be normal oem tc's. Tighter than that and heat is a problem in traffic. They dont want us to destroy the tranny so we dont get those. Unless you dont mind watching a temp gauge and having an additional cooler with an thermostatic electric fan. I would like to find the efficiency rating for the TS tc. I have estimated about 87-89%. Judging by the rpm drop in lockup. This method is highly inaccurate but it gives a guesstimate. In other words dont quote me, but im leaning towards the 87% side of the guesstimate.

 

250 degrees is about the point where you start to hurt the TC and seals become hard. Bits of metal and rubber at this point start to circulate through the tranny causing the clutch plates to fail. 170 is considered optimum and a properly engineered system will cool to this lvl.

Towing in and of itself will not increase temps. Low speed manuevering on the other hand will. Trust me rock crawling is just as hard on a tranny as hauling a load as all manuvers are dead slow. Its easier to rock crawl with a auto than a manual. If you remember I said that for low and slow pulling I would use a manual.


This is not the worst case. At this point the tranny is in lockup, its the best case. Remember the TS in tow mode locks up also in 2nd and 3rd. 1st gear, under stall, extended manuvering is by far the worst case.

Ok, lets correct some things here. First anything below stall is ineffecient, this is a given. But Max multiplication is at stall, not below it. This is also not the most effecient point of the TC. The only way test this, without some very special test epuipment, would have the ability to lockout the lockup. You need to get up to 40-60mph steady cruise and the flip the lockup on. This would at least be close. I'm not saying you aren't right because based on historical data you are in the ball park.

Also a more effecient converter will run cooler not hotter. Higher stall will run hotter because more time is spent under stall. Stall and how effecient a TC is are not related.

P.S. Rumor has it that the PSD will be updated again in 05.5 to 350hp/630tq. I don't have a link just a rumor that is floating around.

 

There have been overheating problems with converters that are too tight. They also have a very low stall so maybe this is a factor. At idle they have too much coupling. Ive driven one like that. It would idle at 20mph. No kidding. Too tight. Bad design maybe.

Max multiplication happens at low rpms. If you stall at 2000 then you have 0 multiplication at 2000. Ignoring the effects of a flash. Multiplication only happens when the front end is spinning faster than the back end. This does not last very long. The back end catches up rather quickly.

In other words you can have both the most efficiency and very poor efficiency at stall. When both ends are spinning at the same speed its the most. When one is turning and the other is not. You are still losing a lot of energy. Im sorry. Converting.

I still am not convinced that a diesel can flash a converter like a gasser can.

Anything over 220 begins to kill the auto. At 250 you can count the lifespan in hundreds of miles. If you are at 250. There is a chance you tc is slipping anyhow. The heat generated is insane.

Towing at highway speeds in not the worst. City driving or creeping at gross is the worst. I mispoke.

You would not like a converter that is too efficient. You actually need a little ineffeciency. Its easier to spool your turbo with a loose converter.

 

Wow. Learned something new. Does anyone here remember switch pitch converters? Both tight and loose.

Tighter does make less heat at highway speeds but looser launches better. Loose for launch tight for top speed. Driving is like launch after launch. Stop sign to stop sign. Light to light. Too tight would drastically effect driveability for us. Ive known people who went tighter and had severe overheating problems. Bad stator probably. I just assumed it was the efficiency.

 

Despite the rhetoric, the orginal thread topic has a valid point. The auto will make more torque than a manual transmission.

Explanation: A TC is, by intentional design, meant to work at 0% efficiency. That is, when you come to a stop at 800 rpm in idle, there is no power transferred to the transmission axle.

At the opening moment that you step on the gas, this is what occurs:

(a) Your impeller revs up to at least 1400rpm or a bit higher
(b) The reactor locks
(c) The turbine, connected to the transmission axle is motionless

At this point, here is what is true:
1- NO power is being transferred (virtually 0% efficiency)
2- Fluid is being accelerated and flung through the reactor and to the turbine with a tremendous force
3- That force is roughly equal to the magnitude of the torque from the impeller added to an equal but opposite torque at the reactor
4- The torque being "felt" by the turbine is tremendous, and is usually 2x or more than the output torque of the engine at the impeller

Of course, you all realize that you can exert TREMENDOUS torque on a gear and have COMPLETELY 0% efficiency, or very low. That is what ALWAYS happens when first starting to turn a gear. Lots of torque. Little power efficiency.

The manual clutch works very similarly. As the clutch first engages, the engine rpm is higher (about 800 rpm to 0 rpm). The friction is first started to be applied at the plate. Virtually NONE of the power is transferred. But only a portion or fraction of the torque is applied. As more friction occurs ... a larger % of the torque is applied.

This is true:
* - a manual clutch can only ever apply a fraction of the engines torque while engaging the clutch
* - a auto TC ALWAYS applies more torque than what is output from the engine

LH and ga302 are simply incorrect. I don't know what else to tell you.

The % of power being transferred through (which is 0) is not pertinent to the fact that major torque is being applied through the TC.

The "multiplication" of the torque is from the output of the impeller ... to the turbine.

The "percentage" inefficiency of the power is between the engine axle and the transmission output axle.

At tow-start we have near 0 to 1% efficiency in the TC .... and about 2x or more torque being applied to the turbine.

That is how it works.

 

LH, your almost there, you just need to put the rest together. Tight, loose have no real meaning and are very vague.

Using your words a tight converter is has a low stall speed and a loose converter has a high stall speed. I see all to often someone build a big cam motor, mate it to there stock tranny and wonder why they can't get it to idle in gear. Well duh, everything is a system and when you change on thing you may need to change another. My guess is this is why you where running around at idle at 20.

Again this has nothing do with effeciency. Anything at or below stall is not effecient and is not even measured. It is only after stall that it is measured. Effeciency is the theoretical difference between what the fuild coupling is and 1:1. Without lockup there is always some slippage. Or another way to put it, the amount of slippage is what determines efficiency. When you see a torque conveter with a effeciency rating of say 88% this you are loosing 12% at speed. That 12% is going up as heat and robbing you of gas mileage. Hence the reason for lockup up converters. The more effecient you make it the cooler it will run. Modern torque converters can achieve 97-98% effeciency prior to lockup.

Max multiplication does happens at the rated stall speed of the TC. Sure anything below stall has multiplication, but you will only see max at stall and WOT. This is why we pick in general a stall speed that matches our peak torque point and select the largest muliplyer we can. This allows for the best acceleration provided we do not exceed the traction of the tires.

What you see happen all to often here is people who put to large of TC in, i.e. high stall. The reuslt is it feels really quick but you get no speed. Also they tend to burn the tranny up very fast because at speed they never get past stall. These is also why when you put a big stall converter in, of course matched to your power band and rear gears you upgrade the cooling capacity on the tranny.

As an example take my 502. Its power band is from 3850-5500, 610lbs@3850, 593hp@5500. I run 4.10 and at 70 I'm about at 2800 rpms. With this motor I need to run at least a 2500rpm stall converter but I can't really run a 3800rpm without changing gears. It would be sucide to run this on the street with a stall of 3800, i'm not sure I could keep up with the heat.

So I will compromise and run some where between 2500 and 3000 with the most effecient and highest multiplication TC I can get. In addition I will be putting a big cooling system in place because for a lot of the time I will be at or below stall speed.

 

Do you have any advertisements for the 95%+ converters. I have no experience with them. The smaller converters it appears will generally have the higher stall but less efficiency.

The 20mph tc had a high efficiency value but perhaps a lame stator.

The less efficient converter will launch better. It will generally have a higher torque multiplication.

I did happen across the information that only two aftermarket companies actually have their efficiency tested correctly. Everyone else makes guesses. The machine used to test tc efficiency is one million dollars. AFAIK only the big three own one of these machines. So you have to pay for test time. Otherwise they just see how much rpm it loses in lockup. Same with flash stall and true stall. Rough estimates.

 

Here is the problem. The auto makes more torque for a split second. That is a fact. That is how it works. Its multiplication factor is 5.75 to 1. This is very close to what the manuals have for a first. So once up to peak torque. 1600 rpm for the cummins 2000 for the powerstroke. The torque will be more for the manual.

The original post is correct. The cummins with the auto has a higher torque multiplication factor. So it has more torque at the start of a tow. An auto equipped psd will have more torque than a cummins with the manual. But for a few tenths of a second. Assuming the driver of the manual did not rev the engine above 1400 rpm before engaging the clutch. In which case the cummins would have more. Also excluding the probable 10% energy loss of the tc. If you factor in the energy loss. The tables are turned. It all comes down to rear wheel torque and if the tc cannot transmit the power in a efficient matter. All of this is for naught. Energy transfer does translate to torque at the wheels. RWT. Which is what this discussion was started about. The more efficient tranny will have more RWT.

Has anyone located efficiency ratings or the true stall of the tc in the TS?

I think Im looking at the problem wrong. We know that an auto eats torque. Or hp depending on how you look at it. Until it reaches lockup. Even in lockup it wastes more hp than a manual but not near as much as before lockup. An auto equipped PSD should lose about 30hp just to the tc before lockup. And that is when the tc is at its most efficient. If you were towing heavy. You might miss that 30hp. Thats power that a manual could transfer to the ground and an auto cannot.

Everything for OTR trucks is about fuel economy. That is why they do not have autos. They cannot afford to lose the mileage to something that converts energy to heat. Just think of how much fuel you are wasting by throwing that 30hp into the tranny cooler. What a waste of good hp. Id rather put it to the ground.

 

Now, LH, you know better than that. The mulitplication drops linearly from max down to 1x, while the efficiency rises exponentially (or actually w/ a 3rd order tail-off) to about 90%.

TEST: Here's how you can test the utter brilliance :-) of this thread topic. Push the 4x4 button and lock the truck into 4-wheel drive. Hold down the brake in the PSD with your left foot. Hold it down hard. Rev up the engine to about 2100 rpm. Hold on to the steering wheel tightly. Let go of the brake.

At that moment, and for about the next 5 seconds ... you will feel something you've probably never felt in a big truck before.

The turbine starting at 0rpm. The impeller is chugging at 2100 rpm. As you launch down the road ... hum the theme-song from TopGun to yourself.

Wave goodbye to the anything-with-manual you see in your rear view mirror.

 

Obviously if you dont know how to shift then the auto is better. The torqe multipacation in the auto does not come out at the rear wheels as more torqe. This is proven, it only counteracts the power loss from the torqe conveter.

 

ferracing66 - the torque converter doesn't multiply the torque to the rear wheels? What on earth was I thinking! Now you have me wondering. All those machines out there using hydraulics and hydraulic principles ... and those dealers who recommend autos for towing ... what are these people doing?

You've convinced me. Going to trade in my PSD/Auto this weekend for the standard transmission .....

 

LOL.

PSK. Another thing to consider. When the flash is present. The turbo most likely isnt spooled. So during the time the tc multiplies the most. The engine makes the least. Powerbraking would be a good way to get at peak mulitplication and peak torque. Im pretty sure that you will find it takes less than 5 seconds for the back half to catch up with the front half. Not sure if that was what you were implying.

You are correct. Multiplication drops off linearly. But, Very quickly. By 2000 rpm. It is no longer present. Save for a flash stall. Efficiency also increases linearly. From about 60% at 1500 to 90% at 2000. Not just lost rpms. Lost energy. I will try to locate an efficiency chart of an average tc. Thats why so much more heat is created at low rpms. A lot more converted energy. About 30% more.