Engine/Transmission (1998.5 - 2002) Reality check - power loss thru transmission, Auto vs manual...

[Gary - K7GLD]

We often recklessly toss around numbers and percentages of power loss thru trannies, autos vs manual - 5 and 6 speed - but in point of fact, with the newer and heavier manuals, how much percentage difference IS there, really?



Sure, in passenger vehicles and their more lightly built manuals, the difference might be greater - but take a look at the sheer MASS of a 6 speed NV5600 or 4500, and imagine the power required to spin all those gears, as well as the heavier flywheel, clutch and pressure plate...



Is there REALLY as much difference as we have thought? Ken at Ken Imler's performance diesel specifies 25-30% power loss even thru a manual transmission such as ours - past percentage figures usually ran around 15% or so loss for manual trannies, 20% or so for auto trannies, but we now have larger and heavier manual AND auto trannies with OD - what do you fellas think?



I suppose a comparison based upon dyno readings, stock, auto vs manual would provide a clue. my own truck with the Comp and boost elbow added, Comp switched off, made an indicated 204 HP at the rear wheels and 437 ft lbs torque - but that's misleading, since max boost pressure was well above stock even with the Comp switched off... That compares with the factory rating of 245 hp and 505 torque at the flywheel...



These 5 and 6 speed trannies are certainly NOT lightweights!

 

[jlccc]

Originally posted by Gary - KJ6Q

Is there REALLY as much difference as we have thought? Ken at Kem Imler's performance diesel specifies 25-30% power loss even thru a manual transmission such as ours - past percentage figures usually ran around 15% or so loss for manual trannies, 20% or so for auto trannies, but we now have larger and heavier manual AND auto trannies with OD - what do you fellas think?



These 5 and 6 speed trannies are certainly NOT lightweights!

Your HO has 245hp peak at the flywheel. Most of the 4x4 HO's I've seen in stock trim dyno about 220-225rwhp. So that's a loss of about 10% through the ENTIRE DRIVETRAIN (tire deformation, u-joints, carrier bearing, transfer case, transmission, differential, etc). Losses through just the NV5600 transmission should be less than 5%.



In my business we use a lot of large gearboxes. We always treat them as having 95% mechanical efficiency when selecting drive motors. I can't see a transmission as being much different.

 

[Gary - K7GLD]

We sure aren't seeing any 225 STOCK rwhp readings in this area from the HO's - at least not the couple of times *I* was at the dyno - any in this group who dynoed that high STOCK 4x4 wanna chime in?



As far as selecting gearboxes and projected power losses thru them, should we assume we will see the SAME 10% power loss thru a model A Ford transmission at, say 2000 rpm, as we would thru the 6 speed in our later Dodges? After all, a manual is a manual - 10% is 10% - OR, does size/mass really matter in the equation at some point... ?

 

[E7mack96]

Bone stock, My H. O. 6 speed dyno'd right at 200 wheel hp.

 

[jlccc]

Originally posted by Gary - KJ6Q

As far as selecting gearboxes and projected power losses thru them, should we assume we will see the SAME 10% power loss thru a model A Ford transmission at, say 2000 rpm, as we would thru the 6 speed in our later Dodges?

On a percentage basis, they are probably pretty close. Keep in mind the losses come from varying sources.



Disk friction

The very action of a large disk spinning in a viscous liquid is one source of loss. Assume two disks of equal mass but different diameter. The one with the larger diameter will generally have the highest disk friction at the same rpm. Two disks of equal mass and the same diameter, but turning different rpms, the one turning faster will have the higher disk friction.



Viscosity losses

Higher viscosity lube will also use more horsepower, all other factors being equal.



Gear face width

Two gears, identical in diameter but one with a wider face than the other, the wider faced one with use more horsepower to turn (generally this is a viscosity phenomenon though).



bearing losses:

The transmisson with the larger bearings will require more power to turn, but as a percentage of the transmitted hp it may be a wash between a HD and light duty transmission.



Gear tooth profile:

Helical gears vs bevel gears will have an effect.



Number of stages of reduction

How many stages of gear reduction are required to reach the final output speed? Most transmissions are single reduction. Add in the transfer case and you have a double reduction gearbox though, which has more losses.



Total power transmitted.

Assume a model A gearbox transmitting 10hp. Transmit the same hp through an NV5600 and the NV5600 has HUGE losses compared to the total power transmitted. But transmit 200hp through the NV5600, and on a percentage basis, the two transmissions are probably fairly close to the same.



Consider two NV5600 transmissions, each transmitting 200hp, but one at 1700rpm and the other at 3000rpm. The one transmitting the hp at the lower rpm MAY have greater efficiency.



Finally, consider an NV5600 transmitting 200hp and one transmitting 400hp. The one transmitting 400hp is probably more efficient because the fixed losses at a certain rpm are a smaller portion of 400 than 200.





In short, all you can have is a "rule of thumb. " Every thumb is different.

 

[Gary - K7GLD]

*I* would think, in the above illustrations, the *RPM* the two trannies are operation would TOTALLY determine the power required to drive them, irregardless of the potential power of the engine involved - after all, the transmission doesn't know how much power the drive engine has - all it knows is how much drive power it consumes at a specific speed.



If a vintage lightweight 3 speed manual requires LESS power at any given speed to operate than a larger, heavier modern 6 speed, then the larger transmission must ALSO be CONSUMING a higher percentage of power at any given speed than the smaller one - at least that's the way I see it... old age, Alzheimers, etc...



... Which was my point in regards to using earlier adopted percentage loss figures that were being loosely applied to smaller passenger vehicles transmission losses and then applying them to our trucks.



I feel it's an apples/oranges thing, and the percentages used to compare power losses in 2 identical Dodge/Cummins rigs - one with and auto transmission and the other with a 6 speed, would probably be much closer than we think, than the percentages used to estimate passenger car drivetrain losses.



A few stock dyno run numbers between similar manual/auto equipped trucks would pretty well tell the tale - any more out there?

 

[Brandon]

25-30% loss on a manual... ... ...



bs, no way that would mean my little sickly 160 pump would loose anywhere from 100-150 hp just in the manual. I dont think so

 

[Wiz]

A year ago my stock 2001 dyno'd in at 202hp, which is about a 20 % loss.

 

[phoekema]

auto vs. manual losses

I have got to believe that since the advent of the lockup converter, the playing field has been leveled considerably between auto vs. manual efficiency.

The torque converter is an advantage when first getting going, but the auto does have a pump running all the time. Generally the manual has thicker oil/grease which take more energy to turn especially in the cold weather. There are many considerations, but in general we don't have to pay the price we once did for the convenience of an automatic. At this point in the state of the art, the losses have to be very similar overall.

There are other considerations that have nothing to do with efficiency too... ... ... ... ... ... . with a turbocharged engine, you can keep up the boost with an auto much better than the manual when shifting.

 

[Jeff Knight]

I have a Jardine 4" exhaust and Afe megacannon. My truck dynoed at 232 rwhp. The truck has 4. 10 gears in it. Jeff

 

[AlFischer]

I have often heard that an automatic will be overall more efficient than a manual because the AVERAGE person does not know how to us a clutch and manual properly.

 

[jlccc]

Originally posted by Gary - KJ6Q

*I* would think, in the above illustrations, the *RPM* the two trannies are operation would TOTALLY determine the power required to drive them, irregardless of the potential power of the engine involved - after all, the transmission doesn't know how much power the drive engine has - all it knows is how much drive power it consumes at a specific speed.



If a vintage lightweight 3 speed manual requires LESS power at any given speed to operate than a larger, heavier modern 6 speed, then the larger transmission must ALSO be CONSUMING a higher percentage of power at any given speed than the smaller one - at least that's the way I see it... old age, Alzheimers, etc...

Read my reply a little closer and you'll see that's what I said. Yes, the larger transmission has a greater loss than the smaller transmission for any given speed. But, on a percentage basis of the total hp transmitted, they are likely very close to each other. The model A transmission probably only transfers what, 20hp? Your Dodge transmits 10 times that amount. So it's entitled to 10x the losses and still have the same "percentage" of losses as the smaller transmission.



jrp

 

[Gary - K7GLD]

"25-30% loss on a manual... ... ...



bs, no way that would mean my little sickly 160 pump would loose anywhere from 100-150 hp just in the manual. I dont think so"



Well, atleast 2 of us so far have fairly well documented that approximate 20% loss - but the above quote DOES bring up an excellent point...



As previously discussed, relative power drain thru ANY transmission, manual or auto, is basically RPM dependent - NOT HP dependent past the threshold point required to reach a specific RPM...



SO, if your dyno reading indicates, say, 100 HP at 2000 RPM - and you dutifully compute a 20% loss thru your manual transmission - for an estimated 120 HP at the flywheel, which means 20 HP lost to the transmission... . THEN you make radical power upgrades to the engine, and another dyno run that gives you 1000 HP at 2000 RPM - everything else is still the same... You CERTAINLY don't STILL use that same 20% correction factor for the transmission losses - shucks, that would now mean *200* HP lost in the same transmission at the same RPM!



THAT sure ain't right!



Instead, once basic power loss at specific RPMs is determined for the drivetrain, THAT power loss remains essentially CONSTANT at those RPMs, regardless of the power applied to REACH those RPMs... Oh yeah, I'm sure increased loads at the higher power levels translate into higher friction and load losses - but surely not in a direct proportion to power applied and RPM delivered...

 

[JyRO]

Ho hum ...

I noticed the grass was getting a little high under my 5'er ... irregardless (is that a word?) I think I'll get eat some ice cream. Who's with me?



- JyRO

 

[phoekema]

Grass under 5th wheel

JyRO,

Boy, I had better move to Adrian. Here in good ol' Grand Rapids, the ground is covered with that horrible 4-letter word , snow.

Ice cream is no substitute for camping, but I guess it is better than nothing. Now if you are eating ice cream A N D camping too... ... ... ... ... ..... thats living! Have to wait a while for that, I guess.



Paul H

 

[JyRO]

Not so much snow...

Phoekema,



We've had some melt, but I don't think we ever get as much snow as you guys further to the west of MI. Regardless, I can still see grass under the 5'er and around the outside edges.



Man, nothin' better than a bowl of ice cream, outside while your camping, with a lit fire and the sun going down. Ahhhh... . camping... .



- JyRO

 

[Brandon]

i meant drivetrain loss would be 100-150 hp(loss)





NO WAY!

 

[klenger]

I really doubt that a manual transmission has anywhere near the power loss of an auto. Have you ever heard of anyone overheating a manual transmission? Why do they install coolers on auto trannys but not manuals. Also, power loos to the rear wheels is not all lost in the transmission. There's the transfer case (remember 2WD's get better milage than 4WD's), the front axle turning in a 4WD, rear axle, u-joints, wheel bearings, etc.

 

[Boldt's Wagon]

Since power loss or drive train efficiency is rule of thumb, I have a handful of thumbs (IMHO) on the topic.



I would guess that total drive train efficiency for a manual transmission is 85 %. Where about 5% is lost in the transmission, 7% lost in the differential gears, and 3 % lost in the wheel bearings and tire flexure.



An automatic transmission in lockup has a hydraulic pump running all the time and the efficency loss would be another 1-2 % for 83-84 % total drivetrain efficiency. 6-7 percent lost in a TC locked auto.



An auto transmission without the torque converter lockup is about 75 % total drivetrain efficiency with the stock TC. A DTT TC I would expect might give a total TC unlocked drive train efficiency of about 80 %. 15 to 10 percent lost in an unlocked TC automatic.