Horsepower is horsepower?

wilber1 wrote:

Turtle n Peeps wrote:

wilber1 wrote:
That heat generated in the unlocked torque converter is lost power and if you insist on putting maximum power through an unlocked torque converter for an extended period, you will fry the transmission. Torque converters are great for getting things moving but not for extended use transmitting large amounts of power.

There is soooooooo much wrong with this post I don't know where to start?

Ok, line by line I guess?

Stop with the fry the trans BS because that is all it is, BS!! :R My T400 did just fine with the TC slipping all the time. 240K when I sold the truck and still going strong. More than likely 50+ towing. C6's, T400's, C4's, T350's, 727's; all slipped and they did just fine. To say you will fry your transmission if your TC does not lock up is either ignorance or hyperbole or both.

My chief complaint with my 2001 Dodge wasn't the 235 HP Cummins but the lack of gears in the mountains. I might still have that truck if it had the six speed that is in my new one.

Once again, gears don't make power. Cummins has one of the broadest torque bands of all the diesels. Would a 5 or 6 speed work better? Sure, but not by much. Your going to be in for a big shock when the Eyetallian Dodge goes up again the Cummins Nisan in a towing contest. 8 speed, 10 speed, 100 speed, it won't matter. 50+ HP is a bunch!

You only have 300 HP if you can get it to the ground. If you take away overdrive ratios, 4 speeds become 3 speeds, 5 and 6 speeds become 4 speeds and the 8 speed becomes a six speed. The 8 speed has double the chance of finding a ratio to get max power to the ground than the 4 speed and a 50% better chance than the 5 or 6 speed. There are times when that 240 hp engine with an 8 speed could be getting more power to the ground than the 300 hp with a 5 or 6 speed. And that isn't just at the 4000 rpm you keep going on about but anywhere in the engines power curve.

:R That has to be one of the silliest comments I have seen on this board. :R Do you really think more gears will overcome a 50+ or 125+ HP advantage?

I think the 5L Cummins is real overkill for the present Titan. Unless they really beef the truck up, all they will have is a very powerful half ton with less payload capacity than the gas model. Better to put it in a new 3/4 ton, then they would have a real bridge between todays 1/2 tons and SRW 1 tons, instead of the present crop of diesel 3/4 tons which are just SRW 1 tons with less payload capacity.

Are you kidding me? What the $%^#$*&^???? A very powerful half ton? ROTFLMAO. Aaaaaaaaaaaaaa look at what the EB and the Yoda is putting out and see if you say 300 HP is a very powerful 1/2 ton truck!

I'll have a lot of fun when PUT's come out with a towing test. I also hope they include the Yoda and EB and other hard hitters in their little contest!

If you try and put an engines maximum rated power through an unlocked torque converter for an extended time, you will fry the transmission. When I was dragging my fiver up 8% grades with my 4 speed I used to see post torque converter temps going above 250 all the time unless I backed off and shifted down to take the stress off the converter. That meant I could not get the engine to make its rated power because the transmission limited it. If I could keep the converter locked, temperatures rarely went up much more than 10 degrees. This transmission also had a double deep finned aluminum pan that held 4 liters more fluid than stock.

Torque converters are not 100% efficient. A typical converter might only be 92% efficient meaning 300 HP from the crank will result in only around 275 HP getting to the transmission. The difference is generated heat.

Let go over the relationship between torque and HP one more time.

The HO Cummins may have a fat torque curve but that doesn't mean it is producing a lot of HP. If you do the calculation, 850 lb ft at 1600 rpm is only 259 HP being generated.

Unless you have a gear available that will allow the Cummins to run full throttle at 2800 RPM, it ain't makin 385 HP

More gears don't make power at the crankshaft but they sure as heck put more to the ground, particularly the 8 speed in question. It only uses the torque converter when idling in gear and to get the vehicle rolling, just liked a conventional clutch, then it locks and stays locked until the vehicle stops. It makes locked shifts unlike our present transmissions which unlock, shift and lock again. ZF claims it takes 200 milliseconds to make a shift. Except for the pump required to supply pressure to do the shifting and keep the clutches locked, it transmits power as efficiently as a manual and shifts much faster than any human.

I think that 3.0 turbo diesel with the 8 speed will surprise a lot of people. We have reached a point in history where simply stuffing bigger engines in most vehicles is not an acceptable solution. New directions are required and I applaud Ford, Chrysler and Nissan for trying just that in 1/2 ton trucks.


Note
Edited torque converter efficency.

My 05 with the 4 speed runs 74 mph at WOT (full hp) in drive (an yes will run that towing my load if I pushed it). With factory tire size that speed was 70. My truck also shifts from drive to overdrive with the TC locked in TH.