[northmiss]

I notice the 250 is tier 3 compliant. Emissions requirements often lead to engine changes in heavy equipment. The difference in engine operating torque is substantial in these two models--198 foot-lbs at 2600 rpm on the newer model, 232 foot-lbs at 2200 on the older one, both figures being gross torque before accessory power loss is substracted. I didn't calculate net torque since that number isn't supplied on the 150 brochure.

 

[northmiss]

Torque rise appears to be 25% in the old model, about 21% in the new so there would appear to be no advantage here for the new machine. Hard to know how important torque rise is for the machines these days. My dozer will only lug down about 100 - 120 rpm under a heavy load so it really doesn't back very far up the torque curve, and it never ever lugs down to peak torque rpm, so these peak numbers don't seem very meaningful to me. Since there appears to be no difference in these two loaders' fuel consumption, the only thing I can guess at is emissions difference warranting the engine change.
As far as AWJ's idea that torque is 100% related to engine size, that really isn't true. Many if not most manufacturers of heavy equipment will equip a given machine series with the same displacement engine and simply vary the turbo boost pressure (along with fuel delivery) to increase torque at a given rpm. The Deere 450J - 650J series dozers would be a good example of the idea. All have the same sized engines, but very different torque numbers.

 

[northmiss]

AWJ,
I think you prove my point by saying that a given engine will have different torque characteristics based on whether it is turbocharged or not. Torque is therefore not just related to displacement, but also to fuel and air flow (a turbocharger increasing the oxygen density in the cylinder) and to compression ratio. Obviously there is a limit to the turbocharging process, so that past a certain point a larger displacement is needed. Torque is not 100% related to engine size or displacement. Komatsu's latest 22 class dozers have REDUCED engine size to produce more torque, at least in the D37-EX22. You may want to examine their specs as an interesting lesson in mechanical engineering.

 

[northmiss]

Lawnworks, you provide an excellent example of the concept. Here is another interesting twist. Around about 2003 Cat added a turbocharger to the D3G 6 cylinder 5 liter diesel to aid with emissions compliance. It appeared there was no change to the engine specs at first glance: 70 net HP before and after. Yet the naturally aspirated engine produced the power at 2400 rpm, and the lightly turbocharged version at 2200 rpm for 153 ft-lbs and 167 ft-lbs operating torque respectively, almost a 10% jump in torque with turbocharging. Now here's the interesting part: the newly-released D3K produces 74 net HP at only 1900 rpm and a whopping 204.5 ft-lbs of operating torque, almost a 22% jump over the prior year's model, but yet with a 4 cylinder diesel with 12% less displacement (4.4L) than its 6 cylinder predecessor. This is about the clearest example I can cite of why the notion that "Torque is 100% related to engine size" is wrong. It is interesting that we use these machines every day but sometimes do not appreciate the mystery going on under the hood.

 

[northmiss]

AWJ,
Your original statement was "torque is 100% related to engine size." It is not. It may be proportional to engine size, but there are clearly other parameters. It is also untrue that one need have a larger cubic inch engine to have efficient spool through of air through the turbocharger, since one may modify parameters of the turbo to get efficient pressure delivery. This is critically important in an age of $5 diesel, since the end user will profit from having the smallest engine possible which will produce sufficient torque for the job at hand. This is why Komatsu has reduced its small dozer engine size to 3.3L from 3.9L, why Cat has reduced its 5 liter 6 cyl to a smaller 4 cylinder 4.4L in its finish dozers. The goal is producing fewer emissions, more power, less fuel consumption, and in dozers a smaller engine which sits lower in the machine frame to lessen center of gravity, hood obstruction of the blade etc. The benefits of optimized smaller engines here ought to be obvious. If you can't see this then just smile as you pay for all that red diesel.

 

[northmiss]

AWJ, I have to hand it to you: if stubborness is a virtue, you're a saint. I have just shown you that other manufacturers are producing small, high-efficiency tier 3 diesels TODAY. Why Yanmar's is not as efficient I can't say. Perhaps it is a cost saving move. But the Yanmar technology isn't the best available. Just compare the numbers as to what's possible: a) Takeuchi TL250, 3.8 liter Yanmar, 2600 operating rpm, 92 net hp (24 hp/liter displacement), 186 ft-lbs operating torque (49 ft-lbs/ liter); b) Komatsu D37-EX22 dozer: 3.26 Liter Komatsu, 89 net hp at 2200 operating rpm (27 hp/liter), 212 ft-lbs op torque (65 ft-lbs/l). THere is little question as to which engine produces more horsepower and torque, and little question as to the efficiencies that are now possible. If I could order the TL250 with the Komatsu engine in it, I would! But you can get the Komatsu dozer for the very cheap price of $96,000 as of last month when I checked. Smaller engine, more torque. How many examples do I have to give you?

 

[northmiss]

AWJ, the comparison I made was with SAE 1349 specs for both, Kubota engine notwithstanding. Our debate is NOT what you seem to contend, that a larger displacement engine with the same turbocharging apparatus will outperform a smaller one. There is no debate about that. The issue is how most efficiently to produce the requisite torque for a given machine application. This is the original question asked by Trailmaker: why did Takeuchi opt for a less efficient engine? If a 10,000# machine requires 200 ft-lbs of torque at operating rpm to perform its task, then producing that torque with the smallest possible engine delivers the best efficiency for the end user. Since torque is NOT 100% related to engine size as you originally asserted, we can move--and manufacturers are moving-- to the smaller engines. By your logic we could simply install a D8 Caterpillar engine in the little Takeuchi loader and produce more torque, but I sure wouldn't want to pay that fuel bill on that monster, nor try to transport it with a small trailer! If you can't see this what this debate is really about in these days of $5 diesel, then I wish you the best as you remain comfortable in your knowledge.

 

[northmiss]

AWJ, once again it is you who are confused. I have given up on trying to convince you, but for anyone else who may have interest in this topic I would suggest reading Nichols and Day's classic Civil Engineering Text "Moving The Earth: The Workbook of Excavation." Though there are many ways of defining the efficiency of an engine, this bible of excavation defines the efficiency of an engine based on its torque output, and in fact it suggest that an efficient engine will produce at least .625 ft-lbs torque per cubic inch, or approx 38 ft-lbs per liter (4th edition, page 12.114). Some engines produce more, some less but regardless of what size the engine is, efficiency can be standardized per unit of displacement. Notice that the definition does not depend on the size of the engine. This is why I compared the Komatsu 3.26 liter diesel to the 3.8 Kubota in the Takeuchi trackloader to show that the smaller Komatsu engine produces more torque per unit of displacement. Per Day and Nichols, it would be more efficient than the Kubota and in fact the Komatsu example produces MUCH more torque per liter than their minimum criterion. And it is interesting to see how much more efficient the newer engines are today compared to the criterion set forth by Day and Nichols as recently as 1999: 65 ft-lbs per liter of the Komatsu is some 70% more efficient than their minimum standard. Given the capability of the newer turbocharging and aftercooling technology, it is no mystery why the manufacturers are moving to smaller engines, and no mystery either why skid-steer and compact track loaders have become so popular in the last 15 years. Landscapers and excavators can do so much with these highly capable machines built around smaller high-tech diesel engines.

 

[northmiss]

MVERICK, you are right to say there is a lot more to this than engine size. More to the problem than just turbocharging, too. Volkswagen, Cummins, CAT and others have been steadily increasing the diesel fuel injection pressures to allow better atomization of the injected fuel the last few years. Greater fuel surface area in the combustion chamber means more horsepower and torque without increasing engine size. Same too with valve timing. Manufacturers of gasoline engines have been experimenting with variable valve (or cam) timing for several years to try to optimize air intake and exhaust outflow across the rpm band, with a goal of increasing low-rpm "grunt." A newer idea that has not yet made it to commercial-scale release is using a camless system of solenoids to actuate the valves electronically, to even more precisely calibrate airflow to the engine based on rpm. I first read about this as a Navistar proposal for its diesel engines. This too would increase power and torque output without increasing engine size. The more expensive fuel gets, the more we need to get beyond the big cubic inch mentality we've had about engines, and the technology is here to do it. All OTHER factors being equal in the past, more engine size meant more torque, but design engineers have been steadily varying those other factors to reduce engine size the last few years. That trend will continue.