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Discussion Starter · #1 ·
Anyone have any thoughts on why TK would drop torque down so much on the new model? I know they have a new Kubota engine in this model but what aspect of the new Kubota warrants the big drop in torque? :confused:
 

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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.
 

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Discussion Starter · #4 ·
AWJ, my question wasn't why does a smaller engine have less torque, it was why would TK go with an engine that has less torque when usually you see new models trying to up all the specs slightly. Thanks Northmiss, it sounds like they made the change to get tier 3 compliance.
 

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Unfortunatley engineers build skid steers and that was what they felt was the best match.
Bobcat uses the same engine in there 330 series as well.

Yanmar supplies all of the engines(Tier III) across the board so not sure why they did not step up on the big engine.
Maybe it was not ready for production?
On there website they no longer have that series engine listed.
 

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Maybe the Torque rise is higher which sometimes makes up for a lower number. I know the torque rise is a rating that is never displayed in earthmoving equipment but is bragged about in the agriculture market.
 

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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.
 

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As far as AWJ's idea that torque is 100% related to engine size, that really isn't true.
Well of course not when you are comparing a non turbo too a turbo engine.
Torque is 100% related too engine size.The larger the engine the more torque.
Engines will make a certain ft/lbs per cubic inch and there is a maximum that they will make.Thats why we have bigger engines and not just bigger turbos.
On the other hand Hp is a derivitive of torque and rpm so you can make the same torque but not the same hp or vice versa as in the case of the smaller Kubota engine.
 

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Most engines will max out the torque in the 1500rpm range. The higher the rpm the more H.P. but not exactly more torque. But depending on the fuel ratio vs cubic inch the engine will spec better on the torque curve. The difference in torque specs per cubic inch is when one engine has ...example 80 hp @2500 rpm or another engine will have 80 hp @ 2000 rpm ......
 

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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.
 

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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.
I agree... torque is not necesarily related to engine size when you have a turbo. I had a dodge cummins w/ factory 500ft tq... added another turbo... and 1400ft tq on the dyno.
 

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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.
 

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You guys read sales literature and drive heavy equipment.
I actually build race engines and have a engine dyno, a cylinder head flow bench and a fully equipped shop.

Don't patronize me.
I don't have any literature to back up what I am saying just a dyno. I had a stock cummins 5.9 that put MAYBE 500 ft tq stock... then added injectors, fuel pump, other goodies, and compound turbos. Torque went from 500 to 1400 to the wheels.

Don't you think the amount of air you can cram into a cylinder via turbo(s) has something to w/ output? With your thinking a turbo is waste of metal.

Turbos are gooooood!!!

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So you are suggesting that you can use a smaller engine and just add a bigger turbo?
Do you not think that if you done the same thing with a larger engine then there would not be an increase in torque?
Yeah I see your point. Might the smaller one be more efficient... (just a question not being a smartazz). Also, I can see the advantage of having a smaller turboed engine in a skid.

But back to the original point when you throw turbos into the mix... cubic inches and torque don't always correlate.
 

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Plus I will add that if you stuck that engine in a steady state application it would burn up pretty darn quick.
There is way more too this than you think.
I am in no way trying too be argumentative just that I really understand this stuff.
Well I think there is a balance... don't you think turbos create an efficiency factor? I guess the larger engines won't have to work as hard as the smaller one and the life span will be more. They say there is no replacement for displacement. I guess it also really depends on how well the bottom end is built... some motors can expect more of a lifespan than others.
 
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