Are some transmissions "dirtier" than others?

[sheepfarmer]

I got to wondering about the different kinds of new Kubota transmissions the other day after reading several threads regarding the typical time interval between regenerations. Within the L series, some folks have intervals around 10 or 15 hours, some are up in the 30 to 40 hour range. The engine design is similar, differing only in number of cylinders and presence or absence of a turbo. Almost all users report keeping the rpm's up, and actual "load" can't easily be assessed. It seemed like the L60 HST's had longer intervals, and some of the DT's were shorter, but don't have much of a sample.

About the same time I was thinking about this, I was following an old diesel semi down the road, and you could tell every time the driver shifted gears by the puff of black smoke out the stacks. So this made me wonder if certain types of transmissions, eg gear driven shifted with a clutch might cause the engine to emit more particles of soot than say some HST's? Or vice versa? My other observation was that loader work (lots of forwarding and backwarding) seemed to up the particle accumulation rate even with an HST.

I am clueless about how these new engines manage the air / fuel ratio during gear changes, can anyone help to see if this makes any sense? How different are the new gear shifting tractors from my old cars and trucks where you decrease the gas, depress the clutch, change the gear, and simultaneously increase the gas and let out the clutch? My old Ford 8n you had to come to a complete stop to change gears.

 

[Grizzy3901]

I'd have to say that the HST is better on emission than a gear shift. With the HST you are keeping the rpms up keeping a hot combustion and exhaust gas temps and can adjust your speed off how much you press the pedal. On gear shifts unless your at a constant speed in one gear for extended period of time your not doing that. Doing loader work for a majority of your time with a gear shift is were I'd see the most problems with regent emissions bc you are having to vary your rpms for shifting using the clutch. Just my thoughts

 

[KennedyFarmer]

My opinion, Little to None, The HST probably does have the advantage but by very little. Typically, the RPMs do not change while your changing gears. Now bogging down the engine, huge drop in RPMs, for a little bit will create more soot causing the filter to block up more.

A engine with turbo I would assume runs a little hotter and more effient which keeps the filter clearer.

 

[lugbolt]

HST should run longer between regen's. The charge pump puts a load on the engine. That and generally with an HST, you're going to have the engine RPM elevated and then regulate your speed with the HST pedal. This should keep the EGT's high enough for the soot filter to more or less self-clean, at least partially.

The larger the engine the less frequent a regen process should be needed. A 4 cylinder 60hp will need regen less than a 30hp 3 cylinder, for several reasons. And this is a generality. There are a lot of variables, how they're used, how they're loaded, fueled, what kind of oil and how much, etc etc.

 

[scdeerslayer]

The larger the engine the less frequent a regen process should be needed. A 4 cylinder 60hp will need regen less than a 30hp 3 cylinder, for several reasons. And this is a generality. There are a lot of variables, how they're used, how they're loaded, fueled, what kind of oil and how much, etc etc.

If they have the same DPF, wouldn't the larger engine need more regens since it burns more fuel? Also if they're doing the same work the larger engine isn't loaded as much. Hopefully it would have a larger DPF, but for series where you have a wide range of HPs in the same tractor, and likely the same DPF, it would seem that the higher HPs would need more regens.

 

[mdhughes]

If they have the same DPF, wouldn't the larger engine need more regens since it burns more fuel? Also if they're doing the same work the larger engine isn't loaded as much. Hopefully it would have a larger DPF, but for series where you have a wide range of HPs in the same tractor, and likely the same DPF, it would seem that the higher HPs would need more regens.

The higher HP engines create more heat in the DPF and you can get passive regen.

 

[scdeerslayer]

The higher HP engines create more heat in the DPF and you can get passive regen.

If the higher horsepower engine is doing the same work, and isn't loaded as much, is it still creating more heat?

From what I've seen on forums with the MX series, it seems that the MX5200 and MX5800 regen more often than the MX4800.

 

[sheepfarmer]

Regrettably it sounds like all we can do is speculate, but besides the heat produced, I was curious about the factors involved in amount of carbon produced. Except maybe research the part numbers to see if the dpfs are different etc.

There is quite the fancy computer controlled graph of the injection cycle, and there are 3 peaks in it, with a 4th being added for the regen cycle, but I just can't find out anything about what the computer does to this when the load changes when shifting or changing speeds. If anything. Maybe someone that works on cars will chime in, most everything has been borrowed from older auto technology.