Engine changes to Diesel x7xx series.

[JDTank]

I just noticed, for 2011 onward, the diesel engines in the x7xx series garden tractors are now smaller.

2006-2010 power-plant:

YANMAR | 3TNV76-CSA

2011 - current power-plant

YANMAR | 3TNM72


I am on the verge of ordering my new X740, probably in the next month or so, and I am wondering if anyone who has a 2011 or 2012 machine has noticed the drop in HP and torque? Given that this is such a small engine, the loss in 1 and a half ponies shouldn't even be noticeable, but then again, it never hurts to ask.

I noticed in the new engine, the stroke is shorter, AND the bore is smaller. The max RPM is now 3600, vs the older engines 3200 RPM.

Horsepower Ratings:

2006 - 2010 = 25.1 HP
2011 - current = 23.6 HP

Torque Ratings:

2006 - 2010 = 49.1 ft pounds at 2,300 RPM
2011 - current = 40.9 ft pounds at 2,600 RPM

Also, the new engine is a whopping 74 pounds lighter! They dropped a 243 pound engine, down to 169 pounds....that is a HUGE weight savings, and it scares me to death that they sacrificed strength for weight savings.

Some other significant differences:

- New engine has electric fuel pump, old engine had a mechanical fuel pump.
- New engine has a 20 amp alternator, old engine had a 40 amp alternator.
- New engine has a 5 blade, 290MM cooling fan, old engine had a 7 blade, 335MM cooling fan
- New engine holds more oil then the old engine, numbers are conflicting between the brochures and tractordata.com information
- New engine dimensions - Length: 17.7 in, Width: 15.7 in, Height: 19.8 in
- Old engine dimensions - Length: 22.4 in, Width: 16.9 in, Height: 22.6 in
- New engine is part of a Yanmar series called MINIMAX

The reduction in physical size is quite impressive, not only in weight, but look at the differences in the dimensions, almost 5 inches shorter then the older engine.

Looking at the brochure, it looks as if this new engine is substantially quieter, and half of the engine is a new, better design, with better valves and less chatter as well. Who knows, maybe with it being a bit smaller, it will be even better on fuel then the old ones, and they were impressive on fuel consumption themselves.

So, does anyone have any experience with the new, smaller Yanmar diesel?

 

[Deere Dude]

I have a 2009 and was going to get a new one and trade in the old one but I may hold on to it for the time being until I read more about this. I know mine has a lot more power than the 2005 or 2006 model I had previously. I thought they would all have the same HP and torque, but I guess not.
I am going to follow this post for a bit.

 

[Bigkrank]

They are both indirect injected engines.

This will probably not apply in your situation or use but something to think about anyways. The similar direct-injected 3TNE78 engines are used in tractor pulling. They are rather weak in the cylinder area compared to a Kubota or Shibaura. Guys are splitting them apart between 1 & 2 cylinders. They have to pour the blocks and run them dry to stabilize the cylinders.

Myself I would be a bit leary of using a lighter yet version of this engine but as I said maybe in a bone stock situation there may be nothing to be concerned about.

 

[JDTank]

They are both indirect injected engines.

This will probably not apply in your situation or use but something to think about anyways. The similar direct-injected 3TNE78 engines are used in tractor pulling. They are rather weak in the cylinder area compared to a Kubota or Shibaura. Guys are splitting them apart between 1 & 2 cylinders. They have to pour the blocks and run them dry to stabilize the cylinders.

Myself I would be a bit leary of using a lighter yet version of this engine but as I said maybe in a bone stock situation there may be nothing to be concerned about.

In all honesty, I wouldn't expect ANY engine of this size to last when your in pulling competitions. These are lawn mower engines, not class 8 highway diesels.

I appreciate the information nonetheless. I am more concerned with leaving the machine bone stock and getting 5,000 hours out of it.

 

[Bigkrank]

I would be more worried about needin a new butt if your going to sit on that thing for 5000 hours

 

[JDTank]

I would be more worried about needin a new butt if your going to sit on that thing for 5000 hours

In 30 or 40 years, I will need a new butt regardless :laughing:

 

[Gonerafting]

Save your butt, just changed over to the Deluxe Seat (Air Seat), well worth it! PS: I have a 2010 and do not know if the changes really matter, the heavier weight of my motor just means less weights if I decide to pull implements and for snow plowing putting more weights on the back. In my case, heavier is better. All things continue to improve, I would not be concerned about the engine change. I would be looking at model differences, I sure wish I could have justified an X749! As far as the alternator differences, I thought all the diesel came with the 40amp or is it now an option?

 

[psdx]

The displacement is 25% less and the torque drop is roughly 20%, and the peak is now at a higher rpm. I can't imagine you could help but notice that difference when cutting tall grass. The general direction over the past 30 years or so has been smaller displacement and spinning the motor faster. I can remember tractors running at 2100 rpms for the 540 PTO output. This is just another step in that progression. I'm guessing this large of a step must be related to emissions?

 

[murphy1244]

2006 - 2010 = 49.1 ft pounds at 2,300 RPM
2011 - current = 40.9 ft pounds at 2,600 RPM

That would be the most concern for me

 

[JDTank]

Obviously it had something to do with meeting emissions requirements, but I honestly didn't think they would have gotten that drastic with it.

What I am very curious about is why the loss of 74 pounds. They dumped more then a quarter of the engines weight, in one redesign. What was that weight before, and where has it all gone? Being that the bore and stroke are smaller, it decreases everything. Smaller pistons/connecting rods in smaller cylinders, in a smaller engine block, with a smaller head. I guess I can see how losing a little bit of metal on a lot of parts could add up to 74 pounds.