GC Series - 23 or 25 HP from the same size engine: How do they do that?

[JerryC999]

From my reading, specs on the engines on the GC MF 23/25 horse tractors are the same. But the higher horse engines run at a couple hundred higher rpm. What all is going on with that? I have a GC1715 (with about 20 hours on it now), so I get that extra couple of horses, but I don't understand how.

And a related question about RPMs: They say breaking the engine in means that you run it full throttle for the first 50 hours. Does that mean all the time? When idling? Just when under load?

 

[tibadoe]

The extra hp on the 25 engine comes from running at a higher rpm - that's it. They set the governor higher to accomplish that.

As far as the full throttle until 50 hours - I still vary it a little. I go through warm up at a lower throttle and bump it up until finally reaching the green zone. I still vary the rpms a little while riding around - just no lugging.

 

[JWR]

A lot of tractors in the last 10 to 15 years -- big and small -- use exactly the same engine but with horsepower ratings that vary over quite a surprising range of HP. The timing and duration of injection bursts (plus many things I do not know about) are controlled electronically and the chips or other electronic controls vary to get the different power out of the same mechanical engine. I know this was true on the larger MF 2600 series 10 years ago and is true on other newer 3 cyl. MF engines if you read the specs carefully. It's neither a governor issue nor an rpm issue , it's programming, software and electronics. They may change the rated rpm numbers some but that is not why your horsepower is changing.

 

[JerryC999]

And so it all begs the question: If this is simply tweaks to the same engine, why not pick the optimum tweak for durability and function, and stay there? If my 1715 is tweaked to deliver a couple more horsepower, does that come at the cost of longevity?

 

[daman1]

On the GC series subcompact from what I can see the difference in HP is RPMs only, as this engine is a mechanical injected DI design no electronics or computer management controls that I can see on my GC1723EB.

I think when they say full throttle they mean when working the tractor, you can idle to warm up or stopping for a moment.

 

[mgstevens]

I'm not sure about these small diesels but when I had my Cummins 12-valve, you could go from 215HP to 1000HP by goosing the fuel and air intake volume. In newer diesels, a computer controlled intake system does the same thing with a "tune.' So diesels can have a power output range within a given displacement based on the fuel and air applied. I agree that in these engines, it is only a governor difference, but it is also only a 2-3 HP increase and at that, what's the point?

 

[flyerdan]

It could be that they have a derated version to defeat some municipality requirements. Remember when Johnson and Evinrude made the 9.9 hp outboards? If I recall that was to get around some state's requirement to license a boat with ten horse or larger engines.

 

[Dmacleo]

anyone check fuel injector part numbers between the 23 and 25hp versions?
that little HP easily could be done simply with different injectors.

 

[daman1]

anyone check fuel injector part numbers between the 23 and 25hp versions?
that little HP easily could be done simply with different injectors.

Hmmm good question

 

[kenmbz]

I know the PTO gearing is different too, to make up for the difference in Revs.