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.

 

[Snobdds]

Yes there is more to it than just RPMS's.

There is different governor settings.
Different PTO gearing.
The injection pump is set a bit different to allow more fuel.

About 5 years ago there was a good detail done on the differences, there are more than I listed, but I think I hit the highlights from memory. In fact, there was parts listing on what had to be changed to get the extra couple of horsepower. The conclusion was, unless you use ground engaging attachments, you would never recoup the cost for the extra benefit.

 

[Username Taken]

Yes there is more to it than just RPMS's.

There is different governor settings.
Different PTO gearing.
The injection pump is set a bit different to allow more fuel.

About 5 years ago there was a good detail done on the differences, there are more than I listed, but I think I hit the highlights from memory. In fact, there was parts listing on what had to be changed to get the extra couple of horsepower. The conclusion was, unless you use ground engaging attachments, you would never recoup the cost for the extra benefit.

There's also injector timing and duration, valve timing and duration, etc.

And they may (or not) build the tractor around the engine to different specs to handlt the different power numbers. Differentials, axles, transmission, castings and frames might be different.

There's a difference. On my Cummins, I'm de-rated to 800 lb-ft of torque because of the transmission. Well.... It used to be de-rated, anyway.

IMO, These aren't like the old 70's chevy paint-and-tape jobs. I believe them to be real differences and you're getting what you pay for most of the time.

 

[daman1]

According to the service/shop manual I see no difference when it explains ignition timing or injectors and injectors pump or injector pop pressures etc between the two models.

Gear for ptos must differ the 25 models need more rpm at pto speed then the 23 models from what I can see

 

[RalphVa]

Same with Kubota B2301 and B2601.

 

[Username Taken]

Same with Kubota B2301 and B2601.

Different engines

TractorData.com Kubota B2301 tractor engine information

www.tractordata.com

TractorData.com Kubota B2601 tractor engine information

www.tractordata.com

 

[Snobdds]

From the past...

Found Actual engine torque/hp/sfc GC1710 vs GC1720. Also actual hydraulic flow to the

Found these in the engine service manual and thought they were worth posting. A lot of conclusions can be drawn from this data! My simple conclusion if your stuck between the 1705/10 vs 1715/20: If you are mainly using PTO attachments at 540rpm you will see just about the same power and much...

www.tractorbynet.com

 

[Snobdds]

According to the service/shop manual I see no difference when it explains ignition timing or injectors and injectors pump or injector pop pressures etc between the two models.

Gear for ptos must differ the 25 models need more rpm at pto speed then the 23 models from what I can see

Well, yes, all those are the same...however, the fuel shims are different and those give more flow through one pump vs the other.

 

[daman1]

fuel shims? I see no reference to any shimming in the injector pump, delivery valves and Springs, or governor ,etc are all showing the same throughout there's no deciphering between models whatsoever. If you have anything you could post to show I would be interested and making notes of it. From what I'm seeing there's nothing that deciphers the 1723 hp from the 1725 but RPMs so I'm just going to go with that

 

[cdaigle430]

Yeah there is some gearing thats diff in the transaxle, this was confirmed last time I asked the question. Still wanted to know if it was ok\safe to run my GC2410 at higher throttle to gain HP.

But it does look like the extra HP is gained by the gearing and not so much the injectors.....the engine does have to run at higher rpm to compensate for the lower gearing I think to gain the extra 2 hp.

So I think to gain low end they changed the gearing in the transaxle but to keep the high end the same speed(forward and reverse movement) they increased the engine rpm threshold?

 

[daman1]

That's what I'm thinking also, the 25 models are running at a higher RPM at PTO speed = more horsepower you would think. I wouldn't be afraid on a 23 model to run RPMs/PTO speed a little faster I do it at work all the time never a problem with anything