How do you get different HP with same engine?

[Cityboyfarmer]

This may have been discussed before, but I could not find it in my search. Can anyone explain how the same diesel engine can be rated at different horse power in different tractor models?

For example, my 5205 has the same engine (2.9 Powertech) as the 5105 but has 56 gross HP as compared to 50 for the 5105. I assume the transmissions are the same, but could not tell for sure from the spec sheets on the JD web site.

I'm curious why two models are so close in specs. I recall other manufacturers do this as well. Is there a business/competition reason for this?

 

[MikeFromVA]

I bought a 4110 last year and it has the exact same engine as the 2210 which has more horsepower. The difference is the RPMs of the engine when they rate it. The 4110 uses lower RPMs.

 

[Bird]

I'm certainly no diesel mechanic, but there are a number of things that can be done to an engine to increase the horsepower. How about a different injection pump, different injectors, different exhaust, as well as the aforementioned different RPM? Of course engines with the same displacement can have lots of other things different. If I remember right, the first 5.9L Cummins engines in the Dodge pickups and RVs were rated at 160hp. What are they up to now? 325hp?

 

[JerryG]

They can have different pistons, different cylinder heads, different injector calibration, different turbo boost, different timing or any combination of this items.

 

[namuh1]

If there is no turbocharger, one of the key changes is the injector timing. Also, with JD's unlike, for example, Kubota, the horsepower rating is sensitive to the 'equiped' state of the tractor as delivered by the factory. John Deere's are rated with all of the equipment operational on the factory version of the tractor but Kubota's are rated 'bare' which means that there isn't even an alternator or any other auxiliary equipment on the engine when it is dyno'd. Last, it isn't uncommon for JD to derate an engine for the next lower model tractor and then bring size, pressure and injector timing up for the next model making the few % (you'd be surprised that you can make 20% the difference here!) horsepower difference. In general, the lower rated horsepower for the same engine (again without turbocharger) is the longer lasting engine. But if you are not a day in day out user, any JD will last your lifetime anyway. A cooperative mechanic can give you the HP boost if you really want it on almost any derated model but it can be expensive.

Cheers