RollTideRam
Veteran Member
These tractors both have the same yanmar engine. Reckon why the 2520 is rated at 26.5 hp and the 790 is rated at 27 hp. I just noticed this and wondered why. JC
790 and 2520
- Thread starter RollTideRam
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jeffinsgf
Veteran Member
That is the infamous "HP loss" from gear drive to hydro drive.
OP
RollTideRam
Veteran Member
I thought the pto hp would be where the loss would come in. 20.5 on the 2520 and 24 for the 790.
rockyridgefarm
Elite Member
The hp numbers are stated at certain rpms. The engine speed chosen may be different. Also, these are 'manufacturer's specs' which are subject to change. Finally since when did anyone trust any JD marketing number? They make some of the funniest mistakes and repeat them over and over...
I can't believe you would say anything against JD. Do you want bared from this forum??? No body would dare say anything but good about them here. Well, anyway to read some posts it would seem that way. I'm not sure anyone would notice 1 hp on the tractor anyway, it really isn't very much anyway. And who could prove what it really is, it would cost more than it would be worth.
rockyridgefarm
Elite Member
HA! Bar me? Who would keep you in line, Prunty? 
jdbower
Platinum Member
I'm guessing it's like the old car HP claims. They used to claim HP from the engine rather than at the wheels, a 300HP engine may only be 250HP after the driveline strips some power away from it. Once they were forced to advertize the power at the wheels, you not only needed a good engine but also a good transmission to be considered a fast car. Since the 2520 and 790 have different drivelines I'd expect different values, but there may be more to it than that.
The engine itself is rated at 30.2HP@3000RPM (assuming I've got the right engine link below). The 790 has 27HP and 24HP PTO and is rated at 2700RPM, the 2520 is 26.5/20.5@2600RPM. The loss in HP from the 790 to the 2520 is probably due to differences in the drive train, but mostly because of the lower RPM rating (Why the lower RPM rating? Could be for longevity or just to reduce the power rating of the 2520 a bit so it doesn't eat into the low-end 3x20 market as much.).
http://www.yanmar.com/store/item.asp?ITEM_ID=45&DEPARTMENT_ID=55
Digging a little deeper, we can look at the power in kW. The 790 is 17.9/17.6kW but the 2520 is 19.8/15.3kW. Needless to say, something's amiss here. If 1kW is 1.34HP, the 790 using metric should be 24/23.6HP and the 2520 should be 26.5/20.5 (which matches advertised US values). Needless to say, it does throw a larger question into the 790s specs, especially for the non-PTO HP claims.
The engine itself is rated at 30.2HP@3000RPM (assuming I've got the right engine link below). The 790 has 27HP and 24HP PTO and is rated at 2700RPM, the 2520 is 26.5/20.5@2600RPM. The loss in HP from the 790 to the 2520 is probably due to differences in the drive train, but mostly because of the lower RPM rating (Why the lower RPM rating? Could be for longevity or just to reduce the power rating of the 2520 a bit so it doesn't eat into the low-end 3x20 market as much.).
http://www.yanmar.com/store/item.asp?ITEM_ID=45&DEPARTMENT_ID=55
Digging a little deeper, we can look at the power in kW. The 790 is 17.9/17.6kW but the 2520 is 19.8/15.3kW. Needless to say, something's amiss here. If 1kW is 1.34HP, the 790 using metric should be 24/23.6HP and the 2520 should be 26.5/20.5 (which matches advertised US values). Needless to say, it does throw a larger question into the 790s specs, especially for the non-PTO HP claims.
