What makes/models are in that bigger/heavier/more capabable than a sub compact, and still in the cheap, small range? I assume the 25hp emissions stuff is the reason for a significant price jump right at that border line.
Bare tractor weight is a tractor specification easily found in sales brochures and web sites, readily comparable across tractor brands and tractor models, new and used.
Every tractor brand includes Compact tractor models weighing from 2,700 to 2,900 pounds bare weight with a less than 26 horsepower engine.
I assume the 25hp emissions stuff is the reason for a significant price jump right at that border line.
Yes.
Stricter Tier IV off-road diesel engine emission reduction standards phased in dealer tractor inventory during 2009 - 2012, impacting tractor prices.
Tier IV emission standards require tractor manufacturers to add or revise pollution reduction technology on new tractors generating over 19 kW power = 25.4794 horsepower.
DPF is used by the majority of tractor manufactures for emissions control on OVER 25.4794 horsepower tractors.
Tier IV technology complicates the engine and exhaust package and is a significant cost factor. However, the pollutants emitted by a Tier IV technology tractor are about 1% of the pollutants emitted by a non Tier IV tractor.
Diesel Particulate Filter (DPF) captures exhaust particulates (soot) in a ceramic matrix. When tractor engine runs sufficiently hot, accumulated particulates burn off periodically without operator intervention. If engine is not run continuously hot long enough to burn off particulates, diesel soot accumulates in the matrix. Once heavy soot accumulates in DPF the tractor forces soot clearance with the tractor parked and throttle open to about 2,200 rpm for about sixteen minutes, which makes the DPF REALLY HOT to burn off all accumulated soot. Burning off accumulated soot, either during operation or parked is called REGENERATION.
If there is no DPF there is an alternative incendiary technology to burn off very fine particulates (soot). Sometimes exhaust heat is elevated all the time, sometimes periodically.
Diesel particulates must be burned. THERE IS NO FREE LUNCH.