If a DPF is collecting soot from an upstream DOC and then needs to regen to burn the collected soot into ash...what happens in a DOC only engine, like Shibaura? If the DOC is still producing soot, where does it go? Is it passed out the exhaust with no filtration, or is it delivered back into the engine to be collected in the oil?
DPF collects soot from engine exhaust manifold. Tier IV compliant exhaust is impressively 99% cleaner than Tier III compliant exhaust.
Almost all Tier IV pollution reduction involves cleaner computer controlled fuel combustion within 'new' engines engineered to meet Tier IV standards. As a byproduct of more efficient combustion most Tier IV tractors have two to four more horsepower than less effecient mechanically injected predecessors.
A minuscule amount of nasty diesel residue, tar, exits the engine, then enters the DPF where residue condenses/accumulates on a ceramic matrix. Fine diesel particulates/soot/tar entering DPF is probably cancer causing, as is tar in tobacco smoke, but DPF tar is periodically incinerated at 1,100 degrees Farenheit, in a process called DPF regeneration. Incineration byproduct which exits DPF into the atmosphere is primarily carbon in the form of ash, weighing a few grams, relative to 30 gallons of fuel (+/-) burned during sixty engine hours of tractor operation between regenerations.
A few Tier IV compliant tractors between 26 and 75 hp use DOC (Diesel Oxidation Catalyst) conversion. Some Mahindra models and some Massey Ferguson models use DOC incineration. DOC is of similar construction to DPF. Both the DPF and the DOC are honeycomb ceramic filters which supercede a muffler.
The DOC forces engine exhaust over a hot honeycomb ceramic structure coated with platinum, palladium, and rhodium. These catalysts oxidize carbon monoxide and hydrocarbons into carbon dioxide and water at hot exhaust temperature.
DOC tractors have an oven hot all the time, DPF tractors have an oven hot intermittently.
There is no free lunch.
