we run old conventional combines, MF and NH, in some very dusty dirty conditions. it was not uncommon for us to put in a new engine air filter every 3 or 4 days of operation even though we stop and clean the air filter 3 times daily. this gets expensive with the cost of filters and the engine oil consumption rate. recently we replaced the primary intake on our combines. moving it to a convenient servicing location, built a box frame with lid, and put "Perfect Pleat" air filters around the 4 sides of the box. these filters are used in industrial environments where air needs to filtered for human use. we considered volume of intake when considering size of the box. we custom combined oats(hulled and hulless),winter wheat, barley, and barley with peas from aug 18 to oct 30. the last of the combining was the dirtiest as the crops had been rained on so much. the results. total filter cost was greatly reduced for the season, inspection and servicing the primary filters was made extremely easy, the secondary air filter (round filter) did not need replacing throughout the complete season and best of all- oil consumption dropped considerably. the "Perfect Pleat" filters cost us about C$12 each for a 16 x 16 filter and for each one used we saved $50(approximately) over the previuos year's operation in the same conditions. my 2 cents worth.
