I did the open air filter mod today. I got base line times for the stock air filter and did times for the open filter this afternoon.
Truck: 1995 F-250 Power Stroke 5 speed extended cab long bed, 3:55 gears, aluminum cab height bed cap, 235/85 x 16 steer tires, 255/85 x 16 drive tires
All measurements on level road with A/C off.
All times are an average of four separate runs
3 - 55 mph was starting at idle, clutch engaged in first gear (did not want to trash my new $1,400 clutch), shift points 3100 rpm.
Mileage figures are for unloaded driving, moderate acceleration (shift points 16 - 1800
rpm, ¼ - ½ throttle) using #2 Marathon diesel. Base line MPG
is over 4-5000 miles, MPG
after modification is for a load of fuel, 400+ miles and will be reported next week some time. Mileages calculated mathematically. I don't have a trip computer and would not trust it if I did.
Base line performance, no modifications.
55 - 75 mph top gear roll on .... 12.04 sec
3 - 55 mph ...................... 13.25 sec
After installing Napa open element air filter with 4" exhaust pipe adapter in place of factory air filter assembly (times measured as above):
55 - 75 mph top gear roll on ...... 12.15
3 - 55 mph ........................ 13.40
To be reported in a week or so.
What this tells me is there is no discernible difference before and after this modification on an otherwise stock engine. My gut feeling is the factory downpipe is the restriction in air flow and the air filter would make a difference with an aftermarket downpipe. Turbo whine is not noticeably louder, there is a little more intake rumble though any time I am over 1/4 throttle.