The Ford F150 Essex V6 engine (4.2L 205-210hp) is an even firing engine. The Ford Ranger Cologne V6 engine (4.0L 155-160hp) is an odd firing engine, just like the F150 4.6L and 5.4L. That’s why the 4.0L Ranger sounds more like a V8.
Even firing engines alternate fire from left to right. Odd firing engines have two double fires on the same side. Odd firing pulses double the exhaust output on the same exhaust bank during rotation. The added exhaust pressure unbalances the exhaust system, which is why odd firing engines need “X” pipes, “H” pipes, or a “Mac Chamber” to re-balance the exhaust.
Both engines have good power to weight ratios. The Cologne was built for smaller engine compartments (cross plane crank and 60 degree angle) to fit Taurus, Explorer, and Ranger. The Essex was built for weight (single plane crank, 90 degree angle) Mustang, Thunderbird, and F150.
Last edited by Stang2; 02-09-2009 at 11:22 PM.