On the "step"

[Kevin Dougherty]

There is a little trick that I use when I'm trying to get the best mpg that I really haven't seen discussed here. I call it getting on the "step"

The "step" refers to the smooth planing on top of the water that a float plane uses for high speed water manuvers...this is the opposite of the low speed "plowing" through the water that a pilot will do when taxiing near shore.

Gettin the Insight "on step", involves gentle acceleration up to and over the desired cruising speed and then gently easing off of the gas pedal to decrease speed to the value.

This tends to facilitate cruising and saves gas.

The opposite effect, gently accelerating up to but not over the desired speed, tends to leave me "behind the power curve"...where I tend to use more gas for a given speed.

[HafNHaf]

the same thing has been discussed for many years as applied to airplane cruising speeds. one camp says to go a bit above your cruising altitude and decend to it, the other camp says just get to the correct altitude and stay there. i dont know if it has ever been proven either way, and i think it will be the same for cars.

[dloop]

Originally Posted by Kevin Dougherty

Gettin the Insight "on step", involves gentle acceleration up to and over the desired cruising speed and then gently easing off of the gas pedal to decrease speed to the value.

Thank you Kevin. I've been struggling to find new ways to describe to my wife and daughter how to drive this car. Your description is perfect.

[trunkout]

just remember how I used to ride my motored skateboard....same principles apply....it's all about momentum....

[chrs]

Originally Posted by Kevin Dougherty

Gettin the Insight "on step", involves gentle acceleration up to and over the desired cruising speed and then gently easing off of the gas pedal to decrease speed to the value.

Yup. Here's what I think is a technical explanation of that:

You want to be in lean burn. Since that's only available in 5th gear, there's a fixed realationship between RPM and speed. If you are below about 35 to 40 mph, you are running the engine slowly enough that it starts to lose torque and efficiency. If you give it, say 75 mpg worth of gas at 35, you might sit there at 75 mpg and 35 mph. Or, depending on conditions, you might actually lose speed and end up at 30 mph and 50 mpg. However, if you get up to 45 mph and thus somwhere around 1500 rpm, the engine gets into its sweet spot, and you might cruise at 100 mpg or better, using less fuel and going faster.

Exact numbers depend on conditions, but I thought it was easier to explain being more concrete.

Charlie

[Willie Williford]

"Lean burn only in 5th gear" is a false conclusion.

Lean burn is available in 3,4,5, gear.......Will normally occur between 2,000 and 2500 rpm. when everything else is in sync. (load, temp, etc)

Extensive testing has proven this theory.
(I posted the results of the test a long time ago on "Turbocharged Insight")
My opinion.


Willie

[highwater]

Willie wrote:

Lean burn is available in 3,4,5, gear.

This is correct. the lean burn window does become smaller and easy to_break_, in the lower gears, though.

Randall

[Mike Dabrowski 2000]

nice one Kevin
The map signal is the best indicator of engine efficiency, therefore my decision to use it as the servo control input for PIMA. The lean burn window as Highwater and Willie indicate is available on the three higher gears, but 5th at over 35MPH is by far the easiest to maintain lean burn in. With PIMA set for 110MPG initial activation, I can run for 10-20 miles at 60-65MPH depending on terrain, without ever dropping out of lean burn. With the boost system on, the range can be extended to 30-50 miles.
The term feathering the throttle is describing that same step condition, where you reach the target speed, or a bit above, then lift the throttle slowley while watching speed, until power output matches the load with maximum MPG for the conditions.