Honda Insight Forum banner
1 - 3 of 3 Posts

44 Posts
Discussion Starter · #1 ·
1) At what speed do you usually attain the lean-burn condition?

2) What does the instantaneous FCD display for mileage whilst in lean-burn

3) Do you only attain lean-burn in the flats or downhill?

4) What is different about a 5 speed besides the transmission (eg. is the ECU different? Is the intake port different?)
I have read somewhere that the intake port 'swirls' the mixture so that lean-burn combusts witht the same speed as a richer burn would. Does this indicate that a CVT and 5 speed have different intake manifolds/ports?
Are these part numbers different from 5-speed and CVT?



2001 Insight CVT (70MPG+)
1968 Mercedes Benz Unimog 404s 4x4 (16mpg)
2005 Toyota Sienna (20.1 lmpg)

89 Posts
As a 5-speed driver, here's what I know about lean burn.

- the car does not have any type of lean burn indicator, you just sense it as a slight bog in power, and the FCD jumps from 75 mpg up to 100mpg+, depending on how light the pressure is on the accelerator pedal.
- There are different levels of lean burn, 75-90 mpg is fairly easy to maintain. 90-150 mpg is hard to maintain (naturally), and requires a very light touch on the accelerator pedal.
- after a few minutes in lean burn, the car will do a "purge", it is felt as a slight surge in power, the speed will jump a couple of mph if you keep steady pressure on the accelerator pedal, and the FCD will fall off slightly. When the purge is complete, everything returns to normal. You can dance on the pedal and try to maintain your FCD number, it takes a little concentration.
- Speed to attain lean burn. Ummmh.... it varies depending on driving styles and driving conditions. Once the engine is warmed up, lean burn can be maintained somewhere from around the lowest speeds (or RPM) that the engine will pull up to approx. 57-63 mph, on level roads. After that, you either are going downhill, drafting, or have a modified Insight to go faster and still keep lean burn. Lean burn can be maintained going uphill, just lock your foot in one position on the pedal and drive by the FCD instead of the speedometer. Bigger inclines may require a downshift.
- Seems like just after a refuel, it's real easy to max out the FCD. Then after a few miles, it kinda fades away and the FCD returns to normal. After the last refuel, I pulled a 113 mpg for the short trip from the pumps to my house. Now it's dropping back to normal.

Differences between engines: lean burn is higher compression ratio and not as clean burning. I'm probably missing a bunch here, but that's what I recall off the top of my head.

1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.