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Discussion Starter · #3 ·
for those that might not know (like myself), what exactly is "lean burn?"
Lean burn refers to the use of lean mixtures in an internal combustion engine. The air-fuel ratios can be as high as 65:1, so the mixture has considerably less fuel in comparison to the stoichiometric combustion ratio (14.7 for petrol for example).

Lean burn - Wikipedia, the free encyclopedia

One draw back, it produces a higher ratio of NOx, therefore a different and expensive catalytic converter is needed to control the emission, in addition to certain other components to assure the "purge" of the system time to time.

If a car is made for this capability, it usually fits with a manual transmission. The manual transmission Generation 1 insight had a lean burn, said to be 22:1 in reports, but I hear 24:1 in some places... It pushes the FE very high in certain conditions (like highway driving, or constant lower speed). You can see it in the FE meter, when you get in lean burn, the FE gauge just goes a good step higher.

The CR-Z being a Honda IMA follower in some aspects of the Gen 1 Insight, with manual transmission, I'm wondering if it has the same capability. The 6th gear ratio would make it quite easy to enable I guess. I haven't seen it written anywhere though.
 

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ok, not to sound like a no0b... but i know the difference between running lean and running rich... but what i thought u were asking here is can we "enable" it while we're driving or something like that... but i see from that link that the computer enables "lean burn" for a more efficient burn...

i haven't read anything on that... that'd be cool if it did come with that tho...

Wikipedia said:
Honda lean burn systems

One of the newest lean-burn technologies available in automobiles currently in production uses very precise control of fuel injection, a strong air-fuel swirl created in the combustion chamber, a new linear air-fuel sensor (LAF type O2 sensor) and a lean-burn NOx catalyst to further reduce the resulting NOx emissions that increase under "lean-burn" conditions and meet NOx emissions requirements.

This stratified-charge approach to lean-burn combustion means that the air-fuel ratio isn't equal throughout the cylinder. Instead, precise control over fuel injection and intake flow dynamics allows a greater concentration of fuel closer to the spark plug tip (richer), which is required for successful ignition and flame spread for complete combustion. The remainder of the cylinders' intake charge is progressively leaner with an overall average air:fuel ratio falling into the lean-burn category of up to 22:1.

The older Honda engines that used lean burn (not all did) accomplished this by having a parallel fuel and intake system that fed a pre-chamber the "ideal" ratio for initial combustion. This burning mixture was then opened to the main chamber where a much larger and leaner mix then ignited to provide sufficient power. During the time this design was in production this system (CVCC, Compound Vortex Controlled Combustion) primarily allowed lower emissions without the need for a catalytic converter. These were carbureted engines and the relative "imprecise" nature of such limited the MPG abilities of the concept that now under MPI (Multi-Port fuel Injection) allows for higher MPG too.

The newer Honda stratified charge (lean burn engines) will operate on air-fuel ratios as high as 22:1. The amount of fuel drawn into the engine is much lower than a typical gasoline engine which operates at 14.7:1, the chemical stoichiometric ideal for complete combustion when averaging gasoline to be the petrochemical industries' accepted standard of C6H8.

This lean-burn ability by the necessity of the limits of physics, and the chemistry of combustion as it applies to a current gasoline engine must be limited to light load and lower RPM conditions. A "top" speed cut-off point is required since leaner gasoline fuel mixtures burn slower and for power to be produced combustion must be "complete" by the time the exhaust valve opens.

Applications


  • 1992–95 Civic VX
  • 1996–2000 Civic Hx
  • 2001-05 Civic Hx
  • 2002–05 Civic Hybrid
  • 2000–06 Insight Manual transmission only
 

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Discussion Starter · #5 ·
May be "enable" is not the right word... "Go in lean burn" might be more accurate. I guess we will have to wait a bit more for the CR-Z owners to try their car to the limit and see if it goes in lean burn. But please do report on it. It would be a very interesting finding.
 
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