Piggy back ECU control

[izzie]

Now i dont own an insight but im really interested in them. now - i was wondering if it would be possible to piggy back the ecu as they are based on obd and modify lean burn values and changeover points like done on honda vtec engines for vtec high and low throttle maps. this would include putting the lean burn change over point to allow better mpg and shorter (leaner) injector openings for increased mpg.

[Insightful Trekker]

Hi izzie and welcome to the forums

And thanks for your note to delete the duplicate post, done.

What most people don't understand about "lean burn" is that its not simply a choice of feeding the engine a lean mixture. There are several other physical, chemical and properties of combustion that limit the conditions that a "lean burn" mixture will work. Attempting to "force" a "lean burn" mixture outside of these conditions will _fail_.

Specifically in regard to your idea think of it this way:

Higher speed requires more power to achieve. A lean burn charge is simply insufficient to produce enough power above "x" RPM or MPH. In other words you'd simply not be sending enough fuel to push the car down the road.

The "trick" in improving MPG in all cars is to either reduce the amount needed to "push" the car, making the car lighter is one. The more complex is to improve combustion efficiency, get more "push" out of every drop of fuel.

Here's a document that may help your understanding:

Insight's Design Document; "Development of Intergated Motor Assist
Hybrid System: Development of the 'Insight', a Personal Hybrid Coupe."

http://www.osti.gov/bridge/product.bibl ... =3&start=0


HTH!

[izzie]

i know the physical factors but its like ecu mapping - injectors have opening times - this increases in proportion with air flow from a map or maf sensor. lean burn could be achieved by means of a remap to take advantage of it.

think of it like this - i know that the same power figures wont be achieved but speed will still increase as the fuel map is increasing injector opening time per each engine load. by possibly creating a system which allowed changeover of the lean burn cycle and the normal burn cycle mpg could be saved - particularly if it had a system allowing it to be switched.

also - why not raise the compression ratio of the insight to create more power from the available fuel. taking on tuning principles would def. make a positive increase to the insight mpg.

[Insightful Trekker]

I'm having a difficult time understanding your reasoning / choice of words. e.g. "...increasing injector opening time per each engine load." Open an injector for a longer time and you use more fuel, period.

Increasing the compression ratio has other detriments. A primary being increased peak combustion chamber temps and a resulting increase in NOx.

Sorry, it won't work.

There's no such thing as something for nothing. If you read the paper I gave the link for pg. 2, fig. 1 graphically shows where the percentage of improvement for the Insight over the Civic came from.

If emissions were of no concern then you could probably eek out another 10-20% MPG improvement without any "new" technology.

Spend some time learning about the losses of efficiency on the conversion of energy forms (chemical, mechanical, electrical) and you'll begin to understand the impossibilities of what your are proposing.

HTH! & end of thread for me

[Foxpaw]

Increasing the compression would theoretically give a boost in power and fuel efficiency, but the Insight already has a fairly high stock compression. Increasing it further, by shaving the heads for instance, might come at a cost of reliability, in addition to costing a fair amount of money for a relatively small gain in efficiency.

As for strictly whether it's POSSIBLE, I would say yes, it's definately possible from a theoretical standpoint. I don't believe that any hobbyists have enough information to actually do it at this time, however.