Anyone have a First Gen Insight?

[Loren]

To get really lean safely, I think you need programmable fuel injection, like MegaSquirt. With that and a wideband O2 (and if you're trying to go to the extreme you're talking about... probably a knock sensor and EGT probe), you can tune the engine for maximum economy while maintaining reasonable drivability. (and potentially even good performance if you tried)

How lean can you go? Somewhere around 16-17:1 is acheivable in a low-load cruise with a good-running modern engine. This is where good programmable EFI comes in. The ECU needs to be able to detect when the load increases (via MAP sensor, throttle position and RPM inputs) and immediately shift from super-lean to something appropriate for the conditions.

The real trick is in managing those transitions and tuning for drivability. You've got to tune both fuel and the timing map, along with a fun little thing called "acceleration enrichment" (same function as an accelerator pump on a carb) to get a smooth transition from that lean cruise to acceleration without hiccups. But, it can be done. Just takes time. Once you've got all the hardware set up, and a good understanding of what you're doing, that is.

[DRMORTY]

I am taking notes... There is always more things to try...

[Loren]

The trick is, how much money are you willing to spend in the name of saving a gallon of fuel? Even with the price of gas at what it is, you're not going to make more than 10-15% improvement... So, you'll save as much as 15% of the cost of a tank of gas... what? Every 2 weeks? Maybe every week if you drive a lot? And even at $4/gallon, a 10-gallon Honda tank only costs $40 to fill. So, you're saving $6 per tank. If you burn a tank a week, that's $312/year. It would take several years to recoup your investment.

Of course, if you're doing it just as a hobby or a learning exercise, or just for bragging rights... well, larger sums have been spent on less noble ideas.

If you're gonna do it, I'd start with a MegaSquirt conversion. Don't change a thing on the engine. Just MegaSquirt it, learn your way around MS, and tune it for better economy. See how much you can squeeze out of it. Then go FI and see how much more (or less) you can get. That would be a good "scientific" approach from which you would learn more about where any economy gains you found actually came from.

[treekiller]

any supercharger takes energy to spin, takes it from the crankshaft that's energy that's not being used to make the car move forward. even if it's 5 horsepower. that's a majority of the power it takes to maintain highway speed.

not my math but... it fits..

At steady velocity you have overcome air resistance to maintain speed.
Drag force on car is given by
F_drag = Cd·A·(1/2)·ρ·v²
Cd drag coefficient
A projected frontal area of the car
ρ air density air
v velocity.

Hence:
P = F_drag · v = (1/2)·Cd·A·ρ·v³

Typical values of Cd·A are in the range from 0.5 to 0.9m².
Smaller cars tend to have a smaller Cd·A.
You can take the values from the net.( two sites are linked below).

e.g.
'92 Honda Civic
Cd = 0.360
A = 1.91m²

v = 55mph = 24.5872m/s
ρ = 1.184kg/m³ (at 25°C ,1atm)

=>
P = F_drag · v = (1/2) · Cd·A·ρ·v²
= (1/2) · 0.36 · 1.91m² · 1.184kg/m³ · (24.5872m/s)³
= 6050W
= 8.1hp
Source(s):
The Mayfield Company Homepage - Coefficient of Drag Tables and Curves
Wikipedia, the free encyclopedia

atkinson cycle is the most logical progression and you can have a vtec cam ground to switch cycles with a switch.. in effect you would be lowering your compression ratio, pumping losses, and creating a longer combustion stroke.. so basically the engine is built as a 13:1 but the intake valves stay open for a bit longer to lower the compression stroke length.. say in atkinson cycle you'll have a super efficent 1.0 litre.. switch lobes and you have a Race gas or ethanol 1.6..

or if you are using the supercharger just grind an atkinson intake cam and you'll have a miller cycle engine.