Can't Get Good Fuel Economy - 2008 Civic Manual

[Christ]

Early shifting still works to an extent, since even in Vtec mode, the higher you rev, the more fuel units per minute you're using.

If your a/f ratio is a constant 13:1, and you're revving 2000 RPM with an engine that has 1.0 liters displacement, vs revving 1000 rpm with the same displacement (not counting volumetric efficiency, as this is just an example), you're using 2x the fuel per minute.

The difference comes with gearing. Are you using more or less fuel per distance?

[NeilBlanchard]

Right, a lot of us have engines with variable valve systems - my xA has a VVTi 1.5L, which is essentially the same thing. The idea is to broaden the power band -- at lower RPM's fewer valves are actually better, and at higher RPM's more valves are used to improve power. So, the engine can have better efficiency at lower RPM's than it could w/o the VTEC.

All ecodriving techniques still apply.

[KJSatz]

Hmm any progress?

I think my next tank will be lower, but there's more city driving, and it's been colder. Today's nice though.

[Orangehonda]

Originally Posted by Christ

I'd chance a guess to say the i-Vtec engagement was designed to be seamless.. You could try a standard vacuum gauge (or tapping the MAP sensor's signal) to check for difference in vacuum that is controllable by modulating the throttle.

Wait for a defined change while you're not moving the throttle, then move it ever so slightly, see if you notice another more defined change in the signal/readout.

I don't know a whole lot about the R18 engine, other than they have a ~0.95 R/S ratio, by standard measurement, but the crank is offset from the bore centerline, helping the combustion stroke's efficiency.

They have an integrated header, plastic intake manifold... that's pretty much what I know about them so far. Until the local dealers get me more information, I'm afraid I can't contribute much more than that.

I am working on my engine and got some values from the fuel pump pressure, lub oil pressure, vacuum gauge reading and the OBD readings for this R18A engine.

For those interested,
My blog is at orangehonda.tumblr.com

[Baltothewolf]

I drove the civic for the first time in almost 2 weeks today. She doesn't have insurance anymore but idc. Anyway, I experimented with my shift points today, I shifted at 2500-3k with medium to light throttle instead of 2000-2250 with heavy throttle and noticed a 2mpg increase, and with that being said, it's gotten colder, like 20 degrees colder then the last time I drove this route.