Civic VX, VTEC-E, D15Z1, etc

[GasSavers_TomO]

Fuel cut will happen within 100RPM of that.

[IndyFetch]

Originally Posted by topher

All vtec-e's do this. It's not to help the swirl but, so the gas does not pool up on top of the vavle.

The 4th valve opens slightly so the fuel can "dribble in" and ignite right next to the plug. This helps quite a bit, since the lean air/fuel mixture does not ignite easily and has a tendency to ignite on a hot spot, such as the top of the piston or cylinder wall. By opening the valve slightly, the fuel spark will create a flash leading away from the top of the combustion chamber, just the way God intended. It reduces hot spots, too.

In a post above, the 92-95 CX motor is listed at 102 hp. It is actually 70 hp, I believe.

[GasSavers_topher]

Good to know.

[imzjustplayin]

Originally Posted by suspendedhatch

I found something interesting in the Honda Repair Manual for the HX. Apparently, the HX/D16Y5 uses the CKF sensor as a means to lean out the mixture until it detects a misfire. Since the VX/D15Z1 doesn't even have a CKF sensor, this means theoretically that the HX runs leaner and is in lean burn more often.

yeah but the emissions are far more stringent in 1996 than in 1995 so it's unlikely that it would be lean while producing the most power (VX can do 15:1-24:1 while HX can only do 17:1-24:1) for example. My example is not verified, it is simply an example of how the emissions are far more strict for OBD-II vehicles vs. OBD-I.

[imzjustplayin]

Originally Posted by suspendedhatch

I found something interesting in the Honda Repair Manual for the HX. Apparently, the HX/D16Y5 uses the CKF sensor as a means to lean out the mixture until it detects a misfire. Since the VX/D15Z1 doesn't even have a CKF sensor, this means theoretically that the HX runs leaner and is in lean burn more often.

Actually that doesn't prove anything about being able to be more lean. What you've seemed to have missed is that the usage of the CKF sensor is what is used for lean-burn on the CVT version of the HX. The benefit of this approach is it allows them to use the cheaper 4-wire O2 sensor instead of the 5 wire (7 wire) wide band O2 sensor. The reason they can do this is because there is no "lockup" with a CVT transmission and consequently the "acceleration" of the crankshaft is completely isolated from the transmission. Therefore the CVT transmission makes it possible to use this method of detecting how lean the fuel mixture is. However when you have the transmission and engine "locked up" like with a Manual transmission, using the crankshaft acceleration to determine how lean the fuel mixture is isn't possible due to the way the engine can be loaded by the transmission. Also keep in mind that while I'm sure this method of lean-burn works pretty well, it's no match for using a wideband O2 sensor and consequently the CVT HX doesn't have the precise control over the leaning of the fuel mixture like the M/T HX does.