Vtec

[hogwylde]

I have come across many a thread about VTEC and what it is/does but there is generally too much technical mumbo jumbo and it leaves me more confused than when I started reading. Could someone explain it to me, in simple terms? :)

[manxman]

I have come across many a thread about VTEC and what it is/does but there is generally too much technical mumbo jumbo and it leaves me more confused than when I started reading. Could someone explain it to me, in simple terms? :)
Vtec engines have a cam shaft with two intake valve lobes per cylinder, and two intake valves per cylinder. Under low torque driving conditions the "default lobe" opens and closes one intake valve, and the other intake valve stays closed. Upon high torque demand conditions, the cam shaft is moved by a solenoid to a position that opens and closes both intake valves, which increases power, but sacrifices gas mileage to an extent. Depending on the driving situations, the cam shaft slides back and forth to suit the needs of the engine under different conditions.

Hope that helps!

[EXWRX]

the Higher Rev setting with all valves opening may actually be more fuel efficient than the low rev setting would be at higher RPM's. I don't have data to back it up, hence the may.

[hogwylde]

Is there a time when I'm supposed to notice VTEC kicking in. Ya'll say that it's all about the torque, so I am assuming we are talking low speed (gear) w/ heavy acceleration. Does the car sound any different? Do I hear VTEC kicking in? Does it feel different?

[manxman]

Is there a time when I'm supposed to notice VTEC kicking in. Ya'll say that it's all about the torque, so I am assuming we are talking low speed (gear) w/ heavy acceleration. Does the car sound any different? Do I hear VTEC kicking in? Does it feel different?
That kind of depends on which gen. Fit you have. The engagement of Vtec is more distinct with a GD3 than it is in a GE8, and your ears have to be pretty well attuned to engine sounds to even notice either one.
Engagement on a GE8 is earlier than with a GD3. Vtec engagement isn't as graphically different an experience as, say, using the afterburner in a jet powered fighter plane. It's fairly subtle, but the more mechanically experienced folks can feel/hear it. Any time that you floor the gas pedal, your engine's Vtec mode is working (unless there is a malfunction- and you would have a warning message on the dash if that were the case). Vtec also is employed at high speeds on the freeway, particularly on steep hills,but is more noticeable at low speed/high torque demand situations.

As a direct answer to your question, whether or not you hear or feel the Vtec engagement depends on your personal "mechanical acuity". Can your hear engine knock? Can you hear or feel an intermittent miss in the ignition system? If so, you will probably hear and/or feel a difference in your engine's behavior when it goes into Vtec. MANY, many, people on the forums do not have this ability, but will claim to have it anyway.

Wouldn't it be nice if your Harley had this feature?

P.s. Depending on which, if any, after-market intake and exhaust that you may have, it can be easier to hear the change in engine note caused by the engagement of the Vtec process. I personally like the fact that my engine "talks" to me with both the PRM Jet Stream Intake (which some feel is too loud) and the Aero Turbine exhaust which I feel is the DEEPEST sounding exhaust for Fits on the market. You may get the impression from that that I have the loudest Fit in the world, but that is not the case. Normal volume conversation in the cabin is never a problem, and I don't need extreme volume to clearly hear and enjoy the stereo.