virginTLS

probably old news... but i still wanna get my facts straight...
so what do you guys know about the differences between the two systems?

as far as i know...

VTEC works more like a dual-personality switch... under the switch point... car behavior is subtle... focused on mileage... after the switchover point... car roars like a beast...

iVTEC seems to be similar to VVTL-i... or Double Vanos... full-time variable valve timing... no switchover... just constant adjustments...

duno... personally... i think i like the traditional VTEC better... more fun to me... love that switchover roar...

but seems like iVTEC is the better way to go in terms of smoothing out the powercurve....

alright... now tell me something i don't know :P

scalbert

iVTEC is the standard VTEC but with variable valve timing added.

drcookie

Please humor me on this. What does the "i" stand for in iVTEC ?

scalbert

intelligent or intelligence, something like that.

kennelm

Well, I thought VTEC stood for Variable Valve Timing and Lift Electronic Control. If that is true, then your answer seems amiss....

scalbert

Nope, it is right on but now it incorporates infinitely (within a range) variable valve timing with the iVTEC.

Previously the only variable valve timing was a set amount which varied only by the amount each cam lobe was set at; low and high lobes. Now the entire cam phasing, within a set range, can be controlled by the ECU.

Think of it as adjustable cam gears but controlled by the ECU.

kennelm

Well, both VTEC and iVTEC do the same thing (that is, provide variable valve timing). I'm pretty sure your original post suggested otherwise.

Anyhow, I understand what you are saying now. Sounds like iVTEC provides more progressive VTEC, whereas the VTEC of old only delivered two discreet settings (high and low).

scalbert

No, the original statement still stands.

VTEC is the change of cam lobes which control the valve. In the first, two lobe VTEC systems, there was a low and high lobe. These varied in lift/duration but also timing. At a certain RPM the ECU would open an oil solenoid which would fill the rocker arm. This would then lock a free floating rocker to the primary rocker via a piston thus causing the valve to open based on the high lift cam lobe.

In iVTEC this same functionality is still retained although they may use a three lobe VTEC (low, mid and high). But they add control of the actual camshaft phasing. The ECU can now, at any RPM, infinitely control +/- X degrees (normally about 20 degrees) of the valve timing through cam phasing.

Put simply, VTEC controlled rocker arm and the following of cam lobes. iVTEC adds to this the ability to control the cam degrees.

kennelm

You have provided an excellent explanation of VTEC vs iVTEC, but I think we are talking past each other now.

In your first post, you said:

iVTEC is the standard VTEC but with variable valve timing added.

Logically, this statement simply cannot stand.

All I'm saying is that VTEC provides variable valve timing too, just as iVTEC does. It just does it in a more limited, primitive way. That's all.

scalbert

I guess I never really considered VTEC as variable valve timing (even though Honda's label states this) since it is simply a shift from one cam lobe to another (although valve timing does change but only from one degree value to another). At least not in the current sense of variable valve timing like BMW's VANOS or Toyota's VVT-i where the position of the cam, in degrees, can be controlled. In today's automotive market, this is what they consider variable valve timing. Ten years ago VTEC was considered variable valve timing even though more emphasis was on the lift and duration changes.

But in the end I hope the original post has been adequately answered.

kennelm

If you accept that variable valve timing is the ability to open and close valves at different points during the engine stroke, depending on RPM, then both VTEC and iVTEC do it. It's just a matter of how it's done.