i-vtec is Honda's answer to Toyota's VVTLi or Variable Valve Lift and Timing.

Original VTEC if I understand correctly, when the RPMS get to a certain level (most Honda's around 5500 to 6000) the valve lifts higher to allow more fuel/air for the combustion.

VVTLi or i-VTEC allows the valve to adjust variable thru out the RPM range supposedly to allow for a stronger, smoother powerband.

Neat in theory, but I think the S2000 has 3 cam profiles, so I think it is just about as good as a variable system as it has a low, mid and high cam. Other VTEC Hondas, I believe only had two cams.

I'm venturing into territory that I am unsure of, so anyone who can confirm, enlighten, please help.

 

Here is some info from the Acura site (RSX info).

In addition to controlling lift and duration, like other VTEC systems, the "intelligent" i-VTEC

 

So for the I-VTEC, would it mean that it is constantly engaged or does it kick in like VTEC? For VTEC it only engages at a certain RPM. I heard that the ITR's had a different type of system, in which VTEC is engaged twice...is that true? Thanks

 

I haven't experienced it, but from what it would appear to me, it should feel like a more linear acceleration, not like the on/off feeling from normal VTEC.

If I understand correctly, the Valves will "adjust" thru out the whole RPM range to allow for more air/fuel.

So to answer your question, I believe it is "constantly engaged", as you rev higher, the valves should lift higher.

At least that is how I understand it.

 

We have the 2002 Honda CRV. It has the new 2.4L iVTEC engine. Like Kraziken said, it has continuous changes base on RPM, so you don't feel it engaging like the VTEC.

 

[QUOTE]Originally posted by Kraziken
[B]... I think the S2000 has 3 cam profiles, so I think it is just about as good as a variable system as it has a low, mid and high cam.

 

i-VTEC combines the signature VTEC system with a new technology called VTC or Variable Timing Control. This allows the intake cam phasing to be varied by as much as + or - 50 degrees. The goal of the VTC is to beef up the available torque in the mid-range of the engine. It also allows some underlap to force exhaust gases back into the intake track to function as a EGR system. It also allows for very aggressive timing under WOT conditions. In a RSX Type-S the VTEC part works exactly like our S2000 engine, thought it switches to the high lift cams a bit earlier. The difference is the intake cam is continuously adjusting on the fly to meet different emissions, and performance requirements.

 

I have power/torque curves of both the S2000 (2.0L VTEC) and the RSX Type S(2.0L i-VTEC)from Honda. The first is from the SAE paper, the second from Ward's engine issue (I assume the curve was from Honda). Both are a bit cartoonish, but if I overlay the points, the curves look very similar. That is, until the RSX's peters out at upper rpm. Basically, the RSX has about 2-3 more lb-ft from 3000-5000 rpm. 2% is not a significant difference. Above 5500 rpm, the S2000 dominates. My read is that even if the S2000 added i-VTEC, you'd probably see little discernable effect.

 

You may be referring to the way both the ITR and the Integra GS-R have a dual-stage VTEC system, in that there's a switch to the high RPM cam at 4400 RPM, then a change in the intake runner length at 5600 RPM. At least this is how the system works in my GS-R Integra. Even with both these mechanical changes taking place at different RPM, you don't really notice any "kick" as you do with the more radical VTEC engagement of the S2K at 6000 RPM.

 

[QUOTE]Originally posted by gernby
[B]

I don't think there are any VTECs with 3 cam profiles.