I-Vtec vs Vtec, compare and contrast

[Bambooseven]

I understand the mechanical aspect of Vtec but what does I-vtec do differently then Vtec? and how does it work (if there is a mechanical difference)?

[Bambooseven]

does nobody know what i-vtec is?

[BLU CIVIC]

have u done a search b/c i'm sure a similar thread was started about this same thing

[darkaccord]

I think it is something like an improved E-Vtec (the one that loses hp, but gains fuel economy), but its better or someting. Read this

[Bambooseven]

yeah, i did a search and didn't come up with anything, and that v-tec article doesn't cover i-vtec. I'm doing more research on k-series engines online, if i find out exactly what the difference is i'll post it.

[loesch8102]

i-VTEC is for Intelligent VTEC and introduces variable cam timing into the mix. It uses a variable valve opening overlap mechanism so that instead of either being on or off, it varies accordingly. It has some sort of intermediate sprocket between the cam shaft and the cam gear. I don't know how it works. It just does.

[Bambooseven]

thanx, we're getting closer. i really wanna figure it out.

[vt3c]

In a nutshell,

VTEC = Valve Lift

i-VTEC = Valve Lift + Timing

Mechanically, you already know that VTEC involves the engagment of a higher profile cam resulting in higher valve lift. i-VTEC combines this with camshaft timing (advancing or retarding the camshaft). This has the effect of changing when and how long the intake and exhaust values open.

How does this effect performance and efficiency you may ask......go to howstuffworks for a very good explaination (i cant be bothered to go through it here).

[PWMAN]

Do you know what VTEC stands for?
Variable valve TIMING and LIFT electronic control. That's what the T is for.
On an I-VTEC there is no set RPM when VTEC kicks in. Instead it goes off of YOUR driving characteristics.

[vt3c]

Originally Posted by PWMAN

Do you know what VTEC stands for?
Variable valve TIMING and LIFT electronic control. That's what the T is for.
On an I-VTEC there is no set RPM when VTEC kicks in. Instead it goes off of YOUR driving characteristics.

Bahahahahahahahah..............................tha ts one of the funniest replies I have ever heard .

The VTEC does not "magically" kick in.

I dont know where you are getting your info, but its wrong and you're making yourself look stupid with your sarcastic reply.

For your information, the TIMING in VTEC refers to the timing of the cam lobes (ie, the "mild" cam and the "agressive" cam).

AND, if you read my reply correctly, the TIMING i refer to in i-VTEC refers to the variable timing of the intake and exhaust camshafts. Honda call this VTC. The VTEC still kicks in at a particular point.

[drift]

Originally Posted by PWMAN

On an I-VTEC there is no set RPM when VTEC kicks in. Instead it goes off of YOUR driving characteristics.

that's not true. SOHC VTEC motors have no set rpm crossover either.



I-VTEC simply has VTC. while it still incorporates the cam lobe crossover a la the original DOHC VTEC system, i-VTEC adds a variably timed intake cam to retard the cam event at low rpm for improved response, while advancing throughout the rpm range to increase top-end horsepower.

on the RSX Type-S and TSX, their motors have VTC on both the intake and exhaust cams.

there is no significant "jump" in power like with the older DOHC VTEC motors as the VTC system is able to smooth over the transition to create less dips in the powerband, resulting in a smoother, flatter torque curve over the first generation of VTEC.