- 3 Post By Dhillon
- 4 Post By Dhhawal
What is i-VTEC
What is i-VTEC
What is i-VTEC and what is the difference between i-VTEC and VTEC ?
VTEC - Variable valve Timing and lift Electronic Control. At low RPM, a VTEC engine uses a normal cam profile to retain a smooth idle, good fuel economy, and good low-end power delivery. The VTEC mechanism engages a high-lift, long-duration "race" cam profile at a set RPM value (i.e., ~5500RPM on the B16A) to increase high-end power delivery.
VTEC-E - Variable valve Timing and lift Electronic Control for Efficiency. This system isn't really VTEC as we know it. At low RPM, the VTEC-E mechanism effectively forces the engine to operate as a 12-valve engine - one of the intake valves does not open fully, thus decreasing fuel consumption. At a set RPM value (i.e., ~2500RPM in the D16Y5), the VTEC-E mechanism engages the 2nd intake valve, effectively resuming operation as a normal 16-valve engine. Note: in a VTEC-E engine, there are no high-RPM performance cam profiles; this engine is supposed to be tuned for fuel economy, right?
VTC - Variable Timing Control. This is a mechanism attached to the end of the intake camshaft only which acts as a continuously variable cam gear - it automatically adjusts the overlap between the intake and exhaust cams, effectively allowing the engine to have the most ideal amount of valve overlap in all RPM ranges. VTC is active at all RPMs.
i-VTEC - intelligent Variable valve Timing and lift Electronic Control. This is a combination of both the VTEC and the VTC technologies - in other words, i-VTEC = VTEC + VTC. Currently, the only engines that use the i-VTEC system are the DOHC K-series engines.
I would like to make an addition to the thread, a high lift cam is relatively easy to design and run on an engine, however, the more agressive the cam profile(lift/duration) for high rpm operation, the harder it is for it to function at low rpm's, low end power delivery will suffer, and managing idle can become problematic which is why vtec can be considered as offering the best of two worlds, to say that vtec has been revolutionary would be an understatment, honda has made over 5 million of cars equipped with this technology and none have failed to date, designers have copied and intergrated this very design in their own production cars, suffice to say that its been quite a contribution to the mass consumer market