Editing VTEC (section)

== VTEC-E ==
{{Unreferenced section|date=July 2013}}

The earliest VTEC-E implementation is a variation of SOHC VTEC which is used to increase [[combustion efficiency]] at low RPM while maintaining the mid range performance of non-vtec engines. VTEC-E is the first version of VTEC to employ the use of roller rocker arms and because of that, it forgoes the need for having 3 intake lobes for actuating the two valves—two lobes for non-VTEC operation (one small and one medium-sized lobe) and one lobe for VTEC operation (the biggest lobe). Instead, there are two different intake cam profiles per cylinder: a very mild cam lobe with little lift and a normal cam lobe with moderate lift. Because of this, at low RPM, when VTEC is not engaged, one of the two intake valves is allowed to open only a very small amount due to the mild cam lobe, forcing most of the intake charge through the other open intake valve with the normal cam lobe. This induces swirl of the intake charge which improves air/fuel atomization in the cylinder and allows for a leaner fuel mixture to be used. As the engine's speed and load increase, both valves are needed to supply a sufficient mixture. When engaging VTEC mode, a pre-defined threshold for MPH (must be moving), RPM and load must be met before the computer actuates a solenoid which directs pressurized oil into a sliding pin, just like with the original VTEC. This sliding pin connects the intake rocker arm followers together so that, now, both intake valves are following the "normal" camshaft lobe instead of just one of them. When in VTEC, since the "normal" cam lobe has the same timing and lift as the intake cam lobes of the SOHC non-VTEC engines, both engines have identical performance in the upper powerband assuming everything else is the same. This variant of the VTEC-E is used in some D-series engines.

With the later VTEC-E implementations, the only difference it has with the earlier VTEC-E is that the second normal cam profile has been replaced with a more aggressive cam profile which is identical to the original VTEC high-speed cam profile. This in essence supersedes VTEC and the earlier VTEC-E implementations since the fuel and low RPM torque benefits of the earlier VTEC-E are combined with the high performance of the original VTEC.
There are 3 intake cam lobes: 2 for the low-RPM mode (1 for almost closed valve, 1 for normally opened) and 1 for the powerful mode when the VTEC solenoid is activated. The lowest RPM for activating the VTEC is 2500, or it may be higher if the load is weak - ECM dependant. With the VTEC solenoid is on the 3-rd biggest lobe begins to push all the intake valves with the more aggressively profile. This variant of the VTEC-E is used in the [[Honda F engine|F23A, F22B and JDM F20B]] SOHC VTEC engines.