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Discussion Starter · #1 · (Edited)
It's 3AM and I have nothing else better to do, so here's a thread about Honda's different i-VTEC systems.

Honda made many versions of their "i-VTEC" systems. The performance oriented i-VTEC incorporated valve lift and timing (VTC) on both the intake and exhaust sides. Engines like the K20A, K20A2, K20Z1, K20Z3, K24A2, and K24A3 have the performance version of i-VTEC. This allowed these engines to rev higher and overall produce more top-end power.

Some engines like the K20A3 and K24A8 only had "i-VTEC-E." Those engines don't incorporate variable valve lift (VVL), only a 12 to 16 valve switch over and variable valve timing (VTC) on the intake side only. These engines usually produce more low-end torque and have better fuel efficiency. However, they don't rev as high and make less top-end power. In addition, their switch over is extremely early in the rev range and barely noticeable compared the performance variants.

There is another version of i-VTEC that incorporates variable valve lift, but only on the intake cam. Engines like the K24Z3 and K24Z7 have this version of i-VTEC where VVL only occurs on the intake side and is also the side that has VTC. This system sets itself in the middle of the previous two systems in terms of performance.

Almost all of the engines look the same with a few subtle differences like the intake manifold or manifold cover, but you can generally tell the different K-Series engines apart by the manifold cover itself. If the lettering is red, then the engine has real "i-VTEC." If the manifold cover has black lettering or no lettering at all, it's most likely the "economy i-VTEC." Of course there's the head stamping and engine code to go off by too.

I'd love to hear more facts from you guys about the different systems. Thanks!



Red Lettering w/ Metal Manifold K20A2

Black Lettering w/ Plastic Manifold K20A3

No Lettering w/ Plastic Manifold K24Z3

K20A3 "i-VTEC-E Head" (2 Lobe VTEC-E Only)

K24Z3 "i-VTEC Head" (3 Lobe VTEC Only Intake Side)

K24A2 "i-VTEC Head" (3 Lobe VTEC Both Sides)
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