VTEC vs iVTEC

Honda VTEC

 You’ve probably heard of VTEC. It’s one of the defining features of Honda engines and it’s one of the reasons so many people love it.

Variable valve timing lifts and electronically controlled also known as VTEC, is a system that uses two separate cam lobes to optimize engine efficiency. It does this by using a cam lobe for low rpm, and a cam lobe for high rpm. By using two separate cam lobes you can optimize valve overlap, lift and duration for two separate sets of Rpms. So you end up with more low-end torque, and high-end horsepower, but you still have great drivability and great fuel efficiency. This kind of a system is usually set to engage at a set rpm, say 5500 rpm, it will engage the second cam lobe. So Honda implements the system and so do many other car manufacturers now, to improve overall engine efficiency. Since the camshaft spins half as fast as a crankshaft, you can really only optimize it for one set of Rpms, now by having two different lobes you can optimize it for two sets, if you had three lobes you could optimize it for three sets, and so on and so forth. But two is pretty much all you need to optimize it for low end and high end power.

vtec system

If you ever wondered why the muscle cars have that really choppy idle, it’s because they’re using an aftermarket camshaft designed for high end power. It’s designed to have duration, lift and valve overlap, specifically at higher rpm that means that low rpm is basically, it’s not designed for low rpm at all, and that’s what gives it that choppy idle. Before I tell you what iVTEC is, let me tell you what VTEC-E is, because that’s a different kind of VTEC that not a lot of people even know about. VTEC-E is different is that it is not designed for power. Basically at all. It’s designed solely for fuel efficiency and nothing else. VTEC-E gets such great fuel economy by turning you 16-valve 4-cylinder engine, into a 12-valve 4-cylinder engine, what it does is it doesn’t allow one of the intake valves to fully open. By not allowing the second intake valve to open all, the way combustion chambers swirl is improved and so is fuel atomization. This allows Honda to use leaner AFR and ultimately improve fuel economy.

Another thing we quickly need to talk about before talking about iVTEC is VTC, which is known as variable timing control. Now variable timing control is typically a mechanism that you’ll find on the end of an intake camshaft, and it’s essentially cam phasing it allows the intake camshaft to be continuously variable, so that the overlap between the intake and exhaust cam can be infinitely adjustable throughout the RPM range. This kind of system can be used on both the intake and exhaust camshaft, but for the most part it’s only used on the intake camshaft because that’s where you’re gonna find the greatest gains. Intelligent variable timing and lift electronically controlled, which is a massive mouthful, is a system that combines VTEC and VTC (Variable Timing Control) into one system. As you can imagine combining VTEC and VTC, or best of both worlds into one system, results in a really efficient and really powerful engine. The VTEC part of the system has two different cam lobes, one for low rpm, one for high rpm, and VTC system it’s constantly adjusting valve overlap to be optimized. So throughout the power band. You pretty much have optimum valve overlap, timing and duration throughout the entire rev range.

Unfortunately Honda make this really confusing by having two different kind of iVTEC. So in the case of the K20A2, which is the performance oriented K20 that we got in the US, that combines VTEC and VTC. By combining those two, Honda got a lot of power out of that little engine. Where this gets really confusing is the K20A3, which combines VTEC-E and VTC. Now combining VTEC-E and VTC, you still get great power, but it’s not performance oriented like iVTEC in the K20A2. It’s still good, but it’s designed for fuel efficiency. It’s really annoying that Honda decided to use iVTEC as the name for both the K20A3 and the K20A2, because really they’re different systems. Now how exactly VTEC increases horsepower can be kind of confusing if you’re new to the whole automotive world. Horsepower is just a measure of torque times Rpm. To increase torque, you need to get more air into the engine, and with more air you can add more fuel. This results in a larger combustion, more downwards force and more torque. By opening the valves further, and for longer at different rev ranges, you can ultimately increase torque and low rpm and increase torque at high rpm. The VTC system optimized how much air is being sucked into the engine at low rpm and high rpm, by constantly adjusting the cam timing. You might be wondering why Honda didn’t just use more cam lobes in their VTEC system instead of just two cam profiles. They could use three or four cam profiles, and the answer is simplicity. The gains from three cam profiles would be so miniscule that it really wouldn’t be worth it. Especially considering it would vastly increase the complexity of the system, ultimately decreasing reliability down the road because you have more moving parts.

The easiest way to remember all this is that iVTEC, is the same is VTEC, except it has VTC included in the system to further improve efficiency. I hope this helped you understand the difference between VTEC and iVTEC better.