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What goes into a VTEC Turbo?


What goes into a VTEC Turbo?

For a lot of car enthusiasts growing up in the 80s and 90s, the word VTEC was synonymous with high-performance engines from renowned Japanese manufacturer, Honda. Over time that acronym, which stands for Variable Timing Electronic Control, has been found on everything from the entry-level Honda City to the family-carrying Honda CR-V.

While there were many versions of VTEC that operated in different ways, the base principle was the same: it allowed Honda to have an engine with variable cam timing (and in some cases, duration and lift) in order to maximize efficiency at the low end without sacrificing performance up top.

For decades, Honda was adamant about staying away from forced induction. They felt that the naturally aspirated form still had some ways to go in terms of development, and arguably all their work culminated in one of the most incredible naturally-aspirated engines available in a road car: the K20A 2.0-litre i-VTEC unit found in the DC5 Integra Type R and FD2 Civic Type R.

But moving forward from there, Honda realized that the only way to keep up with tightening emissions and efficiency regulations, as well as to cater to shifting consumer demands, was to adopt forced induction. Every manufacturer on the market is making this shift as well, although some are caught trying to catch up to the rest. You would expect the same from Honda given how quiet they were about the issue, but you can almost guarantee that they have had turbocharged engines in development for the years leading up to this shift.

The same principles remain. Improve efficiency at the low end while maximizing performance up top. Almost every modern engine has some form of variable timing, executed in a myriad of different ways- but to make it work with a turbocharger requires a little bit more work. Aftermarket tuners who deal with modified turbocharged engines will usually fiddle with the cam timing adjustment to speed up turbo spool times at the low end while doing the opposite at the top to reduce the amount of air-fuel charge that blows out through the exhaust.

But through the magic of direct injection, you can do away with all this tip-toeing around. Direct injection to most people is just another technical term that means “better efficiency”, but combining direct injection with forced induction can lead to some pretty interesting results. Because the engine is spraying fuel into the chamber after the valves shut, this means that no fuel and air mix gets blown out the exhaust valve during the intake stroke of an engine. It also allows for precise fuel injection multiple times to help combat detonation and improve low end performance.

It may be to the dismay of some, but the 1.5-litre VTEC Turbo engines don’t have that VTEC kick of the classic VTEC engines. There is but one cam profile on each cam, rather than the double cam profile associated with the VTEC changeover. Despite this, there is still a Variable Timing Control system that advances and retards the cams in order to spool up the turbo more quickly. On the other hand, the 2.0-litre VTEC Turbo engines such as those found in the FK8R maintain the variable lift system- although the kick is much less pronounced as the engine is already on boost.

From here on, Honda focused on reliability and usability. Some may dismay at how small the turbochargers are on these engines from factory, but the size of a turbocharger directly affects how long it takes to spool up. Small turbochargers allow the engine to hit full boost more quickly and provide that low end torque punch that makes modern turbocharged engines so efficient. To combat high exhaust gas temperatures, the exhaust manifold is water-cooled as well: another problem that comes with running the engine leaner (for efficiency) and having a small turbocharger is high exhaust gas temperatures, and the extra cooling helps to improve reliability of the turbocharger components. 

The result of all of this work is a lineup of engines that can easily rival those of the Europeans, despite their head start on turbocharging. What Honda has achieved is truly impressive considering how dead-set they were on natural aspiration until the very end, and they have applied those same philosophies with the development of these newer engines. One might even say that those original concepts are ingrained in Honda’s engineers, the drive to get the most out of any component without compromising reliability or efficiency.  

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