ALL IN THE FAMILY
By Keith Buglewicz

A sense of nervousness has seeped into the Honda performance community. It comes not from new anti-racing laws, or emissions regulations that will weld the hoods of new cars shut. No, this nervousness comes directly from Honda itself.

K. It's just a letter, but in the coming years its significance to Honda enthusiasts will achieve the status that "B" has now. With the introduction of the Acura RSX, the new Honda Civic Si and CRV, Honda chucked more than 12 years of engine experience and aftermarket support out the window for a clean sheet of paper design. The new engine family is the K series, and on paper, it makes even the highest performance VTEC B series engine look like yesterday's blue plate special.

Look at the specs. The K20A2 in the RSX Type-S churns out a solid 200 hp from its 2.0- liters. That's 100 hp per liter, and you can thank i-VTEC for this specific output. The "VTEC" part of that acronym is already familiar to Honda enthusiasts. When the engine reaches a certain speed, rocker arms are locked together, linking them to a higher-lift cam, and allowing more fuel and air into the engine. In the world of variable valves, this is known as cam shifting right now, only Honda, Toyota, BMW and Porsche sell cam-shifting systems in the United States.

However, that little "i" means a lot. It means the K series engines are also equipped with VTC, or Variable Timing Control. This cam phasing system uses a spool gear, oil pressure and some fancy electronics to change the angle of the intake cam by plus or minus 30 degrees of timing.

The result is an engine with excellent power and especially torque, but one that still manages better fuel efficiency and lower emissions than its predecessor.

Now, this is all fine and good, but what does this mean for an aftermarket that has been centered on the B series engines? What can be done with it? Can it be turbocharged? Can it be swapped? Does it respond to the simplest bolt on mods? These are the questions on the minds of Honda enthusiasts, and we intend to answer as many as we can. First, let's take a close-up look at the engines as they come from the factory.

THE ENGINES
The K series currently consists of four power plants. The K20A3 is found under the hood of the standard RSX. With 160 hp at 6500 rpm and 141 Ib-ft of torque at 4000 rpm, it churns out the same power as the B16A, 10 hp less than the B38C1, but much more torque than either one of them, all at a lower engine speed. The i-VTEC system works only on the intake cam on this engine, and it has a composite two-stage intake manifold.

Similar to the K20A3 is the K20A found under the hood of the new Civic Si. K20A-what? Well, we're not sure. The cars we've seen have all been pre-production vehicles, without the requisite engine code stamp on the block. The best information we have so far is that it's a K20A3, same as the RSX. But that sounds a little off to us. While it has the same i-VTEC system as the RSX, it boasts the fixed, single-stage aluminum intake manifold of the K20A2 under the hood of the RSX Type-S instead of the dual-stage manifold of the base RSX. Whatever the final engine code works out to being (we'll just call it a K20A for now), this manifold swap actually works against the Si, reducing its torque. It weighs in with the same 160 hp, but with only 132 Ib-ft of torque at a higher 5000 rpm than its K20A3 sibling.

Following the logic of Honda's engine codes, the K24A1 is a 2.4-liter version of the K series. Following a philosophy similar to the B20 found in the previous CR-V, it's tuned to be a torque monster with a long, 99 mm stroke. That's a full 13 mm (0.51-in.) longer than any of the K20 engines. The extreme stroke works. With 162 lb-ft available at a low 3600 rpm, the CR-V is a veritable stump puller among small four-cylinder SUVs. At the top of the enthusiast heap is the K20A2 that powers the RSX Type-S. With a lofty 7900-rpm redline, 200 hp and 142 lb-ft of torque, this engine really is as good as its hype. With the exception of the stroked K24, the engines are all very similar structurally. AII three of the 2.0-liter versions share the same 86 mm x 86 mm bore and stroke. This is known as a square design. An oversquare engine has a longer stroke than bore, like the K24. This generally results in more torque, but at the expense of peak power. Conversely an undersquare design (such as the S2000's engine) has a bore larger than stroke, and generally produces more high-end horsepower at the expense of torque. Not surprisingly, a square design like the K20 is a compromise between these two extremes, offering good torque and good horsepower without sacrificing or optimizing either. Aside from the manifold change on the Si's version of the K20, the main difference between these engines is the way they manipulate their valves.

VALVE DANCING
The K20A2 in the Type-S works the way you expect VTEC to work. The two camshafts are equipped with three cam lobes and rocker arms for each cylinder's pair of intake and exhaust valves. At 5800 rpm, oil pressure activates pins that lock the outer rocker arms to the center arm. This forces both valves to use the higher lift, longer duration center camshaft profile. However, this is augmented by VTC on the intake side, which manipulates the timing of the cam itself. This can be used to augment torque, reduce emissions or a variety of different things depending on what the computer thinks is best at the time. The RSX's K20A3, the Si's K20A and the CR-V's K24A1 use i-VTEC differently. First, it only operates on the intake valves. But even then, the philosophy is changed. Until the VTEC threshold is reached, the lesser K engines essentiality only use one intake valve per cylinder. The other is opened just a crack, enough to keep fuel from pooling behind the valve, but that's about it. In addition, the VTC is tuned primarily to keep emissions as low as possible. All this weirdness results in excellent swirl inside the combustion chamber and very efficient combustion. It's great for fuel efficiency and low emissions. However, it isn't so great for driving fun, as the engine inhales less deeply and revs lower.