As you probably already know, the Honda K20 is one of the most popular engines Honda has ever produced, and we’ve already made a few videos on the K20 and K24. With the new FK8 Civic Type R, Honda moved from the naturally aspirated K20A to the turbocharged K20C. Although both of these engines share the K20 name, they’re pretty different from each other, and today we’re going to discover the differences between the Honda K20A and K20C.
Where They Started
The K20A was initially introduced in 2001 and it was designed to replace the B-Series. On paper it appeared to be better than B-Series in almost every single way, however, it was met with skepticism from Honda enthusiasts who feared it wouldn’t be as good as previous Honda performance engines.
The K20A was initially brought to the US market in the 2002 RSX and Civic Si but has since been used in a bunch of different Honda vehicles ranging from performance cars to small SUVs. It has a lot of features that made it significantly different than the outgoing B-Series engine and today we know it’s an awesome engine for swapping into older chassis which used D-Series and B-Series engines.
As Honda moves toward turbocharging their entire lineup of vehicles, they needed a new performance engine. While cars that use to use the K20A, such as the Civic Si, got Honda’s new L15 engine, their new high-performance applications received the K20C. For this video, we’re going to talk about the K20C1 from the FK8 Civic Type R and not the other K20C variants.
N/A vs Boost
The biggest and most obvious difference between these engines is how the get air into the engine. While the K20A is naturally aspirated and revs super high to produce a lot of peak horsepower, the K20C is turbocharged and produces a lot of power throughout the entire rev range, rather than just at the peak.
While the K20A does produce a lot of power for a naturally aspirated engine, the power is made way up at the top of rev-range and it doesn’t offer a lot of power down low. The increase in low-end torque is one of the reasons that Honda is moving toward turbocharged engines because consumers want engines with a lot of low-end torque, rather than something they have to rev the hell out.
The 306 horsepower figure of the K20C1 might seem pretty underwhelming when you consider it uses over 20lbs of boost, but peak power only tells part of the story. Where the K20A makes a peak torque of 140 to 159 lb-ft anywhere from 4,000RPM to 7,000RPM, the K20C makes 295lb-ft at 2,500RPM, making it far more powerful in the lower revs which is where your engine lives most of its life.
The cylinder head of these engines is quite a bit different from each other since one is designed for naturally aspirated performance and the other is designed for forced induction performance.
Depending on which model of the K20A you’re looking at, it either has the performance or the economy version of iVTEC. There are two kinds of iVTEC: one for improved fuel economy and one for performance, both of which combine VTEC and VTC. We’ll look at the K20A2 which uses the performance version of IVTEC.
On the K20A you’ll find variable lift camshafts on both the intake and exhaust cams, with variable cam timing the intake camshaft. This VTEC setup is in part what helps the K20A head flow so much, moving upwards of 300cfm through the head. On the other hand, the K20C uses variable lift on just the exhaust cam with variable cam timing on both the intake and exhaust cam.
Since the K20C is turbocharged, there isn’t much need for variable lift on the intake camshaft, which is why the K20C uses variable lift on just the exhaust camshaft. The K20C also uses direct injection, which sprays fuel directly in the cylinder rather than at the back of the exhaust valve. While the direct injection system is an upgrade in stock form, it becomes a limiting factor if you ever want to make big power.
While the K20A and K20C vary massively is the intake ports. Where the K20A and previous Honda performance engines flow a massive amount of air, the K20C is pretty bad if you were to look at just the CFM numbers, where the K20A flows upwards of 300cfm while the K20C flows a measly 158cfm. The reason for the reduction in CFM is for the direct injection system.
With direction injection, you want to tumble air into the cylinder, rather than just let it flow in straight. Tuners have already played around with the intake ports and with some light work the K20C head becomes capable of flowing around 300CFM, but without the air tumbling into the cylinder, that increase in CFM won’t directly translate to a significant increase in power.
Another interesting feature on the K20C is the integrated exhaust manifold which is a more compact designed than a standard manifold, and it improved how quickly the turbo can spool up.
Cylinder Blocks & Internals
Below the head, you’ll find that both engines use an open deck aluminum block. While aluminum might not be as strong as cast iron, it’s much lighter and plenty strong for both engines. Both engines feature forged crankshafts and piston oil squirters to help keep the pistons cool. The K20C takes this a step further by using an oil cooler gallery.
Because of the increased power, Honda decided to use forged pistons in the K20C, however, that shouldn’t make you think that they’re automatically way better than K20A pistons. It’s fairly well known that the K20A bottom end can hold up to 400whp if you use forced induction. This needs to be noted because the K20C connecting rods are known for bending breaking around this same power figure.
It’s not the horsepower that causes the K20C connecting rods to fail, it’s massive amounts of torque. With zero bolt-ons and just a tune, the K20C is capable of producing over 400lb-ft of torque at a very low RPM which is what is causes the connecting rods to fail. A lot of racers are tuners who are dialing back the low-end torque to improve the longevity of the K20C.
As far as what’s capable at the very peak of racing, it’s not fully known right now. The K20C is relatively new, while the K20A is decades old. At the peak of four-cylinder drag racing, there are plenty of 1000hp K20A engines, but there aren’t many K20C pushing that kind of power yet. Only time will tell which engine is better at the absolute extremes, but as of right now it’s not known.
When you compare these two engines, you need to understand that they come from different eras of Honda engineering and they’re designed with different goals in mind. In the stock form, the K20C is the better engine, providing more power throughout the entire rev range thanks to its turbocharger. Even in lightly modified forms, the K20C is the better engine, pushing out a huge amount of power with just a tune, again thanks to its use of a turbocharger.
We don’t think the K20C will ever become are wildly popular as the K20A with average enthusiasts who are building cars in their garage. The K20C is physically larger and more complicated than the K20A, making it significantly more difficult to swap into older Honda chassis such as the EG or EK. That being said, I’m sure it will become more popular than it is right now, but it might not ever become as popular as the K20A.
Of course, there are a lot of people complaining that the K20C isn’t like what Honda used to make: high-revving naturally aspirated engines. While some enthusiasts might love revving out their engine and hearing it scream, it’s not what most consumers want. Honda’s move to turbocharged engines allows them to compete with other manufacturers who are developing super torquey four-cylinder engines such as Ford.
The K20C might be way different than Honda engines of the past, but it’s a step that Honda had to take. With emissions restrictions becoming stricter and the competition offering more power and more torquey engines, the K20C was Honda’s solution to keeping up.