The K-Series is arguably the best four-cylinder engine Honda has ever produced. It offers a massive amount of potential for both naturally aspirated and boosted builds, with massive amounts of aftermarket support.
Even with the popularity of the K-Series engine, a lot of people don’t know if they should swap a K20 or a K24 in their car. So, today we’re going to break it down and see which one is better!
Before we dive into the difference, we should briefly cover the basics of the K-Series. Initially introduced in 2001, the Honda K-Series is the engine that ultimately replaced the B-Series engine. The K-Series initially met it with a lot of skepticism from Honda die-hards; many feared it would be worse than the B-Series.
Honda initially brought it to the US market in the 2002 RSX and Civic Si. It had a lot of big changes that made it different than any other Honda engine before it. Some of these changes include a direct-fire ignition system, reverse layout, and clockwise rotation.
Comparing the two engines side by side, the big thing that stands out is how the K20 has the intake side toward the front. This is different than the B-series, which has the intake towards the back.
Rather obviously, the big difference between these two engines is the displacement. The K20 is a 2 liter, and the K24 is a 2.4 liter. The K20 uses a square design, with an 86mm bore and an 86mm stroke.
To give the K24 an extra 400cc of displacement compared to the K20, Honda increased bore to 87mm and stroke to 99mm. The huge jump in stroke allows them to make significantly more low-end torque and the cost of a lower redline.
The long stroke forced Honda to increase the deck height of the K24 compared to the K20.
You would think a taller block, slightly bigger pistons, and rods, and a bigger crank, plus the heavier counterbalanced K24 oil pump, would make the K24 significantly heavier. Surprisingly, the total weight difference between the two adds up to around 10 to 15lbs, which isn’t much considering the low-end power benefits.
As far as applications go, you can find the K20 in the Civic, Integra, RSX, Accord, Stream, and CR-V. The K24, on the other hand, can be found in CR-V, Accord, Odyssey, TSX, and Element.
As you can pretty easily tell from the list of applications, Honda used the K20 in their smaller vehicles. The K24 was mostly used in larger vehicles, mostly because the increased low-end power is really helpful in larger vehicles.
VTEC and iVTEC
Both the K20 and K24 use both types of i-VTEC. There are two kinds of iVTEC: one for the economy and one for performance. Both versions combine VTEC and VTC. The heads for the K20 and K24 are extremely similar, with most of the difference being in the camshafts.
Across all K20s and K24s, there are differences such as intake manifolds, throttle bodies, exhaust manifolds, ECUs, stock power output, and more, but all K20s are pretty similar, and all K24s are pretty similar.
The K-Series is super popular for engine swapping into older Honda chassis like EG and EK. In general, the K20 is cheaper to buy and cheaper to swap than the K24, but you can do a K24 swap pretty cheap.
One of the most popular setups for a K-Series swap is to use a K24 bottom end with a K20 head. You might be wondering why not just swap in a full K24 with the performance version of iVTEC, such as the K24A2 from the TSX?
The thing is, the K24A2 from the TSX is hard to find and not cheap. If you’re able to find one, you’ll have to deal with throttle-by-wire and an ECU that isn’t compatible with other K-Series vehicles.
To address these compatibility issues, you’ll need to install an RSX-S or Civic Si intake manifold and throttle body. You’ll also have to find or make a plug for the EGR port on the TSX head since you will expose it by swapping intake manifolds.
Taking a K24 from an Element, CRV, or Accord and pairing it with a K20A2 head solves all the mentioned problems.
K24 + K20A2 Head
Basically, a K24 with a K20A2 head is a good and cheap way to build a high horsepower K-Series. As far as which one is better, it just comes to price.
If you’re on a super tight budget, the K20 is a better choice, as it’s super cheap and easy to find. The K24 is a little bit more expensive, but the extra 400cc of displacement allows for more power.
Both of them serve as great engines for swapping into other chassis, and they’re both great for naturally aspirated or boosted builds. It’s not uncommon to 250 to 300whp naturally-aspirated K24 builds, but that’s significantly more expensive than a standard K20.
There are even companies building K24s that push over 500 horsepower naturally aspirated, but that doesn’t represent what most enthusiasts will be doing with their K-series. For most street applications, the K20 provides more than enough power to push a lightweight Honda around. For those who want more low-end torque and more overall power, the K24 is the better choice; however, it is more expensive than the K20.