Honda K20 vs K24 Engine Guide

The Honda K-series has 44 variants in total, each with their own characteristics and vehicle applications. That’s pretty insane. Within those variants, the K-series has two distinct short blocks that share the same design, but have different deck heights. The K20 has a shorter deck height of 8.3 inches while the K24 block has a deck height of 9.1 inches. The discrepancy in deck height results in a difference in displacement between the K20 and K24. Since the stroke of the K24 was increased significantly over the K20, the two have different performance characteristics and vehicle applications.

In this article, we’ll cover the similarities and differences between the Honda K20 vs K24 engine. 

Honda K20 Engine Specifications

Engine	Honda K20 Engine
Configuration	Inline-4 Cylinder
Displacement	1,996 cc (121.8 cu in)
Aspiration	Naturally Aspirated / Turbocharged
Valvetrain	DOHC W/ i-VTEC or i-VTEC-E on some models
Block/Head	Aluminum/Aluminum
Bore x Stroke	86.0mm x 86mm
Compression Ratio	9.6:1 – 11.0:1
Weight	Long Block ≈ 275lbs
Horsepower	150-316 hp
Torque (lb-ft)	131-295 lb-ft

The K20 (2.0L) engine family has four different variants, each with their own sub-variants. These include the K20A, K20B, K20C, and K20Z. All K20 variants share very similar engine construction, retaining 2.0L of displacement, the same stroke and bore, and DOHC valvetrain. All engines in the K20 family have aluminum head and block construction and have forged steel crankshafts. 

Despite their fundamental similarities, each K20 variant was designed for its own vehicle application and differs slightly from the next. All engines in the K-series lineup have a DOHC valvetrain with some form of i-VTEC variable valve timing. While all K20s utilize variable valve timing, some eco-oriented variants only have VTEC on the intake side. The K20A3 is the most common K20 engine that has the less desirable i-VTEC-E system. 

Outside of variable valve timing differences, the K20 variants differ in a number of other ways. The compression ratios between variants vary by a significant amount. For example, the highly sought-after K20A2 engine from the US-spec 2002-2004 Acura RSX Type-S has an extremely high 11.0:1 compression ratio. In contrast, the K20A3, K20A4, K20A6, K20A7, and K20A9 have a much lower 9.8:1 compression ratio. This boils down to cylinder head and piston differences between the variants.

K20C variants also have comparably low compression ratios, especially when compared to K20A variants. This is due to the fact that K20C variants are turbocharged. Lower compression is favorable for turbocharged engines, as it lowers the strain on the engine’s internal components.

Honda K24 Engine Specifications

Engine	Honda K24 Engine
Configuration	Inline-4 Cylinder
Displacement	2,354 cc (143.6 cu in)
Aspiration	Naturally Aspirated
Valvetrain	DOHC W/ i-VTEC or i-VTEC-E on some models
Block/Head	Aluminum/Aluminum
Bore x Stroke	87.0 mm x 99.0 mm
Compression Ratio	9.7:1 – 11.0:1
Weight	Long Block ≈ 300lbs
Horsepower	160-206 hp
Torque (lb-ft)	160-181 lb-ft

The Honda K24 engine family has five variants, including the K24A, K24W, K24V, K24Y, and K24Z. Like the K20’s variants, each K24 variant also has sub-variants. Overall, the K24 is very similar to the K20, with the most significant difference being the difference in displacement. As we stated earlier, this directly correlates with the K24’s longer stroke. 

The most common and sought-after K24 variant is the K24A, specifically the K24A2. Like the K20A2, the K24A2 features Honda’s performance version of i-VTEC, with VTEC applied to the exhaust and intake sides of the engine. The K24A2 also has the highest stock horsepower figure of the K24 range (outside of the more modern K24W7). Like the K20, each K24 variant differed a bit in terms of compression, ranging from 9.7:1 to 11.0:1 for performance models. 

Earlier K24A variants are generally preferred by the community, as most of the later K24 variants focused primarily on fuel efficiency and emissions requirements. Variants like the K24Z1and Z2 are reworked versions of earlier K24A variants. K24Z variants feature different intake manifolds, throttle body design, reworked catalytic converters, and updated fuel injectors compared to K24A engines. 

If you would rather consume this content via a video, check out our Honda K20 vs K24 video below:

Performance

As we have already established, the K24 has an extra 400 ccs of displacement over the K20. Because of the K24’s increased stroke, it has different performance characteristics than the K20. 

The K20’s square engine geometry – meaning that its stroke and bore are the same lengths – has its own benefits. In general, square engines strike a good balance between high rpm performance and torque. The K20’s square design allows its redline to be higher than the K24. This is an aspect of the K20 that many Honda enthusiasts prefer. Since iVTEC initiates at around 6,800-7,000 rpm on the most popular K20 variants, most of the fun occurs at high rpms.

In contrast to the K20, the K24 has an “under square” engine design, meaning that its stroke length is longer than its cylinder bore. Under square engines tend to produce higher torque than square engines, especially at low-rpms. That is certainly true of the K24 and a solid argument in favor of the K24 for certain applications. However, the K24’s higher low-end torque comes at the expense of high-rpm power. In comparison to the K20, the K24 has a notably lower redline which puts some enthusiasts off. 

The unique characteristics of the K20 and K24 make each engine better for different applications. Due to the K20’s smaller displacement and lower torque figure, it was Honda’s engine of choice for their smaller vehicles like the Civic, Integra, and Accord. The K24 was Honda’s choice for their larger and heavier vehicles that need the extra torque to get going. These models include the Odyssey, CR-V, and Acura TSX. 

Design Differences

There really isn’t a whole lot to mention in terms of truly important differences between the K20 and K24’s design. Many parts are interchangeable throughout the entire K-series lineup and some parts from the K20 can be swapped into a K24 and vice versa. The overall cylinder head design of the K20 and K24 are nearly identical. With that being said, there are some small differences of note. 

One small difference between the K20 and K24 is the shape of the intake ports. The K24 features smaller intake ports which increase overall torque compared to the K20 ports. The K20 and K24 also use different intake manifolds. The popular K20A2 variant uses a PRB intake manifold while the K24A2 uses an RBB intake manifold from the factory. Overall, the K20A2 head flows better than the K24A2 head, if only slightly.

Beyond that, the K20 and K24 feature slightly different camshafts, springs, and spring retainers. Factory K24A2 cams have larger primary lobes than those on K20A2 cams. For that reason, K24 cams typically provide better low/midrange power compared to K20A2 cams. However, the VTEC lobes are more pronounced on K20A cams, making them better for high-rpm performance. 

Despite their differences, K20 and K24 cams are interchangeable. It is important to understand how that will affect each respective engine though. Swapping K20A/A2 cams into a K24 presents a degree of risk due to the added strain on the valvetrain. Due to the K24s engine geometry, it wasn’t built to withstand the revs that the K20 can handle. 

Modifications

Honda’s K-series is a fantastic platform for modifications. That includes both K20 and K24 variants. Both the K20 and K24 are known for their unparalleled build construction and ability to withstand huge amounts of horsepower with relative ease. While it is possible to dip into sizable horsepower numbers with any K-series engine, some are easier and more worthwhile to modify than others. 

In general, the performance K-series variants are more receptive to modification than the more economy-focused variants. The best K20 variants to modify include the K20A, K20A2, K20Z1, and K20Z4. The best K20 variants to modify include the K24A2, and K24A3.

Both the K20 and K24 are said to be able to handle 280-300 horsepower reliably with stock internals. While there are tons of examples of stock K-series pushing far more horsepower than that, 300whp is about the highest safe figure. Both the K20 and K24 are highly receptive to simple bolt-on mods.

Some of the most common K-series mods include an RRC intake manifold upgrade, cold air intake, 4-2-1 header, upgraded exhaust, FD2 throttle body, and upgraded ECU. A full-bolt-on setup like this will garner a horsepower figure close to 220-230 hp depending on the engine variant that you have. That’s a pretty impressive figure for not having to open the engine.

Obviously, even higher horsepower figures are possible with some internal upgrades. Modifications like stronger valve springs and retainers, more aggressive cams, forged pistons, lightweight flywheel, and bigger injectors are all solid options for a naturally aspirated K20 or K24 build. 

Honda K20/K24 Hybrid Engine

The Honda K-series fanbase has gotten pretty creative over the years with mixing and matching components. In fact, one of the most common K-series engine builds involves combining the K20 and K24 into a hybrid engine. The most common method of doing this is by sourcing a K24 bottom end from an Element, Accord, or CR-V and a K20A2 head from an RSX Type-S. 

The K20A2 head is a direct fit on a K24 block, but there are some other considerations that need to be taken into account. For example, the K20A2 uses an oil cooler while the K24 does not. Some choose to not use an oil cooler altogether, while others chose to plumb the oil to an outboard cooler. 

This “Franken-Engine” provides the key benefits of both the K20 and K24, while also being a cheaper alternative to sourcing a K24A2 which can be very pricey. The final result will be a 2.4L K-series with the performance version of iVTEC from the K20A2. The combination motor will have the higher torque characteristics of the K24 without losing the top end power provided by performance iVTEC.

Forced Induction

Forced induction is undoubtedly one of the most common options for building a high horsepower K20 or K24. Both engines are capable of running boost (at a moderate level) right out of the box. As we stated earlier, both the K20 and K24 can both handle 300+whp with stock internals reliably. The same can be said when you introduce forced induction into the equation. 

There are tons of off-the-shelf FI options available for both the K20 and K24. Both engines respond well to either a supercharger or turbocharger, so that decision is mainly based on personal preference. It is generally accepted in the Honda community that supercharging a K20 or K24 is less efficient. If you are shooting for extremely high horsepower numbers, a turbocharger and built internals are the way to go. 

A K20A2 head is generally stated to be better for forced induction as it has better flow figures than the K24. However, the K24A2 head can be ported and polished to achieve similar flow figures as the K20A2. Depending on the base model of the car, the K20 might also be a better option from a transmission standpoint. Most Honda enthusiasts recommend using the EP3 5-speed transmission as it is the most durable option. Read our relevant K24 Turbo Engine Upgrade Guide.

Price

One of the most important aspects of the K20 vs K24 engines debate, especially for those looking to engine swap, is price. Due to the fact that the K20 has been around longer and the Hondas that they originally came in have depreciated over the years, it is easier and cheaper to source a K20 than it is to source a K24. This is especially true for each respective engine’s most sought-after variant.

At this point, it is cheaper to source a K20A2 than it is to source a K24A2. The K24A2 is generally a pretty hard-to-find engine and carries a premium when you do find one. For that reason, most Honda fans recommend doing the K20/K24 hybrid combo. It is a much more cost-effective option to source a K24 block (non-A2) and a comparably inexpensive K20A2 head. If you are looking for the performance characteristics that a K24 provides but don’t want to shell out for one, this is your best bet.

Honda K20 vs K24 Engine Summary

The Honda K-series will go down in history as one of the best inline-4 layouts to ever be released. They are known for their bulletproof reliability, sturdy construction, iVTEC inclusion, and massive aftermarket support. 

In terms of overall construction, the K20 and K24 are very similar in a lot of ways. The primary distinguisher between them is displacement. The K24’s extra 0.4 liters of displacement introduces different engine characteristics than the K20. With its under-square design, the K24 provides better low-end torque than the K20. However, the K20 provides better high-rpm performance than the K24. Most enthusiasts will make a decision on either of these motors for their particular application based on those characteristics.

Both the K20 and K24 are fantastic platforms for modifications and tuning. The K20 and K24 are perhaps two of the most supported engines in the world as far as aftermarket parts are concerned. Forced induction, either via supercharger or turbocharger, is one of the most common K-series modifications for big power. The K20A2 edges out the K24 slightly as the best engine for boost due to its higher flowing cylinder head.

If price is a serious consideration for you in deciding between the K20 and K24, the K20 is the more budget-friendly option. Should you be sold on the idea of better low-end torque, a K20A2 head on a K24 block is a cheaper alternative to sourcing a K24A2. 

If you enjoyed this article and are looking for more Honda content, check out our Honda K20A2 Engine Guide. As always, safe driving!