K20 vs K24
Two engines from one family, separated mostly by 13 millimetres of stroke. That difference decides which one suits your car, and it is not the difference most comparisons lead with.
The K-series arrived in 2001 and took over from the B-series in the cars where Honda cared about revs. Both the K20 and the K24 are aluminium inline-fours with chain-driven twin cams, the intake on the firewall side, and i-VTEC. They share an architecture, a bellhousing pattern and a great deal of hardware.
What separates them is the crankshaft. The K20 is square: bore and stroke are the same number. The K24 keeps a similar bore and adds a much longer stroke, and that one decision produces the extra capacity, the different power delivery and most of the practical consequences below.
| Specification | K20 | K24 |
|---|---|---|
| Displacement | 2.0 L | 2.4 L |
| Bore × stroke | 86.0 mm × 86.0 mm | 87.0 mm × 99.0 mm |
| Configuration | Inline-four | Inline-four |
| Valvetrain | DOHC i-VTEC, 16 valves | DOHC i-VTEC, 16 valves |
| Produced | 2001 onward | 2002 onward |
| Variants on this site | K20A, K20A2, K20A3, K20Z1, K20Z3, K20C1 | K24A, K24A1, K24A2, K24A4, K24A8, K24Z1, K24Z3, K24Z7 |
| Factory applications listed | 9 | 8 |
Power figures are deliberately absent from this site. They vary by market, model year, fuel grade and measurement standard, and a single number quoted without that context is closer to marketing than to a specification.
What the stroke difference actually does
A short stroke means the piston travels a shorter distance per revolution, so mean piston speed climbs more slowly as engine speed rises. That is why the square K20 is the engine Honda used where the power band needed to extend upward, and why it feels like it wants to be worked.
The K24’s longer stroke buys capacity, and capacity is what produces effort at lower engine speeds. In a heavy car doing ordinary work — a CR-V, an Accord, an Element — that is exactly the right trade. It is also why the K24 turns up in replacement demand more than any other Honda four of its generation: it went into an enormous number of ordinary cars.
Neither engine is the better one in the abstract. The question is what the car is for. A light chassis that will be revved is a K20 argument. A car that carries weight, or a build that wants torque without forced induction, is a K24 argument.
The variant spread matters more than the family
This is the part that costs people money. “K20” and “K24” are family names, and within each family the variants differ in head, cams, compression, intake and engine management.
In the K20, a Japanese-market K20A from a Type R model and a K20A3 from a base RSX share a displacement and very little that determines what the car does with them. In the K24, the K24A2 from the Acura TSX uses a different head casting and higher compression than the CR-V and Accord variants, which is why it is the one people go looking for.
Japanese-market units also frequently carry the family code with no trailing digit — K20A, K24A — because that is the Japanese designation rather than a truncation. A listing saying K24A is telling you less than one saying K24A2. Reading the stamped code is how you settle it.
Replacement or swap: answer this first
The comparison above only helps if you are choosing. Most people are not.
If you are replacing a failed engine, the right engine is the one the car was built with, and this page is background rather than a decision. The transmission, engine management, accessory layout, harness and exhaust in your car are already committed to a specification, and matching it is the cheapest path to a running vehicle. Work from the year, model and trim, then confirm against the stamp.
If you are swapping, the engine is the first item on a list rather than the last. Mounts, axles, shift linkage, harness, ECU, immobiliser, hood clearance and the exhaust all follow from the choice, and the cost of the project sits mostly in those items rather than in the difference between the two engines.
The practical swap considerations
Bellhousing
Shared across the K-series, which is the reason the K24 into a K20 chassis is such a common project. Physical bolt-up is usually the straightforward part. What follows it is not: gear ratios, final drive, the shift linkage and the axles are all properties of the transmission rather than the engine, and they do not come along with a matching bolt pattern.
Intake manifold height and hood clearance
Intake manifold height differs enough between K-series variants to create clearance problems the family name gives no warning about. On some chassis this is a non-issue and on others it decides which manifold you run. It is a measurement to take before the engine is on the stand, not after.
ECU and immobiliser
The most common reason a mechanically correct K-series will not start. A Japanese-market K20A and a North American ECU are not automatically a working pair, and the immobiliser pairs keys to the management system without caring what is bolted underneath it. Decide the management plan before the engine arrives.
Balance shafts
Present in some K24 applications and not in others. It changes what a rebuild needs and what a swap needs to account for, and it does not follow from the family name. Establish it for the specific variant.
Accessories and mounting
Alternator, air conditioning compressor and power steering placement vary between applications enough to matter when the engine is going into a chassis that never had one. Two engines with the same stamped code out of different vehicles can present differently once you are trying to mount them.
Tell us whether it is a repair or a swap and what the car is. The answer changes depending on which one you say, so say it up front.
Common questions
What is the actual difference between a K20 and a K24?
Displacement, and it comes from the stroke. The K20 is a square engine at 86.0 mm bore by 86.0 mm stroke. The K24 uses an 87.0 mm bore and a 99.0 mm stroke. Same family, same architecture, same chain-driven twin cams and i-VTEC. The long stroke is what gives the K24 its extra capacity and its different character.
Which one revs higher?
The K20, as a matter of geometry rather than tuning. A shorter stroke means piston speed rises more slowly with engine speed, which is why the short-stroke engine is the one Honda put in the cars built around revs. The K24 makes its effort lower down instead. Neither is better; they suit different jobs.
Will a K24 bolt to a K20 transmission?
The K-series shares a bellhousing pattern across the family, which is why the swap is common. That is the easy part of the question. Gear ratios, final drive, shift linkage, axles, the ECU and the intake manifold clearance all still need answers, and we verify the specific combination against your vehicle rather than treating the family match as the end of it.
Which one should I buy for a replacement?
The one your car was built with. On a replacement the correct answer is dictated by the vehicle, not by preference, because the transmission, engine management, accessory layout and harness in the car are already committed. The comparison on this page matters when you are choosing an engine, which is a swap.
Is the TSX K24A2 worth seeking out?
It depends entirely on what the engine is going into. Replacing a TSX engine makes it the correct part and the question does not arise. For a swap, the A2 head is why people look for it, and whether that is worth paying more than a CR-V K24A1 costs is a judgement about what you want the finished car to do. The stamped code is what settles which one is actually on the pallet.
Where to go next
- K20 EngineThe 2.0 K-series: variants, what they came in, and how to tell them apart.
- K24 EngineThe 2.4 K-series, including the K24A variants sold as JDM units.
- How to Find Your Honda Engine CodeWhere the code is stamped, and what the characters mean.
- How to Verify Engine FitmentThe information that settles fitment, and why a year alone never does.
- Acura TSX EnginesThe K24A2 years, the K24Z years, and the V6.
- Engine FinderTell us the vehicle and we identify the engine before quoting it.
Find the right engine for your vehicle
Tell us the year, model and trim. We identify the engine your vehicle takes and come back with current availability and pricing.