Honda 2.4L K24A i-VTEC Engine Specs, Problems, Reliability

In 2002, Honda released a engine marked K24A. It was planned that the motor would be the basis for the CR-V series, but it was widely used in other brands.

The younger brother K20A served as the base. The engine was intended to replace the outdated F23 series.

Here, we will investigate the characteristics and characteristics of this engine by referring to the data of the K24A type naturally aspirated engine installed in Honda’s CW2 Accord Tourer type-S 2011/02 model.

First of all, as a basic structure, the K24A engine is a long stroke engine with a bore (inner diameter) of 87.0 mm, a stroke (stroke) of 99.0 mm, and a bore stroke ratio of 1.14 (the stroke amount is larger than the piston diameter).

When the displacement and the number of cylinders are the same, the engine has better torque characteristics in the low rpm range than the short stroke type and is easy to handle, but in the high rpm range, the filling efficiency deteriorates and the sliding resistance increases. There is a concern that the output will drop.

Moreover, when the number of revolutions is the same, the average piston speed tends to be higher than that of the short stroke type, so the load on the engine tends to be heavier.

Among the models registered on this site, the oldest model equipped with the K24A type naturally inhaled engine is the second generation Step WGN [RF7 type | 2004/06] released from 2001/04 , and the newest model is 2011. It is the 4th generation CR-V [RM4 type | 2011/12] released from / 12, and 33 models of NA cars and 0 models of turbo / SC cars are registered in all 33 models.

Evaluation from the viewpoint of transient characteristics and liter equivalent horsepower

Image of engine performance curve
Changes in horsepower	142.3PS → 206PS
Transition of torque	23.7kgm → 21.1kgm
Liter horsepower	87.51PS / L
Litter torque	10.1kgm / L

The in-line 4-cylinder 2354cc, high-octane gasoline specification naturally aspirated engine of the Accord Tourer, which is the reference vehicle this time, produces a maximum output of 206 horsepower at 7,000 rpm and a maximum torque of 23.7 kgm at 7,000 rpm.

If you know the horsepower and the number of revolutions, you can know the torque, and if you know the torque and the number of revolutions, you can know the horsepower. The torque at 7000 rpm is 21.1kgm.

The horsepower per liter of displacement is 87.51PS / L and the torque is 10.1kgm / L, and the horsepower per cylinder (single cylinder volume 588.5cc) is 51.5PS and the torque is 5.9kgm.

When the K24A naturally aspirated engine is applied to a 10-step evaluation based on deviation values ​​aggregated from all NA vehicles registered on this site, the evaluation is “quite good” with a converted horsepower of [ 8 ] and a converted torque of [ 7 ]. It is categorized as “high power engine“.

By the way, among the models equipped with the K24A type turbo / SC engine, the one with the highest output was the CW2 type Accord Tourer 206PS / 23.7kgm, and the smallest was the RB1 type Odyssey 160PS / 22.2kgm.

Displacement increase, compression ratio increase, bore stroke ratio change

There are three factors that determine the engine displacement: the number of cylinders, the bore diameter, and the stroke amount. By increasing or decreasing these, engines with various displacements are created.

Here, regardless of whether it is actually possible, the displacement when the piston diameter is expanded from the genuine 87.0 mm to 90.0 mm in 0.5 mm increments and when the stroke is extended from the genuine 99.0 mm to 104.0 mm in 1 mm increments. And, the change of the compression ratio when it is assumed that the volume of the combustion chamber does not change is listed.

* It is easy to say stroke up, but if you want to make a long stroke, you need a crankshaft and a compatible connecting rod, and if you can not use it as a genuine product, you have to make it in one-off, so it is expensive anyway. It is a menu that requires considerable preparedness to put out.

Regarding the compression ratio, in most cases, the uneven capacity of the top surface of the piston changes as the diameter of the piston increases, so the compression ratio values ​​in the list do not match, but the displacement. Please enjoy the atmosphere that the compression ratio will naturally increase as you increase the size.

B / S ratio is an abbreviation for bore stroke ratio, and as the bore diameter is widened, the characteristics of the long stroke type, square type, or short stroke type are approached. In the case of K24A type engine, the ratio changes from 1.14 to 1.10 when the bore is increased by +3.0mm from the genuine piston.

Increased displacement with engines with similar piston diameters

There are 27 engines with pistons that are similar in size to the K24A type engine with a piston diameter of 87.0 mm, so let’s calculate the displacement when the piston is diverted and the bore is increased as a sideshow.

Engines with similar piston diameters are Mitsubishi: 6B31 type 2997cc 87.6mm mounted on the CW6W type Outlander, Subaru: EJ18 type 1820cc 87.9mm mounted on the BD2 type legacy, Subaru: mounted on the GF4 type Impresa Sports Wagon. EJ16 type 1597cc 87.9mm, Mitsubishi: 4B12 type 2359cc 88.0mm mounted on CW5W type Outlander, Suzuki: H27A type 2736cc mounted on TD94W type Escudo 88.0mm, Lexus: 1LR mounted on LFA10 type LFA 88.0mm of type 4805cc is applicable.

(Although the number of people who find pleasure in such a quest has decreased) No matter how close the diameter is, there are factors such as the diameter of the piston pin, the height of the piston, and the convenience of valve recess, so if possible, the same manufacturer, If possible, if you choose the same fuel and the same intake method, and if possible, the one with a similar displacement, the possibility of genuine diversion may increase.

Average piston speed

Next, let’s look at the average piston speed. The average piston speed at 7000 rpm, where an engine with a stroke of 99.0 mm produces maximum output, is 23.1 m / s , which is a piston speed that travels a distance of 23.1 meters per second (83.2 km / h at speed). It means that is moving up and down.

The average speed is 14.2 m / s at 4300 rpm, which generates the maximum torque, and 24.8 m / s when the rev limit is assumed to be 7500 rpm, which is 500 rpm higher than the 7000 rpm where the maximum output is generated.

For reference, I calculated the change in piston speed when a K24A engine with a stroke of 99.0 mm is rotated up to 10000 rpm. Looking at this, it seems that the speed increases by approximately 6.60 m / s as the number of revolutions increases by 2000 revolutions.

Considering only 20.0 m / s, which is a guideline for a general engine premised on mass production, I think that about 6060 rpm is a good rpm, but this engine has the maximum output. It has already exceeded 20.0 m / s at the time of occurrence, and considering the rev limit, it will rotate a little more (300 to 500 rpm?), So it is an engine that is doing its best even though it will be difficult inside.

K24A Engine Modifications

Like almost all Honda engines, the K24A has several modifications that have been actively used and applied. Let’s consider the main ones:

1. K24A1 – the first civilian version, a two-stage intake manifold is installed on the engine, the i-VTEC system on the intake camshaft is tuned for economy and ecology. Compression ratio 9.6, power 160 hp at 6000 rpm, torque 220 Nm at 3600 rpm. Found on Honda CR-V.
2. K24A2 – a motor for larger cars, a different crankshaft is used, reinforced connecting rods, other pistons, the compression ratio is increased to 10.5, the camshafts are replaced with more evil ones, the throttle valve is increased, another inlet / outlet. VTEC shifting occurs at 6000 rpm. Power 200 hp at 6800 rpm, torque 225 Nm at 4500 rpm. In 2006, the engine received an intake tract with a diameter of 80 mm (it was 70 mm), a throttle valve 64 mm (it was 60 mm), an exhaust on a 57 mm pipe (it was 52 mm). As a result, the power rose to 205 hp. at 7000 rpm, torque 231 Nm at 4500 rpm.
3. K24A3 is similar to K24A2 for Europe and Australia.
4. K24A4 (K24A5, K24A6) – civilian engine with i-VTEC on the intake shaft, which can change the phase by + \\ – 25 °, compression ratio 9.7, power 160 forces at 5500 rpm, torque 218 Nm at 4500 rpm .
5. K24A8 – 166 hp version with electronic throttle, i-VTEC starts at 2400 rpm.
6. K24Z1 – an analogue of K24A1, the intake manifold has been changed, SHPG from K24A4, compression ratio 9.7, power 166 hp. at 5800 rpm, torque 218 Nm at 4200 rpm. The engine was put on a Honda SRV.
7. K24Z2 – compression ratio increased to 10.5, different camshafts, power 177 hp. at 6500 rpm, torque 224 Nm at 4300 rpm.
8. K24Z3 – the compression ratio is increased to 11, the shafts are even higher, the power is 190 (201) hp.
9. K24Z4 is an analogue of K24Z1.
10. K24Z5 – analogue of K24Z2, power 181 horses.
11. K24Z6 – analogue of K24Z5, other camshafts are installed, power is 180 forces.
12. K24Z7 – engine for Civic Si and Acura ILX. It has changed pistons, connecting rods, intake manifold, camshafts, VTEC switches to 5000 rpm. Power 205 hp at 7000 rpm, torque 230 Nm at 4400 rpm.
13. K24Y1 – Honda SRV engine for the Thai market, compression ratio 10.5, power 170 hp. at 6000 rpm, torque 220 Nm at 4300 rpm.
14. K24Y2 – Honda Crosstour engine, lower compression ratio – 10, meaner camshafts, power 192 hp at 7000 rpm, torque 220 Nm at 4400 rpm.
15. K24W1 – engine for the Accord, part of the Earth Dreams series (index W) with direct injection. Relative to the K24Y, the intake/exhaust has been changed, now the intake is at the rear, the exhaust is at the front, the compression ratio is 11.1, the camshafts are quiet, VTEC switches to 4800 rpm. Motor power – 185 hp at 6400 rpm, torque 245 Nm at 3900 rpm.
16. K24W2 – analogue of K24W1 with different camshafts, power 188 hp
17. K24W3 – an analogue of K24W2 with a slightly modified exhaust, 190 horsepower.
18. K24W4 – injection system changed, compression ratio 10.1, lower camshafts, power 174 hp. at 6200 rpm, torque 225 Nm at 4000 rpm.

K24A Most Common Faults and Repairs

• Vibration. Often vibration occurs due to a break in one of the pillows. According to practice, you should first check the left.
• Knock. It is caused by a defective exhaust camshaft. The solution to the problem is to replace the part. You should also pay attention to the valves that should be adjusted.
• Oil leak. The leakage is caused by wear of the crankshaft oil seal.
• Floating turnovers. Caused by the effect of a clogged throttle. Cleaning will help solve the problem.

K24A Engine Service

Maintenance of the engine should be carried out every 15,000 km, but, as with any engine, it is recommended to reduce the period by 1.5 times in order to increase the life of the motor. To prevent other malfunctions, during each maintenance it is recommended to diagnose the electronic engine control unit for errors.

Conclusion

The K24A engine is a simple and reliable engine from Honda. Maintenance can be done by yourself. Due to the simplicity of the design, it can be repaired independently. As with any engine, the K24A has its own faults typical of it. So, the main ones are: