Honda R18A

Honda R18A engine (R18Z)

  1. Specifications
  2. Overview, problems
  3. Performance tuning

Honda R18A/R18Z engine specs


Manufacturer Honda Motor Company
Also called Honda R18
Production 2006-present
Cylinder block alloy Aluminum
Configuration Inline-4
Valvetrain SOHC
4 valves per cylinder
Piston stroke, mm (inch) 87.3 (3.44)
Cylinder bore, mm (inch) 81 (3.19)
Compression ratio 10.5
Displacement 1799 cc (109.8 cu in)
Power output 102 kW (140 HP) at 6,300 rpm
103 kW (141 HP) at 6,500 rpm
Torque output 174 Nm (128 lb·ft) at 4,300 rpm
174 Nm (128 lb·ft) at 4,300 rpm
Redline 6,800
HP per liter 78
Fuel type Gasoline
Weight, kg (lbs) 183 (403)
Fuel consumption, L/100 km (mpg)

Honda Civic
9.2 (26)
5.1 (46)

6.6 (36)
Turbocharger  Naturally aspirated
Oil consumption , L/1000 km
(qt. per miles)
up to 1.0
(1 qt. per 600 miles)
Recommended engine oil 0W-20
Engine oil capacity, L (qt.) 3.7 (3.9)
Oil change interval, km (miles) 5,000-10,000
Normal engine operating temperature, °C (F)
Engine lifespan, km (miles)
-Official information

300,000+ (180,000)
Tuning, HP
-Max HP
-No life span loss


The engine is installed in Honda Civic
Honda Stream
Honda Crossroad

Honda R18A engine reliability, problems and repair

R18A engineWith the release of the 8 generation Honda Civic in 2005, the new R18A engine appeared in the then new R-series. It replaced the outdated D17A and D16W engines. A new compact aluminum cylinder block with the deck height of 230 mm was used here. A 87.3 mm stroke crankshaft was installed inside this cylinder block, the length of connecting rods was 157.5 mm, piston size was 81 mm, and their compression height was 10.5 mm. All this ensured the displacement of 1,800 cc.
This cylinder block was covered with a new 16-valve SOHC head, which got intelligent variable valve timing and electronic lift control i-VTEC system. The size of intake valves is 32 mm, of exhaust valves – 26 mm, valve stem diameter is 5.5 mm.
The engine was equipped with a narrow timing chain, which was designed to run through the entire service life. This was so in the reality, and no problems arose with it.
This engine does not use hydraulic tappets, you just have to adjust the valves after every 24,000 miles of mileage, if they are noisy.
The valve clearances for the cold engine are 0.18-0.22 mm for intake valves, and 0.23-0.27 mm for exhaust valves.
For the R18A, a new 2-stage variable length intake manifold was developed that was triggered at 5200 rpm. The exhaust system was also new, with improved catalytic converter to meet the highest environmental standards.
In 2007, the Honda R-series was enriched by a 2-liter R20A version created based on the R18A specially for larger vehicles.

In some countries, a 1.6-liter version called R16A can also be found.

Honda R18 engine modifications and differences

1. R18A1 was the first variant for the North American and Asian Honda Civic, and Honda CR-V and City.
2. R18A2 was an analog to R18A1 for the European Honda Civic.
3. R18Z1 was a variant with the modified i-VTEC system which could disable 4 intake valves at low rpm. Operation modes of the intake manifold are switched at 5,000 rpm.
The engine power was 141 HP @ 6,500 rpm, and the torque was 174 Nm @ 4,300 rpm. This engine can be found in Honda Civic for the South-East Asia.
4. R18Z4 was an analog to R18Z4 for the European Honda Civic.
5. R18Z9 was an analogue to R18Z1, fit for Honda HR-V.

Honda R18A engine problems and malfunctions

1. Knocking sound in the engine. The knocking sound is usually caused by the Evap canister purge valve. Very often users forget to adjust valves in time, and they start making the noise. Check it out.
2. Noise. R18A engines can make noise due to the tensioner pulley failure, which has the service life of about 60,000 miles, sometimes less. Check it and replace if necessary.
3. Vibrations. In case of cold start this is normal, since the engine has low idle speed. If the vibration is too strong, check engine mounts, especially the left one.

It is important to use high quality engine oil, otherwise the i-VTEC system will fail soon. In countries with fuel problems, do not try saving on it. Poor quality gasoline will quickly destroy your catalytic converter and the O2 sensor.
Here a catalytic converter combined with exhaust manifold is used, and this manifold is integrated into the cylinder head, which means the engine is experiencing increased heat load. That’s normal, but it is important to keep an eye on the cooling system, otherwise the engine may overheat.
After about 100,000 miles, crankshaft seals and camshaft seals may leak.
In the end, with normal and regular maintenance, your R18A is an incredibly reliable engine, maybe the most reliable engine in its class.

Honda R18A engine tuning

Naturally aspirated

This engine was created for leisurely driving across the city, it was not prepared for sports achievements. However, one can do something to make it go a bit faster. One can use chip tuning, install a cold air intake system, a header and an aftermarket exhaust system. These performance parts provide extra 15-20 HP.
Add a 60 mm Skunk2 throttle body, a Skunk2 Stage 2 cam, Acura RDX 410 cc fuel injectors, and a Hondata Flash Pro. It would be great if you do head porting. These upgrades will provide up to 180 HP.

R18A turbo

An excellent way to increase the R18A power is buying a supercharger kit, e.g., Jackson Racing. It uses a Rotrex C30-74 supercharger with an intercooler. However, stock internals should better be replaced for CP pistons (compression ratio 9) and Eagle rods. This will give you up to 220-240 HP. Buy a header and a 2.5″ performance exhaust system, and the result will be even better.
You can go ahead with a Rotrex C30-84 supercharger. Buy 630 cc fuel injectors, a Walbro 255 lph fuel pump and a Hondata FlashPro. These mods will let you get about 290 horsepower.
There is also a Kraftwerks supercharger kit based on the Rotrex C30-94 supercharger. Add a Skunk2 Stage 2 cam to it, and your engine will reach 380-400 WHP.

You can build an R18A turbo using a Garrett GT2860RS turbocharger, forged internals (CP pistons + Eagle rods) and a turbo manifold. You will also need an intercooler, a piping kit, a blow-off valve, an oil cooler, a Mishimoto oil catch can, a Walbro 255 fuel pump, 630 cc fuel injectors, a 2.5″ exhaust system, and a Hondata ECU.
Of course, an oil feed line and an oil return line are to be installed for your Garrett.
This turbo kit will easily give you 300 WHP with the boost pressure of 15 PSI.