Honda 1.5T L15B7/Si Turbo Engine: Specs, Problems, Reliability. The L15B7 is a 1.5-liter I-4 turbocharged gasoline direct-injection engine first offered in the 2016 Honda Civic. The engine is a result of Honda’s downsizing strategy that involves using small displacement units along with a turbocharger to overcome the power problem. The 1.5 L turbo engine supplies fuel effectiveness, but at the same time, decent power and torque exceeding the torque of a natural-aspirated 2.4 L engine. The manufacturer already began offering the 1.5 T engine for relatively heavy cars including the Honda CR-V and the Honda Accord.
Let’s take a closer take a look at what makes the Honda 1.5 l turbo engine powerful and so efficient. The engine uses an aluminum open-deck cylinder block and aluminum cylinder head. The engine block is geared up with lightweight steel connecting rods (heat-forged for higher strength) to withstand high loads. There are also new cavity-shaped pistons with an optimized skirt design to minimize vibration and friction and increase operating efficiency. The manufacturers applied plateau honing (grinding process) for cylinder walls to reduce friction between cylinders and pistons even more.
Pistons are cooled by oil spray jets directed at the bottom of the piston. The head design includes four valves for every cylinder and DOHC (dual overhead cam) driven due to the timing chain. The intake and wear down camshafts are equipped with actuators of the VTC. Each multi-hole direct fuel injector is placed between two intake valves; the spark plug is on top in the center of a combustion chamber.
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Honda 1.5T L15B7/Si Turbo Engine: Specs
|Honda Motor Company
|Cylinder block material
|Cylinder head material
|Direct fuel injection
|Number of cylinders
|Valves per cylinder
|73.0 mm (2.87 in)
|89.5 mm (3.52 in)
|1,498 cc (91.4 cu in)
|Type of internal combustion engine
|174-205 hp (130-153 kW)/ 5,500-6,000
|Torque, lb ft
|162-192 lb-ft (220-260 Nm)/ 1,600-5,000
|Engine oil weight
|Engine oil capacity, liter
|3.5 l (3.7 qt)
0.28 l (0.3 qt) – oil filter
|Oil change interval, mile
|9,000 (15,000 km) or 12 month
|Honda Civic turbo, Honda Civic Si, Honda Civic Hatchback Sport/Touring, Honda CR-V, Honda Accord, Acura CDX
The cylinder head has high tumble intake ports (roll ratio is 1.9) that strengthen intake airflow and promote efficient fuel combustion. The 1.5 T engine also has a water-cooled wear down manifold built into the cylinder-head – exhaust-port passages cast directly into the head. Fatigue gas cooling (by 100 degree C) prolongs the life of the turbocharger components and also helps the engine warm-up faster. The L15B7 engine has a mono/single-scroll turbocharger MHI-TD03 with small-diameter turbines and electric wastegate.
The small size turbo with electronic control minimizes a “turbo lag” effect and delivers rapidly reacts to acceleration. Boost pressure is 16.5 psi for a standard US Civic with a 1.5 t engine and a 10.6:1 compression ratio. To reduce the temperature of intake air compressed and heated by the turbocharger, Honda’s 1.5 t engine uses a more common air-to-air intercooler. After the intercooler, air goes into a plastic intake manifold. The engine speed is controlled by the electronic drive-by-wire throttle. That means there is no mechanical connection between the acceleration pedal and the throttle valve.
The manufacturer did not apply truth Honda’s VTEC for the 1.5-liter turbo engine – there is no variable lift mechanism, only dual VT?. Only the 2.0 L VTEC TURBO has i-VTEC (intelligent Variable Valve Timing and Lift Electronic Control) with the dual VTC.
The 1.5 T Si Engine
The 1.5-liter turbo engine for the Honda Civic Si copies the European 1.5 T VTEC Turbo engine specs. It creates 205 hp at 5,700 rpm and 192 lb-ft (260 Nm) at 2,100 rpm. The gain in power was achieved using more performance intake camshaft and higher boost pressure – 20.3 psi. Able to handle raised boost, this version has a lower compression ratio at 10.3 from 10.6 because of other pistons. The standard connecting rods were replaced by reinforced ones. More air needs more fuel – within this case, the Si engine was furnished with more productive fuel direct injectors.
Engines for the Accord and CR-V are based on the Si engine. The CR is 10.3:1. The boost pressure of the Honda CR-V is 18.5 psi; it produces 190 hp and 179 lb-ft. The boost pressure of the Honda Accord is higher – 20.2 psi; power output is 192 hp and 192 lb-ft.
Honda 1.5 T L15B7 Engine Problems and Reliability
The 1.5 T engine doesn’t heat up and creates enough heat while idling. This feature is a disadvantage for a cold climate operation. The engine is so efficient and has low wasted heat. Many owners say it won’t make any heat until they start driving. This issue doesn’t allow the engines to fully reach operating temperature on short trips. A cold engine can develop condensation and excess fuel vapors that travel down into the crankcase and blend with the engine oil in the oil pan. A direct fuel injection aggravates that problem because fuel, sprayed into the combustion chamber directly, sticks to the cylinder walls. That all cause the most reported problem for vehicles with Honda 1.5 L turbo engine – a high or rising engine oil level as a result of oil/gas dilution problem.
The problem with diluted oil has common symptoms: gas smells inside a cabin; a higher-than-normal engine oil level; check engine light comes on; engine misfires. The manufacturer knows about that problem and already offered a solution that consists of several service campaigns that will include software updates, oil change, a new drain plug washer, and in many cases, the replacing of the climate control unit.
Carbon build-up on the backside of the intake valves is a problem of all engines with direct injection and no port injection. This process is worsened much more during short trips on a cold engine. The 1.5 t engine is relatively new and still doesn’t have many consumer reports about carbon deposition, but some other fresh Honda’s DI engines started bringing problems associated with carbon build-up at mileage about 50-60k miles.
- L15BF – 148 hp (110 kW) at 5,500 rpm, 150 lb-ft (203 Nm) at 1,600-5,000 rpm. It is version of the L15B7 with a 10.6:1 compression ratio for the Honda Jade RS available in Chinese market, Japanese Domestic market and Singapore.
- L15B9 – 179 hp (133 kW) at 5,500 rpm, 177 lb-ft (240 Nm) at 1,900-5,000 rpm. The engine is offered in Chinese Market Acura CDX.