Honda L15 engines are a variant of the vast L-series of engines. It appears in many models of Honda cars and created an avenue for compact and subcompact engine cars. L15 engines are sometimes ridiculed, to some, due to L15’s old technology design. However, L15 engines took all of that right in the face and proved that they are worthy of praise, and their different and diverse versions say a lot about what L15 engines can offer.
Honda’s L-series family is the small, compact inline-4 engine that debuted in Honda Fit in 2001. It has four versions: SOHC i-DSi 1.2 L, 1.3L, 1.5 L, and a 1.5 L SOHC VTEC. This L-series feature ideas that eclipsed its previous but well-established D-series engine, eventually replacing them down the road. L series are lighter, smaller, narrower, and have a better fuel economy while attaining lower emission levels.
So, let us talk about L15 engines. Let’s get right to it.
Engine Specifications and Design
- Production Run: 2002 – Present
- Cylinder Head Material: Aluminum Alloy
- Cylinder Block Material: Aluminum Alloy
- Configuration: Inline-4
- Bore: 73 mm
- Stroke: 89.4 mm
- Valvetrain: SOHC 4 valves per cylinder (L15A) and DOHC 4 valves per cylinder (L15B)
- Displacement: 1.5 L
- Compression Ratio:
- Weight: 220 lbs. – L15A
- Max HP: 205 hp at 5,700 RPM
- Max Torque: 192 lb-ft at 2,100 – 5000 RPM
Honda’s L series engine is a petrol engine famous for its super compact design. Complementing Honda’s Global Small Platform, the L series targets the vital aspect of space efficiency by maximizing space. It catered smaller dimensions, reduced interior cabin space, and shorter engine compartments, which are the keys to fit a narrow engine bay than we see in most of Honda’s subcompact series of cars.
L series engines are smaller and thinner compared to the previous D series designs, especially when juxtaposed with the 1.5 Liter VTEC D-series; the reason behind the slimmer profile is that thickness significantly affects the depth of the engine concerning its external dimensions.
L series engines have a much more compact SOHC cylinder head design. Honda combined the intake and exhaust rocker arms axles to attain a much smaller angle between the intake and exhaust valves, which reduced the stretch from 45 degrees to 30 degrees. This allows a narrower head to create a smaller, denser combustion chamber, a crucial environment attribute to expedite and enhance the combustion process of the air-fuel mixture.
Its intake and exhaust system design is highly efficient, with its intake manifold made from hardened plastic – to guarantee structure lightness, designed to achieve high torque while treading in low to mid RPM range. It is lightweight and easy installation on the cylinder head. Still, it takes a lot of space due to its long-runner design that forces the intake manifold to curve up and over, causing the plenum to sit above the engine. So to maintain the narrow profile of the engine, Honda utilized the vertical space available, and it makes a better air circulation and cooling, more accessible engine bay for repairs and service.
The transversely mounted L-series engines have to be equal in, if not more superior, fuel economy and efficient fuel return to compete with the D series. This led Honda to integrate technologies that will lower internal friction, especially during operations, to alleviate power loss and translate that loss to a more usable power from the air-fuel mix combustion.
L series borrowed and applied some piston skirt advice from the 1995 – 2001 DC 2 Integra type R, specifically the B18C spec R engine, which was the first to use Molydebnum-coated piston skirts. L series’ pulverized Molydebnum coating, added to which is already provided, makes better lubrication between the piston and cylinder wall lining that greatly reduces the friction and power loss in this area. There is also an offset in the cylinder shaft and crankshaft which means that the cylinder has a slight disproportion above the crankshaft, giving better leverage on the crankshaft to help excerpt more power out of the combustion. The rocker arm contacts the lobes in the camshaft on roller bearings. L series’ timing chain mechanism is a blade-spring cam tensioner system.
To add to the aforementioned features, L engines are also excellent in terms of emission compliance. Its emission technologies allow them to follow ULEV and EURO 4 standards. Innovations such as the improvement in exhaust pipes made from stainless steel to reduce the weight and conserve the heat lost from the exhaust gas. This property hike up the temperature in the catalytic converter. The catalytic converter is connected at an oblique angle to the downpipe from the engine. It guides the exhaust gases into the cat and increases the contact area between the catalyst inside the cat and exhaust gas, which collectively results in a faster warm-up, cleaning efficiency that leads to cleaner exhaust emissions. It also applies the EGR principle that the engine runs steadily and efficiently when operating at light to medium light efforts. Its power demand parallels with respect to its exertion. EGR redirects some exhaust gas back into the combustion chamber to join and blend with the fresh air-fuel mixture and combust with them.
L series i-Dsi and L-series VTEC
L series core configuration for the i-DSi engine is that it has a thin profile, compact, small inline-4, 8-valve SOHC design with two valves and spark plugs per cylinder. Due to its SOHC design, the original L-series L15A and L13A receive a lot of stigma and derision due to their out-of-date technology. This is because those modern-day engines were equipped with multi-valve designs, DOHC on some higher-end ones. So the prejudice that the engines receive is criminally wrong, especially when they talk about the 16-Valve DOHC with EFi is the standard-bearer of advanced engine technology.
There is an issue with having a very high compression as it produces a knocking or detonation. This greatly affects the engine’s vibration, noise, durability, and sloppy power delivery. The detonation process occurs when parts of the air-fuel mixture instantaneously ignite before the ignition flame from the spark plugs arrives. So to eliminate the knocking and to allow a high compression ratio, Honda introduced and developed the i-DSi system. This technology seeks to combust the air-fuel mixture at the same rate to enable the engine to deliver the right amount of torque at different RPM levels by using two intelligently controlled spark plugs in the cylinder – diagonal and opposite to each other – to reduce the time from the ignition to the actual combustion of the entire mixture.
So i-DSi is basically shortening the elapsed time from the initial ignition of the air-fuel mixture to its complete combustion resulting in maximum combustion pressure. The diagonal and opposite position of each spark plugs matter as it minimizes the travel distance of the flame front from each spark plug before the complete combustion happens. The i-DSi engine uses two valves per cylinder with the basic layout like the typical four valves per cylinder design.
For the i-VTEC system, I know you are pretty familiar with this, so let’s take a brief explanation of it. L-series VTEC engines are used in the 1.5t Honda Fit and 1.5 VTEC Honda Jazz. VTEC focuses mainly on fuel economy and low emission, just like the i-DSi but giving a higher level of power, which equates to higher performance. L15A-VTEC is the fundamental L-series that equips all the key technologies such as the narrow cylinder head, high compression ratio, plastic intake manifold, low internal friction, Molydebnum coated piston skirts, and offset cylinder placement with respect to the crankshaft. The difference between i-DSis and i-VTECs is that VTEC uses 16-valve with VTEC to yield a higher maximum power.
There are lots of L15 variants. Let’s say your fingers are not enough to count those. Anyway, I will introduce and give you some brief knowledge about the variants.
First is the L15A1, used in Honda Fit, Mobilio, Airwave, and Honda City. It has a 1.5 Liter displacement, 10.4 compression ratio, 101 hp, and 94 lb-ft torque available and the first modification with a 16-valve SOHC VTEC head.
Next is the L15A2, which is an engine with the i-DSi system that utilizes the use of two spark plugs per cylinder. It has a power of 90 hp, 10.8 compression ratio, 97 lb-ft of torque available. It appeared in Honda City and Fit Aria four-door Sport-sedan in 2002.
L15A7 is the modified version of the A1s and has been used in the second-generation Honda Jazz. It features a new two-stage i-VTEC system for intake valves and exhaust manifolds, lighter connecting rods and rocker arms, modified pistons, and an enhanced cooling system. It produces 118 hp and 107 lb-ft of torque available.
L15B1 is the L-series variant equipped with an i-VTEC DOHC head, oil jets, lighter camshaft with four counterweights, new pistons, and variable VTC valve timing system for the intake camshaft. It produces 130 hp, 114 lb-ft torque available, and a higher compression ratio of 11.5. This engine appears in third-generation Honda Fit in North America as well as Honda City, Jade, Vezel, and Freed Hybrid.
L15B7 is the turbocharged version that uses oil jets and is installed with a DOHC head with a direct injection system, single-scroll MHI-TD03 turbo, internal wastegate, and VTC Valve timing for the intake and exhaust camshafts. 15B7s produces 174 hp and 162 lb-ft of torque in the standard version. This appears in Honda Civic Turbo – reduced compression ratio and boost pressure increase, Civic Si, and HR-V in Europe.
L15Z is the engine with a 16-valve i-VTEC SOHC head. This engine can be found in South African and Asian vehicles. This produces 118 hp, 107 lb-ft of torque, and has a compression ratio of 10.3.
LEA is the hybrid variant that was made for CR-Zs and Fit Hybrid. It also has a 16-valve VTEC that engages at 2,300 RPM; a better exhaust system made from stainless steel, a new intake manifold, and an electronic throttle body. This engine produces 122 hp, 13 hp coming from the motor, and 129 lb-ft of torque.
Last but not least is the LEB variant, a hybrid made for Honda Vezel and Honda Fit Hybrid. It has a 16-valve i-VTEC DOHC head and a direct injection system. It produces 152 hp, 30 hp coming from the motor, 140 lb-ft of torque, and an 11.5 compression ratio for Honda Vezel. For the Honda Fit Hybrid, the LEB engine is running on an Atkinson Cycle. It has an increased compression ratio of 13.5 and has a multi-point fuel injection system. This engine produces 100 hp and 88 lb-ft of torque.
L15 Engine Tuning and Upgrades
Investing in naturally aspirated engines such as L15 can be a little bit of a loss because you have to spend more and gain less. But, if you really want to stretch it out, why not, so? If you opt to try tuning or to upgrade an L15 engine, consider the L15A VTEC variant. You can buy a cold air intake system, 2.25-inch performance exhaust system, large throttle body, do some head porting, tune the ECU, and you can achieve a 135 boost, at max. You can also buy an aftermarket intake manifold, high compression pistons and throw in some other performance stuff if you are not still satisfied.
You can also buy a turbo kit which will give you at least 150 horsepower, as L15B stock internals can hold up 200 horsepower, so this is not detrimental for the engine. The problem with this arrangement is that this kit and installation might cost you equivalent to a new Honda Fit. Another option, though specific for L15B7s, is a supercharger. You need a tuning chip to elevate the boost pressure and can give you 190 hp. Throwing in some performance parts, cold air intake system, front intercooler, exhaust system, and Hondata ECU can provide you around 210 hp.
Problems surrounding L15A Engines
L15 engines are a solid and reliable piece of masterful craftsmanship. L15 will come a long way and broaden its lifespan as long as you religiously follow the manufacturer’s service schedules or regular maintenance. This includes an oil change using only high-quality engine oil, and always remember that this engine has two spark plugs, and they should both be replaced when needed.
There can also be a carbon build-up risk in the head, specifically around the valves, which can sap the power. That is why some owners though they represent a small portion of the entire community, experience some issues having flat spots or glitches after applying mods and upgrades. This is a much bigger problem on direct-injection engines, but issues are still issues, correct?
Honda’s L-series engine encompasses many expectations and is as efficient, maybe more, in returning equal or better fuel economies just like the D-series did, as well as achieving lower emission levels. The innovations and improvements like the change in external dimensions, such as maximum thickness, do not fully showcase the actual achievement made by Honda’s engineers with this Series. It created its own trend in compact engines and is reliable if you take care and maintain it habitually. Just make sure to check on your engine always.
I hope this article helped to clear and explain some important points to understand Honda’s L15 engine.