Modding tuning and best performance upgrades on the Honda L15 engine!

All you need to know about "L15 Modifications"

L15 Modifications Guide

How to modify and upgrade the Honda L15

"Comprehensive guide to performance tuning the Honda L15 engine!"

Sites like TorqueCars are always getting messages asking how to improve the L15 from people inquiring about getting more power from the L15 and wanting to know what are the best L15 power upgrades. So let us look into Honda L15 upgrades and outline the best modifications on this great engine and point out some common pitfalls along the way.

The Honda L15 offer good returns when tuned and with carefully chosen tuning enhancements like ECU maps, turbo upgrades and camshafts you will positively increase your driving pleasure.

Here we review L15 tuning and summarise the optimum upgrades.

Just because particular tuning mods are are common on L15 it doesn't mean it is good, instead we'll focus on the top tuning mods that will give your L15 the best value for money to power increase.

Without us subscribing to the misaprehension of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

L15 induction kits

Improving air intake on the L15

You need fuel and air for an engine to work. If there is little supply of fuel then it will run lean, if there is a lack of air it runs rich resulting in lost power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the aim to any engine modification task to shove more air into your L15 but this has a knock on effect with the air flow sensor.

It is common that there's a limitation in the air flow sensor MAF/MAP on the L15 when considerably more air is being drawn into the engine.

We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting power at a much lower level.

Engine intake manifolds take the during the engines suck phase from the filter and allow it to be fed into the engine cylinders.

Structure and flow rate of the Intake headers can make a big effect on to fuel delivery on the L15.

On popular production engines plenum chambers are needing motorsport parts, although a few OEM provide fairly well optimized plenum chambers.

Big valve conversions on the L15, doing some 3 or 5 angle valve jobs and porting and head flowing will also lift bhp and torque, this will give you a greater bhp and torque increase on other parts.

L15 performance cam tips.

Each engine responds better to different camshaft durations so set your engine up on a rolling road.

The ecu map and injectors and fuel pump also have a large bearing on the bhp gains you'll hit.

Extending exhaust or intake durations can alter the bhp band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

Altering your L15 camshaft will make a dramatic difference to the engine torque. Choosing a higher performance camshaft profile raises the torque accordingly.

NB: Fast road camshafts normally increase the bhp across the rpm band, you could drop a little low end power but high end rpm power will improve.

Competition camshafts, increase the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Competition cam makes it harder when driving around busy urban areas.

You should ideally optimize your engines power to your cars usage so for a daily driver stick with a mild fast road L15 cam

Stage 1, 2 and 3 mods for the L15

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 L15 parts:

Remaps/piggy back ECU, Drilled & smoothed airbox, Panel air filters, Intake headers, Sports exhaust manifold, Fast road camshaft.

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 2 L15 parts:

Fast road cam, high flow fuel injectors, Ported and polished head, induction kit, fuel pump upgrades, Sports catalyst & performance exhaust.

Stage 3 L15 parts:

Crank and Piston upgrades to alter compression, Adding or Upgrading forced induction (turbo/supercharger), Internal engine upgrades (head flowing porting/bigger valves), Twin charging conversions, Competition cam, Engine balancing & blueprinting.

The L15 power plant respond well to mods and we see that there is a growing number of mods and tuning parts around.

Remaps allows a tuner to fully realize the full potential of all the modifications you've done to your L15.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output will rely on the modifications you've fitted and the condition of your engine.

Turbo modifications on the L15

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the L15.

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes massive power gains.

If your motor has a turbo already fitted tuning parts are more reliable and turbocharged engines are made using harder and stronger components.

There are weak spots for every engine, with some being incredibly solid and some only able to handle stock power

It is important to find these restrictions and install higher quality crank and pistons to utilize the power.

It's not unheard of people spending a lots of money on turbocharger upgrades on the L15 only to suffer the humiliation of seeing the motor go up in smoke soon after it's completed.

Big capacity turbo chargers commonly suffer low end lag, and little turbo chargers spool up really quickly but do not have the peak rpm power band gains.

Over the last 20 years the choice of turbochargers is always increasing and we now see variable vane turbochargers, permitting the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbochargers divert the exhaust gases into a couple of channels and feed these at differently designed vanes in the turbocharger. They also help the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large bhp gains, although more difficult to configure. We have this article covering twinchargers if you want to read more.

Tips about fuel supply on the L15

You will need to ensure that the engine is not starved of fuel so should uprate the fuelling when you start exceeding 20% of a performance hike. We strongly recommend you to over specify your injector capacity.

As a rule of thumb add 15% capacity when buying an injector, helps cope with injector deterioration and gives a little spare capacity should the engine require more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended L15 performance exhaust upgrades

The only time you should look to improve your exhaust system with an upgraded one is if the existing exhaust is creating a restriction in flow.

On most factory exhausts you should find that your flow rate is still good even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Sports exhausts generally help improve air flow from the engine but avoid an exhaust that is too big or you may end up will reduce the flow rate. Stick to one and a half to two and half inches as a rule of thumb.

The usual suspects causing problems in your exhaust flow rate can be located the emissions filters installed, so adding a faster flowing high performance alternative will help avoid this restriction.

Catalyst removal (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the L15

Like most engines an L15, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the L15, failure to do this will exacerbate engine wear, on a tuned L15 this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your L15 why not pop over to the forums at TorqueCars where you can chat about L15 tuning options and read about others projects who may be planning to do similar modifications on their L15.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We want to know your experiences with upgrades on your L15, it helps us improve our tips and keeps us current so please use the comments box to drop a tip.

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Check out TorqueCars new YouTube channel, and see their awesome new content...


Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article