Tuning and Performance Part Guide to the Honda K20"

"Honda K series 2.0 Tuning"

The engine is very free revving, hitting around 8000rpm at the redline.

The K20 replaced the popular B20 series, and we've seen them fitted to a number of sporty cars, including the Arial Atom.

The short intake manifold optimizes power, and the variable timing control and VTEC helps create an engine that has two very distinct personalities.

Some K20 engines were turbocharged, thanks to lower compression and a revised piston, crank, and new engine timing! The redline is generally lower on the turbocharged versions for obvious reasons.

History, Power & Specs of the K20 Engine

The K20A production run from 2001–2011. The K20Z was 2005-2015 and the K20C is stilll in production today.

Such was the success of this block it has been revised and tweaked and was released with power up to 306bhp from the factory, with plenty of leeway and room for the tuner to make more and many reporting the blocks are safe to 400hp (but your mileage will vary depending on the block and version you have, the R versions are much better built).

K20A JDM only (The VTEC comes in at 6000 rpm)

The Spec R engine had a lighter flywheel, high compression pistons, stiffer valve springs and longer camshaft durations. The cylinder heads were also ported and polished and these special engines were hand tooled at the factory. They show the potential of the other engines if you take your time tuning and setting them up.

Check out our video introduction to Honda Tuning, all you need to know about mods and upgrades on your Honda.

• 2001–2006 Honda Civic Type R
  11.5:1 212 hp @ 8000 RPM 149 lbft@ 7000 RPM
• 2001–2006 Honda Integra Type R
  11.5:1 217 hp @ 8000 RPM 152 lbft@ 7000 RPM
• 2002–2008 Honda Accord Euro R
  11.5:1 217 hp @ 8000 RPM 152 lbft@ 6000 RPM
• 2007–2011 Honda Civic Type R
  11.7:1 221 hp @ 8000 RPM 159 lbft@ 6100 RPM (VTEC 5800)

K20A1

There was technically no A1 version - essentially it's still a K20A3 but a lower spec compression to handle the turbo!

Typically a twin scroll Mitsubishi TD04HL-15T turbocharger is fitted with 13.5psi of boost.

• 2001–2006 Honda Stream
  9.7:1 156 hp @ 6500 RPM 139 lbft@ 4000 RPM
• 2001–2006 Honda Stream
  9.8:1 158 hp @ 6500 RPM 140 lbft@ 4000 RPM

K20A2 (The VTEC comes in at 5800rpm)

• 2001–2006 Honda Civic Type R
  11.0:1 200 hp @ 7400 RPM 139 lbft@ 5900 RPM
• 2002–2004 Acura RSX Type S
  11.0:1 200 hp @ 7400 RPM 142 lbft@ 6000 RPM
• 2002–2004 Honda Integra Type R
  11.0:1 200 hp @ 7400 RPM 142 lbft@ 6000 RPM

K20A3 (The VTEC comes in at 2300rpm)

• 2002–2006 Acura RSX
  9.8:1 160 hp @ 6500 RPM 141 lbft@4000 RPM
• 2002–2005 Honda Civic Si
  9.8:1 160 hp @ 6500 RPM 132 lbft@ 4000 RPM
• 2002–2005 Honda Civic SiR
  9.8:1 160 hp @ 6500 RPM 132 lbft@ 4000 RPM
• 2002–2005 Honda Civic Type
  S 9.8:1 160 hp @ 6500 RPM 132 lbft@ 4000 RPM
• 2003–2006 Honda Civic 2.0 i-VTEC
  9.8:1 155 hp @ 6500 RPM 131 lbft@ 5000 RPM

K20A4

• 2002–2006 Honda CR-V
  9.8:1 150 hp @ 6500 RPM 140 lbft@ 4000 RPM
• 2003–2007 Honda Accord
  158 hp @ 6500 RPM 140 lbft@ 4000 RPM

K20A6 (The VTEC comes in at 2500rpm)

• 2003–2006 Honda Accord
  9.8:1 155 hp @ 6500 RPM 140 lbft@ 4000 RPM
• 2003–2006 Honda Accord
  9.8:1 155 hp @ 6500 RPM 140 lbft@ 4000 RPM

K20A9

• 2004-2007 Honda FR-V
  9.8:1 150hp @6500 Rpm 142 lbft @4000 RPM

K20Z

• K20Z1
  2005–2006 Acura RSX Type-S
  11.0:1 210 hp 143 lbft @ 6200 RPM Redline 8100 RPM
  2005–2006 Honda Integra Type S
  11.0:1 210 hp @ 7800 RPM 143 lbft @ 6200 RPM Redline 8100 RPM
• K20Z2
  2006–2011 Acura CSX
  9.8:1 153 hp @ 6000 RPM 139 lbft @ 4500 RPM Redline 6800 RPM
  2006–2011 Honda Civic
  9.8:1 153 hp @ 6000 RPM 139 lbft @ 4500 RPM Redline 6800 RPM
  2006–2015 Honda Accord
  9.8:1 153 hp @ 6000 RPM 139 lbft @ 4500 RPM Redline 6800 RPM
  2006–2010 Honda Civic 2.0 S / S-L
  9.8:1 153 hp @ 6000 RPM 139 lbft @ 4500 RPM Redline 6800 RPM
• K20Z3
  2006–2011 Honda Civic Si
  11.0:1 197 hp 139 lbft 8000 RPM
  2007–2010 Acura CSX Type-S
  11.0:1 197 hp 139 lbft 8000 RPM
• K20Z4
  2007–2010 Honda Civic Type R
  11.0:1 201 hp @ 7800 RPM 142 lbft @ 6800 RPM Redline 8000 RPM

K20C

• K20C1
  2015–present Honda Civic Type R
  9.8:1 306 hp @ 6500 RPM 295 lbft @ 2500 RPM
• K20C2
  2016–present Honda Civic LX
  10.8:1 158 hp @ 6500 RPM 138 lbft @ 4200 RPM
  2016–present United States Formula 4 Championship 10.8:1 158 hp @ 6500 RPM 138 lbft @ 4200 RPM
• K20C3
  2016–present Honda Avancier
  10.8:1 272 hp @ 6500 RPM 273 lbft @ 4200 RPM
• K20C4
  2018–present Honda Accord
  9.8:1 252 hp @ 6500 RPM 273 lbft @ 1500-4000 RPM
  2018–present Acura RDX
  9.8:1 272 hp @ 6500 RPM 280 lbft @ 1600-4500 RPM

K23A1

13.5 psi of turbo boost and dual path turbine housing makes this a special K series variant.

• 2007–2012 Acura RDX 6800 RPM 240 hp @ 6000rpm & 260 lbft 4500rpm

We have a separate tuning guide for the K24 here

Best K20 tuning parts upgrades and mods.

The best modifications on an engine are in our opinion the ones that give the best value for money.

For getting more power from a Honda K20 engine, several modifications can help.

Tuning your K20

The engine timing and injectors and fuel pump also have a large bearing on the torque gains you'll achieve. But let's break the mods down in tuning stages as is our custom and look at the merits of some of these other mods and upgrades.

Check out our video introduction to Honda K20 Tuning, all you need to know and full guide.

Best Mods for your K20

1. Fast road cams are one of the most significant mechanical changes, an easier route is to get the VTEC to kick in earlier as these are essentially a performance cam and standard cam.
2. Internal mods - crank Kfrank etc...
3. Mapping - Mapping Via Kpro or similar aftermarket ECU
4. Intake and Exhaust - Note that on their own these mods will NOT ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
5. Exhaust headers - A higher revving engine like the K20 needs to expel the exhaust gases as efficiently as possible.
6. Fuelling upgrades - fuel pump, pressure regulator and fuel injector upgrades will help avoid flat spots.
7. Intake improvements - make sure there is no restriction in the K20 intake, by upgrading the induction.
8. Forced induction - Upgrades to turbochargers and superchargers are the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. It is one of the most costly upgrades but provides the best gains.

K20 Tuning Stages

Typical stage 1 mods often include: drilled & smoothed airbox, Sports exhaust header/manifold, Panel air filters,  Hondata ECU upgrade, Intake manifolds, altering VTEC timing to lower RPM point.

Typical stage 2 mods often include: induction kit, Ported and polished head, fuel pump upgrades, high flow fuel injectors, Fast road cam, Sports catalyst & performance exhaust.

Typical stage 3 mods often include: Twin charging conversions, Competition cam, Crank and Piston upgrades to alter compression, Internal engine upgrades (head flowing porting/bigger valves), Adding or Upgrading forced induction (turbo/supercharger), Engine balancing & blueprinting.

K20 Camshaft upgrades

Camshaft upgrades on most cars prove to be a great way to get a performance boost as modifying the camshaft profile can change the intake and exhaust durations which can radically alter the output power.

With the VTEC on the K20 you already have a performance cam profile, so getting the VTEC to kick in earlier will be similar to sourcing a fast road cam on other cars. For more aggressive upgrades a performance cam can be fitted, but in our minds seems a step too far, especially as the VTEC engines are so well set up.

Fast road cams commonly bump the performance across the rev range, you may lose a little bottom end power but high end rpm power will be lifted.

With the VTEC engines you can potentially force the VTEC to cut in at lower RPM, effectively giving you more low end power and better pickup as the sacrifice of economy.

This saves the effort of sourcing and fitting a fast road cam and may suit your K20 tuning needs more suitably.

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

For a road car must carefully try to optimize your power band to your driving style.

It's worth noting that the K20A3 VTEC only works on the intake but on the K20A2 it operates intake & exhaust.

You can think of the K20A3 as a 12 valve engine under 2200rpm and over this threshold the additional 4 valves are used thanks to the additional cam lobes.

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

The IPS kme II is used on the similar K24 engine to lift power, giving around 10 degrees more duration, but it can work well with a ported K20 or rebore/stroked K20. Bear in mind the valve lift will need adjusting and setting up to 0.523 gross. Setting 30VTC over 5800 rpm seems sensible for a DIY project.

K20 Internal Engine Mods

There is a mod called the K FRANK, where you fit an Accord 2.4 bottom end with a type R head on the top. This will give you a lot more torque but you will need to lower your rev limit.

The K20Z4 was related to an S2000 engine so dropping in the crank from the S2000 would give good power gains (research your engine and donor engines carefully before doing this).

A stock K20 can usually cope with around 400hp before internal strengthening is required but we've heard of some K20A3 blocks breaking rods at 340hp.

Head swaps are popular mods, for example putting the K20A head and cam profile on the K20A2 to benefit from the cam durations and timing.

The Spec R K20 engine was fitted with a lighter flywheel and boasted high compression pistons, stiffer valve springs and longer camshaft durations.

The cylinder heads were also ported and polished and these special engines were hand tooled at the factory to very tight tolerances.

They show the potential of the other engines if you take your time tuning and setting them up focusing on these areas first.

 

Remapping a K20

Can you map a K20?

Remapping is best done via an aftermarket ECU on the K20.  ECU flashing should help to release the full potential of all the upgrades you've fitted to your K20 and this is typically achieved with a Hondata, K-Pro or Apexi ECU.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is a route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

Reprogramming The ECU on the K20 is generally hard, so consider either the K-Pro or the K Series Pro Hondata Programmable ECU is one great option that is often used by car enthusiasts for getting the most out of their K20 engines.

Hondata parts are expensive which is comprehensible considering the performance of this high-quality component. However, there are several other programmable options from other brands as well which can be used for the same purpose.

It will usually give you around 30% more power on turbocharged vehicles and 15% on NA (naturally aspirated) engines, but your mileage will vary depending on the upgrades you've done and the condition of your engine.

K20 Intake upgrades and mods

Improving your car's air intake is a definite way to bolster its performance. Increasing the diameter of the throttle is key to increasing air intake. A tapered entrance, also adds the ability to gulp in more air. Using an FD2 throttle body can be effective for this purpose.

Aside from that, one of the best performance intake modifications is the RRC intake manifold. A cold air intake system shows significant improvement in terms of power gains.

It is vital to any engine modification project to feed more fuel and air into the K20 engine

The K20 intakes are short and allow for very high velocity air flow, unless you are making large power gains there is little gain to be had by trying to improve the intakes on most K20 engines.

The shape and flow rate of the Air Intake manifolds can make a big difference to fuel mixing and power on the K20.

It's not uncommon that air intake manifolds are in dire need of aftermarket tuning parts, although a few makers like Honda actually provide reasonably good air intake manifolds.

Fitting big valve kits, carrying out port matching and head flowing will also lift torque, and importantly will give you raising the torque increase on other parts. With several options available in the market for K20 engines, you can choose the one that fits your budget.

K20 Exhaust Upgrades

You only need to replace your exhaust if your current exhaust is actually creating a restriction. Performance exhausts are essential components for modified vehicles because they reduce the possibility of exhaust gases spilling back due to backpressure in the pipe, which can reduce the oxygen content and thus the engine's horsepower.

The stock exhaust does pretty well for unmodified vehicles, however as the power increases, the requirements for a bigger exhaust become so much more important for a K20. Replacing the stock exhaust with a 2.5” or a 3” exhaust ensures more power gains.

However, going for the performance exhaust options with catalytic converters is preferred over the decat ones as it keeps the vehicle street legal. Sports Injection Kit Using a sports injection kit is another great way to see a performance increase in terms of power and torque.

Note that with the widest exhaust you can source this will slow up the exhaust flow rate - the best for power gains are usually between 2.5 to 3 inches. It is the shape and material more than the bore size.

Typically exhaust restrictions can be located the catalyst and filters installed, so adding a better flowing performance catalyst removes the restriction. We note that performance cats perform similarly to decats, (test pipes or catless headers), and have the added benefit of keeping your car street legal, as decats or catalyst removal is illegal in most territories for road going cars.

K20 Turbo upgrades

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

Turbo Modifications guide for the K20

Like all other engines, adding a turbo is a great way of boosting the power of a K20 engine. Thankfully the K20 is a good strong engine, and can be easily setup to work with a turbo thanks to the work of many project owners over the years who have done this mod and perfected it.

Getting a Turbo kit like the Full Race Twin Scroll T4 Turbo Kit can show substantial performance improvements.

The added advantage of this kit is that it retains almost all accessories on the K20. While adding these turbochargers, keep in mind to check the list of ECUs supported by different manufacturers. Try to get all the components from one place to ensure you get decent aftermarket support and not a bunch of blame passing between the component makers.

Another factor to bear in mind is that timing, boost, and fuel all matter a lot, and getting them right is critical or you'll have engine failures or flat spots. Adding more power puts more stress on the engine block, so it's always a good idea to keep an eye on the upper limit of how far you can go with a stock one because it's a very common problem that K20s with heavy modifications frequently fail when put to the test.

Low-end lags are common for larger upgraded turbos whereas smaller turbos spool up quickly however they lack peak rpm torque gains. Fuelling, one common problem which most car enthusiasts forget to focus enough on is the need to upgrade a fueling system while modifying cars.

NA (naturally aspirated) engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your K20

If your motor is already turbocharged, tuning parts are giving better power gains and we find turbo engines are made with harder and stronger components.

K20 turbo conversion and injector sizes

Here are some turbo conversions on the K20 blocks, with injector sizes and verified dyno readings all quoting wheel horse power!

Bear in mind some of these engines were extensively modified so these are not the only parts added.

• 400hp GT3076  RC 750cc injectors
• 338hp Mitsubishi T517Z(greddy) RC 750cc injectors
• 590hp GT4094r twin scroll  1200cc PTE
• 600hp GT4094r Inline Pro 1000cc
• 340hp precision 60 trim  precision 1000cc
• 275hp td05/td06 RC 750cc injectors

Stock K20's can reportedly handle up to 25-30psi of boost providing the tuning is spot on!

It really is all about getting the timing, fuel, and boost if you add it just right, or you'll end up with flat spots or engine failure.

Expect around 360 wheel hp for 10psi of boost on the K20.

We did see a stock K20Z1 reach 620hp with a GT35R, AFI sidewinder manifold and 1000RX injectors managed by the APex N1! This was quite an impressive achievement and shows how good the K20Z1 block is.

However you will find an engine typically has weakspots so discover these limitations and fit better conrods, pistons and crankshaft to cope with the power.

Large upgraded turbos commonly experience low-end lag, and small turbos spool up really quickly but do not have the peak rpm torque gains.

We are pleased that the range of turbochargers is always evolving and we commonly find variable vane turbochargers, where the vane profile 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 flow these at differently profiled vanes in the turbocharger. They also improve the scavenging effect of the engine.

It is common that there is a limit in the air flow sensor AFM/MAF on these engines when a lot more air is being pulled into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited bhp and torque at a much lower level.

Adding a supercharger or additional turbo will make large bhp gains, although more complex to configure. We have a twincharger bhp adding guide if you want to read more.

K20 Fuelling Upgrades and Mods

A powerful setup has higher fuel requirements and once the system doesn’t get enough of it, it is bound to fail, no matter how advanced the system is.

The injector capacity must be oversized. Normally it is suggested to keep the injector capacity at least 15% more than that of the stock parts.

As a rule of thumb add 20% capacity when buying an injector.

But why go beyond the requirements? Well, it comes in handy in the long run when the injector performance deteriorates or in the cases when the engine requires more fuel.

The OEM injectors on the K20 are typically rated to 310cc output so are not far from their limits on the more powerful engines.

The most popular K20 injectors we've found people using are....

• RC 750cc injectors
• PTE 1200cc
• Inline Pro 1000cc
• Precision 1000cc

Better injectors WILL NOT INCREASE POWER, but they will ensure you are getting the performance from all your other mods.

The TODA Sports injection kit, specially designed for the K20 engines, features an individual throttle body for each cylinder which improves response.

Weak Spots Issues & Problem Areas on the K20

The K20 engines are generally reliable and solid units, as long as you follow the manufacturer's service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Regular oil changes are vital on the K20, especially when tuned, and will help extend the life and reliability of the engine. The camshaft is usually the first thing to show up problems when the wrong grade of oil is used.

We have broken out this article to a standalone feature on K20 problems so we can go into more detail.

K20 problems after mods

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engine's design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

K20 crankshaft oil seal problems

Oil leakage from the crankshaft’s front seal is another common issue in these engines. A visual inspection should reveal if the front crankshaft oil seal is prone to weep a little oil on your K20. Replacing the seal will solve this problem (don't use oil treatments to "repair leaky seals").

K20 knocking sound problems

There have been reports of knocking sounds heard by K20 owners. In the best case scenario, adjusting the valves will solve the problem.

However, the situation can deteriorate, resulting in the exhaust camshaft wearing out and necessitating replacement after a while.

Engine mounts frequently fail and you'll notice engine vibrations more when this happens but it is not a cause for concern.

K20 rough idle problems

A rough idle can be caused by a dirty throttle body or a faulty idle control valve.

In addition, rough idling may need the throttle body to be cleaned up.

Furthermore, Carbon buildup in the head can create flat spots restricting the viral performance of the vehicle. This is a larger issue on direct injection engines but should be looked out for on all engines especially as the mileage starts to rack up. We have tips on removing carbon build up.

Please help us improve these tips by sending us your feedback in the comments box below.

We love to hear what our visitors have got up to and which parts work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these articles which are kept updated and constantly revised.

Join us in our forums if you want to share tips and advice with other K20 owners, we have a dedicated Honda tuning forum and general car forums, and we don't have the off topic chat and negativity you find on so many car forums these days. So please join us in our friendly forum where you can discuss K20 tuning options in more detail with our K20 owners. It would also be worth reading our unbiased Honda tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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