Tuning the Honda K20

"Comprehensive guide to tuning the Honda K20 engine!"

Herein we review K20 tuning and show the ultimate modifications for your car. Honda K20 are awesome to work on and with the ultimate performance mods like ECU maps, turbo kits and camshafts you will definitely maximize your driving enjoyment.

The ultimate K20 parts on an engine are obviously the ones that give the biggest return for your cash.

We won't be swayed by popular K20 parts, they need to be cost effective.

Significant gains can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

There is a modification known as 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).

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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.

Significant gains on the K20 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

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.

Interestingly it's worth noting that the K20A3 VTEC only works on the intake but on the K20A2 it operates intake and 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.

 

NB: Fast road camshafts tend to increase the performance through the rev band, you could drop a little bottom end bhp but the top end will be lifted.

Motorsport and race camshafts, increase the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Motorsport camshaft is not great driving around busy urban areas.

You should ideally optimize your power band to your preferences so for a daily driver stick with a fast road K20 camshaft

Some K20 engines respond better to less aggressive cam durations check your engine on a rolling road.

The ecu map and fuelling also have an effect on the power gains you'll get.

A longer valve duration can alter the power 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.

Stage 1 modifications: Sports exhaust manifold, Panel air filters, Drilled & smoothed airbox, Fast road camshaft, Intake headers, Remaps/piggy back ECU.

Stage 2 modifications: fuel pump upgrades, high flow fuel injectors, induction kit, Fast road cam, Ported and polished head, Sports catalyst & performance exhaust.

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

ECU flashing allows a tuner to fully realize the full potential of all the tuning parts you've fitted to your K20.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but figures achieved may vary depending on the tuning parts you've fitted and the condition of your engine.

Pushing air into your K20 is the main goal to any engine modification project.

Air Intake manifolds flow the air during the suck phase from the filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

Shape and flow rate of the Intake manifold can make a noticeable improvement to fuel mixing and power on the K20.

I usually find headers are improved through aftermarket parts, although some makers provide reasonably well designed headers.

Larger K20 valves, carrying out port matching and head flowing will also improve bhp and torque, & importantly will permit increasing the bhp and torque increase on other modifications.

Turbo upgrades

NASP 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

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

If your motor is fitted with a turbo tuning parts are going to make more power and turbo charged engines will have many forged and stronger components.

However engines will need better parts at higher power limits

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

However engines will need better parts at higher power limits

Research these limits and fit more solid crank and pistons to survive the power.

We've seen people spending a lots of money on turbocharger upgrades on the K20 only to experience the car throw a rod on it's first outing after it's been finished.

Big turbochargers commonly suffer a bottom end lag, and small turbochargers spool up really quickly but don't have the top end bhp gains.

Thanks to new tech the selection of turbo units is always moving on and we now see variable vane turbo units, where the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbo units divert the exhaust flow into 2 channels and push these at differently designed vanes in the turbo charger. They also improve the scavenging effect of the engine.

It is common that there's a limitation in the air flow sensor AFM/MAF on the K20 when loads more air is being pulled into the engine.

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

Adding a supercharger or additional turbo will make large bhp gains, although more challenging to get working. We have this article covering twinchargers if you want to read more.

Fuelling

Don't overlook the need to boost the fuel system when you are increasing the bhp - it makes the car more thirsty.  We strongly recommend you to over specify your injector capacity.

As a rule of thumb add 20% capacity when buying an injector, helps cope with injector deterioration and allows you some spare capacity should the engine need 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

It is important to over specify your injectors flow rate.

The accepted safe increase is to add another 20% when specifying an injector, this accounts for injector deterioration and allows you some spare capacity should the engine need more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

Exhaust upgrades and mods

Only look to boost your exhaust if the existing exhaust is actually creating a flow problem.

On most factory exhausts you should find that your flow rate is still fine even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Sports exhausts increase the flow of gases through the engine.

But if the exhaust pipe is too big, ie: over 2.5 inches bore, you will lose much of your flow rate and end up sapping power and torque.

Usual exhaust restrictions are in the catalyst installed, so adding a higher flowing high performance alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the K20

The K20 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the K20, particularly when the engine has been modified and is putting down more power than the manufacturer intended. The camshaft is usually the first thing to show up problems when the wrong grade of oil is used.

The front crankshaft oil seal is prone to weep a little oil.

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

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

History 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.

• 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

• K2Z1
  2005–2006 Acura RSX Type-S
  11.0:1 210 hp 143 lbft @ 6200 RPM 8100 RPM
  2005–2006 Honda Integra Type S
  11.0:1 210 hp @ 7800 RPM 143 lbft @ 6200 RPM 8100 RPM
• K20Z2
  2006–2011 Acura CSX
  9.8:1 153 hp @ 6000 RPM 139 lbft @ 4500 RPM 6800 RPM
  2006–2011 Honda Civic
  9.8:1 153 hp @ 6000 RPM 139 lbft @ 4500 RPM 6800 RPM
  2006–2015 Honda Accord
  9.8:1 153 hp @ 6000 RPM 139 lbft @ 4500 RPM 6800 RPM
  2006–2010 Honda Civic 2.0 S / S-L
  9.8:1 153 hp @ 6000 RPM 139 lbft @ 4500 RPM 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 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

For more information on Tuning your Honda engine 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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