Like the K20, the K24A has an aluminum cylinder block with cast
iron. The engine got the new crankshaft with an increased stroke by
13 mm, and cylinders were bored out by 1 mm. That gave a 200cc gain
in displacement. K24A block has a deck height of 231.5 mm. Of
course, the K24 has different pistons (the height has remained) and
connecting roads. The cylinder head design stayed untouched: it's
made from aluminum, 16 valves (four valves per cylinder), dual
overhead camshaft, central-located spark plugs with individual
coils (coil-on-plugs), and i-VTEC system. The chain-driven intake
and exhaust camshafts open and close valves via roller rocker arms
without hydraulic tappets. The periodic valve clearance adjustment
is needed.
The base K24A1 version was produced from 2001 to 2006. It was a
start line for the all K24 engine series. This power unite had the
i-VTEC on the intake camshaft only. The intake valve diameter is 35
mm, exhaust valve - 30 mm; valve stem diameter is 5.5 mm. It was
equipped with a variable geometry intake manifold (Honda's 2-stage
PPA intake manifold made from aluminum and composite material) and
a 60 mm throttle body. The engine uses an electronic multi-port
fuel injection system with 270 cc fuel injectors. The K24A1 had the
lowest compression ratio between others in the series - 9.6:1.
There was one more mass-market modification in the engine range
- the K24A4. This engine has its own pistons and increased
compression ratio up to 9.7:1, modified intake and exhaust ports
inside the cylinder head, an aluminum 1-stage RAA intake manifold,
and other i-VTEC settings over the K24A1 had. The K24A4 was
slightly upgraded in 2006 and got a new index - K24A8. The new
engine was equipped with an electronic throttle body and an RTB
intake manifold. With the following changes, the engine was able to
fit in the more stringent environmental standard.
Besides those regular engines, the K24A series also includes the
true Honda's performance unit for their sporty models. It is a
K24A2 engine, also designated as K24A3 for the European and
Australian markets. First of all, the K24A2 has a deeply revised
bottom end. The engine block came with dual balance shafts, a
forged crankshaft, reinforced connecting rods, and lightweight
pistons. The compression ratio rose to 10.5. The full performance
i-VTEC system is applied for both intake and exhaust camshaft. Cam
specs by themselves are more aggressive. The engine breathes a lot
better thanks to a high-flow exhaust header and a 1-stage RBB
intake manifold with the enlarged throttle valve (60 mm). It also
uses a drive-by-wire throttle and has EGR castings on the manifold.
With VTEC kicking after 6,000 rpm, the engine produces 197 hp and
171 lb-ft (232 Nm) of torque.
2006+ K24A2 engines came with a fully upgraded intake system. It
has an 80 mm air intake duct, new intake camshaft specifications,
36 mm intake valves, and 64 mm throttle body. The 2.25" exhaust was
added as well. Those engines produced 205 hp and 164 lb-ft (222 Nm)
of torque.
The K24Z1 replaced the K24A1 in the 2007 Honda CRV. The new
2.4-liter engine uses a two-piece, die-cast aluminum engine block
with cast-in iron cylinder liners. The oil filter has been
relocated to the lower center portion of the block. Inside, there
are a forged steel crankshaft and an internal balancer unit. The
compression ratio is 9.7:1. The engine also has a 16-valve DOHC
i-VTEC head. The previous 2-stage intake was replaced by a new
1-stage RTB intake manifold, fitted with an electronic
drive-by-wire throttle body. The exhaust system has a high-density
catalytic converter that helps the engine meet emission standards.
In 2008, Honda's engineers had to optimize the K24Z1 to keep it in
compliance with higher environmental standards. As a result, the
less powerful K24Z4 version became an answer for that.
The K24Z3 debuted in the 2008 Acura TSX. This engine was fitted
with chain-driven dual balance shafts, proper i-VTEC system on
intake and exhaust camshafts (engagement at 5,100 rpm),
high-strength connecting rods, lightweight alloy pistons, and
Computer-controlled Programmed Fuel Injection (PGM-FI). The
cylinder head is equipped with 31 mm exhaust valves. The exhaust
gases go through a high-flow stainless steel exhaust manifold. The
CR is 11.0. This description and specs are correct for the K24Z7 as
well. The only difference is an application (The K24Z7 was used in
Honda Civic Si and Acura ILX).
The K24Z3 for the US Honda Accord had a 10.7:1 compression
ratio, produced less power and torque; it was just a K24Z2 engine
but with a high flow exhaust system. The true K24Z2 features a
10.5:1 compression ratio, R40 intake manifold, and an integrated
exhaust manifold. This engine replaced the K24A8 on production and
meets the highest emission standards. The K24Z5 and K24Z6 are the
same K24Z2 with minor differences. The first one is available only
in China, the second was offered for the Honda CR-V (USDM).
In 2013, Honda began production of freshly designed K24W. It was
an entirely new 2.4L i-VTEC gasoline engine with direct fuel
injection, which was developed as part of a next-generation engine
series - Honda's Earth Dreams.
The K24W shares with previous K24 engines only the bore and
stroke sizes. The overall design is completely different. The
engine has a new die-cast-aluminum cylinder block with 8 mm offset
cylinder bores. Inside the engine block, there are a new forged
steel crankshaft and lightweight pistons with dishes in crowns. On
top, the 2.4L Earth Dreams engine has a new lightweight
pressure-cast aluminum cylinder head with four valves per cylinder,
a high-pressure multi-hole injector between the intake valves,
DOHC, i-VTEC system, and an integrated exhaust manifold. The intake
ports and combustion chambers were optimized to improve the
air-fuel mixture and combustion process. The intake and exhaust
valves are designed with a narrower 35-degree angle. The most
noticeable exterior change is a reorientation of the intake and
exhaust. Now the intake faces back while the exhaust is faced
forward.
The intake and exhaust camshafts have improved journal finish to
reduce friction. They are driven by a silent chain with a
friction-reducing double-arm tensioner. At the end of the exhaust
camshaft, there is a high-pressure fuel pump for direct injection.
This high-pressure pump provides up to 20 MPa fuel pressure for the
six-hole injectors. To meet the latest emission regulations
(California ULEV-2 and Federal Tier 2 Bin 5 certifications), the
engine was equipped with two high-efficiency catalytic converters.
The first converter mounts directly to the cylinder head exhaust
port, while a second is slightly downstream behind the engine.
K24A1 - 160 hp (119 kW) at 6,000 rpm,
162 lb-ft (220 Nm) at 3,600 rpm. This engine was offered for Honda
CR-V.
K24A2 - 197/205 hp (147/153 kW) at
6,800/7,000 rpm, 164-171 lb-ft (222-232Nm) at 4,500 rpm.
Application: Honda Odyssey Absolute, Honda Accord Type-S (JDM),
Acura TSX, Acura TSX.
K24A3 - 197 hp (147 kW) at 6,800 rpm, 164
lb-ft (222 Nm) at 4,500 rpm. This engine is a Honda Accord
engine.
K24A4 - 160 hp (119 kW) at 5,500 rpm, 161
lb-ft (218 Nm) at 4,500 rpm. Application: Honda Element, Honda
Accord, Honda Odyssey.
K24A8 - 166 hp (124 kW) at 5,800 rpm, 160
lb-ft (217 Nm) at 4,000 rpm. Application: Honda Element, Honda
Accord.
K24Z1 - 166 hp (124 kW) at 5,800 rpm, 161
lb-ft (218 Nm) at 4,200 rpm. Application: Honda CR-V.
K24Z2 - 177 hp (132 kW) at 6,500 rpm, 161
lb-ft (218 Nm) at 4,300 rpm. Application: Honda Accord LX/LX-P,
Proton Perdana.
K24Z3 - 190-201 hp (142-150 kW) at 7,000
rpm, 162-172 lb-ft (220-233 Nm) at 4,300 rpm. Application: Honda
Accord and Acura TSX.
K24Z4 - 161 hp (120 kW) at 5,800 rpm, 161
lb-ft (218 Nm) at 4,200 rpm. Application: Honda CR-V.
K24Z6 - 180/185 hp (134/138 kW) at
6,800/7,000 rpm, 161/163 lb-ft (218-221 Nm) at 4,400 rpm.
Application: Honda CR-V.
K24Z7 - 201-205 hp (150-153 kW) at 7,000
rpm, 170-174 lb-ft (230-236 Nm) at 4,400 rpm. Application: Honda
Civic Si and Acura ILX.
K24W - 185 hp (138 kW) at 6,400 rpm, 181
lb-ft (245 Nm) at 3,900 rpm. Application: Honda CR-V, Honda
Accord.
K24W7 - 206 hp (138 kW) at 6,800 rpm, 182
lb-ft (247 Nm) at 3,900 rpm - Acura TLX engine.