The JDM H23A VTEC Blue Top engine is a hidden gem within the Honda engine family, often overlooked but packed with performance potential. As a content creator for techcarusa.com and an automotive repair specialist, I’ve dedicated years to understanding and working with this engine, from naturally aspirated (NA) to turbocharged setups, alongside a deep dive into Honda EPC part numbers from around the globe. This article aims to be your comprehensive guide to the H23A VTEC Blue Top OBD2 engine, exceeding the depth of information available elsewhere and optimized for enthusiasts seeking to maximize their engine’s performance.
Delving into the H23A VTEC Blue Top Specifications (1998-2001)
The H23A VTEC Blue Top engine, easily identifiable by its distinctive blue valve cover, was primarily found in the Japanese market 1998-2002 Honda Accord Wagon SiR (CH9) and the Accord Wagon AWD (CL2). Both versions were exclusive to these wagon models and came equipped with automatic transmissions, one featuring a triptronic gearbox similar to the 97-01 Prelude automatics, and the other an AWD variant with the same triptronic setup. Crucially, both versions housed the exact same engine, with no internal differences.
These engines boast impressive factory specifications:
- Horsepower: 200 PS (147 kW; 197 hp)
- Torque: 163 ft·lbf (221 N·m)
Internally, the H23A VTEC Blue Top features robust components:
- Bore and Stroke: 87mm bore x 95mm stroke
- Main Journal Size: 55mm mains
- Cylinder Sleeves: FRM (Fiber Reinforced Metal) sleeves
- Compression Ratio: 10.6:1
A key distinction lies in the cylinder head variations across production years:
- 1998-1999 Versions: Utilized a P13 JDM H22 OBD2 Head, identifiable by the PGMFI logo on the intake manifold plenum.
- 2000-2001 Versions: Featured a PDE Head with JDM OBD2 Internals. These versions lack the PGMFI logo on the intake manifold, presenting a smooth plenum surface.
A detailed view of a JDM H23A VTEC Blue Top engine, highlighting its blue valve cover and overall engine bay layout.
Determining the engine’s production year involves locating a two-digit year stamp under the header shield, positioned between cylinders 2 and 3. Furthermore, the head type (PDE or P13) is stamped above cylinder 2 on the front of the head. Piston size is indicated by four letters stamped “A” or “B” on the back of the block, underneath the intake manifold, near the timing belt plastic cover. The PDE Heads are notable for a slightly modified valve angle, a performance-enhancing feature shared with the PDE Euro R and Type S heads, offering a marginal improvement in engine performance.
Other notable internal characteristics include:
- No oil squirters: Unlike some performance Honda engines.
- No crank angle sensor: A characteristic relevant for OBD2 conversion considerations.
- Unique Rods: The connecting rods are shorter than typical H23A1 rods, by approximately 20k. This shorter length means that using standard H22A1/4 style pistons will result in the piston sitting slightly recessed in the cylinder bore, rather than protruding. These rods also employ thread-in bolts, enhancing strength compared to press-fit designs.
- Alternator-only Crank Pulley: Similar to the Euro R/F20B, as the power steering system was electronic and not driven by the pulley.
- Throttle Body Size: 65mm throttle body.
Replacement and Interchangeability with H22A4 Prelude Parts
For maintenance and repair, the H23A VTEC Blue Top shares compatibility with numerous parts from the 98-01 H22A4 Prelude engine, simplifying parts sourcing:
- Sleeves
- Oil Pump
- Water Pump
- Head Gasket
- Intake Manifold Gasket
- Exhaust Manifold Gasket
- Timing Belt
- Balance Shaft Belt
Interestingly, the H23A VTEC Blue Top utilizes Main Bearings and Thrust Rod Bearings similar to the F22/H23A1 and F23A engines. It also employs an F23A Oil Pan, secured with Honda Bond – a somewhat unusual application as Honda Bond was typically reserved for cast oil pans. The F23A oil pan is deeper than a standard H22 oil pan, potentially offering increased oil capacity.
Power Output: H23A VTEC Blue Top vs. JDM H22 and Euro R/Type S
A common question among Honda enthusiasts is whether the H23A VTEC Blue Top delivers more power than a JDM H22 or Euro R/Type S engine. The answer, definitively, is yes. The longer 95mm stroke of the H23A inherently translates to increased torque and power potential. On average, expect to see a 5-10 horsepower increase and a torque gain of at least 10 ft-lbs compared to the JDM H22.
It’s crucial to note that all H23A VTEC Blue Top engines were originally paired with automatic transmissions. Automatic ECU fuel maps and redlines are typically milder than their manual counterparts. Reported horsepower figures for the H23A VTEC Blue Top vary from 197-215 hp. By combining this engine with a manual transmission and a manual ECU (or a properly tuned ECU for manual operation), you can effectively unlock performance surpassing factory JDM H22/Euro R/Type S horsepower figures. Regardless of varying horsepower claims, consistent data indicates the H23A VTEC Blue Top consistently produces higher torque figures than other H-series engines.
Rebuilding and Performance Upgrades
For those considering rebuilding for either forced induction (turbo) or naturally aspirated performance builds, the H23A VTEC Blue Top offers a strong foundation. For a rebuild, opting for off-the-shelf H23A1 aftermarket rods and forged H22A pistons is a viable strategy, avoiding the need for custom rods. However, this combination will result in the piston protruding approximately 0.020″ (20k) out of the cylinder bore. While not inherently problematic, this must be accounted for in valve-to-piston clearance calculations. Using a thicker head gasket, such as a 0.060″ Cometic MLS head gasket, can help maintain a safe valve-to-piston clearance of around 0.030″ (30k).
For a cost-effective compression bump from the stock 10.6:1 to around 11.5:1, Euro R/Type S pistons are a direct drop-in upgrade. When using factory H23A Blue Top rods with Euro R/Type S pistons, piston protrusion should not be a concern. The H23A Blue Top rod length is approximately 141mm, slightly shorter than the 141.5mm rods found in H23A1/F22 engines.
If precise piston-to-deck height is critical, especially to minimize piston protrusion with H22 pistons, custom connecting rods that are approximately 0.020″ (20k) shorter than stock H23A Blue Top rods can be specified.
Performance Build Examples
The following are examples of H23A VTEC Blue Top performance builds, demonstrating their potential with supporting modifications. Both builds utilized 2000 PDE H23A VTEC engines, were dyno tuned by the same tuner, and featured similar bolt-on modifications, with injector variations being the primary difference. Both engines retained stock internals.
Build 1 (Black CRX Example):
- 2000 JDM H23A PDE VTEC Blue Top
- ESP 4-2-1 H22A Header with 2.5″ collector
- 3″ Thermal Exhaust
- 3″ Short Ram Air Intake with BPI stack and K&N filter
- Euro R intake manifold modified by Rosko Racing
- 68mm Performance Products Throttle Body
- OBD1 JDM H22A injectors (345cc) and Distributor
- P28 ECU, Crome Tuned
- Manual Tensioner Conversion
Dyno Results: 212 whp and 174 ft lbs torque
A black Honda CRX engine bay showcasing the H23A VTEC Blue Top engine installation.
Dyno chart displaying the horsepower and torque curves of a tuned H23A VTEC Blue Top engine.
Build 2 (Silver Civic Example):
- 2000 JDM H23A PDE VTEC Blue Top
- Similar bolt-ons as Build 1, including intake, exhaust, header, and intake manifold.
- Flow Stack intake
- 580cc injectors
Dyno Results: Similar to Build 1 (data not explicitly provided but implied to be comparable in the original text).
Engine bay of a silver Honda Civic, featuring a clean H23A VTEC Blue Top engine swap.
Dyno chart specific to the silver Civic build, showcasing the tuned performance of the H23A VTEC engine.
Emissions and Tuning Considerations for OBD2
For OBD2 vehicles, integrating the H23A VTEC Blue Top requires addressing the lack of a crank angle sensor on the engine. A common solution involves rewiring the crank angle sensor signals from the distributor. Rywire.com may offer pre-made solutions for this conversion. The H23A Blue Top utilizes an internal coil distributor; you can either convert to an external coil setup or retain and use a stock H22 distributor.
While the H23A Blue Top throttle body is 65mm, swapping to an H22 throttle body is a straightforward upgrade. However, the intake manifold swap is generally recommended for ease of installation compared to modifying a standard H22 intake manifold to fit.
For optimal tuning, converting to OBD1 with a P28 ECU and utilizing tuning software like Crome or Neptune is widely considered the best approach. Dyno tuning by a skilled Neptune/Crome tuner or AEM tuner is essential to maximize performance.
OBD2 ECU tuning support for the H23A VTEC Blue Top is limited. If emissions compliance is mandatory, converting to OBD1 may be impractical or impossible. Running a stock P13 H22 ECU is not recommended, as it will not properly control the H23A VTEC and will hinder performance.
Conclusion
The JDM H23A VTEC Blue Top OBD2 engine presents a compelling option for Honda enthusiasts seeking a performance upgrade. Its increased displacement, robust internals, and VTEC technology deliver a noticeable boost in horsepower and, more significantly, torque compared to other H-series engines. While originally designed for automatic transmissions and requiring some considerations for OBD2 integration and tuning, the H23A VTEC Blue Top, when paired with a manual transmission and proper tuning, unlocks significant performance potential, making it a worthwhile engine swap for those looking for a unique and powerful Honda powerplant.
