Highlights of B16B 98 Spec R compared to B16A

Highlights behind the high-RPM, high-output of the B16B 98 SpecR In order to increase the power output by 15 hp, and the max RPM by 200RPM, the engine goes through many upgrades. It should be noted that the B18C spec.R's cylinder block is used for its endurance.


The translations for the numbered labels in the diagram are:

  1. Cylinder Head - Complete port & polish
  2. Exhaust Valve Spring - High-lift, dual-layered spring
  3. Sparkplug - High-heat-type #7 platinum plug
  4. Pistons - High-compression, low-friction, custom pistons
  5. Connecting Rod - High-output, high-durability, lightened, custom conrod
  6. Engine Stiffener - Aluminum die-cast, high-durability, one-piece type
  7. Crankshaft - Full-balancer, 8-weight, high-output, custom crankshaft
  8. Inlet Valves - Lightened inlet valves
  9. Inlet Valve Springs - High-lift, flat-surfaced, dual-layered spring
  10. Camshaft - Wide-angled, high-lift, high-durability camshaft
  11. Intake Manifold - High-RPM type.

Engine specifications between B16A and B16B.

Engine Type B16A B16B 98 Spec.R
Maximum Output 170ps/7800rpm 185ps/8200rpm
Maximum Torque 16.0kg-m/7300rpm 16.3kg-m/7500rpm
Bore x Stroke 81.0x77.4mm <- same
Displacement 1595cc <- same
Compression 10.4 10.8
Maximum RPM 8000rpm 8400rpm
Valve Timing
at 1mm lift		 IN Open/Close BTDC15/ABDC45 BTDC18/ABDC45
EX Open/Close BBDC40/ATDC7 BBDC45/ATDC10
Valve Lift IN 10.7mm, EX 9.4mm IN 11.5mm, EX 10.5mm
Inlet Valve Diamter 33mm x 2mm <- same
Spark Plug Type Heat Rate #6 Heat Rate #7 platinum
Throttle Bore Diameter 60mm <- same
Intake Manifold Single pipe sideflow <- same
Air Intake Diameter 65mm <- same
Exhaust Manifold 4-to-2 <- same
Exhaust Pipe Diameter 48.6-50.8mm 57.2mm
Silencer Flow Capacity 98liter/sec 115liter/sec

The camshaft profiles (wild cam) change from B16A 160ps to 170ps and finally to B16B are :

Cam ProfileB16A 160ps B16A 170psB16B 98R
Max Lift (IN/EX)10.4/9.410.7/9.411.5/10.5
Open Timing (IN/EX) BTDC 10/BBDC 40BTDC 15/BBDC 40BTDC 18/BBDC 45
Close Timing (IN/EX) ABDC 40/ATDC 5ABDC 45/ATDC 7BTDC 45/ATDC 10

Different pistons are responsible for the compression ratio increases between 160ps & 170ps B16A and the 10.8 ratio for B16B. Readily apparent is the relatively modest change in piston top between B16A 160ps and B16A 170ps for the 10.2 to 10.4 change. However, the radically different piston top for B16B is very clear from the picture. The increase in compression ratio between B16B from B16A is 0.4.

The cut-outs on the piston top to accomodate for valve lift are basically the same between all three piston. This could meant that B16B camshafts can be installed into both 160ps and 170ps B16A without the need to change to B16B pistons. (If any reader knows this as correct, please let us know)

On B16B, the inlet ports are manually ported to increase air-flow. The exhaust ports are identical to B16A.
B16B intake valve seats are at a different angle to B16A, 45 degrees vs 60 degrees. The intake valves are also different, being lighter and having a thinner valve stem.


On the left are the power curves for B16A 170ps versus B16B. Note the big gain in power after 6000rpm, the VTEC switch-over point between mild and wild cam profiles. The gain at extreme high rpms is readily apparent on the curves.

Various individual specifications for B16B can teach us about the feasibility of various modifications to B16A. For eg, the throttle bore diameter for B16B is identical to B16A at 60mm. This means that enlarged throttle bodies for B16A might not be an optimal mod or that a compromise in power delivery might result, eg loss of low-end power in return for gain in high-end power. Note that B16B has identical low and mid range power as B16A.

As with B18C Spec R, the wonder of B16B is the assurance of a 15 to 25ps gain in power on a B16A provided the tuning done by Honda can be completely replicated. Nevertheless even if only a portion can be duplicated, combining with properly designed aftermarket exhaust, headers, and intake could still potentially realize this 15ps gain. B16B engine parts are available from Honda and with care, most of them can be used on B16A for good power gains.

April 1999, Wong KN, Temple of VTEC Asia.
Japanese translation, Kaz Mori, Temple of VTEC Asia.
Information source, Hyper-Rev Volume 31 'Civic & CRX #2 (re-visited)'