Translations of the numbered labels in the engine diagrams are :
Engine specifications between B18C and B18C Spec R (1996 & 1998).
|Engine Type||B18C||B18C 96 spec.R|
|Bore x Stroke||81.0x87.2mm||<- same|
at "High" 1mm lift
|Valve Lift||IN 10.6mm, EX 9.4mm||IN 11.5mm, EX 10.5mm|
|Inlet Valve Diamter||33mm x 2mm||margin reduced by 0.5mm|
|Spark Plug Type||Heat Rate #6||Heat Rate #7 platinum|
|Throttle Bore Diameter||60mm||62mm|
|Air Intake Diameter||65mm||70mm|
|Exhaust Pipe Diameter||48.6-50.8mm||57.2mm|
|Important tuning changes for B18C Spec R includes manual porting of the intake ports and change in intake valve seat from 60 degrees to 45 degrees. Another major change is the replacement of the intake manifold from a dual intake VVIS (Variable Volume Intake System) to the single tract intake for B18C Spec R. The original intake runners were optimized for a flat torque curve and the high-rpm runners open by a butterfly valve. This was replaced by a special ultra high-flow manifold in the B18C Spec R.|
For the 98 Spec Integra Type-R, the main change to the B18C 98Spec R engine is the use of a 4-to-1 SUS-stainless exhaust manifold. B18C 98SpecR's max power is still 200ps but the max torque rpm was increased slightly and shifted down to a lower 6200rpm.
The power curves for standard B18C, B18C 96 Spec R and 98 Spec R are above. Clearly seen is the design objective for a flat torque curve for standard B18C acheived via a combination of VTEC/dual cam lobes and the VVIS dual intake manifold. For B18C 96 Spec R, the big gain in torque and power at high-rpms can be clearly seen. Comparing now the power curve for B18C 98 Spec R, the effect of the 4-in-1 headers are very unexpected as B18C 98 Spec R has higher upper-mid rpm power and lower high rpm power than B18C 96 Spec R. This is the direct opposite of the rule-of-thumb for power gains between 4-2-1 and 4-1 headers !
The changes made for B18C Spec R represents tuning by Honda on the 'standard' 180ps B18C engine and for a 20ps gain to 200ps. The greatness of this tuning is not the quantum of power gain - 20ps gain and a max power of 200ps may not be that great in absolute terms - but rather the assurance of this amount of gain provided the tunings by Honda can be completely replicated. Nevertheless even if only a portion can be duplicated, combination with properly designed aftermarket exhaust, headers, and intake (which are subjected to more leanient legal noise restrictions than stock exhaust) can still potentially realize the 20ps gain. B18C Spec R parts are available from Honda and most will swap straight into the standard B18C though some may require some machining work, eg intake valve seats on the B18C Spec R head (which is essentially a B16A head).
Copyright April 1999, Wong KN, Temple of VTEC Asia
Japanese Translation, Kaz Mori, Temple of VTEC Asia
Information Source, Hyper-Rev Volume 27 'Integra'