Power ratings for JDM cars are all specified using the JIS PS rating. As we know, JDM Hondas almost always has a higher PS rating than the export counterparts. For eg, JDM Civic SiR/SiR2 EK4 uses B16A specified to produce 170s at 7800rpm while the export version for UK marketed as the Civic VTi sports a 160hp B16A at 7600rpm.
What is the relationship between the JIS PS rating and the SAE HP rating ? Is it responsible for the large 10ps discrepancy between JDM and export engines ? Actually, the Singapore-based car mag 'Torque Class' once calculated the relationship as 1 JIS PS to about 1.01 SAE HP. That is to say, the JIS PS rating gives at most slightly over 1% optimistic ratings as compared to using SAE HP.
For the case of the Civic, the export version most probably has a different engine from the JDM EK4. The fact that the export B16A actually produces its maximum power at different rpm value (7600rpm vs 7800rpm) testifies to that. In addition, the export B16A's max power is really 160ps at 7600rpm and some auto magazines, eg UK's Performance Car actually accurately lists the UK Civic VTi to produce 158hp at 7600rpm.
So in general, the differences using the JIS PS rating instead of an
SAE HP rating will in fact give the JDM models only very small advantages
in max power ratings. For anything less than 100, the JIS PS and SAE HP
can in fact be used interchangeable without much losses in accuracy. The
various JDM engines really do produce quite a bit more power than their
equivalent export versions.
Temple of VTEC - Asia. May 18 1998