In my article on how the Civic 1.8S delivers on the dyno, I have compared the R18A's dyno result against the old K20A from the ET1 Civic 2.0 i-VTEC and with interesting results. On the dyno, the R18A showed exactly the 'fat midrange' that Honda designed it to deliver, with the result that it actually deliver more torque/power than the old K20A at some points in the rev range ! Of course that was against the 'old' K20A so the more pertinent question for R18 vs K20 is more like how the R18A compares against this 'new' K20Z. Of course at that time I have not published the dyno-result for the new K20Z so I did not do this comparison. But now in this article I will compare the dyno results between the R18A and the 'new' K20Z engine.
The side-by-side comparison chart is again shown on the left. Two things are apparent. One is how much more torque and power the K20Z has over the R18A. This should settle any and all debates about whether the R18A can outperform the K20Z or not. It most definitely does not and in fact is outperformed by the K20Z all across the rev-range. The other thing is how the R18A succcessfully delivers the 'fat midrange' torque/power it is designed to while the K20Z clearly fails in delivering that. Now remember while the i-VTEC for both R18A and K20Z stands for 'intelligent', in reality the R18A does NOT feature VTC while the K20Z does. So this do lend some support for my conjecture that perhaps the cause for the K20Z's failure to deliver its design objective with regards to mid-range torque and power could be that the VTC mapping is out of tune for ASEAN conditions
The other thing to note would be how (relatively) close the R18A manages to stay with the K20Z for torque/power in the low-end/mid-range rpm range but that after 5,500rpm, how the K20Z quickly out-delivers it. This of course shows how much superior VTEC is for high-rpm power delivery, against alternate technologies like variable intake tracts like that used on the R18A. Remember that while the R18A also use VTEC, it is used to switch an economy cam profile while the basic cam profiles are actually the 'high-cams'. So high-cams on the R18A which are active for normal operations on the R18A, will need to be compromised for good torque/power delivery at WOT across the whole rpm range since it is used throughout. This is in contract to i-VTEC on the K20Z which has two separate cam lobes for low/mid and high-rpms and so can go much further in terms of aggressive valve timing for the 'hi-cams'.