It doesn't take a genius, or someone with incredible insight, to realize that RSX Type-S is a true successor to the 3rd generation Integra. Combining a high reving engine with a lithe chassis the
RSX-S ups the technology ante in almost every way its predecessor, the Integra GS-R. How is it better? Let us count the ways.
To begin with, the RSX provides suspension enhancements over the Integra GS-R. Are we calling the Macpherson strut front and multi-link rear suspension in the RSX an enhancement over the previous modified double wishbone front of the GS-R? Well, theoretically no, but in function, yes. Theoretically, a double wishbone should be more advanced, but Acura has found a way to take the strut suspension and make it outperform the setup from the GS-R. Acura combines a relatively simple lower control arm and a free moving pivot for the strut to create a front suspension which provides good camber control, long wheel travel and good ride. Compared to the older GS-R, the
RSX-S has the ability to soak up larger bumps, better, while still providing a good ride and good wheel control in hard driving.
RSX Macpherson strut design
At the rear Acura is using a rather unusual looking multi-link setup that is based around a large diameter tubular control arm. Such an arm is simpler to manufacture than a cast piece, and provides good strength. However, it probably could be lighter (note to aftermarket manufacturers). This lower control arm acts as a locater for the hub as well as a modified toe control link. A secondary link higher up in the suspension acts to position the wheel in camber. A short shock/spring combo manages to allow good wheel travel while keeping intrusion into the hatch area to a minimum. In use, the suspension changes combine to create a controlled, almost European ride/handling combo. In hard cornering the chassis remains predictable while avoiding bottoming over mid-corner bumps - a problem that the GS-R was known for. The RSX remains very stable mid-corner with reasonable neutrality, yet can be rotated on the brakes without fear of unpredictable
RSX rear trailing arm
In the engine room, the RSX takes a major step up from the GS-R. Acura realized that after a lifespan of over a decade that the B-series engine wasn't going to cut it for much longer. Thus, the K-series engine was born. While we haven't been able to get anyone within the Honda/Acura universe to confirm that the K-series is based on the F-series from the S2000, it seems quite clear to us that the engineers applied what they learned from developing the F20C directly to the K engine. From the location of the oil filter, to the two-piece block design (the lower half the of the block acts as the crankshaft bearing caps, reinforcement and oil pan mounting), to the cylinder head, the K-series is a near carbon copy of the F20C. In fact, we've even taken the camshaft caps from an F20C and bolted them directly onto an RSX-S head. Yes, they're that similar. Port dimensions on the RSX-S are also nearly identical to the F20C. Short of slightly smaller valves (1mm all around) and a lack of touch up work on the ports, this could be an F20C head.
Air filter element
But while it may seem that the K20A2 is a slightly poorer cousin of the F20C, it completely blows away the old B-series. Bore is increased by 5mm vs. the B18C. This means that much larger valves can be used (2 mm larger). Bigger valves mean more airflow and more airflow (properly used) means more power. You can't get a B-series head to flow with a K20 head unless you weld it up and start over again from scratch. The transition to roller followers for the valvetrain vs. the sliders on the B-series also reduces valvetrain friction and has the potential to allow more aggressive cams as well.
The new K20A2 engine
Of course, no mention of the top end of the RSX would be complete without discussing the "i" in i-VTEC. Allowing intake cam timing to vary by up to 50 degrees, i-VTEC has the potential to allow for tremendous improvements in midrange torque. And indeed, the gains are significant on paper. Below 4000 rpm the K20A2 is stronger than even the F20C and feels very good. However, the execution isn't perfect. There is a nasty hole in the torque curve between 5k and 6k rpm that doesn't suit the car at all. See the Dyno Plot on the right. While we've already been privy to ECU changes that allow modifications to the i-VTEC cam advance, that dip has been hard to remove. We believe that it's probably due to the RSX-S' use of a single runner intake manifold. Such a manifold is useful in producing high rpm power, but usually carries the penalty of a mid-range dip in torque due to unfavorable resonances. The old GS-R was superior in this range (accounting for displacement) but it doesn't have the top end potential of the
The oil filter requires only a little bit of wriggling to reach.
On the bottom end, the RSX-S uses a shorter stroke and longer rods to provide a more favorable rod ratio than the GS-R. In fact, long term, the RSX-S has the potential to handle a lot more revs than the GS-R. And under hard use, the better rod ratio may allow the rings to hold up better than the B18C's, which are known to get a little lax on oil control after 50k-75k miles of hard use. Combined with a more durable chain drive for the cam's, the bottom end of the K20 looks like a nice step up for enthusiasts.
Thanks for reading this article. As a bonus, here is your chance to download this video before we make it fully pubic in the News Section.
Analysis of under the car of the RSX Type-S: RSX Under Car (320x240 MPEG1 21.3MB)
RSX Type-S on the Dyno: RSX Dyno (320x240 MPEG1 7.5MB)
We'll have more videos in future articles, so be sure to read and comment on them all.