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Specific Output Marches On

Last month Acura rolled out the allnew RL for the North American press. Comparisons with the previous RL, which served well in its day, demonstrate light years of improvement in looks, safety, handling and performance.

When evaluating the progress, I always start with the improvement in specific output per unit of displacement or the power density since that will essentially establish the limits of what might be accomplished in the overall performance package.

So when I look at the 2004 Acura RL and compare it to the all-new 2005 RL, which goes on sale in mid-October, I see a 1990s platform that was competitive for its time but no match for the new iron.  The 2004 RL is powered by a 3.5 L V-6 that produces 225 hp at 5,200 rpm, peak torque of 231 lb.ft. at 2,800 rpm. So it has a specific output of 64 hp/L, and 37.5 hp per cylinder. The 2004 model engine is redlined at 6,000 rpm.

The new RL, equipped with the new 3.5 L SOHC V-6 with variable valve timing and electronic lift control, is rated 300 hp at 6200 rpm with peak torque of 260 lb.ft. at 5,000. rpm. That is really stepping up significantly.

Yes, power has been increased by a full 33 percent and it’s accomplished within the identical displacement as the former package. The new V-6 produces an impressive 85 hp/L (1.4 hp/, or 50 hp per cylinder.

The output of the V-6 is great enough that Acura does not see the need for a V-8 engine in this market segment (the MSRP for the RL is $48,900).

From a specific output point of view the V-8 may no longer be viable, but that configuration has other attractions that keep it in the game. Certainly it is smoother, although a higher revving V-6 might be so comparable that most wouldn’t notice any difference.

The role of the V-8 as a marketing draw is also still great, as in the case of the DCX Hemi in the Chrysler 300 where the V-8 plays a crucial role.

It might seem surprising, but the first Hemi way back in the mid-1950s was a rather modest 241 cu. in. ( 3.9L) V-8 that was rated at 140 hp at 4,400 rpm, with specific output of only 39 hp/L.

The image is far different, of course, and so the current 5.7L Hemi simply has to be a V-8. Set up with the Multi Displacement System (MDS), this engine is really not being pushed all that hard.

In the Chrysler 300 it has a rating of 340 hp at 5,000 rpm, plenty of poke in the overall but only 60 hp/L if thinking about specific output per unit of displacement.

Consider that if the 5.7L Hemi had the same specific output as the 3,5L V-6 in the Acura RL, it would have output in the 485 hp range.

From a technical vantage, the V-8 may seem almost an anachronism. And yet it retains a strong marketing allure. For the Acura RL, it’s hardly an issue. But for the DCX Hemi program, the V-8 is “gotta have” stuff, no question about that either.

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Sat. July 13th, 2024

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