Oh dear, it seems that another manufacturer has misstated the horsepower ratings of one of their vehicles. However, unlike the fiascos faced by certain automakers in recent years because of overrated powertrains, Honda seems to have chosen to provide its owners with a series of pleasant surprises.
For example, the 2004 S2000 is rated at the same 240 hp as its older siblings. It is also rated at 162 lbs-ft of torque, 9 lbs-ft more than previous models. But when we put it on our Dynapack chassis dynamometer and compared it to a 2002 S2000 (which consistently makes a few more hp than the early 2000-2001 models) we got a big surprise. Peak hp was up - a lot. A greater than 26 hp gain at peak is nothing to sneeze at! Torque was also up by over 21 lbs-ft at peak. Down low the torque curve is flatter and fatter than the previous model as well for more relaxed around town driving.
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After getting over the initial shock of the big numbers (o.k., not so shocked, Honda seems to be making a habit of underrating their engines lately), we started examining the results a little more closely and several interesting items jumped out at us. First of all, note where the torque peak occurs. On the 2004 its a double peak high in the rpm range at approximately 6500 and again at 7800 rpm. The 2002 sees peak torque at 6500 rpm as well. Not what you'd expect with a bigger engine. Its this second, high rpm torque peak that really gives the 2004 its sprint to the rev limiter. Its also a bit of a pain when driving because there is no overrev capacity. You hit the power peak and you hit the rev limiter while the early models had a good 600 rpm after the peak to play with. That last little spike in torque (which was very repeatable in case you wondered) also brings up the peak hp numbers a bit. When you look at the averages, the more typical gains on the high cam are closer to 20 hp - still quite substantial for an engine rated at "the same" 240 hp as the early models.
How did Honda get these large gains? Well, yes, the displacement does count, but there are other factros to consider. Lower revs usually means that proportional gains due to displacement are reduced. With 8% more displacement, we would have expected about 17-18 more hp if peak power was made at the same rpm. With the 300-400 rpm reduction in that peak that we see on the dyno, we'd expect to see the gains drop to 7-9 hp. Where did the rest come from? In our opinion, the secret is in the mixture and ignition timing. While we didn't map the latter, we did datalog A/F mixtures and compare them to earlier models.
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The 2004 consistently runs about a point leaner and never less than a half point leaner on the mixture than the 2000-2003 models. Where the previous models benefited substantially from fuel tuning, Honda gets the mixture pretty darn close to optimal right off the showroom floor. Given that we've seen 7-9 hp gains from fuel tuning alone on early models, now the gains begin to make more sense. Combined with changes in ignition timing, cam profiles, etc. the power gains are quite reasonable - although we are looking for a consumer purchased model (vs. our press car) to test as a verification. (Contact firstname.lastname@example.org if you're in Southern California and want a free dyno test.)
So, the 2004 S2000 makes more power - a lot more power. But that's the dyno, what's it like on the road? Stick around as we put it through its paces alongside an early model for comparison.