Blurb/rumor on Honda V10

[TC]

<TABLE cellSpacing=0 cellPadding=4 width="100%" align=center border=0><TBODY><TR><TD class=td4 vAlign=top width="100%">From vtec.net:

Rumor: Honda targets 23.5mpg efficiency for upcoming 500+hp V10


</TD></TR><TR><TD class=td4 vAlign=top width="100%">Winding Road reports that the latest rumors in Tokyo concerning the next-gen NSX's development path indicate that Honda's aiming for the all-new naturally-aspirated V10 motor (rumored to displace 5.0L and develop 500+hp) to deliver 10.0km/liter (approximately 23.5mpg).

In theory, it shouldn't be super difficult to hit that mark (at least on the Highway portion of the US's EPA ratings) - Chevy's already done it with the 505hp 7.0L LS7 monster that powers the Corvette Z06 with a highway rating of 26mpg. The secret: super-tall gearing for the top two cogs (6th is 1:2) resulting in a cruising rpm that's only a few hundred rpms above idle. Another advantage to the Z06 is that it only weighs in at a shade over 3100lbs. With an SH-AWD drivetrain we can only pray that the NSX even approaches that number.


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[ericwgnsx]

This article makes it sound like using "super tall" gearing for highway speeds is some kind of engineering breakthrough. Let's see...making the engine turn slower to save fuel... anyone with half a brain could tell you that you'll save fuel with slower engine speeds. My question is, why doesn't every vehicle have gearing that allows for engine speeds "a few hundred RPM's above idle"? Seems like there is more to it than that.

 

[White98LS]

My question is, why doesn't every vehicle have gearing that allows for engine speeds "a few hundred RPM's above idle"? Seems like there is more to it than that.

Because most vehicles don't have 470lb/ft like the Z06 does, or over 500lb/ft like a Viper does. If you put a super-duper-tall top gear on, say, a 4-cyl Accord with 170lb/ft, it's not going to be happy at all doing 1600rpm at 70mph. It may not do it at all! You have to have a lot of torque (which more or less means a lot of displacement) to pull off the extra-long top gear trick.

As the link says though, Honda is aiming for 23.5mpg as a combined average between city and highway. Meaning they won't be able to just slap a tall gear on there for good highway mileage and accomplish their goal. The actual source article mentions that the old NSX-R got 8.6km/L mileage (20.2mpg) by the Japanese rating standard, and with the new V10 they're shooting for 10.0km/L. Increasing displacement by 36% and peak hp by 60%+ while increasing gas mileage by 16% is a huge accomplishment.

Especially if it's the unfortunate front-engined SH-AWD GT-style barge that it's going to have to lug around I don't see how that monstrosity is going to weigh less than 3500lbs.