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Old 01-18-2012, 03:50 PM   #1 (permalink)
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Location: Vermont
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Gaptooth (retired) - '00 Honda Insight
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90 day: 54.26 mpg (US)

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90 day: 41.27 mpg (US)

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Honda R-series

This has probably been posted here before but it's new to me and I don't see any threads on the main page.

Technical Overview of Honda's new R18 i-VTEC Implementation

^ This article details the technical innovations that went into Honda's R-series, the motor in the non-Si models of the 2006+ Civic. The biggest innovation I see is Honda's removal of the butterfly valve and instead using variable valve timing to control the amount of air that enters a cylinder. They claim similar cruising fuel efficiency to a 1.5L engine in the 1.8L R18A1 (~20% smaller displacement) by reducing pumping losses.

If I'm not mistaken, it spins backwards like the Honda D and B series (could be mated to their transmissions?), while weighing less. I wonder if this engine would produce similar (or better?) economy numbers compared to the HF/HX motors when dropped in a vehicle that doesn't weight nearly as much as the new Civics?

Some random info:

The 2012 Civic Auto claims 39mpg highway, with a 5th gear * FD ratio of 2.33. The manual claims 36mpg, but has a 5th * FD of 3.12, meaning the motor spins 33% faster relative to the velocity of the car. Imagine mating it to a CRX HF's tranny, with a ratio of 2.05.

I'd love to get my hands on one of the 1.6L R motors they sell in other markets.


I'd also like to point out that complicated mechanisms like variable length intake manifolds, as well as variable timing and valve lift, can be done away with in serial hybrids, as these are bandaids used to increase efficiency across a wide band of throttle and RPM, making for significantly cheaper and lighter motors.

Last edited by Ecky; 01-18-2012 at 04:07 PM..
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