Saturday, January 22, 2005


GM Ecotec Line-Up

The purpose of this post is simply to follow-up on a lunchtime discussion (or was it via e-mail?) from a couple of weeks ago, where we kicked around the different engine options for GM small cars; specifically, the Ecotec options in the Cobalt and Solstice.

One of the main questions was concerning the way GM achieved the displacement of the 2.0 L supercharged, 2.2 L, and 2.4 L VTT Ecotecs. Wonder no more:

2.0 L bore x stroke: 86 x 86 mm
2.2 L bore x stroke: 86 x 94.6 mm
2.4 L bore x stroke: 88 x 98 mm

It's interesting to me that all three have different stroke lengths, and that the 2.0 L didn't get another decrease in bore size to strengthen it for supercharging (presumably, the 2.4 L got more bore to improve breathing, as the 2.2 obviously stinks in that department given its 140 HP rating, compared to 170 HP for the 2.4). Myself, I don't care for the undersquare bore/stroke relationship, but Honda's been quite successful at it (the most-recent S2000 engine gets its 2.2 L from a 87 mm bore and 90.7 mm stroke; that's a mean piston speed of 4700 ft/min at its redline of 8000 RPM with a rod ratio of only 1.65:1).

Just to provide a point of reference, the original 2.3 L Quad4 had a bore and stroke of 92 and 85 mm, respectively, and provided 150 HP from a 10:1 compression ratio. Ignore the fact that this was happening 15 years ago (or that Honda was producing 160 HP from the B16 back in '88, or that GM managed 190 HP from the W41 Quad4 in '92).

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