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Old 05-15-2009, 09:41 AM   #16 (permalink)
Master EcoModder
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OurInsight - '06 Honda Insight
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I have to defend the design engineers on this question. The throwout bearing in most cars is rather small and not designed for continuous duty at all. Therefore, IMO, one should go to neutral when coasting either engine-on or engine-off. As someone remarked it is very easy to slip the out of gear by applying slight pressure when the throttle is lifted. This practice, when done with a bit of skill, causes no extra wear at all. Of course, the reverse procedure, going into gear without clutching, is bound to be difficult and cause damage.

Incidently, neutral engine-on coasting probably delivers worse FE than engine-on coasting in gear on most modern cars. As mentioned earlier lots of newer cars will go into fuel cut-off when deaccelerating in gear. Go to neutral and you are stuck with engine idle consumption if the engine is on.

So, if you want to experiment with coasting, slip the transmission into neutral, shut off the engine, coast, clutch and re-engage 4th, bump start. I continue to believe that the process imposes some extra wear, but apparently many folks have gotten away with it for years I would not do it unless the benefit/wear equation is clearly positive. That is to say, I would only do it if the coast was reasonably long. Otherwise, you are just hammering your equipment for nothing.

I think I know of what I speak. In my racing program I built lots of engines and transmissions.
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